| Rfc | 5414 |
|---|
| Title | Wireless LAN Control Protocol (WiCoP) |
|---|
| Author | S. Iino, S. Govindan, M.
Sugiura, H. Cheng |
|---|
| Date | February 2010 |
|---|
| Format: | TXT, HTML |
|---|
| Obsoleted by | RFC5415 |
|---|
| Status: | HISTORIC |
|---|
|
Independent Submission S. Iino
Request for Comments: 5414 S. Govindan
Obsoleted by: 5415 M. Sugiura
Category: Historic H. Cheng
ISSN: 2070-1721 Panasonic
February 2010
Wireless LAN Control Protocol (WiCoP)
Abstract
The popularity of wireless local area networks (WLANs) has led to
widespread deployments across different establishments. It has also
translated into an increasing scale of the WLANs. Large-scale
deployments made of large numbers of wireless termination points
(WTPs) and covering substantial areas are increasingly common.
The Wireless LAN Control Protocol (WiCoP) described in this document
allows for the control and provisioning of large-scale WLANs. It
enables central management of these networks and realizes the
objectives set forth for the Control And Provisioning of Wireless
Access Points (CAPWAP).
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for the historical record.
This document defines a Historic Document for the Internet community.
This is a contribution to the RFC Series, independently of any other
RFC stream. The RFC Editor has chosen to publish this document at
its discretion and makes no statement about its value for
implementation or deployment. Documents approved for publication by
the RFC Editor are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5414.
IESG Note
This RFC documents the WiCoP protocol as it was when submitted to the
IETF as a basis for further work in the CAPWAP Working Group, and
therefore it may resemble the CAPWAP protocol specification in RFC
5415, as well as other IETF work. This RFC is being published solely
for the historical record. The protocol described in this RFC has
not been thoroughly reviewed and may contain errors and omissions.
RFC 5415 documents the standards track solution for the CAPWAP
Working Group and obsoletes any and all mechanisms defined in this
RFC. This RFC itself is not a candidate for any level of Internet
Standard and should not be used as a basis for any sort of Internet
deployment.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http:trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................6
3. Protocol Overview ...............................................6
4. WiCoP Format ....................................................7
4.1. WiCoP Header ...............................................8
4.2. WiCoP Control Packet ......................................11
4.2.1. WiCoP Control Messages .............................12
4.2.2. WiCoP Control Message Elements .....................12
4.2.3. WiCoP Control Message Description ..................27
4.3. WiCoP Data Packet .........................................36
4.4. WiCoP Timers ..............................................37
4.4.1. Active Presence Timer ..............................37
4.4.2. Feedback Interval ..................................37
4.4.3. Response Timer .....................................37
4.4.4. Wireless Connectivity Timer ........................38
5. WiCoP Processes ................................................38
5.1. Initialization ............................................38
5.2. Capabilities Exchange .....................................38
5.3. Connection ................................................39
5.4. Configuration .............................................40
5.4.1. Logical Groups .....................................41
5.4.2. Resource Control ...................................41
5.5. Operation .................................................41
5.5.1. Updates ............................................42
5.5.2. Feedback and Statistics ............................42
5.5.3. Non-Periodic Events ................................43
5.5.4. Firmware Trigger ...................................43
5.5.5. Wireless Terminal Management .......................43
5.5.6. Key Configuration ..................................46
6. WiCoP Performance ..............................................51
6.1. Operational Efficiency ....................................51
6.2. Semantic Efficiency .......................................51
7. Summary and Conclusion .........................................51
8. Security Considerations ........................................52
9. Informative References .........................................53
1. Introduction
The popularity of wireless local area networks (WLANs) has led to
numerous but incompatible designs and solutions. The CAPWAP
Architecture Taxonomy [RFC4118] describes major variations of these
designs. Among them, the Local MAC (Media Access Control) and Split
MAC architecture designs are notable categories.
Wireless LAN Control Protocol (WiCoP) recognizes the major
architecture designs and presents a common platform on which WLAN
entities of different designs can be accommodated. This enables
interoperability among wireless termination points (WTPs) and WLAN
access controllers (ACs) of distinct architecture designs. WiCoP
therefore allows for cost-effective WLAN expansions. It can also
accommodate future developments in WLAN technologies. Figure 1
illustrates the WiCoP operational structure in which distinct control
elements are utilized for Local MAC and Split MAC WTPs.
WiCoP also addresses the increasing trend of shared infrastructure
WLANs. Here, WLAN management needs to distinguish and isolate
control for the different logical groups sharing a single physical
WLAN. WiCoP manages WLANs through a series of tunnels that separate
traffic based on logical groups.
The WiCoP operational structure in Figure 1 shows that each WTP uses
a number of tunnels to distinguish and separate traffic for control
and for each logical group. The protocol allows for managing WLANs
in a manner consistent with the logical groups that share the
physical infrastructure.
Local MAC WTP
+-------+ +-------+
| | | | Logical Groups
| (=====Control Tunnel======) |
| | | | ~~~~~~~
| | | | / /
| <=====Logical Group A=====> | / A /~~~~
| | | | / / /
| <=====Logical Group B=====> | ~~~~~~~ /~~~~
| | | | / B / /
| <=====Logical Group C=====> | ~~~~~~~ /
| | | | / C /
| | +-------+ ~~~~~~~
| |
| |
| AC |
| |
| | Split MAC WTP
| |
| | +-------+ Logical Groups
| | | |
| [=====Control Tunnel======] | ~~~~~~~
| | | | / /
| | | | / 1 /~~~~
| <=====Logical Group 1=====> | / / /
| | | | ~~~~~~~ /
| <=====Logical Group 2=====> | / 2 /
| | | | ~~~~~~~
+-------+ +-------+
Figure 1
In Figure 1, WiCoP establishes and operates control tunnels and
logical group tunnels between the AC and two types of WTPs. The
control tunnels are used to transport WiCoP messages dealing with the
configuration, monitoring, and management of WTPs as a physical
whole. The logical group tunnels serve to separate traffic among
each of the logical groups constituting a physical WTP.
2. Terminology
This document follows the terminologies of [RFC4118] and [RFC4564].
3. Protocol Overview
The Wireless LAN Control Protocol (WiCoP) focuses on enabling
interoperability in shared infrastructure WLANs. It is designed for
use with different wireless technologies. This document provides
both the general operations of WiCoP and also specific use-cases with
respect to IEEE 802.11-based systems.
The state machine for WiCoP is illustrated in Figure 2.
+--------------------------------+
| |
| +------------------+ |
V V | |
+-------------+ +-------------+ +-------------+ |
| | | | | | |
| Initial- |-------->| Capabilities|-------->| Connection | |
| ization | | Exchange | | | |
| | | | | | |
+-------------+ +-------------+ +-------------+ |
A A | |
| | | |
| | | |
| | | |
| | V |
| | +-------------+ |
| | | | |
| +----------------| Configur- | |
| | ation | |
| | | |
| +-------------+ |
| | |
| | |
| | |
| | |
| V |
| +--------------+ |
| | | |
+----------------------------------------| |-+
| Operation |
| |
+--------------+
Figure 2
The Initialization state represents the initial states of WTPs and
AC. A WTP or AC in this state powers on, clears internal registers,
runs hardware self-tests, and resets network interfaces.
The Capabilities Exchange state represents initial protocol exchange
between a WTP and AC. A WTP in this state determines possible ACs
from which it can receive management services. An AC in this state
determines the capabilities of the WTP and the WTP's compatibility
with the management services it offers.
The Connection state represents the creation of a security
infrastructure between a WTP and AC. This involves mutual
authentication and the establishment of a secure connection between
the WiCoP entities.
The Configuration state represents the exchange of long-term
operational parameters and settings between a WTP and AC. A WTP in
this state receives configuration information to allow it to operate
consistently within the WLAN managed by the AC. An AC in this state
provides configuration information to the WTP based on the WTP's
capabilities and network policies.
The Operation state represents the active exchange of WiCoP
monitoring and management messages. WTPs send regular status updates
to and receive corresponding management instructions from the AC.
This state also involves firmware and configuration updates arising
from changes in network conditions and administrative policies.
4. WiCoP Format
WiCoP uses separate packets for control and data message transfer
between the AC and WTPs. A common header is used for both types of
packets in which a single-bit flag distinguishes between them. This
section presents the packet formats for WiCoP packets.
