| Rfc | 3821 |
|---|
| Title | Fibre Channel Over TCP/IP (FCIP) |
|---|
| Author | M. Rajagopal, E. Rodriguez, R.
Weber |
|---|
| Date | July 2004 |
|---|
| Format: | TXT, HTML |
|---|
| Updated by | RFC7146 |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Network Working Group M. Rajagopal
Request for Comments: 3821 E. Rodriguez
Category: Standards Track R. Weber
July 2004
Fibre Channel Over TCP/IP (FCIP)
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
Fibre Channel Over TCP/IP (FCIP) describes mechanisms that allow the
interconnection of islands of Fibre Channel storage area networks
over IP-based networks to form a unified storage area network in a
single Fibre Channel fabric. FCIP relies on IP-based network
services to provide the connectivity between the storage area network
islands over local area networks, metropolitan area networks, or wide
area networks.
Table Of Contents
1. Purpose, Motivation, and Objectives. . . . . . . . . . . . . . 3
2. Relationship to Fibre Channel Standards. . . . . . . . . . . . 4
2.1. Relevant Fibre Channel Standards . . . . . . . . . . . . 4
2.2. This Specification and Fibre Channel Standards . . . . . 5
3. Terminology. . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Summary . . . . . . . . . . . . . . . . . . . . . . . 7
5. The FCIP Model . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. FCIP Protocol Model. . . . . . . . . . . . . . . . . . . 9
5.2. FCIP Link. . . . . . . . . . . . . . . . . . . . . . . . 10
5.3. FC Entity. . . . . . . . . . . . . . . . . . . . . . . . 11
5.4. FCIP Entity. . . . . . . . . . . . . . . . . . . . . . . 12
5.5. FCIP Link Endpoint (FCIP_LEP). . . . . . . . . . . . . . 13
5.6. FCIP Data Engine (FCIP_DE) . . . . . . . . . . . . . . . 14
5.6.1. FCIP Encapsulation of FC Frames. . . . . . . . . 16
5.6.2. FCIP Data Engine Error Detection and Recovery. . 19
6. Checking FC Frame Transit Times in the IP Network. . . . . . . 22
7. The FCIP Special Frame (FSF) . . . . . . . . . . . . . . . . . 23
7.1. FCIP Special Frame Format. . . . . . . . . . . . . . . . 23
7.2. Overview of FSF Usage in Connection Establishment. . . . 26
8. TCP Connection Management. . . . . . . . . . . . . . . . . . . 28
8.1. TCP Connection Establishment . . . . . . . . . . . . . . 28
8.1.1. Connection Establishment Model . . . . . . . . . 28
8.1.2. Creating New TCP Connections . . . . . . . . . . 29
8.1.3. Processing Incoming TCP Connect Requests . . . . 32
8.1.4. Simultaneous Connection Establishment. . . . . . 36
8.2. Closing TCP Connections. . . . . . . . . . . . . . . . . 36
8.3. TCP Connection Parameters. . . . . . . . . . . . . . . . 36
8.3.1. TCP Selective Acknowledgement Option . . . . . . 36
8.3.2. TCP Window Scale Option. . . . . . . . . . . . . 36
8.3.3. Protection Against Sequence Number Wrap. . . . . 37
8.3.4. TCP_NODELAY Option . . . . . . . . . . . . . . . 37
8.4. TCP Connection Considerations. . . . . . . . . . . . . . 37
8.5. Flow Control Mapping between TCP and FC. . . . . . . . . 37
9. Security . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
9.1. Threat Models. . . . . . . . . . . . . . . . . . . . . . 38
9.2. FC Fabric and IP Network Deployment Models . . . . . . . 40
9.3. FCIP Security Components . . . . . . . . . . . . . . . . 40
9.3.1. IPsec ESP Authentication and Confidentiality . . 40
9.3.2. Key Management . . . . . . . . . . . . . . . . . 41
9.3.3. ESP Replay Protection and Rekeying Issues. . . . 43
9.4. Secure FCIP Link Operation . . . . . . . . . . . . . . . 44
9.4.1. FCIP Link Initialization Steps . . . . . . . . . 44
9.4.2. TCP Connection Security Associations (SAs) . . . 44
9.4.3. Handling Data Integrity and Confidentiality
Violations . . . . . . . . . . . . . . . . . . . 45
10. Performance. . . . . . . . . . . . . . . . . . . . . . . . . . 45
10.1. Performance Considerations . . . . . . . . . . . . . . . 45
10.2. IP Quality of Service (QoS) Support. . . . . . . . . . . 46
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 47
11.1. Normative References . . . . . . . . . . . . . . . . . . 47
11.2. Informative References . . . . . . . . . . . . . . . . . 49
12. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 50
Appendix A Fibre Channel Bit and Byte Numbering Guidance. . . . . 51
B IANA Considerations. . . . . . . . . . . . . . . . . . 51
C FCIP Usage of Addresses and Identifiers. . . . . . . . 52
D Example of synchronization Recovery Algorithm. . . . . 53
E Relationship between FCIP and IP over FC (IPFC). . . . 58
F FC Frame Format. . . . . . . . . . . . . . . . . . . . 59
G FC Encapsulation Format. . . . . . . . . . . . . . . . 61
H FCIP Requirements on an FC Entity. . . . . . . . . . . 63
Editors and Contributors Acknowledgements. . . . . . . . . . . . . 69
Editors and Contributors Addresses . . . . . . . . . . . . . . . . 70
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 74
1. Purpose, Motivation, and Objectives
Warning to Readers Familiar With Fibre Channel: Both Fibre Channel
and IETF standards use the same byte transmission order. However,
the bit and byte numbering is different. See appendix A for
guidance.
Fibre Channel (FC) is a gigabit or multi-gigabit speed networking
technology primarily used to implement Storage Area Networks (SANs).
See section 2 for information about how Fibre Channel is standardized
and the relationship of this specification to Fibre Channel
standards. An overview of Fibre Channel can be found in [34].
This specification describes mechanisms that allow the
interconnection of islands of Fibre Channel SANs over IP Networks to
form a unified SAN in a single Fibre Channel fabric. The motivation
behind defining these interconnection mechanisms is a desire to
connect physically remote FC sites allowing remote disk access, tape
backup, and live mirroring.
Fibre Channel standards have chosen nominal distances between switch
elements that are less than the distances available in an IP Network.
Since Fibre Channel and IP Networking technologies are compatible, it
is logical to turn to IP Networking for extending the allowable
distances between Fibre Channel switch elements.
The fundamental assumption made in this specification is that the
Fibre Channel traffic is carried over the IP Network in such a manner
that the Fibre Channel Fabric and all Fibre Channel devices on the
Fabric are unaware of the presence of the IP Network. This means
that the FC datagrams must be delivered in such time as to comply
with existing Fibre Channel specifications. The FC traffic may span
LANs, MANs, and WANs, so long as this fundamental assumption is
adhered to.
The objectives of this document are to:
1) specify the encapsulation and mapping of Fibre Channel (FC) frames
employing FC Frame Encapsulation [19].
2) apply the mechanism described in 1) to an FC Fabric using an IP
network as an interconnect between two or more islands in an FC
Fabric.
3) address any FC concerns arising from tunneling FC traffic over an
IP-based network, including security, data integrity (loss),
congestion, and performance. This will be accomplished by
utilizing the existing IETF-specified suite of protocols.
4) be compatible with the referenced FC standards. While new work
may be undertaken in T11 to optimize and enhance FC Fabrics, this
specification REQUIRES conformance only to the referenced FC
standards.
5) be compatible with all applicable IETF standards so that the IP
Network used to extend an FC Fabric can be used concurrently for
other reasonable purposes.
The objectives of this document do not include using an IP Network as
a replacement for the Fibre Channel Arbitrated Loop interconnect. No
definition is provided for encapsulating loop primitive signals for
transmission over an IP Network.
Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119 [1].
2. Relationship to Fibre Channel Standards
2.1. Relevant Fibre Channel Standards
FC is standardized as a family of American National Standards
developed by the T11 technical committee of INCITS (InterNational
Committee for Information Technology Standards). T11 has specified a
number of documents describing FC protocols, operations, and
services. T11 documents of interest to readers of this specification
include (but are not limited to):
- FC-BB - Fibre Channel Backbone [2]
- FC-BB-2 - Fibre Channel Backbone -2 [3]
- FC-SW-2 - Fibre Channel Switch Fabric -2 [4]
- FC-FS - Fibre Channel Framing and Signaling [5]
FC-BB and FC-BB-2 describe the relationship between an FC Fabric and
interconnect technologies not defined by Fibre Channel standards
(e.g., ATM and SONET). FC-BB-2 is the Fibre Channel document
describing the relationships between FC and TCP/IP, including the FC
use of FCIP.
FC-SW-2 describes the switch components of an FC Fabric and FC-FS
describes the FC Frame format and basic control features of Fibre
Channel.
Additional information regarding T11 activities is available on the
committee's web site www.t11.org.
2.2. This Specification and Fibre Channel Standards
When considering the challenge of transporting FC Frames over an IP
Network, it is logical to divide the standardization effort between
TCP/IP requirements and Fibre Channel requirements. This
specification covers the TCP/IP requirements for transporting FC
Frames; the Fibre Channel documents described in section 2.1 cover
the Fibre Channel requirements.
This specification addresses only the requirements necessary to
properly utilize an IP Network as a conduit for FC Frames. The
result is a specification for an FCIP Entity (see section 5.4).
A product that tunnels an FC Fabric through an IP Network MUST
combine the FCIP Entity with an FC Entity (see section 5.3) using an
implementation specific interface. The requirements placed on an FC
Entity by this specification to achieve proper delivery of FC Frames
are summarized in appendix H. More information about FC Entities can
be found in the Fibre Channel standards and an example of an FC
Entity can be found in FC-BB-2 [3].
No attempt is being made to define a specific API between an FCIP
Entity and an FC Entity. The approach is to specify required
functional interactions between an FCIP Entity and an FC Entity (both
of which are required to forward FC frames across an IP Network), but
allow implementers to choose how these interactions will be realized.
3. Terminology
Terms used to describe FCIP concepts are defined in this section.
FC End Node - An FC device that uses the connection services provided
by the FC Fabric.
FC Entity - The Fibre Channel specific functional component that
combines with an FCIP Entity to form an interface between an FC
Fabric and an IP Network (see section 5.3).
FC Fabric - An entity that interconnects various Nx_Ports (see [5])
attached to it, and is capable of routing FC Frames using only the
destination ID information in an FC Frame header (see appendix F).
FC Fabric Entity - A Fibre Channel specific element containing one
or more Interconnect_Ports (see FC-SW-2 [4]) and one or more
FC/FCIP Entity pairs. See FC-BB-2 [3] for details about FC Fabric
Entities.
FC Frame - The basic unit of Fibre Channel data transfer (see
appendix F).
FC Frame Receiver Portal - The access point through which an FC
Frame and time stamp enter an FCIP Data Engine from the FC Entity.
FC Frame Transmitter Portal - The access point through which a
reconstituted FC Frame and time stamp leave an FCIP Data Engine to
the FC Entity.
FC/FCIP Entity pair - The combination of one FC Entity and one FCIP
entity.
FCIP Data Engine (FCIP_DE) - The component of an FCIP Entity that
handles FC Frame encapsulation, de-encapsulation, and transmission
FCIP Frames through a single TCP Connection (see section 5.6).
FCIP Entity - The entity responsible for the FCIP protocol exchanges
on the IP Network and encompasses FCIP_LEP(s) and FCIP Control and
Services module (see section 5.4).
FCIP Frame - An FC Frame plus the FC Frame Encapsulation [19]
header, encoded SOF and encoded EOF that contains the FC Frame
(see section 5.6.1).
FCIP Link - One or more TCP Connections that connect one FCIP_LEP to
another (see section 5.2).
FCIP Link Endpoint (FCIP_LEP) - The component of an FCIP Entity
that handles a single FCIP Link and contains one or more FCIP_DEs
(see section 5.5).
Encapsulated Frame Receiver Portal - The TCP access point through
which an FCIP Frame is received from the IP Network by an FCIP
Data Engine.
Encapsulated Frame Transmitter Portal - The TCP access point through
which an FCIP Frame is transmitted to the IP Network by an FCIP
Data Engine.
FCIP Special Frame (FSF) - A specially formatted FC Frame containing
information used by the FCIP protocol (see section 7).
4. Protocol Summary
The FCIP protocol is summarized as follows:
1) The primary function of an FCIP Entity is forwarding FC Frames,
employing FC Frame Encapsulation described in [19].
2) Viewed from the IP Network perspective, FCIP Entities are peers
and communicate using TCP/IP. Each FCIP Entity contains one or
more TCP endpoints in the IP-based network.
3) Viewed from the FC Fabric perspective, pairs of FCIP Entities, in
combination with their associated FC Entities, forward FC Frames
between FC Fabric elements. The FC End Nodes are unaware of the
existence of the FCIP Link.
4) FC Primitive Signals, Primitive Sequences, and Class 1 FC Frames
are not transmitted across an FCIP Link because they cannot be
encoded using FC Frame Encapsulation [19].
5) The path (route) taken by an encapsulated FC Frame follows the
normal routing procedures of the IP Network.
6) An FCIP Entity MAY contain multiple FCIP Link Endpoints, but each
FCIP Link Endpoint (FCIP_LEP) communicates with exactly one other
FCIP_LEP.
7) When multiple FCIP_LEPs with multiple FCIP_DEs are in use,
selection of which FCIP_DE to use for encapsulating and
transmitting a given FC Frame is covered in FC-BB-2 [3]. FCIP
Entities do not actively participate in FC Frame routing.
8) The FCIP Control and Services module MAY use TCP/IP quality of
service features (see section 10.2).
9) It is necessary to statically or dynamically configure each FCIP
entity with the IP addresses and TCP port numbers corresponding to
FCIP Entities with which it is expected to initiate communication.
If dynamic discovery of participating FCIP Entities is supported,
the function SHALL be performed using the Service Location
Protocol (SLPv2) [17]. It is outside the scope of this
specification to describe any static configuration method for
participating FCIP Entity discovery. Refer to section 8.1.2.2 for
a detailed description of dynamic discovery of participating FCIP
Entities using SLPv2.
10) Before creating a TCP Connection to a peer FCIP Entity, the FCIP
Entity attempting to create the TCP connection SHALL statically or
dynamically determine the IP address, TCP port, expected FC Fabric
Entity World Wide Name, TCP Connection Parameters, and Quality of
Service Information.
11) FCIP Entities do not actively participate in the discovery of FC
source and destination identifiers. Discovery of FC addresses
(accessible via the FCIP Entity) is provided by techniques and
protocols within the FC architecture as described in FC-FS [5] and
FC-SW-2 [4].
12) To support IP Network security (see section 9), FCIP Entities
MUST:
1) implement cryptographically protected authentication and
cryptographic data integrity keyed to the authentication
process, and
2) implement data confidentiality security features.
13) On an individual TCP Connection, this specification relies on
TCP/IP to deliver a byte stream in the same order that it was
sent.
14) This specification assumes the presence of and requires the use of
TCP and FC data loss and corruption mechanisms. The error
detection and recovery features described in this specification
complement and support these existing mechanisms.
