| Rfc | 3048 |
|---|
| Title | Reliable Multicast Transport Building Blocks for One-to-Many
Bulk-Data Transfer |
|---|
| Author | B. Whetten, L. Vicisano, R. Kermode, M. Handley,
S. Floyd, M. Luby |
|---|
| Date | January 2001 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | INFORMATIONAL |
|---|
|
Network Working Group B. Whetten
Request for Comments: 3048 Talarian
Category: Informational L. Vicisano
Cisco
R. Kermode
Motorola
M. Handley
ACIRI 9
S. Floyd
ACIRI
M. Luby
Digital Fountain
January 2001
Reliable Multicast Transport Building Blocks for One-to-Many
Bulk-Data Transfer
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
This document describes a framework for the standardization of bulk-
data reliable multicast transport. It builds upon the experience
gained during the deployment of several classes of contemporary
reliable multicast transport, and attempts to pull out the
commonalities between these classes of protocols into a number of
building blocks. To that end, this document recommends that certain
components that are common to multiple protocol classes be
standardized as "building blocks". The remaining parts of the
protocols, consisting of highly protocol specific, tightly
intertwined functions, shall be designated as "protocol cores".
Thus, each protocol can then be constructed by merging a "protocol
core" with a number of "building blocks" which can be re-used across
multiple protocols.
Table of Contents
1 Introduction .................................................. 2
1.1 Protocol Families ........................................... 5
2 Building Blocks Rationale ..................................... 6
2.1 Building Blocks Advantages .................................. 6
2.2 Building Block Risks ........................................ 7
2.3 Building Block Requirements ................................. 8
3 Protocol Components ........................................... 8
3.1 Sub-Components Definition ................................... 9
4 Building Block Recommendations ................................ 12
4.1 NACK-based Reliability ...................................... 13
4.2 FEC coding .................................................. 13
4.3 Congestion Control .......................................... 13
4.4 Generic Router Support ...................................... 14
4.5 Tree Configuration .......................................... 14
4.6 Data Security ............................................... 15
4.7 Common Headers .............................................. 15
4.8 Protocol Cores .............................................. 15
5 Security ...................................................... 15
6 IANA Considerations ........................................... 15
7 Conclusions ................................................... 16
8 Acknowledgements .............................................. 16
9 References .................................................... 16
10 Authors' Addresses ........................................... 19
11 Full Copyright Statement ..................................... 20
1. Introduction
RFC 2357 lays out the requirements for reliable multicast protocols
that are to be considered for standardization by the IETF. They
include:
o Congestion Control. The protocol must be safe to deploy in the
widespread Internet. Specifically, it must adhere to three
mandates: a) it must achieve good throughput (i.e., it must not
consistently overload links with excess data or repair traffic),
b) it must achieve good link utilization, and c) it must not
starve competing flows.
o Scalability. The protocol should be able to work under a variety
of conditions that include multiple network topologies, link
speeds, and the receiver set size. It is more important to have a
good understanding of how and when a protocol breaks than when it
works.
o Security. The protocol must be analyzed to show what is necessary
to allow it to cope with security and privacy issues. This
includes understanding the role of the protocol in data
confidentiality and sender authentication, as well as how the
protocol will provide defenses against denial of service attacks.
These requirements are primarily directed towards making sure that
any standards will be safe for widespread Internet deployment. The
advancing maturity of current work on reliable multicast congestion
control (RMCC) [HFW99] in the IRTF Reliable Multicast Research Group
(RMRG) has been one of the events that has allowed the IETF to
charter the RMT working group. RMCC only addresses a subset of the
design space for reliable multicast. Fortuitously, the requirements
it addresses are also the most pressing application and market
requirements.