4.1. WiCoP Header
Figure 3 illustrates the WiCoP common header for control and data
packets.
0 31
| 7 15 23 |
|-------|-------|-------|-------|-------|-------|-------|-------|
| |
+---------------+-+-+-+-+-+-+-+-+-------------------------------+
| Version |M|D|C|R|E|F|L| | Reserve |
+---------------+-+-+-+-+-+-+-+-+-------------------------------+
| Fragment ID | Fragment No. | Length |
+---------------+---------------+-------------------------------+
Figure 3
Version Field
This field indicates the protocol version.
'M' Field
The MAC-type field, 'M', distinguishes between Local MAC WTPs and
Split MAC WTPs. It is used to efficiently realize interoperability
between WTPs of the two different designs. A '0' value indicates
WiCoP exchanges with a Split MAC WTP while a '1' value indicates
WiCoP exchanges with a Local MAC WTP.
The presence of this classification bit in the WiCoP common header
serves to expedite processing of WiCoP and WLAN traffic at the AC.
With a single parsing of the WiCoP common header once, the AC will be
able to determine the appropriate processing required for the
particular WiCoP packet.
'D' Field
The differentiator field, 'D', is used to distinguish between WTP
variants within a type of WTP design. The CAPWAP Architecture
Taxonomy [RFC4118] illustrates that the Split MAC design allows
encryption/decryption to be performed at either the WTP or the AC.
The Architecture Taxonomy also indicates that the Local MAC design
allows authentication to take place at either the WTP or the AC.
WiCoP acknowledges these major variants and accommodates them using
the 'D' field in conjunction with the 'M' field. For a Split MAC
WTP, the 'D' field is used to indicate location of
encryption/decryption while for a Local MAC WTP, the 'D' field is
used to indicate location of authentication. The following table
highlights their usage.
'M' 'D' Description
0 0 Split MAC WTP - Encryption/decryption
is performed at WTP
0 1 Split MAC WTP - Encryption/decryption
is performed at AC
1 0 Local MAC WTP - Authentication is
performed by WTP
1 1 Local MAC WTP - Authentication is
performed by AC
Similar to the 'M' field, the presence of this classification in the
WiCoP common header helps expedite processing at the AC with a single
parsing. By incorporating the classification bits in the WiCoP
common header, where it is available for all packets of a session,
the AC processing can be expedited. Alternatively, the AC would have
to check each arriving packet against an internal register and
consequently delay processing.
'C' Field
This field distinguishes between a WiCoP control and WiCoP data
packet. Each type of information is tunneled separately across the
WiCoP tunnel interfaces between WTPs and the AC. A '0' value for the
'C' field indicates a data packet, while a '1' value indicates a
control packet.
The 'C' field is also used to assign WiCoP packets to distinct data
and control tunnels between the AC and WTP. WiCoP also maintains
logical groups in WLANs with the 'C' field.
'R' Field
The retransmission field, 'R', is used to differentiate between the
first and subsequent transmissions of WiCoP packets. The 'R' field
is used for critical WiCoP packets such as those relating to security
key exchanges. A '0' value for the 'R' field indicates the first
transmission of a WiCoP packet, while a '1' value indicates a
retransmission.
'E' Field
The encryption field, 'E', is used to indicate if the WiCoP packet is
encrypted between the AC and WTPs. The 'E' field is used for those
WiCoP packets that are exchanged during initialization. A '0' value
indicates the WiCoP packet is unencrypted, while a '1' value
indicates the packet is encrypted.
'F' Field
The fragmentation field indicates if the packet is a fragment of a
larger packet. A '0' value indicates a non-fragmented packet while a
'1' value indicates a fragmented packet. The 'F', 'L', 'Fragment
ID', and 'Fragment No.' fields are used together.
'L' Field
This field is used to indicate the last fragment of a larger packet.
It is only valid when the 'F' field has a '1' value. A '0' value for
the 'L' field indicates the last fragment of a larger packet while a
'1' value indicates an intermediate fragment of a larger packet. The
'F', 'L', 'Fragment ID', and 'Fragment No.' fields are used together.
Fragment ID Field
The Fragment ID identifies the larger packet that has been
fragmented. It is used to distinguish between fragments of different
large packets. This field is valid only when the 'F' field has a '1'
value. The 'F', 'L', 'Fragment ID', and 'Fragment No.' fields are
used together.
Fragment No. Field
The fragment number field identifies the sequence of fragments of a
larger packet. The value of the Fragment No. field is incremented
for each fragment of a larger packet so as to show the order of
fragments. This field is valid only when the 'F' field has a '1'
value. The 'F', 'L', 'Fragment ID', and 'Fragment No.' fields are
used together.
Length Field
This field specifies the length of the WiCoP payload following the
header.
4.2. WiCoP Control Packet
The WiCoP control header follows the WiCoP common header. It is
highlighted in Figure 5.
0 31
| 7 15 23 |
|-------|-------|-------|-------|-------|-------|-------|-------|
| |
+---------------+---------------+-------------------------------+
| Msg Type | Reserve | Seq Num |
+---------------+---------------+-------------------------------+
| Msg Element Length |
+-------------------------------+
Figure 5
The control packet adds four additional fields to the common header.
These are described below:
Msg Type Field
The message type field specifies the type of control message
transported in the packet. The list of control messages is presented
in Section 5.2.1.
Seq Num Field
The sequence number field is used to map WiCoP request and response
sequences. The initiator of a WiCoP request message increments the
Seq Num field for each new request message. The responder then uses
these values of the Seq Num fields in its corresponding response
messages.
Msg Element Length Field
This field specifies the length in bytes of the subsequent WiCoP
control message element.
4.2.1. WiCoP Control Messages
The list of WiCoP control messages is shown below:
Message Msg Type
------------------------------------------------------------
Capabilities 1
Capabilities Response 2
Connection 3
Connection Response 4
Configuration Request 5
Configuration Response 6
Configuration Data 7
Configuration Data Response 8
Configuration Trigger 9
Configuration Trigger Response 10
Feedback 11
Feedback Response 12
Reset 13
Reset Response 14
Firmware Download 15
Firmware Download Response 16
Terminal Addition 17
Terminal Addition Response 18
Terminal Deletion 19
Terminal Deletion Response 20
Key Configuration 21
Key Configuration Response 22
Notification 23
Notification Response 24
4.2.2. WiCoP Control Message Elements
WiCoP control messages each include a control message header followed
by one or more message elements. The message elements are shown in
the following table:
+-----------------+-----------+-------------------------------------+
| Message Element | Type | Description |
+-----------------+-----------+-------------------------------------+
| WTP-Info | 1 | Information regarding WTPs, such as |
| | | manufacturer ID, MAC address, etc. |
| | | |
| Cap-from-WTP | 2 | Quality-of-Service (QoS) abilities |
| | | (WME-Wireless Multimedia Extension) |
| | | and security abilities |
| | | (IEEE 802.11i) are included |
| | | |
| Conf-If-Data | 3 | Physical Layer (PHY) information for|
| | | each wireless interface |
| | | |
| Conf-WTP-Data | 4 | Information regarding logical |
| | | groups on a per-logical group basis |
| | | (e.g., per-virtual AP) |
| | | |
| Cap-to-WTP | 5 | Setup data sent to WTPs by an AC on |
| | | a per-logical group basis |
| | | |
| QoS-Value | 6 | QoS setup (access categories) |
| | | |
|Timer-Init-Value | 7 | Initial values of timers such as |
| | | aging, echo interval, etc. |
| | | |
| Terminal-Data | 8 | Information relevant to wireless |
| | | terminals - Basic Service Set |
| | | Identifier (BSSID), association ID, |
| | | etc. |
| | | |
| BSSID | 9 | BSSID, and terminal MAC address |
| | | |
| Encryption-Data | 10 | Details of the security framework - |
| | | cipher suit, operation mode, etc. |
| | | |
| EAP-Frame | 11 | Extensible Authentication Protocol |
| | | (EAP) frame |
| | | |
| Statistics | 12 | Various statistics information - |
| | | transmission attempts, Frame Check |
| | | Sequence (FCS) errors, etc. |
| | | |
| Interface-Error | 13 | Type of wireless interface failure |
| | | |
| FROM-Error | 14 | Flash ROM Error information |
| | | |
| QoS-Capability | 15 | Network congestion information |
| | | |
| TFTP-Data | 16 | Firmware-related details |
| | | |
| Result | 17 | Result of protocol operations - |
| | | success or failure |
| | | |
| OID | 18 | Simple Network Management Protocol |
| | | (SNMP) Object Identifiers (OIDs) |
| | | |
| GTK-Flag | 19 | Determines type of Group Temporal |
| | | Key (GTK) - new or existing |
+-----------------+-----------+-------------------------------------+
Each message element comprises a number of information items that are
detailed below. The length of each information item is specified in
bytes.