5. The FCIP Model
5.1. FCIP Protocol Model
The relationship between FCIP and other protocols is illustrated in
figure 1.
+------------------------+ FCIP Link +------------------------+
| FCIP |===========| FCIP |
+--------+------+--------+ +--------+------+--------+
| FC-2 | | TCP | | TCP | | FC-2 |
+--------+ +--------+ +--------+ +--------+
| FC-1 | | IP | | IP | | FC-1 |
+--------+ +--------+ +--------+ +--------+
| FC-0 | | LINK | | LINK | | FC-0 |
+--------+ +--------+ +--------+ +--------+
| | PHY | | PHY | |
| +--------+ +--------+ |
| | | |
| | IP Network | |
V +--------------------+ V
to Fibre to Fibre
Channel Channel
Fabric Fabric
Key: FC-0 - Fibre Channel Physical Media Layer
FC-1 - Fibre Channel Encode and Decode Layer
FC-2 - Fibre Channel Framing and Flow Control Layer
TCP - Transmission Control Protocol
IP - Internet Protocol
LINK - IP Link Layer
PHY - IP Physical Layer
Figure 1: FCIP Protocol Stack Model
Note that the objective of the FCIP Protocol is to create and
maintain one or more FCIP Links to transport data.
5.2. FCIP Link
The FCIP Link is the basic unit of service provided by the FCIP
Protocol to an FC Fabric. As shown in figure 2, an FCIP Link
connects two portions of an FC Fabric using an IP Network as a
transport to form a single FC Fabric.
/\/\/\/\/\/\ /\/\/\/\/\/\ /\/\/\/\/\/\
\ FC / \ IP / \ FC /
/ Fabric \=========/ Network \=========/ Fabric \
\/\/\/\/\/\/ \/\/\/\/\/\/ \/\/\/\/\/\/
| |
|<--------- FCIP Link -------->|
Figure: 2 FCIP Link Model
At the points where the ends of the FCIP Link meet portions of the FC
Fabric, an FCIP Entity (see section 5.4) combines with an FC Entity
as described in section 5.3 to serve as the interface between FC and
IP.
An FCIP Link SHALL contain at least one TCP Connection and MAY
contain more than one TCP Connection. The endpoints of a single TCP
Connection are FCIP Data Engines (see section 5.6). The endpoints of
a single FCIP Link are FCIP Link Endpoints (see section 5.5).
5.3. FC Entity
An implementation that tunnels an FC Fabric through an IP Network
MUST combine an FC Entity with an FCIP Entity (see section 5.4) to
form a complete interface between the FC Fabric and IP Network as
shown in figure 3. An FC Fabric Entity may contain multiple
instances of the FC/FCIP Entity pair shown on either the right-hand
or left-hand side of figure 3.
|<--------- FCIP Link -------->|
| |
+----------+ /\/\/\/\/\/\ +----------+
| FCIP | \ IP / | FCIP |
| Entity |=========/ Network \=========| Entity |
+----------+ \/\/\/\/\/\/ +----------+
| FC | | FC |
| Entity | | Entity |
+----------+ +----------+
| |
/\/\/\/\/\/\ /\/\/\/\/\/\
\ FC / \ FC /
/ Fabric \ / Fabric \
\/\/\/\/\/\/ \/\/\/\/\/\/
Figure 3: Model for Two Connected FC/FCIP Entity Pairs
In general, the combination of an FCIP Link and two FC/FCIP Entity
pairs is intended to provide a non-Fibre Channel backbone transport
between Fibre Channel components. For example, this combination can
be used to function as the hard-wire connection between two Fibre
Channel switches.
The interface between the FC and FCIP Entities is implementation
specific. The functional requirements placed on an FC Entity by this
specification are listed in appendix H. More information about FC
Entities can be found in the Fibre Channel standards and an example
of an FC Entity can be found in FC-BB-2 [3].
5.4. FCIP Entity
The model for an FCIP Entity is shown in figure 4.
.......................................................
: FCIP Entity :
: :
: +-----------+ :
: | FCIP | :
: |Control and|------------------------------------+ :
: | Services | | :
: | Module | | :
: +-----------+ | :
: | +--------------------+ | :
: | +-------+--------------------+|----+ | :
: | |+-----+--------------------+|----+| | :
: | ||+----| FCIP Link Endpoint |----+|| | :
: | ||| +--------------------+ ||| | :
:.............................................|||.....:
| ||| ||| |
| ||| ||| o<--+
| ||| unique TCP ||| | |
| ||| connections-->||| | |
| ||| ||| | |
+----------+ /\/\/\/\/\/\ |
| FC | \ IP / |
| Entity | / Network \ |
+----------+ \/\/\/\/\/\/ |
| |
/\/\/\/\/\/\ +------------------+
\ FC / +->TCP port for
/ Fabric \ incoming
\/\/\/\/\/\/ connections
Figure 4: FCIP Entity Model
The FCIP Entity receives TCP connect requests on behalf of the
FCIP_LEPs that it manages. In support of this, the FCIP Entity is
the sole owner of at least one TCP port/IP Address combination used
to form TCP Connections. The TCP port may be the FCIP well known
port at a given IP Address. An FC Fabric to IP Network interface
product SHALL provide each FC/FCIP Entity pair contained in the
product with a unique combination of FC Fabric Entity World Wide
Identifier and FC/FCIP Entity Identifier values (see section 7).
An FCIP Entity contains an FCIP Control and Services Module to
control FCIP link initialization, FCIP link dissolution, and to
provide the FC Entity with an interface to key IP Network features.
The interfaces to the IP Network features are implementation
specific, however, REQUIRED TCP/IP functional support is specified in
this document, including:
- TCP Connections - see section 8
- Security - see section 9
- Performance - see section 10
- Dynamic Discovery - see section 8.1.2.2
The FCIP Link Endpoints in an FCIP Entity provide the FC Frame
encapsulation and transmission features of FCIP.
5.5. FCIP Link Endpoint (FCIP_LEP)
As shown in figure 5, the FCIP Link Endpoint contains one FCIP Data
Engine for each TCP Connection in the FCIP Link.
................................................
: FCIP Link Endpoint :
: +------------------+ :
: +-------+------------------+|----+ :
: |+-----+------------------+|----+| :
: ||+----| FCIP Data Engine |----+|| :
: ||| +------------------+ ||| :
:..............................................:
||| |||
+----------+ /\/\/\/\/\/\
| FC | \ IP /
| Entity | / Network \
+----------+ \/\/\/\/\/\/
|
/\/\/\/\/\/\
\ FC /
/ Fabric \
\/\/\/\/\/\/
Figure 5: FCIP Link Endpoint Model
Each time a TCP Connection is formed with a new FC/FCIP Entity pair
(including all the actions described in section 8.1), the FCIP
Entity SHALL create a new FCIP Link Endpoint containing one FCIP Data
Engine.
An FCIP_LEP is a transparent data translation point between an FC
Entity and an IP Network. A pair of FCIP_LEPs communicating over one
or more TCP Connections create an FCIP Link to join two islands of an
FC Fabric, producing a single FC Fabric.
The IP Network over which the two FCIP_LEPs communicate is not aware
of the FC payloads that it is carrying. Likewise, the FC End Nodes
connected to the FC Fabric are unaware of the TCP/IP based transport
employed in the structure of the FC Fabric.
An FCIP_LEP uses normal TCP based flow control mechanisms for
managing its internal resources and matching them with the advertised
TCP Receiver Window Size (see sections 8.3.2, 8.5). An FCIP_LEP MAY
communicate with its local FC Entity counterpart to coordinate flow
control.
5.6. FCIP Data Engine (FCIP_DE)
The model for one of the multiple FCIP_DEs that MAY be present in an
FCIP_LEP is shown in figure 6.
+--------------------------------+
| |
F |-+ +------------------+ +-|
C |p| | Encapsulation | |p| N
-->|1|--->| Engine |--->|2|--> e
E |-+ +------------------+ +-| t
n | | I w
t |-+ +------------------+ +-| P o
i |p| | De-Encapsulation | |p| r
t <--|4|<---| Engine |<---|3|<-- k
y |-+ +------------------+ +-|
| |
+--------------------------------+
Figure 6: FCIP Data Engine Model
Data enters and leaves the FCIP_DE through four portals (p1 - p4).
The portals do not process or examine the data that passes through
them. They are only the named access points where the FCIP_DE
interfaces with the external world. The names of the portals are as
follows:
p1) FC Frame Receiver Portal - The interface through which an FC
Frame and time stamp enters an FCIP_DE from the FC Entity.
p2) Encapsulated Frame Transmitter Portal - The TCP interface through
which an FCIP Frame is transmitted to the IP Network by an
FCIP_DE.
p3) Encapsulated Frame Receiver Portal - The TCP interface through
which an FCIP Frame is received from the IP Network by an
FCIP_DE.
p4) FC Frame Transmitter Portal - The interface through which a
reconstituted FC Frame and time stamp exits an FCIP_DE to the FC
Entity.
The work of the FCIP_DE is done by the Encapsulation and De-
Encapsulation Engines. The Engines have two functions:
1) Encapsulating and de-encapsulating FC Frames using the
encapsulation format described in FC Frame Encapsulation [19] and
in section 5.6.1 of this document, and
2) Detecting some data transmission errors and performing minimal
error recovery as described in section 5.6.2.
Data flows through a pair of IP Network connected FCIP_DEs in the
following seven steps:
1) An FC Frame and time stamp arrives at the FC Frame Receiver Portal
and is passed to the Encapsulation Engine. The FC Frame is
assumed to have been processed by the FC Entity according to the
applicable FC rules and is not validated by the FCIP_DE. If the
FC Entity is in the Unsynchronized state with respect to a time
base as described in the FC Frame Encapsulation [19]
specification, the time stamp delivered with the FC Frame SHALL be
zero.
2) In the Encapsulation Engine, the encapsulation format described in
FC Frame Encapsulation [19] and in section 5.6.1 of this document
SHALL be applied to prepare the FC Frame and associated time stamp
for transmission over the IP Network.
3) The entire encapsulated FC Frame (a.k.a. the FCIP Frame) SHALL be
passed to the Encapsulated Frame Transmitter Portal where it SHALL
be inserted in the TCP byte stream.
4) Transmission of the FCIP Frame over the IP Network follows all the
TCP rules of operation. This includes, but is not limited to, the
in-order delivery of bytes in the stream, as specified by TCP [6].
5) The FCIP Frame arrives at the partner FCIP Entity where it enters
the FCIP_DE through the Encapsulated Frame Receiver Portal and is
passed to the De-Encapsulation Engine for processing.
6) The De-Encapsulation Engine SHALL validate the incoming TCP byte
stream as described in section 5.6.2.2 and SHALL de-encapsulate
the FC Frame and associated time stamp according to the
encapsulation format described in FC Frame Encapsulation [19] and
in section 5.6.1 of this document.
7) In the absence of errors, the de-encapsulated FC Frame and time
stamp SHALL be passed to the FC Frame Transmitter Portal for
delivery to the FC Entity. Error handling is discussed in section
5.6.2.2.
Every FC Frame that arrives at the FC Frame Receiver Portal SHALL be
transmitted on the IP Network as described in steps 1 through 4
above. In the absence of errors, data bytes arriving at the
Encapsulated Frame Receiver Portal SHALL be de-encapsulated and
forwarded to the FC Frame Transmitter Portal as described in steps 5
through 7.
5.6.1. FCIP Encapsulation of FC Frames
The FCIP encapsulation of FC Frames employs FC Frame Encapsulation
[19].
The features from FC Frame Encapsulation that are unique to
individual protocols SHALL be applied as follows for the FCIP
encapsulation of FC Frames.
The Protocol# field SHALL contain 1 in accordance with the IANA
Considerations annex of FC Frame Encapsulation [19].
The Protocol Specific field SHALL have the format shown in figure 7.
Note: the word numbers in figure 7 are relative to the complete FC
Frame Encapsulation header, not to the Protocol Specific field.
W|------------------------------Bit------------------------------|
o| |
r| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3|
d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
+---------------------------------------------------------------+
1| replication of encapsulation word 0 |
+---------------+---------------+---------------+---------------+
2| pFlags | Reserved | -pFlags | -Reserved |
+---------------+---------------+---------------+---------------+
Figure 7: FCIP Usage of FC Frame Encapsulation Protocol Specific
field
Word 1 of the Protocol Specific field SHALL contain an exact copy of
word 0 in FC Frame Encapsulation [19].
The pFlags (protocol specific flags) field provides information about
the protocol specific usage of the FC Encapsulation Header. Figure 8
shows the defined pFlags bits.
|----------------Bit--------------------|
| |
| 0 1 2 3 4 5 6 7 |
+----+-----------------------------+----+
| Ch | Reserved | SF |
+----+-----------------------------+----+
Figure 8: pFlags Field Bits
The SF (Special Frame) bit indicates whether the FCIP Frame is an
encapsulated FC Frame or an FSF (FCIP Special Frame, see section 7).
When the FCIP Frame contains an encapsulated FC Frame, the SF bit
SHALL be 0. When the FCIP Frame is an FSF, the SF bit SHALL be 1.
The FSF SHALL only be sent as the first bytes transmitted in each
direction on a newly formed TCP Connection and only one FSF SHALL be
transmitted in each direction at that time (see section 8.1). After
that all FCIP Frames SHALL have the SF bit set to 0.
The Ch (Changed) bit indicates whether an echoed FSF has been
intentionally altered (see section 8.1.3). The Ch bit SHALL be 0
unless the FSF bit is 1. When the initial TCP Connection FSF is
sent, the Ch bit SHALL be 0. If the recipient of a TCP connect
request echoes the FSF without any changes, then the Ch bit SHALL
continue to be 0. If the recipient of a TCP connect request alters
the FSF before echoing it, then the Ch bit SHALL be changed to 1.
The -pFlags field SHALL contain the ones complement of the contents
of the pFlags field.
Table 1 summarizes the usage of the pFlags SF and Ch bits.
+----+----+------------+--------------------------------------+
| | | Originated | |
| SF | Ch | or Echoed | Validity/Description |
+----+----+------------+--------------------------------------+
| 0 | 0 | n/a | Encapsulated FC Frame |
+----+----+------------+--------------------------------------+
| 0 | 1 | n/a | Always Illegal |
+----+----+------------+--------------------------------------+
| 1 | 0 | Originated | Originated FSF |
+----+----+------------+--------------------------------------+
| 1 | 1 | Originated | Always Illegal |
+----+----+------------+--------------------------------------+
| 1 | 0 | Echoed | Echoed FSF without changes |
+----+----+------------+--------------------------------------+
| 1 | 1 | Echoed | Echoed FSF with changes |
+----+----+------------+--------------------------------------+
| Note 1: Echoed FSFs may contain changes resulting from |
| transmission errors, necessitating the comparison between |
| sent and received FSF bytes by the FSF originator described |
| in section 8.1.2.3. |
| |
| Note 2: Column positions in this table do not reflect the |
| bit positions of the SF and Ch bits in the pFlags field. |
+-------------------------------------------------------------+
Table 1: pFlags SF and Ch bit usage summary
The Reserved pFlags bits SHALL be 0.