A protocol's ability to meet the requirements of congestion control,
scalability, and security is affected by a number of secondary
requirements that are described in a separate document [RFC2887]. In
summary, these are:
o Ordering Guarantees. A protocol must offer at least one of either
source ordered or unordered delivery guarantees. Support for
total ordering across multiple senders is not recommended, as it
makes it more difficult to scale the protocol, and can more easily
be implemented at a higher level.
o Receiver Scalability. A protocol should be able to support a
"large" number of simultaneous receivers per transport group. A
typical receiver set could be on the order of at least 1,000 -
10,000 simultaneous receivers per group, or could even eventually
scale up to millions of receivers in the large Internet.
o Real-Time Feedback. Some versions of RMCC may require soft real-
time feedback, so a protocol may provide some means for this
information to be measured and returned to the sender. While this
does not require that a protocol deliver data in soft real-time,
it is an important application requirement that can be provided
easily given real-time feedback.
o Delivery Guarantees. In many applications, a logically defined
unit or units of data is to be delivered to multiple clients,
e.g., a file or a set of files, a software package, a stock quote
or package of stock quotes, an event notification, a set of
slides, a frame or block from a video. An application data unit
is defined to be a logically separable unit of data that is useful
to the application. In some cases, an application data unit may
be short enough to fit into a single packet (e.g., an event
notification or a stock quote), whereas in other cases an
application data unit may be much longer than a packet (e.g., a
software package). A protocol must provide good throughput of
application data units to receivers. This means that most data
that is delivered to receivers is useful in recovering the
application data unit that they are trying to receive. A protocol
may optionally provide delivery confirmation, i.e., a mechanism
for receivers to inform the sender when data has been delivered.
There are two types of confirmation, at the application data unit
level and at the packet level. Application data unit confirmation
is useful at the application level, e.g., to inform the
application about receiver progress and to decide when to stop
sending packets about a particular application data unit. Packet
confirmation is useful at the transport level, e.g., to inform the
transport level when it can release buffer space being used for
storing packets for which delivery has been confirmed. Packet
level confirmation may also aid in application data unit
confirmation.
o Network Topologies. A protocol must not break the network when
deployed in the full Internet. However, we recognize that
intranets will be where the first wave of deployments happen, and
so are also very important to support. Thus, support for
satellite networks (including those with terrestrial return paths
or no return paths at all) is encouraged, but not required.
o Group Membership. The group membership algorithms must be
scalable. Membership can be anonymous (where the sender does not
know the list of receivers), or fully distributed (where the
sender receives a count of the number of receivers, and optionally
a list of failures).
o Example Applications. Some of the applications that a RM protocol
could be designed to support include multimedia broadcasts, real
time financial market data distribution, multicast file transfer,
and server replication.
In the rest of this document the following terms will be used with a
specific connotation: "protocol family", "protocol component",
"building block", "protocol core", and "protocol instantiation". A
"protocol family" is a broad class of RM protocols which share a
common characteristic. In our classification, this characteristic is
the mechanism used to achieve reliability. A "protocol component" is
a logical part of the protocol that addresses a particular
functionality. A "building block" is a constituent of a protocol
that implements one, more than one or a part of a component. A
"protocol core" is the set of functionality required for the
instantiation of a complete protocol, that is not specified by any
building block. Finally a "protocol instantiation" is an actual RM
protocol defined in term of building blocks and a protocol core.
1.1. Protocol Families
The design-space document [RFC2887] also provides a taxonomy of the
most popular approaches that have been proposed over the last ten
years. After congestion control, the primary challenge has been that
of meeting the requirement for ensuring good throughput in a way that
scales to a large number of receivers. For protocols that include a
back-channel for recovery of lost packets, the ability to take
advantage of support of elements in the network has been found to be
very beneficial for supporting good throughput for a large numbers of
receivers. Other protocols have found it very beneficial to transmit
coded data to achieve good throughput for large numbers of receivers.
This taxonomy breaks proposed protocols into four families. Some
protocols in the family provide packet level delivery confirmation
that may be useful to the transport level. All protocols in all
families can be supplemented with higher level protocols that provide
delivery confirmation of application data units.
1 NACK only. Protocols such as SRM [FJM95] and MDP2 [MA99] attempt
to limit traffic by only using NACKs for requesting packet
retransmission. They do not require network infrastructure.
2 Tree based ACK. Protocols such as RMTP [LP96, PSLM97], RMTP-II
[WBPM98] and TRAM [KCW98], use positive acknowledgments (ACKs).