WTP-Info:
Information included in the WTP-Info message element is provided on a
per-WTP basis, i.e., each WTP exchanges one WTP-Info message element.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| Manufacturer | 8 | DisplayString | Manufacturer ID |
| ID | | | |
| | | | |
| MAC Address | 6 | PhyAddress | WTP MAC Address |
| | | | |
| Firmware | 8 | DisplayString | Firmware version of |
| Version | | | WTP |
| | | | |
| Start Time | 4 | TimeTicks | Starting time of WTP |
| | | | (UNIX Time) |
+--------------+----------+----------------+------------------------+
Cap-from-WTP:
Information included in the Cap-from-WTP message element is provided
on a per-WTP basis, i.e., each WTP exchanges one Cap-from-WTP message
element.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| 802.11e Cap | 2 | Integer | Length of 802.11e |
| Length | | | capabilities |
| | | | |
| 802.11e | Variable | OCTETString | 802.11e capabilities |
| Capabilities | | | of WTP. If WTP does |
| | | | not have such |
| | | | capabilities, this |
| | | | field is filled with |
| | | | '0' |
| | | | |
| 802.11i Cap | 2 | Integer | Length of 802.11i |
| Length | | | capabilities |
| | | | |
| 802.11i | Variable | OCTETString | 802.11i capabilities |
| Capabilities | | | of WTP. If WTP does |
| | | | not have such |
| | | | capabilities,this |
| | | | field is filled with |
| | | | '0' |
| | | | |
| AuthType | 2 | OCTETString | Type of authentication |
| | | | mechanism used between |
| | | | WTPs and the AC |
+--------------+----------+----------------+------------------------+
Conf-If-Data
The Conf-If-Data message element relates to the wireless interface.
A WTP with many interfaces will include corresponding numbers of
Conf-If-Data message elements within its control messages to the AC.
Conf-If-Data message elements are indexed by the If ID information
item.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| If ID | 1 | Integer | Denotes identification |
| | | | of a wireless |
| | | | interface |
| | | | |
| Current | 1 | Integer | Current Power Level |
| Power | | | ('1' = Max; '2' = 1/2; |
| | | | '3' = 1/4; '4' = 1/8 |
| | | | |
| Radio | 1 | Integer | Radio channel of |
| Channel | | | operation |
| | | | |
| 2Dot4Mode | 1 | Integer | Interface mode in |
| | | | 2.4GHz. ('1' = IEEE |
| | | | 802.11b; '2' = IEEE |
| | | | 802.11g; '3' = Both) |
+--------------+----------+----------------+------------------------+
Conf-WTP-Data
Configuration information is provided on the basis of logical groups
such as virtual APs. There are multiple Conf-WTP-Data message
elements to address the many logical groups within a WLAN managed by
WiCoP. Conf-WTP-Data message elements are indexed by the BSSID
information item.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| BSSID | 6 | OCTETString | BSSID |
| | | | |
| ESSID | 32 | OCTETString | Extended Service Set |
| | | | Identifier (ESSID) |
| | | | |
| BSSID - | 32 | OCTETString | Mapping for logical |
| TunnelID | | | groups across BSSID |
| | | | and WiCoP tunnels |
| | | | |
| Beacon | 1 | Integer | Time interval between |
| Period | | | Beacon transmissions |
| | | | |
| DTIM Period | 1 | Integer | Delivery Traffic |
| | | | Indication Message |
| | | | (DTIM) period of |
| | | | Beacon transmissions |
| | | | |
| AnyRejectFla | 1 | Integer | Flag indicating WTP |
| g | | | rejection of any Probe |
| | | | Request within any |
| | | | SSID - ('1' = |
| | | | Rejected; '2' = Not |
| | | | Rejected) |
| | | | |
| SSID Stealth | 1 | Integer | Flag indicating |
| Flag | | | inclusion of ESSID |
| | | | within Beacon Frames |
| | | | ('1' = ESSID included; |
| | | | '2' = ESSID not |
| | | | included) |
| | | | |
| Operation | 2 | Integer | Data rates supported |
| Rate Set | | | by WTP for terminal |
| | | | being added using a |
| | | | 12-bit format for 1.1, |
| | | | 2.2, 3.55, 4.6, 5.9, |
| | | | 6.11, 7.12, 8.18, |
| | | | 9.24, 10.36, 11.48, |
| | | | and 12.54 Mbps |
| | | | |
| Encryption | 1 | Integer | Encryption Type - |
| Type | | | （'1' = OFF; '2' |
| | | | = WEP40; '3' = WEP104; |
| | | | '4' = WEP128) |
| | | | |
| Encryption | 16 | OCTETString | Static Encryption Key |
| Key | | | |
+--------------+----------+----------------+------------------------+
Cap-to-WTP:
Capabilities information is provided on the basis of logical groups
such as virtual APs. So, there are multiple Cap-to-WTP message
elements to address the many logical groups within a WLAN managed by
WiCoP. Conf-to-WTP message elements are indexed by the BSSID
information item. If logical groups are created by other means,
their corresponding identifier is used as the index.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| BSSID | 6 | OCTETString | BSSID |
| | | | |
| 802.11e Cap | 2 | Integer | Length of 802.11e |
| Length | | | capabilities |
| | | | |
| 802.11e | Variable | OCTETString | 802.11e capabilities |
| Capabilities | | | of WTP. If WTP does |
| | | | not have such |
| | | | capabilities, this |
| | | | field is filled with |
| | | | '0' |
| | | | |
| 802.11i Cap | 2 | Integer | Length of 802.11i |
| Length | | | capabilities |
| | | | |
| 802.11i | Variable | OCTETString | 802.11i capabilities |
| Capabilities | | | of WTP. If WTP does |
| | | | not have such |
| | | | capabilities, this |
| | | | field is filled with |
| | | | '0' |
+--------------+----------+----------------+------------------------+
QoS-Value:
QoS parameters are assigned for each logical group to address their
respective individual conditions and requirements. QoS-Value message
elements are provided on a per-logical group basis. They are indexed
by the BSSID information item. If logical groups are created by
other means, their corresponding identifier is used as the index.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| BSSID | 6 | OCTETString | BSSID |
| | | | |
| WTP AC_BE | 2 | Integer | AC Parameters Record |
| | | | AC_BE in WTP |
| | | | |
| WTP AC_BK | 2 | Integer | AC Parameters Record |
| | | | AC_BK in WTP |
| | | | |
| WTP AC_VI | 2 | Integer | AC Parameters Record |
| | | | AC_VI in WTP |
| | | | |
| WTP AC_VO | 2 | Integer | AC Parameters Record |
| | | | AC_VO in WTP |
| | | | |
| TE AC_BE | 2 | Integer | AC Parameters Record |
| | | | AC_BE in terminals |
| | | | |
| TE AC_BK | 2 | Integer | AC Parameters Record |
| | | | AC_BK in terminals |
| | | | |
| TE AC_VI | 2 | Integer | AC Parameters Record |
| | | | AC_VI in terminals |
| | | | |
| TE AC_VO | 2 | Integer | AC Parameters Record |
| | | | AC_VO in terminals |
+--------------+----------+----------------+------------------------+
Timer-Init-Value:
WiCoP timers are used for the WTP as a whole. So, the Timer-Init-
Value message element is provided on a per-WTP basis.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| BSSID | 6 | OCTETString | BSSID |
| | | | |
| Response | 4 | Integer | Initial value of |
| Timer | | | Response Timer |
| | | | |
| Active | 4 | Integer | Initial value of |
| Presence | | | Active Presence Timer |
| Timer | | | |
| | | | |
| Feedback | 4 | Integer | Initial value of |
| Interval | | | Feedback Interval |
| Timer | | | Timer |
+--------------+----------+----------------+------------------------+
Terminal-Data:
The Terminal-Data message element is applicable for both Local MAC
and Split MAC WTP designs. In the case of Local MAC, Terminal-Data
is sent from WTPs to the AC. In the case of Split MAC, Terminal-Data
is sent from the AC to WTPs. So, the direction of usage depends on
the type of WTP at which wireless terminal operations are performed.