The Reserved field (bits 23-16 in word 2): SHALL contain 0.
The -Reserved field (bits 7-0 in word 2): SHALL contain 255 (or
0xFF).
The CRCV (CRC Valid) Flag SHALL be set to 0.
The CRC field SHALL be set to 0.
In FCIP, the SOF and EOF codes listed as Class 2, Class 3, and Class
4 in the FC Frame Encapsulation [19] are legal.
5.6.2. FCIP Data Engine Error Detection and Recovery
5.6.2.1. TCP Assistance With Error Detection and Recovery
TCP [6] requires in order delivery, generation of TCP checksums, and
checking of TCP checksums. Thus, the byte stream passed from TCP to
the FCIP_LEP will be in order and free of errors detectable by the
TCP checksum. The FCIP_LEP relies on TCP to perform these functions.
5.6.2.2. Errors in FCIP Headers and Discarding FCIP Frames
Bytes delivered through the Encapsulated Frame Receiver Portal that
are not correctly delimited as defined by the FC Frame Encapsulation
[19] are considered to be in error.
The failure of the Protocol# and Version fields in the FCIP Frame
header to contain the values defined for an FCIP Frame SHALL be
considered an error.
Further, some errors in the encapsulation will result in the FCIP_DE
losing synchronization with the FC Frames in the byte stream entering
through the Encapsulated Frame Receiver Portal.
The Frame Length field in the FC Frame Encapsulation header is used
to determine where in the data stream the next FC Encapsulated Header
is located. The following tests SHALL be performed to verify
synchronization with the byte stream entering the Encapsulated Frame
Receiver Portal, and synchronization SHALL be considered lost if any
of the tests fail:
1) Frame Length field validation -- 15 < Frame Length < 545;
2) Comparison of Frame Length field to its ones complement; and
3) A valid EOF is found in the word preceding the start of the next
FCIP header as indicated by the Frame Length field, to be tested
as follows:
1) Bits 24-31 and 16-23 contain identical legal EOF values (the
list of legal EOF values is in the FC Frame Encapsulation
[19]); and
2) Bits 8-15 and 0-7 contain the ones complement of the EOF value
found in bits 24-31.
Note: The range of valid Frame Length values is derived as follows.
The FCIP Frame header is seven words, one word each is required for
the encoded SOF and EOF values, the FC Frame header is six words, and
the FC CRC requires one word, yielding a base Frame Length of 16
(7+1+1+6+1) words, if no FC Payload is present. Since the FC Payload
is optional, any Frame Length value greater than 15 is valid. The
maximum FC Payload size is 528 words, meaning that any Frame Length
value up to and including 544 (528+16) is valid.
If synchronization is lost, the FC Frame SHALL NOT be forwarded on to
the FC Entity and further recovery SHALL be handled as defined by
section 5.6.2.3.
In addition to the tests above, the validity and positioning of the
following FCIP Frame information SHOULD be used to detect
encapsulation errors that may or may not affect synchronization:
a) Protocol# ones complement field (1 test);
b) Version ones complement field (1 test);
c) Replication of encapsulation word 0 in word 1 (1 test);
d) Reserved field and its ones complement (2 tests);
e) Flags field and its ones complement (2 tests);
f) CRC field is equal to zero (1 test);
g) SOF fields and ones complement fields (4 tests);
h) Format and values of FC header (1 test);
i) CRC of FC Frame (2 tests);
j) FC Frame Encapsulation header information in the next FCIP
Frame (1 test).
At least 3 of the 16 tests listed above SHALL be performed. Failure
of any of the above tests actually performed SHALL indicate an
encapsulation error and the FC Frame SHALL NOT be forwarded on to the
FC Entity. Further, such errors SHOULD be considered carefully,
since some may be synchronization errors.
Whenever an FCIP_DE discards bytes delivered through the Encapsulated
Frame Receiver Portal, it SHALL cause the FCIP Entity to notify the
FC Entity of the condition and provide a suitable description of the
reason bytes were discarded.
The burden for recovering from discarded data falls on the FC Entity
and other components of the FC Fabric, and is outside the scope of
this specification.
5.6.2.3. Synchronization Failures
If an FCIP_DE determines that it cannot find the next FCIP Frame
header in the byte stream entering through the Encapsulated Frame
Receiver Portal, the FCIP_DE SHALL do one of the following:
a) close the TCP Connection [6] [7] and notify the FC Entity with the
reason for the closure;
b) recover synchronization by searching the bytes delivered by the
Encapsulated Frame Receiver Portal for a valid FCIP Frame header
having the correct properties (see section 5.6.2.2), and
discarding bytes delivered by the Encapsulated Frame Receiver
Portal until a valid FCIP Frame header is found; or
c) attempt to recover synchronization as described in b) and if
synchronization cannot be recovered, close the TCP Connection as
described in a), including notification of the FC Entity with the
reason for the closure.
If the FCIP_DE attempts to recover synchronization, the
resynchronization algorithm used SHALL meet the following
requirements:
a) discard or identify with an EOFa (see appendix section F.1) those
FC Frames and fragments of FC Frames identified before
synchronization has again been completely verified. The number of
FC Frames not forwarded may vary based on the algorithm used;
b) return to forwarding FC Frames through the FC Frame Transmitter
Portal only after synchronization on the transmitted FCIP Frame
stream has been verified; and
c) close the TCP/IP connection if the algorithm ends without
verifying successful synchronization. The probability of failing
to synchronize successfully and the time necessary to determine
whether or not synchronization was successful may vary with the
algorithm used.
An example algorithm meeting these requirements can be found in
appendix D.
The burden for recovering from the discarding of FCIP Frames during
the optional resynchronization process described in this section
falls on the FC Entity and other components of the FC Fabric, and is
outside the scope of this specification.
6. Checking FC Frame Transit Times in the IP Network
FC-BB-2 [3] defines how the measurement of IP Network transit time is
performed, based on the requirements stated in the FC Frame
Encapsulation [19] specification. The choice to place this
implementation requirement on the FC Entity is based on a desire to
include the transit time through the FCIP Entities when computing the
IP Network transit time experienced by the FC Frames.
Each FC Frame that enters the FCIP_DE through the FC Frame Receiver
Portal SHALL be accompanied by a time stamp value that the FCIP_DE
SHALL place in the Time Stamp [integer] and Time Stamp [fraction]
fields of the encapsulation header of the FCIP Frame that contains
the FC Frame. If no synchronized time stamp value is available to
accompany the entering FC Frame, a value of zero SHALL be used.
Each FC Frame that exits the FCIP_DE through the FC Frame Transmitter
Portal SHALL be accompanied by the time stamp value taken from the
FCIP Frame that encapsulated the FC Frame.
The FC Entity SHALL use suitable internal clocks and either Fibre
Channel services or an SNTP Version 4 server [26] to establish and
maintain the required synchronized time value. The FC Entity SHALL
verify that the FC Entity it is communicating with on an FCIP Link is
using the same synchronized time source, either Fibre Channel
services or SNTP server.
Note that since the FC Fabric is expected to have a single
synchronized time value throughout, reliance on the Fibre Channel
services means that only one synchronized time value is needed for
all FCIP_DEs regardless of their connection characteristics.
7. The FCIP Special Frame (FSF)
7.1. FCIP Special Frame Format
Figure 9 shows the FSF format.
W|------------------------------Bit------------------------------|
o| |
r| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3|
d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
+---------------+---------------+---------------+---------------+
0| Protocol# | Version | -Protocol# | -Version |
| (0x01) | (0x01) | (0xFE) | (0xFE) |
+---------------+---------------+---------------+---------------+
1| Protocol# | Version | -Protocol# | -Version |
| (0x01) | (0x01) | (0xFE) | (0xFE) |
+---------------+---------------+---------------+---------------+
2| pFlags | Reserved | -pFlags | -Reserved |
| | (0x00) | | (0xFF) |
+-----------+---+---------------+-----------+---+---------------+
3| Flags | Frame Length | -Flags | -Frame Length |
| (0b000000)| (0b0000010011) | (0b111111)| (0b1111101100) |
+-----------+-------------------+-----------+-------------------+
4| Time Stamp [integer] |
+---------------------------------------------------------------+
5| Time Stamp [fraction] |
+---------------------------------------------------------------+
6| CRC (Reserved in FCIP) |
| (0x00-00-00-00) |
+-------------------------------+-------------------------------+
7| Reserved | -Reserved |
| (0x00-00) | (0xFF-FF) |
+-------------------------------+-------------------------------+
8| |
+----- Source FC Fabric Entity World Wide Name -----+
9| |
+---------------------------------------------------------------+
10| |
+----- Source FC/FCIP Entity Identifier -----+
11| |
+---------------------------------------------------------------+
12| |
+----- Connection Nonce -----+
13| |
+---------------+---------------+-------------------------------+
(Continued)
Figure 9: FSF Format (part 1 of 2)
W|------------------------------Bit------------------------------|
o| |
r| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3|
d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
| |
| (Concluded) |
+---------------------------------------------------------------+
14| Connection | Reserved | Connection Usage Code |
| Usage Flags | (0x00) | <defined in FC-BB-2> |
+---------------+---------------+-------------------------------+
15| |
+----- Destination FC Fabric Entity World Wide Name -----+
16| |
+---------------------------------------------------------------+
17| K_A_TOV |
+-------------------------------+-------------------------------+
18| Reserved | -Reserved |
| (0x00-00) | (0xFF-FF) |
+-------------------------------+-------------------------------+
Figure 9: FSF Format (part 2 of 2)
The FSF SHALL only be sent as the first bytes transmitted in each
direction on a newly formed TCP Connection, and only one FSF SHALL be
transmitted in each direction.
The contents of the FSF SHALL be as described for encapsulated FC
Frames, except for the fields described in this section.
All FSFs SHALL have the pFlags SF bit set to 1 (see section 5.6.1).
The Source FC Fabric Entity World Wide Name field SHALL contain the
Fibre Channel Name_Identifier [5] for the FC Fabric entity associated
with the FC/FCIP Entity pair that generates (as opposed to echoes)
the FSF. For example, if the FC Fabric entity is a FC Switch, the FC
Fabric Entity World Wide Name field SHALL contain the Switch_Name
[4]. The Source FC Fabric Entity World Wide Name SHALL be world wide
unique.
The Source FC/FCIP Entity Identifier field SHALL contain a unique
identifier for the FC/FCIP Entity pair that generates (as opposed to
echoes) the FSF. The value is assigned by the FC Fabric entity whose
world wide name appears in the Source FC Fabric Entity World Wide
Name field.
Note: The combination of the Source FC Entity World Wide Name and
Source FC/FCIP Entity Identifier fields uniquely identifies every
FC/FCIP Entity pair in the IP Network.
The Connection Nonce field shall contain a 64-bit random number
generated to uniquely identify a single TCP connect request. In
order to provide sufficient security for the connection nonce, the
Randomness Recommendations for Security [9] SHOULD be followed.
The Connection Usage Flags field identifies the types of SOF values
[19] to be carried on the connection as shown in figure 10.
|------------------------------Bit------------------------------|
| |
| 0 1 2 3 4 5 6 7 |
+-------+-------+-------+-------+-------------------------------+
| SOFf | SOF?2 | SOF?3 | SOF?4 | Reserved |
+-------+-------+-------+-------+-------------------------------+
Figure 10: Connection Usage Flags Field Format
If the SOFf bit is one, then FC Frames containing SOFf are intended
to be carried on the connection.
If the SOF?2 bit is one, then FC Frames containing SOFi2 and SOFn2
are intended to be carried on the connection.
If the SOF?3 bit is one, then FC Frames containing SOFi3 and SOFn3
are intended to be carried on the connection.
If the SOF?4 bit is one, then FC Frames containing SOFi4, SOFn4, and
SOFc4 are intended to be carried on the connection.
All or none of the SOFf, SOF?2, SOF?3, and SOF?4 bits MAY be set to
one. If all of the SOFf, SOF?2, SOF?3, and SOF?4 bits are zero, then
the types of FC Frames intended to be carried on the connection have
no specific relationship to the SOF code.
The FCIP Entity SHALL NOT enforce the SOF usage described by the
Connection Usage Flags field and SHALL only use the contents of the
field as described below.
The Connection Usage Code field contains Fibre Channel defined
information regarding the intended usage of the connection as
specified in FC-BB-2 [3].
The FCIP Entity SHALL use the contents of the Connection Usage Flags
and Connection Usage Code fields to locate appropriate QoS settings
in the "shared" database of TCP Connection information (see section
8.1.1) and apply those settings to a newly formed connection.
The Destination FC Fabric Entity World Wide Name field MAY contain
the Fibre Channel Name_Identifier [5] for the FC Fabric entity
associated with the FC/FCIP Entity pair that echoes (as opposed to
generates) the Special Frame.
The K_A_TOV field SHALL contain the FC Keep Alive Timeout value to be
applied to the new TCP Connection as specified in FC-BB-2 [3].
For each new incoming TCP connect request and subsequent FSF
received, the FCIP Entity SHALL send the contents of the Source FC
Fabric Entity World Wide Name, Source FC/FCIP Identifier, Connection
Usage Flags and Connection Usage Code fields to the FC Entity along
with the other connection information (e.g., FCIP_LEP and FCIP_DE
information).
7.2. Overview of FSF Usage in Connection Establishment
When a new TCP Connection is established, an FCIP Special Frame makes
one round trip from the FCIP Entity initiating the TCP connect
operation to the FCIP Entity receiving the TCP connect request and
back. This FSF usage serves three functions:
- Identification of the FCIP Link endpoints
- Conveyance of a few critical parameters shared by the FC/FCIP
Entity pairs involved in the FCIP Link
- Configuration discovery (used in place of SLP only when allowed by
site security policies)
The specific format and protocol requirements for this usage of the
FSF are found in sections 7.1 and 8.1.2.3. This section provides an
overview of the FSF usage without stating requirements.
Because FCIP is only a tunnel for a Fibre Channel Fabric and because
the Fabric has its own complex link setup algorithm that can be
employed for many FCIP link setup needs, it is desirable to minimize
the complexity of the FSF usage during TCP Connection setup. With
this in mind, this FSF usage is not a login or parameter negotiation
mechanism. A single FSF transits each newly established TCP
connection as the first bytes sent in each direction.
Note: This usage of the FSF cannot be eliminated entirely because a
newly created TCP Connection must be associated with the correct FCIP
Link before FC Fabric initialization of the connection can commence.
The first bytes sent from the TCP connect request initiator to the
receiver are an FSF identifying both the sender and who the sender
thinks is the receiver. If the contents of this FSF are correct and
acceptable to the receiver, the unchanged FSF is echoed back to the
sender. This send/echo process is the only set of actions that
allows the TCP Connection to be used to carry FC Fabric traffic. If
the send and unchanged echo process does not occur, the algorithm
followed at one or both ends of the TCP Connection results in the
closure of the TCP Connection (see section 8.1 for specific algorithm
requirements).
Note: Owing to the limited manner in which the FSF is used and the
requirement that the FSF be echoed without changes before a TCP
Connection is allowed to carry user data, no error checking beyond
that provided by TCP is deemed necessary.