ACK based protocols reduce the need for supplementary protocols
that provide delivery confirmation, as the ACKS can be used for
this purpose. In order to avoid ACK implosion in scaled up
deployments, the protocol can use servers placed in the network.
3 Asynchronous Layered Coding (ALC). These protocols (examples
include [RV97] and [BLMR98]) use sender-based Forward Error
Correction (FEC) methods with no feedback from receivers or the
network to ensure good throughput. These protocols also used
sender-based layered multicast and receiver-driven protocols to
join and leave these layers with no feedback to the sender to
achieve scalable congestion control.
4 Router assist. Like SRM, protocols such as PGM [FLST98] and
[LG97] also use negative acknowledgments for packet recovery.
These protocols take advantage of new router software to do
constrained negative acknowledgments and retransmissions. Router
assist protocols can also provide other functionality more
efficiently than end to end protocols. For example, [LVS99] shows
how router assist can provide fine grained congestion control for
ALC protocols. Router assist protocols can be designed to
complement all protocol families described above.
Note that the distinction in protocol families in not necessarily
precise and mutually exclusive. Actual protocols may use a
combination of the mechanisms belonging to different classes. For
example, hybrid NACK/ACK based protocols (such as [WBPM98]) are
possible. Other examples are protocols belonging to class 1 through
3 that take advantage of router support.
2. Building Blocks Rationale
As specified in RFC 2357 [MRBP98], no single reliable multicast
protocol will likely meet the needs of all applications. Therefore,
the IETF expects to standardize a number of protocols that are
tailored to application and network specific needs. This document
concentrates on the requirements for "one-to-many bulk-data
transfer", but in the future, additional protocols and building-
blocks are expected that will address the needs of other types of
applications, including "many-to- many" applications. Note that
bulk-data transfer does not refer to the timeliness of the data,
rather it states that there is a large amount of data to be
transferred in a session. The scope and approach taken for the
development of protocols for these additional scenarios will depend
upon large part on the success of the "building-block" approach put
forward in this document.
2.1. Building Blocks Advantages
Building a large piece of software out of smaller modular components
is a well understood technique of software engineering. Some of the
advantages that can come from this include:
o Specification Reuse. Modules can be used in multiple protocols,
which reduces the amount of development time required.
o Reduced Complexity. To the extent that each module can be easily
defined with a simple API, breaking a large protocol in to smaller
pieces typically reduces the total complexity of the system.
o Reduced Verification and Debugging Time. Reduced complexity
results in reduced time to debug the modules. It is also usually
faster to verify a set of smaller modules than a single larger
module.
o Easier Future Upgrades. There is still ongoing research in
reliable multicast, and we expect the state of the art to continue
to evolve. Building protocols with smaller modules allows them to
be more easily upgraded to reflect future research.
o Common Diagnostics. To the extent that multiple protocols share
common packet headers, packet analyzers and other diagnostic tools
can be built which work with multiple protocols.
o Reduces Effort for New Protocols. As new application requirements
drive the need for new standards, some existing modules may be
reused in these protocols.
o Parallelism of Development. If the APIs are defined clearly, the
development of each module can proceed in parallel.
2.2. Building Block Risks
Like most software specification, this technique of breaking down a
protocol in to smaller components also brings tradeoffs. After a
certain point, the disadvantages outweigh the advantages, and it is
not worthwhile to further subdivide a problem. These risks include:
o Delaying Development. Defining the API for how each two modules
inter-operate takes time and effort. As the number of modules
increases, the number of APIs can increase at more than a linear
rate. The more tightly coupled and complex a component is, the
more difficult it is to define a simple API, and the less
opportunity there is for reuse. In particular, the problem of how
to build and standardize fine grained building blocks for a
transport protocol is a difficult one, and in some cases requires
fundamental research.
o Increased Complexity. If there are too many modules, the total
complexity of the system actually increases, due to the
preponderance of interfaces between modules.
o Reduced Performance. Each extra API adds some level of processing
overhead. If an API is inserted in to the "common case" of packet
processing, this risks degrading total protocol performance.
o Abandoning Prior Work. The development of robust transport
protocols is a long and time intensive process, which is heavily
dependent on feedback from real deployments. A great deal of work
has been done over the past five years on components of protocols
such as RMTP-II, SRM, and PGM. Attempting to dramatically re-
engineer these components risks losing the benefit of this prior
work.