Some information items may be optional for use with specific WTP
designs.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| BSSID | 6 | PhyAddress | BSSID in which |
| | | | terminal is being |
| | | | added |
| | | | |
| MAC Address | 6 | PhyAddress | MAC address of |
| | | | terminal being added |
| | | | |
| Association | 2 | Integer | Association ID of |
| ID | | | terminal being added |
| | | | |
| Operation | 2 | Integer | Data rates supported |
| Rate Set | | | by WTP for terminal |
| | | | being added using a |
| | | | 12-bit format for 1.1, |
| | | | 2.2, 3.55, 4.6, 5.9, |
| | | | 6.11, 7.12, 8.18, |
| | | | 9.24, 10.36, 11.48, |
| | | | and 12.54 Mbps |
| | | | |
| Listen | 2 | Integer | Listen period |
| Period | | | |
+--------------+----------+----------------+------------------------+
BSSID:
The BSSID message element is used to identify logical groups within a
WLAN. WiCoP may be extended for other types of logical groups by
simply including additional message elements.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| BSSID | 6 | PhyAddress | BSSID in which |
| | | | terminal is being |
| | | | added |
| | | | |
| MAC Address | 6 | PhyAddress | MAC address of |
| | | | terminal being added |
+--------------+----------+----------------+------------------------+
Encryption-Data:
The Encryption-Data message element contains information relevant for
configuring security keys at WTPs. It is used in architectures in
which the authentication and encryption points are located in
distinct WLAN entities.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| MAC Address | 6 | PhyAddress | MAC address of |
| | | | terminal |
| | | | |
| Operation | 1 | Integer | Operational Mode ('1' |
| | | | = Set Key; '2' = |
| | | | Delete Key) |
| | | | |
| Key Index | 1 | Integer | Key Index - valid when |
| | | | Operational Mode = Set |
| | | | Key |
| | | | |
| Key Flag | 1 | Integer | Key Flag ('1' = |
| | | | Unicast Key or PTK; |
| | | | '2' = Broadcast Key or |
| | | | GTK) - valid only when |
| | | | Operational Mode = Set |
| | | | Key |
| | | | |
| Cipher Suit | 1 | Integer | Encryption Type ('1' = |
| | | | WEP40; '2' = WEP104; |
| | | | '3' = WEP128; '4' = |
| | | | TKIP; '5' = AES) - |
| | | | valid only when |
| | | | Operational Mode = Set |
| | | | Key |
| | | | |
| Key | 32 | OCTETString | Key body - valid only |
| | | | when Operational Mode |
| | | | = Set Key |
+--------------+----------+----------------+------------------------+
EAP-Frame:
The EAP-Frame message element is used to carry EAP frames used in the
configuration and management of the WLAN.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| MAC Address | 6 | PhyAddress | MAC address of |
| | | | terminal |
| | | | |
| EAP | Variable | OCTETString | EAP Frames |
+--------------+----------+----------------+------------------------+
Statistics:
Statistics information covers all aspects of WTPs. As such, this
message element is provided on a per-WTP basis. WiCoP messages
containing the Statistics message element simultaneously serve as
keepalive signals between WTPs and the AC.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| OutOctet | 4 | Counter 32 | Octet number of frame |
| | | | WTP transmits |
| | | | |
| Transmit | 4 | Counter 32 | Total number of frames |
| Count | | | transmitted by WTP |
| | | | |
| Successful | 4 | Counter 32 | Total number of ACKs |
| Transmit | | | received |
| Count | | | |
| | | | |
| ACK Failure | 4 | Counter 32 | Total number of failed |
| Count | | | ACKs |
| | | | |
| InOctets | 4 | Counter 32 | Octet number of frame |
| | | | WTP receives |
| | | | |
| Receive | 4 | Counter 32 | Total number of frames |
| Count | | | received by WTP |
| | | | |
| Receive | 4 | Counter 32 | Total number of |
| Discard | | | received frames that |
| | | | are discarded |
| | | | |
| Retransmissi | 4 | Counter 32 | Number of WTP |
| on Count | | | retransmission |
| | | | attempts" |
| | | | |
| Duplicate | 4 | Counter 32 | Number of duplicate |
| Receive | | | frames received by WTP |
| Count | | | |
| | | | |
| FCS Error | 4 | Counter32 | Number of frames |
| Receive | | | received with FCS |
| Count | | | errors |
| | | | |
| Unknown | 4 | Counter 32 | Number of unknown |
| Frame | | | protocol frames |
| Receive | | | received |
| Count | | | |
| | | | |
| Beacon | 4 | Counter 32 | Number of transmitted |
| Transmit | | | Beacon frames |
| Count | | | |
| | | | |
| Probe | 4 | Counter 32 | Number of transmitted |
| Transmit | | | Probe Response frames |
| Count | | | |
| | | | |
| Probe | 4 | Counter 32 | Number of received |
| Receive | | | Probe Response frames |
| Count | | | |
| | | | |
| Decrypt CRC | 4 | Counter 32 | Number of received |
| Error Count | | | frames that cannot |
| | | | decrypt |
+--------------+----------+----------------+------------------------+
Interface-Error:
This message element is used to exchange information on error
conditions related to the wireless interface.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| Interface | 1 | Integer | Interface ID |
| Index | | | |
| | | | |
| Error Type | 1 | Integer | Type of error ('1' = |
| | | | Unrecoverable; '2' = |
| | | | Recoverable) |
+--------------+----------+----------------+------------------------+
FROM-Error:
The FROM-Error message element is used to exchange information on
error conditions related to flash ROMs in WTPs or the AC.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| FROM Index | 1 | Integer | FROM ID |
| | | | |
| Error Type | 1 | Integer | Type of error ('1' = |
| | | | Unrecoverable; '2' = |
| | | | Recoverable) |
+--------------+----------+----------------+------------------------+
QoS Capability:
The QoS-Capability message element is used to exchange information
concerning the Enhanced Distributed Channel Access (EDCA) and HCF
Controlled Channel Access (HCCA) capabilities of WTPs.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| EDCA | 1 | Integer | EDCA Capability ('1' = |
| | | | Capable; '2' = Not |
| | | | capable) |
| | | | |
| HCCA | 1 | Integer | HCCA Capability ('1' = |
| | | | Capable; '2' = Not |
| | | | capable) |
+--------------+----------+----------------+------------------------+
TFTP-Data:
This message element is for firmware data from an AC to WTPs.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| TFTP Data | Variable | OCTETString | Details of Trivial File|
| | | | Transfer Protocol |
| | | | (TFTP) |
+--------------+----------+----------------+------------------------+
Result:
The Result message element is used in all WiCoP response messages to
indicate the status of WiCoP request messages.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| Result Code | 1 | Integer | '1' = OK; '2' = NG |
+--------------+----------+----------------+------------------------+
OID:
The OID message element is used for general configuration information
specified by OIDs.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| Length | 1 | Integer | Length of OID String |
| | | | and OID Value |
| | | | |
| OID String | Variable | OCTETString | Object Identifier that |
| | | | is assigned according |
| | | | to Basic Encoding |
| | | | Rules (BER) |
| | | | |
| Value | Variable | OCTETString | Value |
+--------------+----------+----------------+------------------------+
GTK-Flag:
The GTK-Flag message element is used to inform the WTP on the type of
GTK used and correspondingly how the KeyMIC is to be computed.
+--------------+----------+----------------+------------------------+
| Item | Length | Syntax | Description |
+--------------+----------+----------------+------------------------+
| GTK Flag | 1 | Integer | Determines the type of |
| | | | GTK ('1' = New; '2' = |
| | | | Existing) |
+--------------+----------+----------------+------------------------+
4.2.3. WiCoP Control Message Description
Message: Capabilities
Direction: WTP -> AC
Type: Request
Description: WTPs send a Capabilities message upon transitioning from
the Initialization state to the Capabilities Exchange state. The
message serves to discover and identify the controlling AC of the
WLAN and to provide it with identification and capabilities
information. In the IEEE 802.11 use-case, the Capabilities message
also specifies the WTP's IEEE 802.11e and IEEE 802.11i features.
TLV: The Capabilities message includes message elements of types 1
and 2.