As described above, the primary purpose of the FSF usage during TCP
Connection setup is identifying the FCIP Link to which the new TCP
Connection belongs. From these beginnings, it is only a small
stretch to envision using the FSF as a simplified configuration
discovery tool, and the mechanics of such a usage are described in
section 8.1.
However, use of the FSF for configuration discovery lacks the broad
range of capabilities provided by SLPv2 and most particularly lacks
the security capabilities of SLPv2. For these reasons, using the FSF
for configuration discovery is not appropriate for all environments.
Thus the choice to use the FSF for discovery purposes is a policy
choice to be included in the TCP Connection Establishment "shared"
database described in section 8.1.1.
When FSF-based configuration discovery is enabled, the normal TCP
Connection setup rules outlined above are modified as follows.
Normally, the algorithm executed by an FCIP Entity receiving an FSF
includes verifying that its own identification information in the
arriving FSF is correct and closing the TCP Connection if it is not.
This can be viewed as requiring the initiator of a TCP connect
request to know in advance the identity of the FCIP Entity that is
the target of that request (using SLP, for example), and through the
FSF effectively saying, "I think I'm talking to X." If the party at
the other end of the TCP connect request is really Y, then it simply
hangs up.
FSF-based discovery allows the "I think I'm talking to X" to be
replaced with "Please tell me who I am talking to?", which is
accomplished by replacing an explicit value in the Destination FC
Fabric Entity World Wide Name field with zero.
If the policy at the receiving FCIP Entity allows FSF-based
discovery, the zero is replaced with the correct Destination FC
Fabric Entity World Wide Name value in the echoed FSF. This is still
subject to the rules of sending with unchanged echo, and so closure
of TCP Connection occurs after the echoed FSF is received by the TCP
connect initiator.
Despite the TCP Connection closure, however, the TCP connect
initiator now knows the correct Destination FC Fabric Entity World
Wide Name identity of the FCIP Entity at a given IP Address and a
subsequent TCP Connection setup sequence probably will be successful.
The Ch bit in the pFlags field (see section 5.6.1) allows for
differentiation between changes in the FSF resulting from
transmission errors and changes resulting from intentional acts by
the FSF recipient.
8. TCP Connection Management
8.1. TCP Connection Establishment
8.1.1. Connection Establishment Model
The description of the connection establishment process is a model
for the interactions between an FC Entity and an FCIP Entity during
TCP Connection establishment. The model is written in terms of a
"shared" database that the FCIP Entity consults to determine the
properties of the TCP Connections to be formed combined with routine
calls to the FC Entity when connections are successfully established.
Whether the FC Entity contributes information to the "shared"
database is not critical to this model. However, the fact that the
FCIP Entity MAY consult the database at any time to determine its
actions relative to TCP Connection establishment is important.
It is important to remember that this description is only a model for
the interactions between an FC Entity and an FCIP Entity. Any
implementation that has the same effects on the FC Fabric and IP
Network as those described using the model meets the requirements of
this specification. For example, an implementation might replace the
"shared" database with a routine interface between the FC and FCIP
Entities.
8.1.2. Creating New TCP Connections
8.1.2.1. Non-Dynamic Creation of New TCP Connections
When an FCIP Entity discovers that a new TCP Connection needs to be
established, it SHALL determine the IP Address to which the TCP
Connection is to be made and establish all enabled IP security
features for that IP Address as described in section 9. Then the
FCIP Entity SHALL determine the following information about the new
connection in addition to the IP Address:
- The expected Destination FC Fabric Entity World Wide Name of the
FC/FCIP Entity pair to which the TCP Connection is being made
- TCP Connection Parameters (see section 8.3)
- Quality of Service Information (see section 10)
Based on this information, the FCIP Entity SHALL generate a TCP
connect request [6] to the FCIP Well-Known Port of 3225 (or other
configuration specific port number) at the specified IP Address.
If the TCP connect request is rejected, the FCIP Entity SHALL act to
limit unnecessary repetition of attempts to establish similar
connections. For example, the FCIP Entity might wait 60 seconds
before trying to re-establish the connection.
If the TCP connect request is accepted, the FCIP Entity SHALL follow
the steps described in section 8.1.2.3 to complete the establishment
of a new FCIP_DE.
It is RECOMMENDED that an FCIP Entity not initiate TCP connect
requests to another FCIP Entity if incoming TCP connect requests from
that FCIP Entity have already been accepted.
8.1.2.2. Dynamic Creation of New TCP Connections
If dynamic discovery of participating FCIP Entities is supported, the
function SHALL be performed using the Service Location Protocol
(SLPv2) [17] in the manner defined for FCIP usage [20].
Upon discovering that dynamic discovery is to be used, the FCIP
Entity SHALL enable IP security features for the SLP discovery
process as described in [20] and then:
1) Determine the one or more FCIP Discovery Domain(s) to be used in
the dynamic discovery process;
2) Establish an SLPv2 Service Agent to advertise the availability of
this FCIP Entity to peer FCIP Entities in the identified FCIP
Discovery Domain(s); and
3) Establish an SLPv2 User Agent to locate service advertisements for
peer FCIP Entities in the identified FCIP Discovery Domain(s).
For each peer FCIP Entity dynamically discovered through the SLPv2
User Agent, the FCIP Entity SHALL establish all enabled IP security
features for the discovered IP Address as described in section 9 and
then determine the following information about the new connection:
- The expected Destination FC Fabric Entity World Wide Name of the
FC/FCIP Entity pair to which the TCP Connection is being made
- TCP Connection Parameters (see section 8.3)
- Quality of Service Information (see section 10)
Based on this information, the FCIP Entity SHALL generate a TCP
connect request [6] to the FCIP Well-Known Port of 3225 (or other
configuration specific port number) at the IP Address specified by
the service advertisement. If the TCP connect request is rejected,
act to limit unnecessary repetition of attempts to establish similar
connections. If the TCP connect request is accepted, the FCIP Entity
SHALL follow the steps described in section 8.1.2.3 to complete the
establishment of a new FCIP_DE.
It is recommended that an FCIP Entity not initiate TCP connect
requests to another FCIP Entity if incoming TCP connect requests from
that FCIP Entity have already been accepted.
8.1.2.3. Connection Setup After a Successful TCP Connect Request
Whether Non-Dynamic TCP Connection creation (see section 8.1.2.1) or
Dynamic TCP Connection creation (see section 8.1.2.2) is used, the
steps described in this section SHALL be followed to take the TCP
Connection setup process to completion.
After the TCP connect request has been accepted, the FCIP Entity
SHALL send an FCIP Special Frame (FSF, see section 7) as the first
bytes transmitted on the newly formed connection, and retain a copy
of those bytes for later comparisons. All fields in the FSF SHALL be
filled in as described in section 7, particularly:
- The Source FC Fabric Entity World Wide Name field SHALL contain
the FC Fabric Entity World Wide Name for the FC/FCIP Entity pair
that is originating the TCP connect request;
- The Source FC/FCIP Entity Identifier field SHALL contain a unique
identifier that is assigned by the FC Fabric entity whose world
wide name appears in the Source FC Fabric Entity World Wide Name
field;
- The Connection Nonce field SHALL contain a 64-bit random number
that differs in value from any recently used Connection Nonce
value. In order to provide sufficient security for the connection
nonce, the Randomness Recommendations for Security [9] SHOULD be
followed; and
- The Destination FC Fabric Entity World Wide Name field SHALL
contain 0 or the expected FC Fabric Entity World Wide Name for the
FC/FCIP Entity pair whose destination is the TCP connect request.
After the FSF is sent on the newly formed connection, the FCIP Entity
SHALL wait for the FSF to be echoed as the first bytes received on
the newly formed connection.
The FCIP Entity MAY apply a timeout of not less than 90 seconds while
waiting for the echoed FSF bytes. If the timeout expires, the FCIP
Entity SHALL close the TCP Connection and notify the FC Entity with
the reason for the closure.
If the echoed FSF bytes do not exactly match the FSF bytes sent
(words 7 through 17 inclusive) or if the echoed Destination FC Fabric
Entity World Wide Name field contains zero, the FCIP Entity SHALL
close the TCP Connection and notify the FC Entity with the reason for
the closure.
The FCIP Entity SHALL only perform the following steps if the echoed
FSF bytes exactly match the FSF bytes sent (words 7 through 17
inclusive).
1) Instantiate the appropriate Quality of Service (see section 10)
conditions on the newly created TCP Connection,
2) If the IP Address and TCP Port to which the TCP Connection was
made is not associated with any other FCIP_LEP, create a new
FCIP_LEP for the new FCIP Link,
3) Create a new FCIP_DE within the newly created FCIP_LEP to service
the new TCP Connection, and
4) Inform the FC Entity of the new FCIP_LEP, FCIP_DE, Destination FC
Fabric Entity World Wide Name, Connection Usage Flags, and
Connection Usage Code.
8.1.3. Processing Incoming TCP Connect Requests
The FCIP Entity SHALL listen for new TCP Connection requests [6] on
the FCIP Well-Known Port (3225). An FCIP Entity MAY also accept and
establish TCP Connections to a TCP port number other than the FCIP
Well-Known Port, as configured by the network administrator in a
manner outside the scope of this specification.
The FCIP Entity SHALL determine the following information about the
requested connection:
- Whether the "shared" database (see section 8.1.1) allows the
requested connection
- Whether IP security setup has been performed for the IP security
features enabled on the connection (see section 9)
If the requested connection is not allowed, the FCIP Entity SHALL
reject the connect request using appropriate TCP means. If the
requested connection is allowed, the FC Entity SHALL ensure that
required IP security features are enabled and accept the TCP connect
request.
After the TCP connect request has been accepted, the FCIP Entity
SHALL wait for the FSF sent by the originator of the TCP connect
request (see section 8.1.2) as the first bytes received on the
accepted connection.
The FCIP Entity MAY apply a timeout of no less than 90 seconds while
waiting for the FSF bytes. If the timeout expires, the FCIP Entity
SHALL close the TCP Connection and notify the FC Entity with the
reason for the closure.
Note: One method for attacking the security of the FCIP Link
formation process (detailed in section 9.1) depends on keeping a TCP
connect request open without sending an FSF. Implementations should
bear this in mind in the handling of TCP connect requests where the
FSF is not sent in a timely manner.
Upon receipt of the FSF sent by the originator of the TCP connect
request, the FCIP Entity SHALL inspect the contents of the following
fields:
- Connection Nonce,
- Destination FC Fabric Entity World Wide Name,
- Connection Usage Flags, and
- Connection Usage Code.
If the Connection Nonce field contains a value identical to the most
recently received Connection Nonce from the same IP Address, the FCIP
Entity SHALL close the TCP Connection and notify the FC Entity with
the reason for the closure.
If an FCIP Entity receives a duplicate FSF during the FCIP Link
formation process, it SHALL close that TCP Connection and notify the
FC Entity with the reason for the closure.
If the Destination FC Fabric Entity World Wide Name contains 0, the
FCIP Entity SHALL take one of the following three actions:
1) Leave the Destination FC Fabric Entity World Wide Name field and
Ch bit both 0;
2) Change the Destination FC Fabric Entity World Wide Name field to
match FC Fabric Entity World Wide Name associated with the FCIP
Entity that received the TCP connect request and change the Ch bit
to 1; or
3) Close the TCP Connection without sending any response.
The choice between the above actions depends on the anticipated usage
of the FCIP Entity. The FCIP Entity may consult the "shared"
database when choosing between the above actions.
If:
a) The Destination FC Fabric Entity World Wide Name contains a non-
zero value that does not match the FC Fabric Entity World Wide
Name associated with the FCIP Entity that received the TCP connect
request, or
b) The contents of the Connection Usage Flags and Connection Usage
Code fields is not acceptable to the FCIP Entity that received the
TCP connect request, then the FCIP Entity SHALL take one of the
following two actions:
1) Change the contents of the unacceptable fields to correct/
acceptable values and set the Ch bit to 1; or
2) Close the TCP Connection without sending any response.
If the FCIP Entity makes any changes in the content of the FSF, it
SHALL also set the Ch bit to 1.
If any changes have been made in the received FSF during the
processing described above, the following steps SHALL be performed:
1) The changed FSF SHALL be echoed to the originator of the TCP
connect request as the only bytes transmitted on the accepted
connection;
2) The TCP Connection SHALL be closed (the FC Entity need not be
notified of the TCP Connection closure in this case because it is
not indicative of an error); and
3) All of the additional processing described in this section SHALL
be skipped.
The remaining steps in this section SHALL be performed only if the
FCIP Entity has not changed the contents of the above mentioned
fields to correct/acceptable values.
If the Source FC Fabric Entity World Wide Name and Source FC/FCIP
Entity Identifier field values in the FSF do not match the Source FC
Fabric Entity World Wide Name and Source FC/FCIP Entity Identifier
associated with any other FCIP_LEP, the FCIP Entity SHALL:
1) Echo the unchanged FSF to the originator of the TCP connect
request as the first bytes transmitted on the accepted connection;
2) Instantiate the appropriate Quality of Service (see section 10.2)
conditions on the newly created TCP Connection, considering the
Connection Usage Flags and Connection Usage Code fields, and
"shared" database information (see section 8.1.1) as appropriate,
3) Create a new FCIP_LEP for the new FCIP Link,
4) Create a new FCIP_DE within the newly created FCIP_LEP to service
the new TCP Connection, and
5) Inform the FC Entity of the new FCIP_LEP, FCIP_DE, Source FC
Fabric Entity World Wide Name, Source FC/FCIP Entity Identifier,
Connection Usage Flags, and Connection Usage Code.
If the Source FC Fabric Entity World Wide Name and Source FC/FCIP
Entity Identifier field values in the FCIP Special Frame match the
Source FC Fabric Entity World Wide Name and Source FC/FCIP Entity
Identifier associated with an existing FCIP_LEP, the FCIP Entity
SHALL:
1) Request that the FC Entity authenticate the source of the TCP
connect request (see FC-BB-2 [3]), providing the following
information to the FC Entity for authentication purposes:
a) Source FC Fabric Entity World Wide Name,
b) Source FC/FCIP Entity Identifier, and
c) Connection Nonce.
The FCIP Entity SHALL NOT use the new TCP Connection for any
purpose until the FC Entity authenticates the source of the TCP
connect request. If the FC Entity indicates that the TCP connect
request cannot be properly authenticated, the FCIP Entity SHALL
close the TCP Connection and skip all of the remaining steps in
this section.
The definition of the FC Entity SHALL include an authentication
mechanism for use in response to a TCP connect request source that
communicates with the partner FC/FCIP Entity pair on an existing
FCIP Link. This authentication mechanism should use a previously
authenticated TCP Connection in the existing FCIP Link to
authenticate the Connection Nonce sent in the new TCP Connection
setup process. The FCIP Entity SHALL treat failure of this
authentication as an authentication failure for the new TCP
Connection setup process.
2) Echo the unchanged FSF to the originator of the TCP connect
request as the first bytes transmitted on the accepted connection;
3) Instantiate the appropriate Quality of Service (see section 10.2)
conditions on the newly created TCP Connection, considering the
Connection Usage Flags and Connection Usage Code fields, and
"shared" database information (see section 8.1.1) as appropriate,
4) Create a new FCIP_DE within the existing FCIP_LEP to service the
new TCP Connection, and
5) Inform the FC Entity of the FCIP_LEP, Source FC Fabric Entity
World Wide Name, Source FC/FCIP Entity Identifier, Connection
Usage Flags, Connection Usage Code, and new FCIP_DE.