2.3. Building Block Requirements
Given these tradeoffs, we propose that a building block must meet the
following requirements:
o Wide Applicability. In order to have confidence that the
component can be reused, it should apply across multiple protocol
families and allow for the component's evolution.
o Simplicity. In order to have confidence that the specification of
the component APIs will not dramatically slow down the standards
process, APIs must be simple and straight forward to define. No
new fundamental research should be done in defining these APIs.
o Performance. To the extent possible, the building blocks should
attempt to avoid breaking up the "fast track", or common case
packet processing.
3. Protocol Components
This section proposes a functional decomposition of RM bulk-data
protocols from the perspective of the functional components provided
to an application by a transport protocol. It also covers some
components that while not necessarily part of the transport protocol,
are directly impacted by the specific requirements of a reliable
multicast transport. The next section then specifies recommended
building blocks that can implement these components.
Although this list tries to cover all the most common transport-
related needs of one-to-many bulk-data transfer applications, new
application requirements may arise during the process of
standardization, hence this list must not be interpreted as a
statement of what the transport layer should provide and what it
should not. Nevertheless, it must be pointed out that some
functional components have been deliberately omitted since they have
been deemed irrelevant to the type of application considered (i.e.,
one-to-many bulk-data transfer). Among these are advanced message
ordering (i.e., those which cannot be implemented through a simple
sequence number) and atomic delivery.
It is also worth mentioning that some of the functional components
listed below may be required by other functional components and not
directly by the application (e.g., membership knowledge is usually
required to implement ACK-based reliability).
The following list covers various transport functional components and
splits them in sub-components.
o Data Reliability (ensuring good throughput) |
| - Loss Detection/Notification
| - Loss Recovery
| - Loss Protection
o Congestion Control |
| - Congestion Feedback
| - Rate Regulation
| - Receiver Controls
o Security
o Group membership |
| - Membership Notification
| - Membership Management
o Session Management |
| - Group Membership Tracking
| - Session Advertisement
| - Session Start/Stop
| - Session Configuration/Monitoring
o Tree Configuration
Note that not all components are required by all protocols, depending
upon the fully defined service that is being provided by the
protocol. In particular, some minimal service models do not require
many of these functions, including loss notification, loss recovery,
and group membership.
3.1. Sub-Components Definition
Loss Detection/Notification. This includes how missing packets are
detected during transmission and how knowledge of these events are
propagated to one or more agents which are designated to recover from
the transmission error. This task raises major scalability issues
and can lead to feedback implosion and poor throughput if not
properly handled. Mechanisms based on TRACKs (tree-based positive
acknowledgements) or NACKs (negative acknowledgements) are the most
widely used to perform this function. Mechanisms based on a
combination of TRACKs and NACKs are also possible.
Loss Recovery. This function responds to loss notification events
through the transmission of additional packets, either in the form of
copies of those packets lost or in the form of FEC packets. The
manner in which this function is implemented can significantly affect
the scalability of a protocol.
Loss Protection. This function attempts to mask packet-losses so
that they don't become Loss Notification events. This function can
be realized through the pro-active transmission of FEC packets. Each
FEC packet is created from an entire application data unit [LMSSS97]
or a portion of an application data unit [RV97], [BKKKLZ95], a fact
that allows a receiver to recover from some packet loss without
further retransmissions. The number of losses that can be recovered
from without requiring retransmission depends on the amount of FEC
packets sent in the first place. Loss protection can also be pushed
to the extreme when good throughput is achieved without any Loss
Detection/Notification and Loss Recovery functionality, as in the ALC
family of protocols defined above.
Congestion Feedback. For sender driven congestion control protocols,
the receiver must provide some type of feedback on congestion to the
sender. This typically involves loss rate and round trip time
measurements.
Rate Regulation. Given the congestion feedback, the sender then must
adjust its rate in a way that is fair to the network. One proposal
that defines this notion of fairness and other congestion control
requirements is [Whetten99].