+----------------+
| Capabilities |
+----------------+
| WTP-Info |
| |
| Cap-from-WTP |
+----------------+
Message: Capabilities Response
Direction: AC -> WTP
Type: Response
Description: This message is sent by an AC after examining the
compatibility of the WTP and its capabilities. The compatibility is
with respect to the MAC architecture that can be supported by the AC.
If the WTP is determined to be compatible, the Capabilities Response
message also contains information on the capabilities of the AC.
TLV: The Capabilities Response message includes message elements of
types 5 and 17. The Cap-to-WTP message elements are distinguished
based on BSSIDs to represent different logical groups.
+-----------------------+
| Capabilities Response |
+-----------------------+
| Cap-to-WTP 1 |
| |
| Cap-to-WTP ... |
| |
| Cap-to-WTP n |
| |
| Result |
+-----------------------+
Message: Connection
Direction: WTP -> AC
Type: Request
Description: The Connection message initiates the mutual security
association between an AC and WTPs. This message carries the first
message of the chosen security protocol. The specific security
mechanism for the authentication is out of scope of the WiCoP
specifications.
TLV: The Connection message includes message elements of type 2.
+---------------+
| Connection |
+---------------+
| Cap-from-WTP |
+---------------+
Message: Connection Response
Direction: AC -> WTP
Type: Response
Description: After completion of the security protocol exchange, this
message indicates the result of the WTP-AC security association. If
successful, it also represents the admission of the WTP into the
WLAN.
TLV: Type 17 message element is included.
+---------------------+
| Connection Response |
+---------------------+
| Result |
+---------------------+
Message: Configuration Request
Direction: WTP -> AC
Type: Request
Description: This message starts the Configuration state for the WTP.
It is a request for configuration information from the WTPs to the
AC.
Message: Configuration Response
Direction: AC -> WTP
Type: Response
Description: This is an acknowledgement for the Configuration Request
message.
TLV: Type 17 message element is included.
+------------------------+
| Configuration Response |
+------------------------+
| Result |
+------------------------+
Message: Configuration Data
Direction: AC -> WTP
Type: Request
Description: Configuration information including operational
parameters, QoS settings, and timer values is sent using the
Configuration Data message. This message is also used for
configuration updates in the Operation state of WiCoP.
TLV: This message includes message elements of types 3, 4, 5, 6, and
7. The Conf-WTP-Data and QoS-Value message elements are identified
by BSSIDs to denote logical groups, while the Conf-If-Data message
elements are identified by If-IDs to denote multiple wireless radios.
+---------------------+
| Configuration Data |
+---------------------+
| Conf-If-Data 1 |
| |
| Conf-If-Data ... |
| |
| Conf-If-Data n |
| |
| Conf-WTP-Data 1 |
| |
| Conf-WTP-Data ... |
| |
| Conf-WTP-Data n |
| |
| Cap-to-WTP 1 |
| |
| Cap-to-WTP ... |
| |
| Cap-to-WTP n |
| |
| QoS-Value 1 |
| |
| QoS-Value ... |
| |
| QoS-Value n |
| |
| Timer-Init-Value |
+---------------------+
Message: Configuration Data Response
Direction: WTP -> AC
Type: Response
Description: This is an acknowledgement for the Configuration Data
message.
TLV: Type 17 message element is included.
+-----------------------------+
| Configuration Data Response |
+-----------------------------+
| Result |
+-----------------------------+
Message: Configuration Trigger
Direction: AC -> WTP
Type: Request
Description: This message is used to trigger the activation of the
configuration information sent in earlier Configuration messages.
Message: Configuration Trigger Response
Direction: WTP -> AC
Type: Response
Description: This is an acknowledgement of the Configuration Trigger.
This response message is sent before activation of the configuration
information.
TLV: Message elements of type 17 are included.
+--------------------------------+
| Configuration Trigger Response |
+--------------------------------+
| Result |
+--------------------------------+
Message: Reset
Direction: AC -> WTP
Type: Request
Description: This message from the AC instructs the WTP to clear
registers and revert to initial conditions.
Message: Reset Response
Direction: WTP -> AC
Type: Response
Description: This is an acknowledgement for the Reset message to the
AC.
TLV: Message elements of type 17 are included.
+----------------+
| Reset Response |
+----------------+
| Result |
+----------------+
Message: Feedback
Direction: WTP <-> AC
Type: Request
Description:
WTP: The Feedback message is used to send regular statistics
information to the AC. It also serves as a keepalive
indicator used to update the Active Presence Timer
maintained by the AC.
AC: The Feedback message is used to determine the active state
of WTPs.
TLV: This message includes message elements of type 12.
+-------------+
| Feedback |
+-------------+
| Statistics |
+-------------+
Message: Feedback Response
Direction: WTP <-> AC
Type: Response
Description: This is an acknowledgement for Feedback messages.
TLV: Message elements of type 17 are included.
+-------------------+
| Feedback Response |
+-------------------+
| Result |
+-------------------+
Message: Firmware Download
Direction: AC -> WTP
Type: Request
Description: This message is used to instruct WTPs to update their
firmware. The message element contains information regarding the new
firmware.
TLV: Message elements of type 16 are included.
+-------------------+
| Firmware Download |
+-------------------+
| TFTP-Data |
+-------------------+
Message: Firmware Download Response
Direction: WTP -> AC
Type: Request Response
Description: This is an acknowledgement for the Firmware Download
message.
TLV: Message elements of type 17 are included.
+----------------------------+
| Firmware Download Response |
+----------------------------+
| Result |
+----------------------------+
Message: Notification
Direction: WTP <-> AC
Type: Request
Description: This message is used to indicate non-periodic events.
It may be sent by either WTPs or the AC. Notification messages
indicate failures, non-periodic changes, etc.
TLV: Message elements of types 13 and 14 are included.
+------------------+
| Notification |
+------------------+
| Interface-Error |
| |
| FROM-Error |
+------------------+
Message: Notification Response
Direction: WTP <-> AC
Type: Response
Description: This is an acknowledgement for the Notification message.
It may be followed by Configuration messages to rectify errors.
TLV: Message elements of type 17 are included.
+-----------------------+
| Notification Response |
+-----------------------+
| Result |
+-----------------------+
Message: Terminal Addition
Direction: WTP <-> AC
Type: Request
Description: This message may be sent from WTPs or the AC, depending
on the WTP type in consideration. In both cases, it is sent in
response to an IEEE 802.11 association frame.
For Split MAC WTPs, Terminal Addition is sent from the AC to the WTPs
and includes information on the wireless terminal relevant to the
WTP.
For Local MAC WTPs, Terminal Addition is sent from a WTP to the AC
and contains information on the wireless terminal relevant to the AC.
TLV: Message elements of type 8 are included.
+-------------------+
| Terminal Addition |
+-------------------+
| Terminal-Data |
+-------------------+
Message: Terminal Addition Response
Direction: WTP <-> AC
Type: Response
Description: This is an acknowledgement sent from either WTPs or the
AC, depending on the WTP type in consideration.
TLV: Message elements of type 17 are included.
+----------------------------+
| Terminal Addition Response |
+----------------------------+
| Result |
+----------------------------+
Message: Terminal Deletion
Direction: WTP <-> AC
Type: Request
Description: This message is sent in response to a disconnection of a
wireless terminal. It can be sent from WTPs or the AC. In both
cases, Terminal Deletion instructs the recipient to remove any state
information relating to the specific wireless terminal. The message
is sent in response to an IEEE 802.11 disassociation frame, IEEE
802.11 deauthentication frame, or due to the expiration of the Active
Presence Timer.
For Split MAC WTPs, Terminal Deletion is sent from the AC to the
WTPs.
For Local MAC WTPs, Terminal Deletion is sent from the WTPs to the
AC.
TLV: Message elements of type 9 are included.
+-------------------+
| Terminal Deletion |
+-------------------+
| BSSID |
+-------------------+
Message: Terminal Deletion Response
Direction: WTP <-> AC
Type: Response
Description: This is an acknowledgement sent from either WTPs or the
AC, depending on the WiCoP interface.
TLV: Message elements of type 17 are included.
+----------------------------+
| Terminal Addition Response |
+----------------------------+
| Result |
+----------------------------+
Message: Key Configuration
Direction: AC -> WTP
Type: Request
Description: This message is used when authentication and encryption
points are located in distinct WLAN entities. WiCoP uses it in cases
where 'M' = 0 and 'D' = 0 or where 'M' = 1 and 'D' = 1. It is used
to configure security key information from the AC to the WTPs.