Note that the originator of TCP connect requests uses the IP Address
and TCP Port to identify which TCP Connections belong to which
FCIP_LEPs while the recipient of TCP connect requests uses the Source
FC Fabric Entity World Wide Name, and Source FC/FCIP Entity
Identifier fields from the FSF to identify which TCP Connection
belong to which FCIP_LEPs. For this reason, an FCIP Entity that both
originates and receives TCP connect requests is unable to match the
FCIP_LEPs associated with originated TCP connect requests to the
FCIP_LEPs associated with received TCP connect requests.
8.1.4. Simultaneous Connection Establishment
If two FCIP Entities perform simultaneous open operations, then two
TCP Connections are formed and the SF originates at one end on one
connection and at the other end on the other. Connection setup
proceeds as described above on both connections, and the steps
described above properly result in the formation of two FCIP Links
between the same FCIP Entities.
This is not an error. Fibre Channel is perfectly capable of handling
two approximately equal connections between FC Fabric elements.
The decision to setup pairs of FCIP Links in this manner is
considered to be a site policy decision that can be covered in the
"shared" database described in section 8.1.1.
8.2. Closing TCP Connections
The FCIP Entity SHALL provide a mechanism with acknowledgement by
which the FC Entity is able to cause the closing of an existing TCP
Connection at any time. This allows the FC Entity to close TCP
Connections that are producing too many errors, etc.
8.3. TCP Connection Parameters
In order to provide efficient management of FCIP_LEP resources as
well as FCIP Link resources, consideration of certain TCP Connection
parameters is recommended.
8.3.1. TCP Selective Acknowledgement Option
The Selective Acknowledgement option RFC 2883 [18] allows the
receiver to acknowledge multiple lost packets in a single ACK,
enabling faster recovery. An FCIP Entity MAY negotiate use of TCP
SACK and use it for faster recovery from lost packets and holes in
TCP sequence number space.
8.3.2. TCP Window Scale Option
The TCP Window Scale option [8] allows TCP window sizes larger than
16-bit limits to be advertised by the receiver. It is necessary to
allow data in long fat networks to fill the available pipe. This
also implies buffering on the TCP sender that matches the
(bandwidth*delay) product of the TCP Connection. An FCIP_LEP uses
locally available mechanisms to set a window size that matches the
available local buffer resources and the desired throughput.
8.3.3. Protection Against Sequence Number Wrap
It is RECOMMENDED that FCIP Entities implement protection against
wrapped sequence numbers PAWS [8]. It is quite possible that within
a single connection, TCP sequence numbers wrap within a timeout
window.
8.3.4. TCP_NODELAY Option
FCIP Entities should disable the Nagle Algorithm as described in RFC
1122 [7] section 4.2.3.4. By tradition, this can be accomplished by
setting the TCP_NODELAY option to one at the local TCP interface.
8.4. TCP Connection Considerations
In idle mode, a TCP Connection "keep alive" option of TCP is normally
used to keep a connection alive. However, this timeout is fairly
large and may prevent early detection of loss of connectivity. In
order to facilitate faster detection of loss of connectivity, FC
Entities SHOULD implement some form of Fibre Channel connection
failure detection (see FC-BB-2 [3]).
When an FCIP Entity discovers that TCP connectivity has been lost,
the FCIP Entity SHALL notify the FC Entity of the failure including
information about the reason for the failure.
8.5. Flow Control Mapping between TCP and FC
The FCIP Entity and FC Entity are connected to the IP Network and FC
Fabric, respectively, and they need to follow the flow control
mechanisms of both TCP and FC, which work independently of each
other.
This section provides guidelines as to how the FCIP Entity can map
TCP flow control to status notifications to the FC Entity.
There are two scenarios in which the flow control management becomes
crucial:
1) When there is line speed mismatch between the FC and IP
interfaces.
Even though it is RECOMMENDED that both of the FC and IP
interfaces to the FC Entity and FCIP Entity, respectively, be of
comparable speeds, it is possible to carry FC traffic over an IP
Network that has a different line speed and bit error rate.
2) When the FC Fabric or IP Network encounters congestion.
Even when both the FC Fabric or IP network are of comparable
speeds, during the course of operation, the FC Fabric or the IP
Network could encounter congestion due to transient conditions.
The FC Entity uses Fibre Channel mechanisms for flow control at the
FC Frame Receiver Portal based on information supplied by the FCIP
Entity regarding flow constraints at the Encapsulated Frame
Transmitter Portal. The FCIP Entity uses TCP mechanisms for flow
control at the Encapsulated Frame Receiver Portal based on
information supplied by the FC Entity regarding flow constraints at
the FC Frame Transmitter Portal.
Coordination of these flow control mechanisms, one of which is credit
based and the other of which is window based, depends on a
painstaking design that is outside the scope of this specification.
9. Security
FCIP utilizes the IPsec protocol suite to provide data
confidentiality and authentication services, and IKE as the key
management protocol. This section describes the requirements for
various components of these protocols as used by FCIP, based on FCIP
operating environments. Additional consideration for use of IPsec
and IKE with the FCIP protocol can be found in [21]. In the event
that requirements in [21] conflict with requirements stated in this
document, the requirements in this document SHALL prevail.
9.1. Threat Models
Using a general purpose, wide-area network, such as an IP Network, as
a functional replacement for physical cabling introduces some
security problems not normally encountered in Fibre Channel Fabrics.
FC interconnect cabling is typically protected physically from
outside access. Public IP Networks allow hostile parties to impact
the security of the transport infrastructure.
The general effect is that the security of an FC Fabric is only as
good as the security of the entire IP Network that carries the FCIP
Links used by that FC Fabric. The following broad classes of attacks
are possible:
1) Unauthorized Fibre Channel elements can gain access to resources
through normal Fibre Channel Fabric and processes. Although this
is a valid threat, securing the Fibre Channel Fabrics is outside
the scope of this document. Securing the IP Network is the issue
considered in this specification.
2) Unauthorized agents can monitor and manipulate Fibre Channel
traffic flowing over physical media used by the IP Network and
accessible to the agent.
3) TCP Connections may be hijacked and used to instantiate an invalid
FCIP Link between two peer FCIP Entities.
4) Valid and invalid FCIP Frames may be injected on the TCP
Connections.
5) The payload of an FCIP Frame may be altered or transformed. The
TCP checksum, FCIP ones complement checks, and FC frame CRC do not
protect against this because all of them can be modified or
regenerated by a malicious and determined adversary.
6) Unauthorized agents can masquerade as valid FCIP Entities and
disturb proper operation of the Fibre Channel Fabric.
7) Denial of Service attacks can be mounted by injecting TCP
Connection requests and other resource exhaustion operations.
8) An adversary may launch a variety of attacks against the discovery
process [17].
9) An attacker may exploit the FSF authentication mechanism of the
FCIP Link formation process (see section 8.1.3). The attacker
could observe the FSF contents sent on an initial connection of an
FCIP Link and use the observed nonce, Source FC/FCIP Entity
Identifier, and other FSF contents to form an FCIP Link using the
attacker's own previously established connection, while
resetting/blocking the observed connection. Although the use of
timeout for reception of FSF reduces the risk of this attack, such
an attack is possible. See section 9.3.1 to protect against this
specific attack.
The existing IPsec Security Architecture and protocol suite [10]
offers protection from these threats. An FCIP Entity MUST implement
portions of the IPsec protocol suite as described in this section.
9.2. FC Fabric and IP Network Deployment Models
In the context of enabling a secure FCIP tunnel between FC SANs, the
following characteristics of the IP Network deployment are useful to
note.
1) The FCIP Entities share a peer-to-peer relationship. Therefore,
the administration of security policies applies to all FCIP
Entities in an equal manner. This differs from a true Client-
Server relationship, where there is an inherent difference in how
security policies are administered.
2) Policy administration as well as security deployment and
configuration are constrained to the set of FCIP Entities, thereby
posing less of a requirement on a scalable mechanism. For
example, the validation of credentials can be relaxed to the point
where deploying a set of pre-shared keys is a viable technique.
3) TCP Connections and the IP Network are terminated at the FCIP
Entity. The granularity of security implementation is at the
level of the FCIP tunnel endpoint (or FCIP Entity), unlike other
applications where there is a user-level termination of TCP
Connections. User-level objects are not controllable by or
visible to FCIP Entities. All user-level security related to FCIP
is the responsibility of the Fibre Channel standards and is
outside the scope of this specification.
4) When an FCIP Entity is deployed, its IP addresses will typically
be statically assigned. However, support for dynamic IP address
assignment, as described in [33], while typically not required,
cannot be ruled out.
9.3. FCIP Security Components
FCIP Security compliant implementations MUST implement ESP and the
IPsec protocol suite based cryptographic authentication and data
integrity [10], as well as confidentiality using algorithms and
transforms as described in this section. Also, FCIP implementations
MUST meet the secure key management requirements of IPsec protocol
suite.
9.3.1. IPsec ESP Authentication and Confidentiality
FCIP Entities MUST implement IPsec ESP [12] in Tunnel Mode for
providing Data Integrity and Confidentiality. FCIP Entities MAY
implement IPsec ESP in Transport Mode, if deployment considerations
require use of Transport Mode. When ESP is utilized, per-packet data
origin authentication, integrity, and replay protection MUST be used.
If Confidentiality is not enabled but Data Integrity is enabled, ESP
with NULL Encryption [15] MUST be used.
IPsec ESP for message authentication computes a cryptographic hash
over the payload that is protected. While IPsec ESP mandates
compliant implementations to support certain algorithms for deriving
this hash, FCIP implementations:
- MUST implement HMAC with SHA-1 [11]
- SHOULD implement AES in CBC MAC mode with XCBC extensions [23]
- DES in CBC mode SHOULD NOT be used due to inherent weaknesses
For ESP Confidentiality, FCIP Entities:
- MUST implement 3DES in CBC mode [16]
- SHOULD implement AES in CTR mode [22]
- MUST implement NULL Encryption [15]
9.3.2. Key Management
FCIP Entities MUST support IKE [14] for peer authentication,
negotiation of Security Associations (SA), and Key Management using
the IPsec DOI [13]. Manual keying SHALL NOT be used for establishing
an SA since it does not provide the necessary elements for rekeying
(see section 9.3.3). Conformant FCIP implementations MUST support
peer authentication using pre-shared keys and MAY support peer
authentication using digital certificates. Peer authentication using
public key encryption methods outlined in IKE [14] sections 5.2 and
5.3 SHOULD NOT be used.
IKE Phase 1 establishes a secure, MAC-authenticated channel for
communications for use by IKE Phase 2. FCIP implementations MUST
support IKE Main Mode and SHOULD support Aggressive Mode.
IKE Phase 1 exchanges MUST explicitly carry the Identification
Payload fields (IDii and IDir). Conformant FCIP implementations MUST
use ID_IPV4_ADDR, ID_IPV6_ADDR (if the protocol stack supports IPv6),
or ID_FQDN Identification Type values. The ID_USER_FQDN, IP Subnet,
IP Address Range, ID_DER_ASN1_DN, and ID_DER_ASN1_GN Identification
Type values SHOULD NOT be used. The ID_KEY_ID Identification Type
values MUST NOT be used. As described in [13], the port and protocol
fields in the Identification Payload MUST be set to zero or UDP port
500.
FCIP Entities negotiate parameters for SA during IKE Phase 2 only
using "Quick Mode". For FCIP Entities engaged in IKE "Quick Mode",
there is no requirement for PFS (Perfect Forward Secrecy). FCIP
implementations MUST use either ID_IPV4_ADDR or ID_IPV6_ADDR
Identification Type values (based on the version of IP supported).
Other Identification Type values MUST NOT be used.
Since the number of Phase 2 SAs may be limited, Phase 2 delete
messages may be sent for idle SAs. The receipt of a Phase 2 delete
message SHOULD NOT be interpreted as a reason for tearing down an
FCIP Link or any of its TCP connections. When there is new activity
on that idle link, a new Phase 2 SA MUST be re-established.
For a given pair of FCIP Entities, the same IKE Phase 1 negotiation
can be used for all Phase 2 negotiations; i.e., all TCP Connections
that are bundled into the single FCIP Link can share the same Phase 1
results.
Repeated rekeying using "Quick Mode" on the same shared secret will
reduce the cryptographic properties of that secret over time. To
overcome this, Phase 1 SHOULD be invoked periodically to create a new
set of IKE shared secrets and related security parameters.
IKE Phase 1 establishment requires the following key distribution and
FCIP Entities:
- MUST support pre-shared IKE keys.
- MAY support certificate-based peer authentication using digital
signatures.
- SHOULD NOT use peer authentication using the public key encryption
methods outlined in sections 5.2 and 5.3 of [14].
When pre-shared keys are used, IKE Main Mode is usable only when both
peers of an FCIP Link use statically assigned IP addresses. When
support for dynamically assigned IP Addresses is attempted in
conjunction with Main Mode, use of group pre-shared keys would be
forced, and the use of group pre-shared keys in combination with Main
Mode is not recommended as it exposes the deployed environment to
man-in-the-middle attacks. Therefore, if either peer of an FCIP Link
uses dynamically assigned addresses, Aggressive Mode SHOULD be used
and Main Mode SHOULD NOT be used.
When Digital Signatures are used, either IKE Main Mode or IKE
Aggressive Mode may be used. In all cases, access to locally stored
secret information (pre-shared key, or private key for digital
signing) MUST be suitably restricted, since compromise of secret
information nullifies the security properties of IKE/IPsec protocols.
Such mechanisms are outside the scope of this document. Support for
IKE Oakley Groups [27] is not required.
For the purpose of establishing a secure FCIP Link, the two
participating FCIP Entities consult a Security Policy Database (SPD).
The SPD is described in IPsec [10] Section 4.4.1. FCIP Entities may
have more than one interface and IP Address, and it is possible for
an FCIP Link to contain multiple TCP connections whose FCIP endpoint
IP Addresses are different. In this case, an IKE Phase 1 SA is
established for each FCIP endpoint IP Address pair. Within IKE Phase
1, FCIP implementations must support the ID_IPV4_ADDR, ID_IPV6_ADDR
(if the protocol stack supports IPv6), and ID_FQDN Identity Payloads.
If FCIP Endpoint addresses are dynamically assigned, it may be
beneficial to use ID_FQDN, and for this reason, IP_FQDN Identity
Payload MUST be supported. Other identity payloads (ID_USER_FQDN,
ID_DER_ASN1_GN, ID_KEY_ID) SHOULD NOT be used.
At the end of successful IKE negotiations both FCIP Entities store
the SA parameters in their SA database (SAD). The SAD is described
in IPsec [10] Section 4.4.3. The SAD contains the set of active SA
entries, each entry containing Sequence Counter Overflow, Sequence
Number Counter, Anti-replay Window, and the Lifetime of the SA. FCIP
Entities SHALL employ a default SA Lifetime of one hour and a default
Anti-replay window of 32 sequence numbers.