Receiver Controls. In order to avoid allowing a receiver that has an
extremely slow connection to the sender to stop all progress within
single rate schemes, a congestion control algorithm will often
require receivers to leave groups. For multiple rate approaches,
receivers of all connection speeds can have data delivered to them
according to the rate of their connection without slowing down other
receivers.
Security. Security for reliable multicast contains a number of
complex and tricky issues that stem in large part from the IP
multicast service model. In this service model, hosts do not send
traffic to another host, but instead elect to receive traffic from a
multicast group. This means that any host may join a group and
receive its traffic. Conversely, hosts may also leave a group at any
time. Therefore, the protocol must address how it impacts the
following security issues:
o Sender Authentication (since any host can send to a group),
o Data Encryption (since any host can join a group)
o Transport Protection (denial of service attacks, through
corruption of transport state, or requests for unauthorized
resources)
o Group Key Management (since hosts may join and leave a group at
any time) [WHA98]
In particular, a transport protocol needs to pay particular attention
to how it protects itself from denial of service attacks, through
mechanisms such as lightweight authentication of control packets
[HW99].
With Source Specific Multicast service model (SSM), a host joins
specifically to a sender and group pair. Thus, SSM offers more
security against hosts receiving traffic from a denial of service
attack where an arbitrary sender sends packets that hosts did not
specifically request to receive. Nevertheless, it is recommended
that additional protections against such attacks should be provided
when using SSM, because the protection offered by SSM against such
attacks may not be enough.
Sender Authentication, Data Encryption, and Group Key Management.
While these functions are not typically part of the transport layer
per se, a protocol needs to understand what ramifications it has on
data security, and may need to have special interfaces to the
security layer in order to accommodate these ramifications.
Transport Protection. The primary security task for a transport
layer is that of protecting the transport layer itself from attack.
The most important function for this is typically lightweight
authentication of control packets in order to prevent corruption of
state and other denial of service attacks.
Membership Notification. This is the function through which the data
source--or upper level agent in a possible hierarchical
organization--learns about the identity and/or number of receivers or
lower level agents. To be scalable, this typically will not provide
total knowledge of the identity of each receiver.
Membership Management. This implements the mechanisms for members to
join and leave the group, to accept/refuse new members, or to
terminate the membership of existing members.
Group Membership Tracking. As an optional feature, a protocol may
interface with a component which tracks the identity of each receiver
in a large group. If so, this feature will typically be implemented
out of band, and may be implemented by an upper level protocol. This
may be useful for services that require tracking of usage of the
system, billing, and usage reports.
Session Advertisement. This publishes the session name/contents and
the parameters needed for its reception. This function is usually
performed by an upper layer protocol (e.g., [HPW99] and [HJ98]).
Session Start/Stop. These functions determine the start/stop time of
sender and/or receivers. In many cases this is implicit or performed
by an upper level application or protocol. In some protocols,
however, this is a task best performed by the transport layer due to
scalability requirements.
Session Configuration/Monitoring. Due to the potentially far
reaching scope of a multicast session, it is particularly important
for a protocol to include tools for configuring and monitoring the
protocol's operation.
Tree Configuration. For protocols which include hierarchical
elements (such as PGM and RMTP-II), it is important to configure
these elements in a way that has approximate congruence with the
multicast routing topology. While tree configuration could be
included as part of the session configuration tools, it is clearly
better if this configuration can be made automatic.
4. Building Block Recommendations
The families of protocols introduced in section 1.1 generally use
different mechanisms to implement the protocol functional components
described in section 3. This section tries to group these mechanisms
in macro components that define protocol building blocks.
A building block is defined as
"a logical protocol component that results in explicit APIs for use
by other building blocks or by the protocol client."
Building blocks are generally specified in terms of the set of
algorithms and packet formats that implement protocol functional
components. A building block may also have API's through which it
communicates to applications and/or other building blocks. Most
building blocks should also have a management API, through which it
communicates to SNMP and/or other management protocols.
In the following section we will list a number of building blocks
which, at this stage, seem to cover most of the functional components
needed to implement the protocol families presented in section 1.1.