TLV: The following message elements are included for Key
Configuration.
+-------------------+
| Key Configuration |
+-------------------+
| GTK-Flag |
| |
| Encryption-Data |
| |
| EAP-Frame |
+-------------------+
Message: Key Configuration Response
Direction: WTP -> AC
Type: Response
Description: This is an acknowledgement for the Key Configuration
message.
TLV: Message elements of type 17 are included.
+----------------------------+
| Key Configuration Response |
+----------------------------+
| Result |
+----------------------------+
4.3. WiCoP Data Packet
WiCoP data packets include the WiCoP common header followed by a
payload. Data packets are used to distinguish traffic from control
when both control and data paths are identical. Such a scenario
would involve data traffic of the WTPs traversing the AC. However,
given the diversity of large-scale WLAN deployments, there are
scenarios in which data and control paths are distinct. WiCoP can be
used in both cases.
The WiCoP data packet format is illustrated below in Figure 7,
together with the WiCoP common header.
0 31
| 7 15 23 |
|-------|-------|-------|-------|-------|-------|-------|-------|
| |
+---------------+-+-+-+-+-+-+-+-+-------------------------------+
| Version |M|D|C|R|E|F|L| | Reserve |
+---------------+-+-+-+-+-+-+-+-+-------------------------------+
| Fragment ID | Fragment No. | Length |
+---------------+---------------+-------------------------------+
| Payload |
+---------------------------------------------------------------+
Figure 7
4.4. WiCoP Timers
WiCoP uses a number of timers to determine WLAN status and maintain
system performance. Timers are maintained by all WiCoP entities.
4.4.1. Active Presence Timer
The Active Presence Timer is used by each WiCoP entity -- AC and WTPs
-- to verify the presence of each other. The absence of a reply to
the Feedback message within the expiration of the Active Presence
Timer indicates the corresponding entity is inactive. Contingency
operations such as reset are used in this case. The value of the
Active Presence Timer ranges from 10 to 300 seconds with a default
value of 30 seconds.
4.4.2. Feedback Interval
Feedback messages are periodic with the frequency defined by the
Feedback Interval. The interval is set during WTP configuration. It
has a value ranging from 1 to 100 seconds and a default value of 10
seconds.
The Feedback Interval timer sets the periodicity of WLAN system
audits. So with this timer, the WLAN controller receives regular
information on the state of the WLAN and all its WTPs.
4.4.3. Response Timer
This is a general-purpose timer used to limit the elapsed time
between transmission of a request message and receipt of a
corresponding response message. The value of this timer ranges from
1 to 3 seconds with a default value of 1 second.
4.4.4. Wireless Connectivity Timer
This timer triggers any changes in wireless connectivity. WiCoP uses
this timer to send Notification and other messages relating to
wireless conditions. It is also used to trigger the disconnection of
mobile terminals without disassociation. The value of the Wireless
Connectivity Timer ranges from 1 minute to 86,400 minutes with a
default value of 10 minutes.
5. WiCoP Processes
The processes of the Wireless LAN Control Protocol are described in
this section with respect to the operational state in which they
occur.
5.1. Initialization
The Initialization state represents the initial conditions of WiCoP
entities. WTPs and ACs in this state are powered on, run hardware
self-check tests, and reset network interfaces.
State transition: Initialization -> Capabilities Exchange
WTP: Automatically upon detecting an active network interface
AC: Upon receiving a Capabilities message from a WTP
5.2. Capabilities Exchange
The Capabilities Exchange state allows WTPs to first find an AC and
then to exchange capabilities information with it.
WiCoP is designed to control WLANs with both Local MAC and Split MAC
WTPs. The differences in their respective functional characteristics
are determined in this state.
The WTP first broadcasts a Capabilities message as soon as it
transitions from its Initialization state. The Capabilities message
serves to discover ACs and contains information on its identity and
capabilities.
The AC receiving the Capabilities message transitions from its
Initialization state. It examines compatibility with respect to the
WTP type, its capabilities, and responds with an appropriate
Capabilities Response message.
The WTP continues to send Capabilities messages at an interval
specified by the Response Timer until it receives a Capabilities
Response message from an AC.
The AC maintains a count of Capabilities messages received from a
given WTP, which it uses to ignore WTPs after a limit. This is to
ensure that rogue WTPs that are not compatible with the AC do not
repeatedly attempt connections. The limit of connection attempts is
3 within 60 seconds.
State transition: Capabilities Exchange -> Connection
WTP: Upon receiving a positive Capabilities Response message
from an AC
AC: Upon receiving a Connection Request message from a WTP
5.3. Connection
The Connection state involves establishing a security infrastructure
between WTPs and an AC.
The WTP sends a Connection message to trigger the authentication and
security mechanism, i.e., this message initiates an IPsec security
association.
The AC sends a positive Connection Response message after
establishment of the security association or a negative Connection
Response message if an error occurs. The AC also monitors the
receipt of WiCoP control messages to prevent replay attacks.
The security association between an AC and WTPs covers mutual
authentication and also protection for integrity, confidentiality,
and modification protection for subsequent traffic exchanges.
In order to avoid forceful disconnections of legitimate WTPs after a
successful Connection, the AC ignores Capabilities messages received
with a previously registered WTP identification.
State transition: Connection -> Configuration
WTP: Upon successful establishment of security infrastructure
marked by sending of a Configuration Request message
AC: Upon receiving Configuration Request message from a WTP
after successful establishment of security infrastructure
State transition: Connection -> Capabilities Exchange
WTP: Upon expiry of the WTP Response Timer before receipt of a
positive Connection Response message from an AC or upon
receipt of a negative Connection Response message
AC: Upon expiry of AC Response Timer before receipt of
Configuration Request message from WTP
5.4. Configuration
The Configuration state is one in which relatively long-term
operational parameters, such as those for identification and logical
groups, are exchanged. These parameters are based on previously
exchanged capabilities information and network policies.
The WTP sends a Configuration Request message to the AC.
The AC first acknowledges the WTP's Configuration Request, after
which it sends appropriate configuration information in subsequent
Configuration Data messages. WiCoP includes MIB objectives as
message elements in some Configuration Data messages so as to
simplify WTP configuration.
The WTP acknowledges Configuration Data messages individually or en
bloc with Configuration Data Response messages. The Response Timer
is maintained at both WTP and AC to track the exchanges.
The AC also establishes relevant processing schedules according to
the WTP's architecture design. For example, for Split MAC WTPs, the
AC arranges its processing schedule to parse IEEE 802.11 control and
management messages while for Local MAC WTPs, the AC arranges
schedules processing so as to bypass parsing of IEEE 802.11
management messages.
The AC sends a Configure Trigger message after sending all relevant
configuration information to the WTP.
The WTP acknowledges a Configure Trigger message with a Configure
Trigger Response message before activating the previously exchanged
configuration parameters.
In order to avoid forceful disconnections of legitimate WTPs after
successful Configuration, the AC ignores Capabilities messages
received with a previously registered WTP identification.
State transition: Configuration -> Operation
WTP: After receiving final Configuration Data message from the
AC marked by receipt of a Configure Trigger message from
the AC
AC: Upon receiving acknowledgement for Configure Trigger
message marked by receipt of a Configure Trigger Response
message from WTP
State transition: Configuration -> Capabilities Exchange
WTP: Upon expiry of the WTP Response Timer before receipt of a
Configure Trigger message from the AC
AC: Upon expiry of the AC Response Timer before receipt of
Configure Data Response message or Configure Trigger
Response message
The following describes major configuration aspects of WiCoP.
5.4.1. Logical Groups
Configuration Data messages are used to establish logical groups in
the WLAN and also to separate traffic among them. The logical groups
are established based on network administrative policies and other
external considerations. In the IEEE 802.11 use-case, logical groups
are established with BSSID-based virtual APs and are separated over
the WiCoP interface using tunnels.
The AC assigns particular BSSIDs of the WTP to specific VLAN tunnels.
This assignment is specified to the WTP using the BSSID-TunnelID
parameter in the Configuration Data message. The logical group
mapping therefore works across the wireless and WiCoP interfaces.
The WTP then identifies the specified BSSID and VLAN tunnel as
corresponding to one logical group. It creates internal state such
that traffic belonging to the logical group is kept distinct from
that of other logical groups.