When a TCP Connection is established between two FCIP_DEs, two
unidirectional SAs are created for that connection and each SA is
identified in the form of a Security Parameter Index (SPI). One SA
is associated with the incoming traffic flow and the other SA is
associated with the outgoing traffic flow. The FCIP_DEs at each end
of the TCP connection MUST maintain the SPIs for both its incoming
and outgoing FCIP Encapsulated Frames.
FCIP Entities MAY provide administrative management of
Confidentiality usage. These management interfaces SHOULD be
provided in a secure manner, so as to prevent an attacker from
subverting the security process by attacking the management
interface.
9.3.3. ESP Replay Protection and Rekeying Issues
FCIP Entities MUST implement Replay Protection against ESP Sequence
Number wrap, as described in [14]. In addition, based on the cipher
algorithm and the number of bits in the cipher block size, the
validity of the key may become compromised. In both cases, the SA
needs to be re-established.
FCIP Entities MUST use the results of IKE Phase 1 negotiation for
initiating an IKE Phase 2 "Quick Mode" exchange and establish new
SAs.
To enable smooth transition of SAs, it is RECOMMENDED that both FCIP
Entities refresh the SPI when the sequence number counter reaches
2^31 (i.e., half the sequence number space). It also is RECOMMENDED
that the receiver operate with multiple SPIs for the same TCP
Connection for a period of 2^31 sequence number packets before aging
out an SPI.
When a new SPI is created for the outgoing direction, the sending
side SHALL begin using it for all new FCIP Encapsulated Frames.
Frames that are either in-flight, or re-sent due to TCP
retransmissions, etc. MAY use either the new SPI or the one being
replaced.
9.4. Secure FCIP Link Operation
9.4.1. FCIP Link Initialization Steps
FCIP implementations may allow enabling and disabling security
mechanisms at the granularity of an FCIP Link. If enabled, the
following FCIP Link Initialization steps MUST be followed.
When an FCIP Link is initialized, before any FCIP TCP Connections are
established, the local SPD is consulted to determine if IKE Phase 1
has been completed with the FCIP Entity in the peer FCIP Entity, as
identified by the WWN.
If Phase 1 is already completed, IKE Phase 2 proceeds. Otherwise,
IKE Phase 1 MUST be completed before IKE Phase 2 can start. Both IKE
Phase 1 and Phase 2 transactions use UDP Port 500. If IKE Phase 1
fails, the FCIP Link initialization terminates and notifies the FC
entity with the reason for the termination. Otherwise, the FCIP Link
initialization moves to TCP Connection Initialization.
As described in section 8.1, FCIP Entities exchange an FSF for
forming an FCIP Link. The use of ESP Confidentiality is an effective
countermeasure against any perceived security risks of FSF.
9.4.2. TCP Connection Security Associations (SAs)
Each TCP connection MUST be protected by an IKE Phase 2 SA. Traffic
from one or more than one TCP connection may flow within each IPsec
Phase 2 SA. While it is possible for an IKE Phase 2 SA to protect
multiple TCP connections, all packets of a TCP connection are
protected using only one IKE Phase 2 SA.
If different Quality of Service settings are applied to TCP
connections, it is advisable to use a different IPsec SA for these
connections. Attempting to apply a different quality of service to
connections handled by the same IPsec SA can result in reordering,
and falling outside the replay window. For additional details, see
[21].
FCIP implementations need not verify that the IP addresses and port
numbers in the packet match any locally stored per-connection values,
leaving this check to be performed by the IPsec layer.
An implementation is free to perform several IKE Phase 2 negotiations
and cache them in its local SPIs, although entries in such a cache
can be flushed per current SA Lifetime settings.
9.4.3. Handling Data Integrity and Confidentiality Violations
Upon datagram reception, when the ESP packet fails an integrity
check, the receiver MUST drop the datagram, which will trigger TCP
retransmission. If many such datagrams are dropped, a receiving FCIP
Entity MAY close the TCP Connection and notify the FC Entity with the
reason for the closure.
An implementation SHOULD follow guidelines for auditing all auditable
ESP events per IPsec [10] Section 7.
Integrity checks MUST be performed if Confidentiality is enabled.
10. Performance
10.1. Performance Considerations
Traditionally, the links between FC Fabric components have been
characterized by low latency and high throughput. The purpose of
FCIP is to provide functionality equivalent to these links using an
IP Network, where low latency and high throughput are not as certain.
It follows that FCIP Entities and their counterpart FC Entities
probably will be interested in optimal use of the IP Network.
Many options exist for ensuring high throughput and low latency
appropriate for the distances involved in an IP Network. For
example, a private IP Network might be constructed for the sole use
of FCIP Entities. The options that are within the scope of this
specification are discussed here.
One option for increasing the probability that FCIP data streams will
experience low latency and high throughput is the IP QoS techniques
discussed in section 10.2. This option can have value when applied
to a single TCP Connection. Depending on the sophistication of the
FC Entity, further value may be obtained by having multiple TCP
Connections with differing QoS characteristics.
There are many reasons why an FC Entity might request the creation of
multiple TCP Connections within an FCIP_LEP. These reasons include a
desire to provide differentiated services for different TCP data
connections between FCIP_LEPs, or a preference to separately queue
different streams of traffic not having a common in-order delivery
requirement.
At the time a new TCP Connection is created, the FC Entity SHALL
specify to the FCIP Entity the QoS characteristics (including but not
limited to IP per-hop-behavior) to be used for the lifetime of that
connection. This MAY be achieved by having:
a) only one set of QoS characteristics for all TCP Connections;
b) a default set of QoS characteristics that the FCIP Entity applies
in the absence of differing instructions from the FC Entity; or
c) a sophisticated mechanism for exchanging QoS requirements
information between the FC Entity and FCIP Entity each time a new
TCP Connection is created.
Once established, the QoS characteristics of a TCP Connection SHALL
NOT be changed, since this specification provides no mechanism for
the FC Entity to control such changes. The mechanism for providing
different QoS characteristics in FCIP is the establishment of a
different TCP Connections and associated FCIP_DEs.
When FCIP is used with a network with a large (bandwidth*delay)
product, it is RECOMMENDED that FCIP_LEPs use the TCP mechanisms
(window scaling and wrapped sequence protection) for Long Fat
Networks (LFNs) as defined in RFC 1323 [24].
10.2. IP Quality of Service (QoS) Support
Many methods of providing QoS have been devised or proposed. These
include (but are not limited to) the following:
- Multi-Protocol Label Switching (MPLS) -- RFC 3031 [32]
- Differentiated Services Architecture (diffserv) -- RFC 2474 [28],
RFC 2475 [29], RFC 2597 [30], and RFC 2598 [31] -- and other forms
of per-hop-behavior (PHB)
- Integrated Services, RFC 1633 [25]
- IEEE 802.1p
The purpose of this specification is not to specify any particular
form of IP QoS, but rather to specify only those issues that must be
addressed in order to maximize interoperability between FCIP
equipment that has been manufactured by different vendors.
It is RECOMMENDED that some form of preferential QoS be used for FCIP
traffic to minimize latency and packet drops. No particular form of
QoS is recommended.
If a PHB IP QoS is implemented, it is RECOMMENDED that it
interoperate with diffserv (see RFC 2474 [28], RFC 2475 [29], RFC
2597 [30], and RFC 2598 [31]).
If no form of preferential QoS is implemented, the DSCP field SHOULD
be set to '000000' to avoid negative impacts on other network
components and services that may be caused by uncontrolled usage of
non-zero values of the DSCP field.
11. References
11.1. Normative References
The references in this section were current as of the time this
specification was approved. This specification is intended to
operate with newer versions of the referenced documents and looking
for newer reference documents is recommended.
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Fibre Channel Backbone (FC-BB), ANSI INCITS.342:2001, December
12, 2001.
[3] Fibre Channel Backbone -2 (FC-BB-2), ANSI INCITS.372:2003, July
25, 2003.
[4] Fibre Channel Switch Fabric -2 (FC-SW-2), ANSI INCITS.355:2001,
December 12, 2001.
[5] Fibre Channel Framing and Signaling (FC-FS), ANSI
INCITS.373:2003, October 27, 2003.
[6] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981.
[7] Braden, R., "Requirements for Internet Hosts -- Communication
Layers", STD 3, RFC 1122, October 1989.
[8] Jacobson, V., Braden, R. and D. Borman, "TCP Extensions for High
Performance", RFC 1323, May 1992.
[9] Eastlake, D., Crocker, S. and J. Schiller, "Randomness
Recommendations for Security", RFC 1750, December 1994.
[10] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[11] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed- Hashing
for Message Authentication", RFC 2104, February 1997.
[12] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload
(ESP)", RFC 2406, November 1998.
[13] Piper, D., "The Internet IP Security Domain of Interpretation of
ISAKMP", RFC 2407, November 1998.
[14] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)",
RFC 2409, November 1998.
[15] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and Its
Use With IPsec", RFC 2410, November 1998.
[16] Pereira, R. and R. Adams, "The ESP CBC-Mode Cipher Algorithms",
RFC 2451, November 1998.
[17] Guttman, E., Perkins, C., Veizades, J. and M. Day, "Service
Location Protocol, version 2", RFC 2608, July 1999.
[18] Floyd, S., Mahdavi, J., Mathis, M. and M. Podolsky, "SACK
Extension", RFC 2883, July 2000.
[19] Weber, R., Rajagopal, M., Travostino, F., O'Donnell, M., Monia,
C. and M. Merhar, "Fibre Channel (FC) Frame Encapsulation", RFC
3643, December 2003.
[20] Peterson, D., "Finding Fibre Channel over TCP/IP (FCIP) Entities
Using Service Location Protocol version 2 (SLPv2)", RFC 3822,
July 2004.
[21] Aboba, B., Tseng, J., Walker, J., Rangan, V. and F. Travostino,
"Securing Block Storage Protocols over IP", RFC 3723, April
2004.
[22] Frankel, S., Glenn, R. and S. Kelly, "The AES-CBC Cipher
Algorithm and Its Use with IPsec", RFC 3602, September 2003.
[23] Frankel, S. and H. Herbert, "The AES-XCBC-MAC-96 Algorithm and
Its Use With IPsec", RFC 3566, September 2003.
11.2. Informative References
[24] Jacobson, V., Braden, R. and D. Borman, "TCP Extensions for High
Performance", RFC 1323, May 1992.
[25] Braden, R., Clark, D. and S. Shenker, "Integrated Services in
the Internet Architecture: an Overview", RFC 1633, June 1994.
[26] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for
IPv4, IPv6 and OSI", RFC 2030, October 1996.
[27] Orman, H., "The OAKLEY Key Determination Protocol", RFC 2412,
November 1998.
[28] Nichols, K., Blake, S., Baker, F. and D. Black, "Definition of
the Differentiated Services Field (DS Field) in the IPv4 and
Ipv6 Headers", RFC 2474, December 1998.
[29] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z. and W.
Weiss, "An Architecture for Differentiated Services", RFC 2475,
December 1998.
[30] Heinanen, J., Baker, F., Weiss, W. and J. Wroclawski, "An
Assured Forwarding PHB", RFC 2597, June 1999.
[31] Jacobson, V., Nichols, K. and K. Poduri, "An Expedited
Forwarding PHB Group", RFC 2598, June 1999.
[32] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol Label
Switching Architecture", RFC 3031, January, 2001.
[33] Patel, B., Aboba, B., Kelly, S. and V. Gupta, "Dynamic Host
Configuration Protocol (DHCPv4) Configuration of IPsec Tunnel
Mode", RFC 3456, January 2003.
[34] Kembel, R., "The Fibre Channel Consultant: A Comprehensive
Introduction", Northwest Learning Associates, 1998.
12. Acknowledgments
The developers of this specification thank Mr. Jim Nelson for his
assistance with FC-FS related issues.
The developers of this specification express their appreciation to
Mr. Mallikarjun Chadalapaka and Mr. David Black for their detailed
and helpful reviews.
Appendix A - Fibre Channel Bit and Byte Numbering Guidance
Both Fibre Channel and IETF standards use the same byte transmission
order. However, the bit and byte numbering is different.
Fibre Channel bit and byte numbering can be observed if the data
structure heading, shown in figure 11, is cut and pasted at the top
of figure 7, figure 9, and figure 17.
W|------------------------------Bit------------------------------|
o| |
r|3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 |
d|1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0|
Figure 11: Fibre Channel Data Structure Bit and Byte Numbering
Fibre Channel bit numbering for the pFlags field can be observed if
the data structure heading, shown in figure 12, is cut and pasted at
the top of figure 8.
|----------------Bit--------------------|
| |
| 31 30 29 28 27 26 25 24 |
Figure 12: Fibre Channel pFlags Bit Numbering
Fibre Channel bit numbering for the Connection Usage Flags field can
be observed if the data structure heading, shown in figure 13, is cut
and pasted at the top of figure 10.
|------------------------------Bit------------------------------|
| |
| 31 30 29 28 27 26 25 24 |
Figure 13: Fibre Channel Connection Usage Flags Bit Numbering
Appendix B - IANA Considerations
IANA has made the following port assignments to FCIP:
- fcip-port 3225/tcp FCIP
- fcip-port 3225/udp FCIP
IANA has changed the authority for these port allocations to
reference this RFC.
Use of UDP with FCIP is prohibited even though IANA has allocated a
port.
The FC Frame encapsulation used by this specification employs
Protocol# value 1, as described in the IANA Considerations appendix
of the FC Frame Encapsulation [19] specification.
Appendix C - FCIP Usage of Addresses and Identifiers
In support of network address translators, FCIP does not use IP
Addresses to identify FCIP Entities or FCIP_LEPs. The only use of IP
Addresses for identification occurs when initiating new TCP connect
requests (see section 8.1.2.3) where the IP Address destination of
the TCP connect request is used to answer the question: "Have
previous TCP connect requests been made to the same destination FCIP
Entity?" The correctness of this assumption is further checked by
sending the Destination FC Fabric Entity World Wide Name in the FCIP
Special Frame (FSF) and having the value checked by the FCIP Entity
that receives the TCP connect request and FSF (see section 8.1.3).
For the purposes of processing incoming TCP connect requests, the
source FCIP Entity is identified by the Source FC Fabric Entity World
Wide Name and Source FC/FCIP Entity Identifier fields in the FSF sent
from the TCP connect requestor to the TCP connect recipient as the
first bytes following the TCP connect request (see section 8.1.2.3
and section 8.1.3).
FC-BB-2 [3] provides the definitions for each of the following FSF
fields:
- Source FC Fabric Entity World Wide Name,
- Source FC/FCIP Entity Identifier, and
- Destination FC Fabric Entity World Wide Name.
As described in section 8.1.3, FCIP Entities segregate their
FCIP_LEPs between:
- Connections resulting from TCP connect requests initiated by the
FCIP Entity, and
- Connections resulting from TCP connect requests received by the
FCIP Entity.
Within each of these two groups, the following information is used to
further identify each FCIP_LEP:
- Source FC Fabric Entity World Wide Name,
- Source FC/FCIP Entity Identifier, and
- Destination FC Fabric Entity World Wide Name.
Appendix D - Example of Synchronization Recovery Algorithm
The contents of this annex are informative.