Nevertheless this list represents the "best current guess", and as
such it is not meant to be exhaustive. The actual building block
decomposition, i.e., the division of functional components into
building blocks, may also have to be revised in the future.
4.1. NACK-based Reliability
This building block defines NACK-based loss detection/notification
and recovery. The major issues it addresses are implosion prevention
(suppression) and NACK semantics (i.e., how packets to be
retransmitted should be specified, both in the case of selective and
FEC loss repair). Suppression mechanisms to be considered are:
o Multicast NACKs
o Unicast NACKs and Multicast confirmation
These suppression mechanisms primarily need to both minimize delay
while also minimizing redundant messages. They may also need to have
special weighting to work with Congestion Feedback.
4.2. FEC coding
This building block is concerned with packet level FEC information
when FEC codes are used either proactively or as repairs in reaction
to lost packets. It specifies the FEC codec selection and the FEC
packet naming (indexing) for both reactive FEC repair and pro-active
FEC.
4.3. Congestion Control
There will likely be multiple versions of this building block,
corresponding to different design policies in addressing congestion
control. Two main approaches are considered for the time being: a
source-based rate regulation with a single rate provided to all the
receivers in the session, and a multiple rate receiver-driven
approach with different receivers receiving at different rates in the
same session. The multiple rate approach may use multiple layers of
multicast traffic [VRC98] or router filtering of a single layer
[LVS99]. The multiple rate approach is most applicable for ALC
protocols.
Both approaches are still in the phase of study, however the first
seems to be mature enough [HFW99] to allow the standardization
process to begin.
At the time of writing this document, a third class of congestion
control algorithm based on router support is beginning to emerge in
the IRTF RMRG [LVS99]. This work may lead to the future
standardization of one or more additional building blocks for
congestion control.
4.4. Generic Router Support
The task of designing RM protocols can be made much easier by the
presence of some specific support in routers. In some application-
specific cases, the increased benefits afforded by the addition of
special router support can justify the resulting additional
complexity and expense [FLST98].
Functional components which can take advantage of router support
include feedback aggregation/suppression (both for loss notification
and congestion control) and constrained retransmission of repair
packets. Another component that can take advantage of router support
is intentional packet filtering to provide different rates of
delivery of packets to different receivers from the same multicast
packet stream. This could be most advantageous when combined with
ALC protocols [LVS99].
The process of designing and deploying these mechanisms inside
routers can be much slower than the one required for end-host
protocol mechanisms. Therefore, it would be highly advantageous to
define these mechanisms in a generic way that multiple protocols can
use if it is available, but do not necessarily need to depend on.
This component has two halves, a signaling protocol and actual router
algorithms. The signaling protocol allows the transport protocol to
request from the router the functions that it wishes to perform, and
the router algorithms actually perform these functions. It is more
urgent to define the signaling protocol, since it will likely impact
the common case protocol headers.
An important component of the signaling protocol is some level of
commonality between the packet headers of multiple protocols, which
allows the router to recognize and interpret the headers.
4.5. Tree Configuration
It has been shown that the scalability of RM protocols can be greatly
enhanced by the insertion of some kind of retransmission or feedback
aggregation agents between the source and receivers. These agents
are then used to form a tree with the source at (or near) the root,
the receivers at the leaves of the tree, and the aggregation/local
repair nodes in the middle. The internal nodes can either be
dedicated software for this task, or they may be receivers that are
performing dual duty.
The effectiveness of these agents to assist in the delivery of data
is highly dependent upon how well the logical tree they use to
communicate matches the underlying routing topology. The purpose of
this building block would be to construct and manage the logical tree
connecting the agents. Ideally, this building block would perform
these functions in a manner that adapts to changes in session
membership, routing topology, and network availability.
4.6. Data Security
At the time of writing, the security issues are the subject of
research within the IRTF Secure Multicast Group (SMuG). Solutions
for these requirements will be standardized within the IETF when
ready.
4.7. Common Headers
As pointed out in the generic router support section, it is important
to have some level of commonality across packet headers. It may also
be useful to have common data header formats for other reasons. This
building block would consist of recommendations on fields in their
packet headers that protocols should make common across themselves.