The AC and WTP also use distinct VLAN tunnels for data and control
traffic. The 'C' field in the WiCoP header is used to distinguish
and assign WiCoP packets to particular data and control VLAN tunnels.
5.4.2. Resource Control
The AC sends QoS information using QoS-Value message elements in
Configuration Data messages. The QoS-Value message element contains
values for EDCA and HCCA parameters. This information is specified
for each of the logical groups. In the IEEE 802.11 use-case, QoS-
Value message elements are specified for each BSSID.
The WTP configures QoS parameters locally and also forwards relevant
settings to wireless terminals in appropriate encapsulations. In the
IEEE 802.11 use-case, QoS parameters are sent to wireless terminals
in corresponding Beacon or Probe Response frames.
5.5. Operation
This is the active operation state of the WLAN in which short-term
dynamics are examined.
The WTP begins operations according to the operational parameters
exchanged in the previous Configuration state.
The AC monitors WTPs according to network administrative policies and
configurations.
In order to avoid forceful disconnections of legitimate WTPs after
successful Operation setup, the AC ignores Capabilities messages
received with a previously registered WTP identification.
State transition: Operation -> Capabilities Exchange
WTP: Upon expiry of the WTP Active Presence Timer before receipt
of a Feedback Response message from the AC
AC: Upon expiry of the AC Active Presence Timer before receipt
of a Feedback message from the WTP
State transition: Operation -> Initialization
WTP: Upon receipt of a Reset message from an AC
AC: Upon receipt of a Reset Response message from a WTP
The following describes major operation aspects of WiCoP.
5.5.1. Updates
The dynamic nature of WLAN systems requires regular updates to
network operations.
The AC sends additional configuration information in the
Configuration Data messages. This is applicable to establishment of
new logical groups, changes to existing logical groups, changes in
QoS settings, etc. Configuration information is followed by a
Configure Trigger message.
The WTP sends a Configure Trigger Response before activating the
additional configuration information.
Configuration updates can be used to clear statistics information by
reflecting initial values.
An extreme case of a configuration update involves use of the Reset
message from the AC, which instructs the WTP to revert to initial
conditions. The WTP replies with a Reset Response message before
reverting to its initial state.
5.5.2. Feedback and Statistics
The Operation state also sees regular feedback being sent by WTPs to
the AC.
The WTP sends Feedback messages to indicate various statistics and
congestion condition information. Feedback also includes information
on the state of the WTP and wireless medium such as queue levels and
channel interference. Feedback messages are sent with a frequency
defined by the Feedback Interval. In addition to statistics, the
Feedback message also serves as a WTP keepalive indicator to the AC.
Feedback messages combine statistics information together with WTP
status information.
The AC monitors Feedback messages for their statistics value and
implicit indication of WTP activity. The AC also tracks the state of
congestion at wireless terminals and WTPs. This information enables
the AC to adapt its downstream transmissions, such as scheduling
transmission away from congested WTPs, so as to relieve congestion.
The AC additionally uses the Feedback message to randomly determine
the active state of WTPs. An active WTP replies with a corresponding
Feedback Response message.
5.5.3. Non-Periodic Events
The WTP and AC use the Notification message for non-periodic events.
They send Notification messages to indicate error conditions or
drastic changes in congestion state.
The recipient of the Notification message acknowledges with a
Notification Response message. The response may contain information
on rectifying the error or may simply be an acknowledgement of the
Notification.
5.5.4. Firmware Trigger
The AC sends a Firmware Download message to update firmware at WTPs.
The Firmware Download message contains TFTP information, which the
WTP uses to refresh its firmware. This is used when a new version of
firmware is available for the WTPs.
The WTP acknowledges new firmware with a Firmware Download Response
message after which it is activated.
5.5.5. Wireless Terminal Management
The Operation state of WiCoP also involves configuration of WTPs and
the AC with wireless terminal-specific information.
Here the Terminal Addition message is used in response to a new
wireless terminal entering the WLAN. This message may be sent by
either the WTPs or the AC, depending on the WiCoP interface being
used. The recipient of this message replies with the Terminal
Addition Response message.
The Terminal Deletion message is used when a wireless terminal leaves
the WLAN. This is used to delete state information that was
maintained by either the WTPs or the AC. It is acknowledged with the
Terminal Deletion Response message.
Figure 8 below illustrates the exchange of Terminal Addition and
Terminal Deletion messages for both Local-MAC- and Split-MAC-based
WiCoP interfaces.
Here the WiCoP Terminal Addition message is triggered as a response
to an IEEE 802.11 Association message. In the case of Local MAC
architecture, the WTP sends the message to the AC. However, in the
Split MAC architecture, Terminal Addition is sent from an AC to the
WTP.
+----------+ +---------------+ +------+
| Terminal | | Local MAC WTP | | AC |
+----------+ +---------------+ +------+
| | |
| | |
| IEEE 802.11 Association | WiCoP |
|------------------------->| Terminal Addition |
| |===========================>|
| | |
| | WiCoP Terminal |
| |<===========================|
| IEEE 802.11 Association | Addition Response |
|<-------------------------| |
| Response | |
| | |
| | |
| |
| |
| |
| +---------------+ |
| | Split MAC WTP | |
| +---------------+ |
| | |
| | |
| IEEE 802.11 Association | |
|------------------------->| |
| | IEEE 802.11 Association |
| |===========================>|
| | (Over WiCoP) |
| | |
| | |
| | WiCoP |
| | Terminal Addition |
| |<===========================|
| | |
| | |
| | WiCoP Terminal |
| |===========================>|
| | Addition Response |
| | |
| | |
| | IEEE 802.11 Association |
| |<===========================|
| | Response (Over WiCoP) |
| IEEE 802.11 Association | |
|<-------------------------| |
| Response | |
Figure 8
5.5.6. Key Configuration
One of the differences between Split MAC and Local MAC WTPs is the
location of the over-the-air encryption. Some Split MAC and Local
MAC WTPs perform encryption locally while others leave it to the AC.
WiCoP accommodates these differences by enabling security key
configuration in those cases where encryption is performed at the
WTP. The encryption setup process is therefore contingent on the
WiCoP protocol interface.
When dynamic WEP is used, the WiCoP Key Configuration message is used
to notify WTPs of encryption keys for each associated wireless
terminal. Here, the EAP over LAN (EAPoL) Key frame is encapsulated
in the Key Configuration message and sent to a WTP. Upon receiving
the Key Configuration message, the WTP sets the encryption key in its
local security table, decapsulates the EAPOL Key frame and forwards
it to the wireless terminal. This is illustrated in Figure 9.
+----------+ +-----+ +------+
| Terminal | | WTP | | AC |
+----------+ +-----+ +------+
| | |
| 802.1x Authentication |
|<=====================================================>|
| | |
| | |
PMK | PMK
| | |
| | |
|<-------------------------|<===========================|
| EAPoL Packet | WiCoP Control Packet |
| | (Key Configuration) |
| | | +-----------------------+
| | \|- Encryption-Data |
| | | Unicast-Key |
Set Receive |- EAP-Frame |
Unicast-Key Unicast-Key | Key Signature |
| | +-----------------------+
| | |
| |===========================>|
| | WiCoP Control Packet |
| | (Key Configuration |
| | Response ) |
| | |
| | |
| | |
| | |
|<-------------------------|<===========================|
| EAPoL Packet | WiCoP Control Packet |
| | (Key Configuration) |
| | | +-----------------------+
| | \|- Encryption-Data |
| | | Broadcast-Key |
Set Receive |- EAP-Frame |
Broadcast-Key Broadcast-Key | Key Signature |
| | | Broadcast Key |
| | +-----------------------+
| | |
| |===========================>|
| | WiCoP Control Packet |
| | (Key Configuration |
| | Response ) |
Figure 9
When WPA or IEEE 802.11i is used in WLAN architectures in which the
authenticator is located at the AC and encryption points at WTPs, the
exchanges of the 4-way handshake are managed distinctly. This is
because the AC is no longer in a position to calculate the KeyMIC as
it is not aware of the KeyRSC sequence counter. So here, a WiCoP Key
Configuration message is used to transport the 3rd message of the
4-way handshake -- containing the EAPoL-Key -- with unassigned KeyRSC
and KeyMIC fields. When the WTP receives the WiCoP Key Configuration
message, it first assigns the sequence number value to the KeyRSC
field. Then, the WTP calculates the KeyMIC value using the PTK and
KeyRSC. So, the WiCoP Key Configuration message allows the KeyMIC to
be calculated at the WTPs instead of the AC. The GTK-Flag message
element is used to determine how the KeyMIC is calculated -- in case
of a new GTK, KeyMIC is computed with a KeyRSC value of 0 and in case
of an existing GTK, KeyMIC is computed with a KeyRSC value
corresponding to the actual counter.