Synchronization may be recovered as specified in section 5.6.2.3. An
example of an algorithm for searching the bytes delivered to the
Encapsulated Frame Receiver Portal for a valid FCIP Frame header is
provided in this annex.
This resynchronization uses the principle that a valid FCIP data
stream must contain at least one valid header every 2176 bytes (the
maximum length of an encapsulated FC Frame). Although other data
patterns containing apparently valid headers may be contained in the
stream, the FC CRC or FCIP Frame validity of the data patterns
contained in the data stream will always be either interrupted by or
resynchronized with the valid FCIP Frame headers.
Consider the case shown in figure 14. A series of short FCIP Frames,
perhaps from a trace, are embedded in larger FCIP Frames, say as a
result of a trace file being transferred from one disk to another.
The headers for the short FCIP Frames are denoted SFH and the long
FCIP Frame headers are marked as LFH.
+-+--+-+----+-+----+-+----+-+-+-+---+-+---
|L| |S| |S| |S| |S| |L| |S|
|F| |F| |F| |F| |F| |F| |F|...
|H| |H| |H| |H| |H| |H| |H|
+-+--+-+----+-+----+-+----+-+-+-+---+-+---
| |
|<---------2176 bytes-------->|
Figure 14: Example of resynchronization data stream
A resynchronization attempt that starts just to the right of an LFH
will find several SFH FCIP Frames before discovering that they do not
represent the transmitted stream of FCIP Frames. Within 2176 bytes
plus or minus, however, the resynchronization attempt will encounter
an SFH whose length does not match up with the next SFH because the
LFH will fall in the middle of the short FCIP Frame pushing the next
header farther out in the byte stream.
Note that the resynchronization algorithm cannot forward any
prospective FC Frames to the FC Frame Transmitter Portal because,
until synchronization is completely established, there is no
certainty that anything that looked like an FCIP Frame really was
one. For example, an SFH might fortuitously contain a length that
points exactly to the beginning of an LFH. The LFH would identify
the correct beginning of a transmitted FCIP Frame, but that in no way
guarantees that the SFH was also a correct FCIP Frame header.
There exist some data streams that cannot be resynchronized by this
algorithm. If such a data stream is encountered, the algorithm
causes the TCP Connection to be closed.
The resynchronization assumes that security and authentication
procedures outside the FCIP Entity are protecting the valid data
stream from being replaced by an intruding data stream containing
valid FCIP data.
The following steps are one example of how an FCIP_DE might
resynchronize with the data stream entering the Encapsulated Frame
Receiver Portal.
1) Search for candidate and strong headers:
The data stream entering the Encapsulated Frame Receiver Portal is
searched for 12 bytes in a row containing the required values for:
a) Protocol field,
b) Version field,
c) ones complement of the Protocol field,
d) ones complement of the Version field,
e) replication of encapsulation word 0 in word 1, and
f) pFlags field and its ones complement.
If such a 12-byte grouping is found, the FCIP_DE assumes that it
has identified bytes 0-2 of a candidate FCIP encapsulation header.
All bytes up to and including the candidate header byte are
discarded.
If no candidate header has been found after searching a specified
number of bytes greater than some multiple of 2176 (the maximum
length of an FCIP Frame), resynchronization has failed and the
TCP/IP connection is closed.
Word 3 of the candidate header contains the Frame Length and Flags
fields and their ones complements. If the fields are consistent
with their ones complements, the candidate header is considered a
strong candidate header. The Frame Length field is used to
determine where in the byte stream the next strong candidate
header should be and processing continues at step 2).
2) Use multiple strong candidate headers to locate a verified
candidate header:
The Frame Length in one strong candidate header is used to skip
incoming bytes until the expected location of the next strong
candidate header is reached. Then the tests described in step 1)
are applied to see if another strong candidate header has
successfully been located.
All bytes skipped and all bytes in all strong candidate headers
processed are discarded.
Strong candidate headers continue to be verified in this way for
at least 4352 bytes (twice the maximum length of an FCIP Frame).
If at any time a verification test fails, processing restarts at
step 1 and a retry counter is incremented. If the retry counter
exceeds 3 retries, resynchronization has failed and the TCP
Connection is closed, and the FC entity is notified with the
reason for the closure.
After strong candidate headers have been verified for at least
4352 bytes, the next header identified is a verified candidate
header, and processing continues at step 3).
Note: If a strong candidate header was part of the data content of
an FCIP Frame, the FCIP Frame defined by that or a subsequent
strong candidate header will eventually cross an actual header in
the byte stream. As a result it will either identify the actual
header as a strong candidate header or it will lose
synchronization again because of the extra 28 bytes in the length,
returning to step 1 as described above.
3) Use multiple strong candidate headers to locate a verified
candidate header:
Incoming bytes are inspected and discarded until the next verified
candidate header is reached. Inspection of the incoming bytes
includes testing for other candidate headers using the criteria
described in step 1. Each verified candidate header is tested
against the tests listed in section 5.6.2.2 as would normally be
the case.
Verified candidate headers continue to be located and tested in
this way for a minimum of 4352 bytes (twice the maximum length of
an FCIP Frame). If all verified candidate headers encountered are
valid, the last verified candidate header is a valid header. At
this point the FCIP_DE stops discarding bytes and begins normal
FCIP de-encapsulation, including for the first time since
synchronization was lost, delivery of FC Frames through the FC
Frame Transmitter Portal according to normal FCIP rules.
If any verified candidate headers are invalid but meet all the
requirements of a strong candidate header, increment the retry
counter and return to step 2). If any verified candidate headers
are invalid and fail to meet the tests for a strong candidate
header, or if inspection of the bytes between verified candidate
headers discovers any candidate headers, increment the retry
counter and return to step 1. If the retry counter exceeds 4
retries, resynchronization has failed and the TCP/IP connection is
closed.
A flowchart for this algorithm can be found in figure 15.
Synchronization is lost
|
_____________v_______________
| |
| Search for candidate header |
+----------->| |
| | Found Not Found |
| | (Strong candidate) |
| |_____________________________|
| | |
| | + --------->close TCP
| _______v_____________________ Connection
| | | and notify
| | Enough strong candidate | the FC Entity
| +---->| headers identified? | with the reason
| | | | for closure
| | | No Yes |
| | | (Verified candidate) |
| | |_____________________________|
|___________________| |
^ | |
| | |
| | _______________________v_____
| | | |
| | | Enough verified candidate |
| | | headers validated? |
| | | |
| | | No Yes |
| | | (Resynchronized) |
| | |_____________________________|
| | | |
| | ______v__________ | Resume
| | | | + ---> Normal
| | | Synchronization | De-encapsulation
| | | Lost? |
| | | |
| | | No Yes |
| | |_________________|
| | | |
| |________| |
|___________________________|
Figure 15: Flow diagram of simple synchronization example
Appendix E - Relationship between FCIP and IP over FC (IPFC)
The contents of this annex are informative.
IPFC (RFC 2625) describes the encapsulation of IP packets in FC
Frames. It is intended to facilitate IP communication over an FC
network.
FCIP describes the encapsulation of FC Frames in TCP segments, which
in turn are encapsulated inside IP packets for transporting over an
IP network. It gives no consideration to the type of FC Frame that
is being encapsulated. Therefore, the FC Frame may actually contain
an IP packet as described in the IP over FC specification (RFC
2625). In such a case, the data packet would have:
- Data Link Header
- IP Header
- TCP Header
- FCIP Header
- FC Header
- IP Header
Note: The two IP headers would not be identical to each other. One
would have information pertaining to the final destination, while the
other would have information pertaining to the FCIP Entity.
The two documents focus on different objectives. As mentioned above,
implementation of FCIP will lead to IP encapsulation within IP.
While perhaps inefficient, this should not lead to issues with IP
communication. One caveat: if a Fibre Channel device is
encapsulating IP packets in an FC Frame (e.g., an IPFC device), and
that device is communicating with a device running IP over a non-FC
medium, a second IPFC device may need to act as a gateway between the
two networks. This scenario is not specifically addressed by FCIP.
There is nothing in either of the specifications to prevent a single
device from implementing both FCIP and IP-over-FC (IPFC), but this is
implementation specific, and is beyond the scope of this document.
Appendix F - FC Frame Format
Note: All users of the words "character" or "characters" in this
section refer to 8bit/10bit link encoding wherein each 8 bit
"character" within a link frame is encoded as a 10 bit "character"
for link transmission. These words do not refer to ASCII, Unicode,
or any other form of text characters, although octets from such
characters will occur as 8 bit "characters" for this encoding. This
usage is employed here for consistency with the ANSI T11 standards
that specify Fibre Channel.
The contents of this annex are informative.
All FC Frames have a standard format (see FC-FS [5]) much like LAN's
802.x protocols. However, the exact size of each FC Frame varies
depending on the size of the variable fields. The size of the
variable field ranges from 0 to 2112-bytes as shown in the FC Frame
Format in figure 16, resulting in the minimum size FC Frame of 36
bytes and the maximum size FC Frame of 2148 bytes. Valid FC Frame
lengths are always a multiple of four bytes.
+------+--------+-----------+----//-------+------+------+
| SOF |Frame |Optional | Frame | CRC | EOF |
| (4B) |Header |Header | Payload | (4B) | (4B) |
| |(24B) |<----------------------->| | |
| | | Data Field = (0-2112B) | | |
+------+--------+-----------+----//-------+------+------+
Figure 16: FC Frame Format
SOF and EOF Delimiters
On an FC link, Start-of-Frame (SOF) and End-Of-Frame (EOF) are
called Ordered Sets and are sent as special words constructed from
the 8B/10B comma character (K28.5) followed by three additional
8B/10B data characters making them uniquely identifiable in the
data stream.
On an FC link, the SOF delimiter serves to identify the beginning
of an FC Frame and prepares the receiver for FC Frame reception.
The SOF contains information about the FC Frame's Class of
Service, position within a sequence, and in some cases, connection
status.
The EOF delimiter identifies the end of the FC Frame and the final
FC Frame of a sequence. In addition, it serves to force the
running disparity to negative. The EOF is used to end the
connection in connection-oriented classes of service.
A special EOF delimiter called EOFa (End Of Frame - Abort) is used
to terminate a partial FC Frame resulting from a malfunction in a
link facility during transmission. Since an FCIP Entity functions
like a transmission link with respect to the rest of the FC
Fabric, FCIP_DEs may use EOFa in their error recovery procedures.
It is therefore important to preserve the information conveyed by
the delimiters across the IP-based network, so that the receiving
FCIP Entity can correctly reconstruct the FC Frame in its original
SOF and EOF format before forwarding it to its ultimate FC
destination on the FC link.
When an FC Frame is encapsulated and sent over a byte-oriented
interface, the SOF and EOF delimiters are represented as sequences
of four consecutive bytes, which carry the equivalent Class of
Service and FC Frame termination information as the FC ordered
sets.
The representation of SOF and EOF in an encapsulation FC Frame is
described in FC Frame Encapsulation [19].
Frame Header
The FC Frame Header is transparent to the FCIP Entity. The FC
Frame Header is 24 bytes long and has several fields that are
associated with the identification and control of the payload.
Current FC Standards allow up to 3 Optional Header fields [5]:
- Network_Header (16-bytes)
- Association_Header (32-bytes)
- Device_Header (up to 64-bytes).
Frame Payload
The FC Frame Payload is transparent to the FCIP Entity. An FC
application level payload is called an Information Unit at the
FC-4 Level. This is mapped into the FC Frame Payload of the FC
Frame. A large Information Unit is segmented using a structure
consisting of FC Sequences. Typically, a Sequence consists of
more than one FC Frame. FCIP does not maintain any state
information regarding the relationship of FC Frames within an FC
Sequence.
CRC
The FC CRC is 4 bytes long and uses the same 32-bit polynomial
used in FDDI and is specified in ANSI X3.139 Fiber Distributed
Data Interface. This CRC value is calculated over the entire FC
header and the FC payload; it does not include the SOF and EOF
delimiters.
Note: When FC Frames are encapsulated into FCIP Frames, the FC
Frame CRC is untouched by the FCIP Entity.
Appendix G - FC Encapsulation Format
This annex contains a reproduction of the FC Encapsulation Format
[19] as it applies to FCIP Frames that encapsulate FC Frames. The
information in this annex is not intended to represent the FCIP
Special Frame (FSF) that is described in section 7.
The information in this annex was correct as of the time this
specification was approved. The information in this annex is
informative only.
If there are any differences between the information here and the FC
Encapsulation Format specification [19], the FC Encapsulation Format
specification takes precedence.
If there are any differences between the information here and the
contents of section 5.6.1, then the contents of section 5.6.1 take
precedence.
Figure 17 applies the requirements stated in section 5.6.1 and in the
FC Encapsulation Frame format resulting in a summary of the FC Frame
format. Where FCIP requires specific values, those values are shown
in hexadecimal in parentheses. Detailed requirements for the FCIP
usage of the FC Encapsulation Format are in section 5.6.1.
W|------------------------------Bit------------------------------|
o| |
r| 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3|
d|0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1|
+---------------+---------------+---------------+---------------+
0| Protocol# | Version | -Protocol# | -Version |
| (0x01) | (0x01) | (0xFE) | (0xFE) |
+---------------+---------------+---------------+---------------+
1| Protocol# | Version | -Protocol# | -Version |
| (0x01) | (0x01) | (0xFE) | (0xFE) |
+---------------+---------------+---------------+---------------+
2| pFlags | Reserved | -pFlags | -Reserved |
| (0x00) | (0x00) | (0xFF) | (0xFF) |
+-----------+---+---------------+-----------+---+---------------+
3| Flags | Frame Length | -Flags | -Frame Length |
| (0x00) | | (0x3F) | |
+-----------+-------------------+-----------+-------------------+
4| Time Stamp [integer] |
+---------------------------------------------------------------+
5| Time Stamp [fraction] |
+---------------------------------------------------------------+
6| CRC (Reserved in FCIP) |
| (0x00-00-00-00) |
+---------------+---------------+---------------+---------------+
7| SOF | SOF | -SOF | -SOF |
+---------------+---------------+---------------+---------------+
8| |
+----- FC Frame content (see appendix F) -----+
| |
+---------------+---------------+---------------+---------------+
n| EOF | EOF | -EOF | -EOF |
+---------------+---------------+---------------+---------------+
Figure 17: FCIP Frame Format
The names of fields are generally descriptive on their contents and
the FC Encapsulation Format specification [19] is referenced for
details. Field names preceded by a minus sign are ones complement
values of the named field.
Note: Figure 17 does not represent the FSF that is described in
section 7.
Appendix H - FCIP Requirements on an FC Entity
The contents of this annex are informative for FCIP but might be
considered normative on FC-BB-2.
The capabilities that FCIP requires of an FC Entity include:
1) The FC Entity must deliver FC Frames to the correct FCIP Data
Engine (in the correct FCIP Link Endpoint).
2) Each FC Frame delivered to an FCIP_DE must be accompanied by a
time value synchronized with the clock maintained by the FC Entity
at the other end of the FCIP Link (see section 6). If a
synchronized time value is not available, a value of zero must
accompany the FC Frame.