4.8. Protocol Cores
The above building blocks consist of the functional components listed
in section 3 that appear to meet the requirements for being
implemented as building blocks presented in section 2.
The other functions from section 3, which are not covered above,
should be implemented as part of "protocol cores", specific to each
protocol standardized.
5. Security Considerations
RFC 2357 specifically states that "reliable multicast Internet-Drafts
reviewed by the Transport Area Directors must explicitly explore the
security aspects of the proposed design." Specifically, RMT building
block works in progress must examine the denial-of-service attacks
that can be made upon building blocks and affected by building blocks
upon the Internet at large. This requirement is in addition to any
discussions regarding data-security, that is the manipulation of or
exposure of session information to unauthorized receivers. Readers
are referred to section 5.e of RFC 2357 for further details.
6. IANA Considerations
There will be more than one building block, and possibly multiple
versions of individual building blocks as their designs are refined.
For this reason, the creation of new building blocks and new building
block versions will be administered via a building block registry
that will be administered by IANA. Initially, this registry will be
empty, since the building blocks described in sections 4.1 to 4.3 are
presented for example and design purposes. The requested IANA
building block registry will be populated from specifications as they
are approved for RFC publication (using the "Specification Required"
policy as described in RFC 2434 [RFC2434]). A registration will
consist of a building block name, a version number, a brief text
description, a specification RFC number, and a responsible person, to
which IANA will assign the type number.
7. Conclusions
In this document, we briefly described a number of building blocks
that may be used for the generation of reliable multicast protocols
to be used in the application space of one-to-many reliable bulk-data
transfer. The list of building blocks presented was derived from
considering the functions that a protocol in this space must perform
and how these functions should be grouped. This list is not intended
to be all-inclusive but instead to act as guide as to which building
blocks are considered during the standardization process within the
Reliable Multicast Transport WG.
8. Acknowledgements
This document represents an overview of a number of building blocks
for one to many bulk data transfer that may be ready for
standardization within the RMT working group. The ideas presented
are not those of the authors, rather they are a summarization of many
years of research into multicast transport combined with the varied
presentations and discussions in the IRTF Reliable Multicast Research
Group. Although they are too numerous to list here, we thank
everyone who has participated in these discussions for their
contributions.
9. References
[BKKKLZ95] J. Bloemer, M. Kalfane, M. Karpinski, R. Karp, M. Luby,
D. Zuckerman, "An XOR-based Erasure Resilient Coding
Scheme," ICSI Technical Report No. TR-95-048, August
1995.
[BLMR98] J. Byers, M. Luby, M. Mitzenmacher, A. Rege, "A Digital
Fountain Approach to Reliable Distribution of Bulk Data,"
Proc ACM SIGCOMM 98.
[FJM95] S. Floyd, V. Jacobson, S. McCanne, "A Reliable Multicast
Framework for Light-weight Sessions and Application Level
Framing," Proc ACM SIGCOMM 95, Aug 1995 pp. 342-356.
[FLST98] D. Farinacci, S. Lin, T. Speakman, and A. Tweedly, "PGM
reliable transport protocol specification," Work in
Progress.
[HFW99] M. Handley, S. Floyd, B. Whetten, "Strawman Specification
for TCP Friendly (Reliable) Multicast Congestion Control
(TFMCC)," Work in Progress.
[HJ98] Handley, M. and V. Jacobson, "SDP: Session Description
Protocol", RFC 2327, April 1998.
[HPW99] M. Handley, C. Perkins, E. Whelan, "Session Announcement
Protocol," Work in Progress, June 1999.
[HW99] T. Hardjorno, B. Whetten, "Security Requirements for
RMTP-II," Work in Progress, June 1999.
[RFC2887] Handley, M., Whetten, B., Kermode, R., Floyd, S.,
Vicisano, L. and M. Luby, "The Reliable Multicast Design
Space for Bulk Data Transfer", RFC 2887, August 2000.
[KCW98] M. Kadansky, D. Chiu, and J. Wesley, "Tree-based reliable
multicast (TRAM)," Work in Progress.
[Kermode98] R. Kermode, "Scoped Hybrid Automatic Repeat Request with
Forward Error Correction," Proc ACM SIGCOMM 98, Sept
1998.