Figure 10 illustrates this case where the WiCoP common header is
either 'M' = 0 and 'D' = 0 or 'M' = 1 and 'D' = 1.
+----------+ +-----+ +------+
| Terminal | | WTP | | AC |
+----------+ +-----+ +------+
| | |
| 802.1x Authentication |
|<=====================================================>|
| | |
PMK | PMK
| | |
Generate | Generate
SNonce | ANonce
| | |
| | |
| Message 1 |
|<-------------------------|<---------------------------|
| EAPoL Packet | WiCoP Data Packet |
Receive | |
ANonce | |
Generate | |
PTK | |
| | |
| Message 2 |
|------------------------->|--------------------------->|
| EAPoL Packet | WiCoP Data Pakcet |
| | Receive
| | SNonce
| | |
| | Generate
| | PTK
| | GTK
| Message 3 |
|<-------------------------|<===========================|
| EAPoL Packet | WiCoP Control Packet |
| | (Key Configuration) |
| | | +-----------------------+
| | \|- GTK-Flag |
Receive Receive |- Encryption-Data(PTK) |
GTK PTK |- Encryption-Data(GTK) |
| GTK |- EAP-Frame |
| | +-----------------------+
| | |
| | |
| | |
| Message 4 |
|------------------------->|--------------------------->|
| EAPoL Packet | WiCoP Data Pakcet |
| | |
Figure 10
The 1st, 2nd, and 4th messages of the 4-way handshake are transported
in WiCoP data packets that are assigned priorities similar to that of
WiCoP control packets.
Similarly, for the group key handshake in WPA and IEEE 802.11i, the
1st message of the handshake is transported using the WiCoP Key
Configuration message with unassigned KeyRSC. The WTP again assigns
the sequence number value to the KeyRSC and then calculates the
KeyMIC. The 2nd message of the handshake however is transported in
WiCoP data packets with priorities similar to that of WiCoP control
packets. This is illustrated in Figure 11.
+----------+ +-----+ +------+
| Terminal | | WTP | | AC |
+----------+ +-----+ +------+
| | |
| Message 1 |
|<-------------------------|<===========================|
| EAPoL Packet | WiCoP Control Packet |
| | (Key Configuration) |
| | | +-----------------------+
| | \|- GTK-Flag |
Receive Receive |- Encryption-Data(GTK) |
GTK GTK |- EAP-Frame |
| | +-----------------------+
| | |
| | |
| | |
| | |
| Message 2 |
|------------------------->|--------------------------->|
| EAPoL Packet | WiCoP Data Pakcet |
| | |
Figure 11
The Key Configuration Response message is used by the WTP to notify
the AC of the encryption setup process.
6. WiCoP Performance
WiCoP is an efficient protocol. This section illustrates various
examples of its efficiency.
6.1. Operational Efficiency
The fact that WiCoP requires a single operation to distinguish and
manage WTPs of different designs makes it operationally efficient.
Because WiCoP assigns dedicated classification bits in the common
header, an AC needs to parse incoming packets only once to determine
the particular manner in which it is to be processed. Without the
dedicated classifications in the common header, an AC would have to
perform a lookup after parsing every incoming packet, which would
result in delaying processing. The scale and sensitivity of large-
scale deployments require that WLAN control protocols be efficient in
operation.
6.2. Semantic Efficiency
In certain cases, WiCoP combines utilities in a single operation.
One particular case is that of statistics and activity feedback.
Here, WTPs regularly send a single Feedback message containing
statistics and other state information, which also acts as an
implicit keepalive mechanism. This helps to reduce the number of
message exchanges and also simplifies protocol implementation.
Similarly, the Capabilities messages serve the purpose of finding ACs
as well as informing them of WTP capabilities and design.
7. Summary and Conclusion
The Wireless LAN Control Protocol presents a solution for managing
large-scale WLANs with diverse elements. It addresses the challenges
presented in the CAPWAP Problem Statement [RFC3990] and realizes the
requirements of the CAPWAP Objectives [RFC4564].
WiCoP enables integral control of Split MAC and Local MAC WTPs by
defining appropriate differentiators within the protocol message
exchanges and processes. It addresses architecture designs in which
the authenticator and encryption points are located on distinct
entities. In doing so, WiCoP realizes the interoperability objective
and its benefits.
WiCoP also addresses shared WLAN deployments by configuring and
managing WTPs on a logical group basis. It is further provisioned to
separate control and data traffic within WLANs. So, the protocol
addresses the objectives of logical groups and traffic separation.
Overall, the specifications presented in this document allow for an
effective WLAN control and provisioning protocol.
8. Security Considerations
Illegitimate WTPs and ACs pose a significant threat to WLAN security.
This can be mitigated by requiring all WiCoP entities to be mutually
authenticated before initiating critical protocol exchanges. WiCoP
includes a trigger for a suitable authentication mechanism. This is
to accommodate a different security mechanism that may be used
between WTPs and the AC, depending on the nature of the deployment.
In extension to mutual authentication, the subsequent exchange of
protocol information between WTPs and the AC need to be protected.
The exchanges have to be protected against alterations of any sort
and Denial-of-Service (DoS) attacks. Also, the information should
not be accessible to any third party. Encryption of protocol
exchanges is therefore necessary. WiCoP includes appropriate
procedures to select and establish a security association between
WTPs and the AC in the Connection state.
Architecture designs in which authentication is performed at the AC
and encryption at the WTPs can be exposed to the threat of replay
attacks. Since the AC will not be aware of the exact value of the
sequence counter, it will not make the corresponding assignment
within the 4-way handshake. This leaves the wireless terminal to
accept all incoming frames, including illegitimate frames, as it
cannot verify the sequence counter value. Such a threat needs to
protected against by allowing the WTP to assign the correct value of
the sequence counter. WiCoP accomplishes this by sending the 3rd
message of the 4-way handshake within a control message to the WTP,
which then updates the sequence counter field before forwarding it to
the wireless terminals.
Another issue to consider is that of rogue WTPs using identifiers
similar to that of legitimate WTPs. In such instances, a rogue WTP
can send a Capabilities message to the AC, thereby causing
disconnection of the existing legitimate WTP of the same identifier.
It is important for the AC to ignore Capabilities messages received
with existing identifiers.
9. Informative References
[RFC4118] Yang, L., Zerfos, P., and E. Sadot, "Architecture Taxonomy
for Control and Provisioning of Wireless Access Points
(CAPWAP)", RFC 4118, June 2005.
[RFC4564] Govindan, S., Ed., Cheng, H., Yao, ZH., Zhou, WH., and L.
Yang, "Objectives for Control and Provisioning of Wireless
Access Points (CAPWAP)", RFC 4564, July 2006.
[RFC3990] O'Hara, B., Calhoun, P., and J. Kempf, "Configuration and
Provisioning for Wireless Access Points (CAPWAP) Problem
Statement", RFC 3990, February 2005.
Authors' Addresses
Satoshi Iino
Panasonic Mobile Communications
600, Saedo-cho
Tsuzuki-ku
Yokohama 224 8539
Japan
Phone: +81 45 938 3789
EMail: iino.satoshi@jp.panasonic.com
Saravanan Govindan
Panasonic Singapore Laboratories
Block 1022, Tai Seng Industrial Estate
#06-3530, Tai Seng Avenue
Singapore 534 415
Singapore
Phone: +65 6550 5441
EMail: saravanan.govindan@sg.panasonic.com
Mikihito Sugiura
Panasonic Mobile Communications
600, Saedo-cho
Tsuzuki-ku
Yokohama 224 8539
Japan
Phone: +81 45 938 3789
EMail: sugiura.mikihito@jp.panasonic.com
Hong Cheng
Panasonic Singapore Laboratories
Block 1022, Tai Seng Industrial Estate
#06-3530, Tai Seng Avenue
Singapore 534 415
Singapore
Phone: +65 6550 5447
EMail: hong.cheng@sg.panasonic.com