3) When FC Frames exit FCIP Data Engine(s) via the FC Frame
Transmitter Portal(s), the FC Entity should forward them to the FC
Fabric. However, before forwarding an FC Frame, the FC Entity
must compute the end-to-end transit time for the FC Frame using
the time value supplied by the FCIP_DE (taken from the FCIP
header) and a synchronized time value (see section 6). If the
end-to-end transit time exceeds the requirements of the FC Fabric,
the FC Entity is responsible for discarding the FC Frame.
4) The only delivery ordering guarantee provided by FCIP is correctly
ordered delivery of FC Frames between a pair of FCIP Data Engines.
FCIP expects the FC Entity to implement all other FC Frame
delivery ordering requirements.
5) When a TCP connect request is received and that request would add
a new TCP Connection to an existing FCIP_LEP, the FC Entity must
authenticate the source of the TCP connect request before use of
the new TCP connection is allowed.
6) The FC Entity may participate in determining allowed TCP
Connections, TCP Connection parameters, quality of service usage,
and security usage by modifying interactions with the FCIP Entity
that are modelled as a "shared" database in section 8.1.1.
7) The FC Entity may require the FCIP Entity to perform TCP close
requests.
8) The FC Entity may recover from connection failures.
9) The FC Entity must recover from events that the FCIP Entity cannot
handle, such as:
a) loss of synchronization with FCIP Frame headers from the
Encapsulated Frame Receiver Portal requiring resetting the TCP
Connection; and
b) recovering from FCIP Frames that are discarded as a result of
synchronization problems (see section 5.6.2.2 and section
5.6.2.3).
10) The FC Entity must work cooperatively with the FCIP Entity to
manage flow control problems in either the IP Network or FC
Fabric.
11) The FC Entity may test for failed TCP Connections.
Note that the Fibre Channel standards must be consulted for a
complete understanding of the requirements placed on an FC
Entity.
Table 2 shows the explicit interactions between the FCIP Entity
and the FC Entity.
+-------------+-----------------+-----------------------------------+
| | | Information/Parameter Passed and |
| | | Direction |
| Reference | +-----------------+-----------------+
| Section | Condition | FCIP Entity---> | <---FC Entity |
+-------------+-----------------+-----------------+-----------------+
| 5.6 | FC Frame ready | | Provide FC |
| FCIP Data | for IP transfer | | Frame and |
| Engine | | | time stamp at |
| | | | FC Frame |
| | | | Receiver Portal |
+-------------+-----------------+-----------------+-----------------+
| WWN = World Wide Name |
+-------------------------------------------------------------------+
| continued |
+-------------------------------------------------------------------+
Table 2: FC/FCIP Entity pair interactions (part 1 of 5)
+-------------+-----------------+-----------------------------------+
| | | Information/Parameter Passed and |
| | | Direction |
| Reference | +-----------------+-----------------+
| Section | Condition | FCIP Entity---> | <---FC Entity |
+-------------+-----------------+-----------------+-----------------+
| continued |
+-------------+-----------------+-----------------+-----------------+
| 5.6 | FCIP Frame | Provide FC | |
| FCIP Data | received from | Frame and | |
| Engine | IP Network | time stamp at | |
| | | FC Frame Trans- | |
| | | mitter Portal | |
+-------------+-----------------+-----------------+-----------------+
| 5.6.2.2 | FCIP_DE | Inform FC | |
| Errors | discards bytes | Entity that | |
| in FCIP | delivered | bytes have been | |
| Headers and | through | discarded with | |
| Discarding | Encapsulated | reason | |
| FCIP Frames | Frame Receiver | | |
| | Portal | | |
+-------------+-----------------+-----------------+-----------------+
| 5.6.2.3 | FCIP Entity | Inform FC | |
| Synchron- | closes TCP | Entity that TCP | |
| ization | Connection due | Connection has | |
| Failures | to synchron- | been closed | |
| | ization failure | with reason | |
| | | for closure | |
+-------------+-----------------+-----------------+-----------------+
| 8.1.2.3 | Receipt of the | Inform FC | |
| Connection | echoed FSF | Entity that TCP | |
| Setup | takes too long | Connection has | |
| Following a | or the FSF | been closed | |
| Successful | contents have | with reason | |
| TCP Connect | changed | for closure | |
| Request | | | |
+-------------+-----------------+-----------------+-----------------+
| WWN = World Wide Name |
+-------------------------------------------------------------------+
| continued |
+-------------------------------------------------------------------+
Table 2: FC/FCIP Entity pair interactions (part 2 of 5)
+-------------+-----------------+-----------------------------------+
| | | Information/Parameter Passed and |
| | | Direction |
| Reference | +-----------------+-----------------+
| Section | Condition | FCIP Entity---> | <---FC Entity |
+-------------+-----------------+-----------------+-----------------+
| continued |
+-------------+-----------------+-----------------+-----------------+
| 8.1.2.1 | New TCP | Inform FC | |
| Non-Dynamic | Connection | Entity of | |
| Creation of | created based | new or existing | |
| a New TCP | on "shared" | FCIP_LEP and | |
| Connections | database | new FCIP_DE | |
| | information | along with | |
| | | Destination FC | |
| | | Fabric Entity | |
| | | WWN, Connection | |
| | | Usage Flags, | |
| | | Connection | |
| | | Usage Code and | |
| | | Connection | |
| | | Nonce | |
+-------------+-----------------+-----------------+-----------------+
| 8.1.2.2 | New TCP | Inform FC | |
| Dynamic | Connection | Entity of | |
| Creation of | created based | new or existing | |
| a New TCP | on SLP service | FCIP_LEP and | |
| Connections | advertisement | new FCIP_DE | |
| | and "shared" | along with | |
| | database | Destination FC | |
| | information | Fabric Entity | |
| | | WWN, Connection | |
| | | Usage Flags, | |
| | | Connection | |
| | | Usage Code and | |
| | | Connection | |
| | | Nonce | |
+-------------+-----------------+-----------------+-----------------+
| WWN = World Wide Name |
+-------------------------------------------------------------------+
| continued |
+-------------------------------------------------------------------+
Table 2: FC/FCIP Entity pair interactions (part 3 of 5)
+-------------+-----------------+-----------------------------------+
| | | Information/Parameter Passed and |
| | | Direction |
| Reference | +-----------------+-----------------+
| Section | Condition | FCIP Entity---> | <---FC Entity |
+-------------+-----------------+-----------------+-----------------+
| continued |
+-------------+-----------------+-----------------+-----------------+
| 8.1.3 | New TCP | Inform FC | |
| Processing | Connection | Entity of | |
| Incoming | created based | new or existing | |
| TCP Connect | on incoming TCP | FCIP_LEP and | |
| Requests | Connect request | new FCIP_DE | |
| | and "shared" | along with | |
| | database | Source FC | |
| | information | Fabric Entity | |
| | | WWN, Source | |
| | | FC/FCIP Entity | |
| | | Identifier, | |
| | | Connection | |
| | | Usage Flags, | |
| | | Connection | |
| | | Usage Code and | |
| | | Connection | |
| | | Nonce | |
+-------------+-----------------+-----------------+-----------------+
| 8.1.3 | TCP Connect | Request FC | Yes or No |
| Processing | Request wants | Entity to | answer about |
| Incoming | to add a new | authenticate | whether the |
| TCP Connect | TCP Connection | the source of | source of the |
| Requests | to an existing | the TCP Connect | TCP Connect |
| | FCIP_LEP | Request | Request can be |
| | | | authenticated |
+-------------+-----------------+-----------------+-----------------+
| 8.1.3 | Receipt of the | Inform FC | |
| Processing | FSF takes too | Entity that TCP | |
| Incoming | long or | Connection has | |
| TCP Connect | duplicate | been closed | |
| Requests | Connection | with reason | |
| | Nonce value | for closure | |
+-------------+-----------------+-----------------+-----------------+
| WWN = World Wide Name |
+-------------------------------------------------------------------+
| continued |
+-------------------------------------------------------------------+
Table 2: FC/FCIP Entity pair interactions (part 4 of 5)
+-------------+-----------------+-----------------------------------+
| | | Information/Parameter Passed and |
| | | Direction |
| Reference | +-----------------+-----------------+
| Section | Condition | FCIP Entity---> | <---FC Entity |
+-------------+-----------------+-----------------+-----------------+
| concluded |
+-------------+-----------------+-----------------+-----------------+
| 8.2 | FC Entity | Acknowledgement | Identification |
| Closing TCP | determines | of TCP | of the FCIP_DE |
| Connections | that a TCP | Connection | whose TCP |
| | Connection | closure | Connection |
| | needs to be | | needs to be |
| | closed | | closed |
+-------------+-----------------+-----------------+-----------------+
| 8.4 | Discovery that | Inform FC | |
| TCP | TCP connectiv- | Entity that TCP | |
| Connection | ity has been | Connection has | |
| Considera- | lost | been closed | |
| tions | | with reason | |
| | | for closure | |
+-------------+-----------------+-----------------+-----------------+
| 9.4.1 | IKE phase 1 | Inform FC | |
| FCIP | failed, result- | Entity that TCP | |
| Link | ing in termin- | Connection can | |
| Initializ- | ation of link | not be opened | |
| ation Steps | initialization | with reason for | |
| | | failure | |
+-------------+-----------------+-----------------+-----------------+
| 9.4.3 | Excessive | Inform FC | |
| Handling | numbers of | Entity that TCP | |
| data | dropped | Connection has | |
| integrity | datagrams | been closed | |
| and confi- | detected and | with reason | |
| dentiality | TCP Connection | for closure | |
| violations | closed | | |
+-------------+-----------------+-----------------+-----------------+
| RFC 3723 | TCP Connection | Inform FC | |
| | closed due to | Entity that TCP | |
| Handling SA | SA parameter | Connection has | |
| parameter | mismatch | been closed | |
| mismatches | problems | with reason | |
| | | for closure | |
+-------------+-----------------+-----------------+-----------------+
| WWN = World Wide Name |
+-------------------------------------------------------------------+
Table 2: FC/FCIP Entity pair interactions (part 5 of 5)
Editors and Contributors Acknowledgements
During the development of this specification, Murali Rajagopal,
Elizabeth Rodriguez, Vi Chau, and Ralph Weber served consecutively as
editors. Raj Bhagwat contributed substantially to the initial basic
FCIP concepts.
Venkat Rangan contributed the Security section and continues to
coordinate security issues with the ips Working Group and IETF.
Andy Helland contributed a substantial revision of Performance
section, aligning it with TCP/IP QoS concepts.
Dave Peterson contributed the dynamic discovery section and edits to
RFC 3822.
Anil Rijhsinghani contributed material related to the FCIP MIB and
edits the FCIP MIB document.
Bob Snively contributed material related to error detection and
recovery including the bulk of the synchronization recovery example
annex.
Lawrence J. Lamers contributed numerous ideas focused on keeping FCIP
compatible with B_Port devices.
Milan Merhar contributed several of the FCIP conceptual modifications
necessary to support NATs.
Don Fraser contributed material related to link failure detection and
reporting.
Bill Krieg contributed a restructuring of the TCP Connection setup
sections that made them more linear with respect to time and more
readable.
Several T11 leaders supported this effort and advised the editors of
this specification regarding coordination with T11 documents and
projects. These T11 leaders are: Jim Nelson (Framing and Signaling),
Neil Wanamaker (Framing and Signaling), Craig Carlson (Generic
Services), Ken Hirata (Switch Fabric), Murali Rajagopal (Backbone),
Steve Wilson (Switch Fabric), and Michael O'Donnell (Security
Protocols).
Editors and Contributors Addresses
Neil Wanamaker
Akara
10624 Icarus Court
Austin, TX 78726
USA
Phone: +1 512 257 7633
Fax: +1 512 257 7877
EMail: nwanamaker@akara.com
Ralph Weber
ENDL Texas, representing Brocade
Suite 102 PMB 178
18484 Preston Road
Dallas, TX 75252
USA
Phone: +1 214 912 1373
EMail: roweber@ieee.org
Elizabeth G. Rodriguez
Dot Hill Systems Corp.
6305 El Camino Real
Carlsbad, CA 92009
USA
Phone: +1 760 431 4435
EMail: elizabeth.rodriguez@dothill.com
Steve Wilson
Brocade Comm. Systems, Inc.
1745 Technology Drive
San Jose, CA. 95110
USA
Phone: +1 408 333 8128
EMail: swilson@brocade.com
Bob Snively
Brocade Comm. Systems, Inc.
1745 Technology Drive
San Jose, CA 95110
USA
Phone: +1 408 303 8135
EMail: rsnively@brocade.com
David Peterson
Cisco Systems - SRBU
6450 Wedgwood Road
Maple Grove, MN 55311
USA
Phone: +1 763 398 1007
Cell: +1 612 802 3299
EMail: dap@cisco.com
Donald R. Fraser
Hewlett-Packard
301 Rockrimmon Blvd., Bldg. 5
Colorado Springs, CO 80919
USA
Phone: +1 719 548 3272
EMail: Don.Fraser@HP.com
R. Andy Helland
LightSand Communications, Inc.
375 Los Coches Street
Milpitas, CA 95035
USA
Phone: +1 408 404 3119
Fax: +1 408 941 2166
EMail: andyh@lightsand.com
Raj Bhagwat
LightSand Communications, Inc.
24411 Ridge Route Dr.
Suite 135
Laguna Hills, CA 92653
USA
Phone: +1 949 837 1733 x104
EMail: rajb@lightsand.com
Bill Krieg
Lucent Technologies
200 Lucent Lane
Cary, NC 27511
USA
Phone: +1 919 463 4020
Fax: +1 919 463 4041
EMail: bkrieg@lucent.com
Michael E. O'Donnell
McDATA Corporation
310 Interlocken Parkway
Broomfield, CO 80021
USA
Phone: +1 303 460 4142
Fax: +1 303 465 4996
EMail: modonnell@mcdata.com
Anil Rijhsinghani
McDATA Corporation
310 Interlocken Parkway
Broomfield, CO 80021
USA
Phone: +1 508 870 6593
EMail: anil.rijhsinghani@mcdata.com
Milan J. Merhar
43 Nagog Park
Pirus Networks
Acton, MA 01720
USA
Phone: +1 978 206 9124
EMail: Milan@pirus.com
Craig W. Carlson
QLogic Corporation
6321 Bury Drive
Eden Prairie, MN 55346
USA
Phone: +1 952 932 4064
EMail: craig.carlson@qlogic.com
Venkat Rangan
Rhapsody Networks Inc.
3450 W. Warren Ave.
Fremont, CA 94538
USA
Phone: +1 510 743 3018
Fax: +1 510 687 0136
EMail: venkat@rhapsodynetworks.com
Lawrence J. Lamers
SAN Valley Systems, Inc.
6320 San Ignacio Ave.
San Jose, CA 95119-1209
USA
Phone: +1 408 234 0071
EMail: ljlamers@ieee.org
Murali Rajagopal
Broadcom Corporation
16215 Alton Parkway
Irvine,CA 92619
USA
Phone: +1 949 450 8700
EMail: muralir@broadcom.com
Ken Hirata
Vixel Corporation
15245 Alton Parkway, Suite 100
Irvine, CA 92618
USA
Phone: +1 949 788 6368
Fax: +1 949 753 9500
EMail: ken.hirata@vixel.com
Vi Chau
USA
Email: vchau1@cox.net
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