[LDW98] M. Lucas, B. Dempsey, A. Weaver, "MESH: Distributed Error
Recovery for Multimedia Streams in Wide-Area Multicast
Networks".
[LESZ97] C-G. Liu, D. Estrin, S. Shenkar, L. Zhang, "Local Error
Recovery in SRM: Comparison of Two Approaches," USC
Technical Report 97-648, Jan 1997.
[LG97] B.N. Levine, J.J. Garcua-Luna-Aceves, "Improving Internet
Multicast Routing with Routing Labels," IEEE
International Conference on Network Protocols (ICNP-97),
Oct 28-31, 1997, p.241-250.
[LP96] K. Lin and S. Paul. "RMTP: A Reliable Multicast Transport
Protocol," IEEE INFOCOMM 1996, March 1996, pp. 1414-1424.
[LMSSS97] M. Luby, M. Mitzenmacher, A. Shokrollahi, D. Spielman, V.
Stemann, "Practical Loss-Resilient Codes", Proc ACM
Symposium on Theory of Computing, 1997.
[LVS99] M. Luby, L. Vicisano, T. Speakman. "Heterogeneous
multicast congestion control based on router packet
filtering", RMT working group, June 1999, Pisa, Italy.
[MA99] J. Macker, B. Adamson. "Multicast Dissemination Protocol
version 2 (MDPv2)," Work in Progress,
http://manimac.itd.nrl.navy.mil/MDP
[MRBP98] Mankin, A., Romanow, A., Brander, S. and V.Paxson, "IETF
Criteria for Evaluating Reliable Multicast Transport and
Application Protocols", RFC 2357, June 1998.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[OXB99] O. Ozkasap, Z. Xiao, K. Birman. "Scalability of Two
Reliable Multicast Protocols", Work in Progress, May
1999.
[PSLB97] "Reliable Multicast Transport Protocol (RMTP)," S. Paul,
K. K. Sabnani, J. C. Lin, and S. Bhattacharyya, IEEE
Journal on Selected Areas in Communications, Vol. 15, No.
3, April 1997.
[RV97] L. Rizzo, L. Vicisano, "A Reliable Multicast Data
Distribution Protocol Based on Software FEC Techniques,"
Proc. of The Fourth IEEE Workshop on the Architecture and
Implementation of High Performance Communication Systems
(HPCS'97), Sani Beach, Chalkidiki, Greece June 23-25,
1997.
[VRC98] L. Vicisano, L. Rizzo, J. Crowcroft, "TCP-Like Congestion
Control for Layered Multicast Data Transfer", Proc. of
IEEE Infocom'98, March 1998.
[WBPM98] B. Whetten, M. Basavaiah, S. Paul, T. Montgomery, N.
Rastogi, J. Conlan, and T. Yeh, "THE RMTP-II PROTOCOL,"
Work in Progress.
[WHA98] D. Wallner, E. Hardler, R. Agee, "Key Management for
Multicast: Issues and Architectures," Work in Progress.
[Whetten99] B. Whetten, "A Proposal for Reliable Multicast
Congestion Control Requirements," Work in Progress.
http://www.talarian.com/rmtp-ii/overview.htm
10. Authors' Addresses
Brian Whetten
Talarian Corporation,
333 Distel Circle,
Los Altos, CA 94022, USA
EMail: whetten@talarian.com
Lorenzo Vicisano
Cisco Systems,
170 West Tasman Dr.
San Jose, CA 95134, USA
EMail: lorenzo@cisco.com
Roger Kermode
Motorola Australian Research Centre
Level 3, 12 Lord St,
Botany NSW 2019, Australia
EMail: Roger.Kermode@motorola.com
Mark Handley, Sally Floyd
ATT Center for Internet Research at ICSI,
International Computer Science Institute,
1947 Center Street, Suite 600,
Berkeley, CA 94704, USA
EMail: mjh@aciri.org, floyd@aciri.org
Michael Luby
600 Alabama Street
San Francisco, CA 94110
Digital Fountain, Inc.
EMail: luby@digitalfountain.com
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