2.8.10 Reliable Multicast Transport (rmt)

NOTE: This charter is a snapshot of the 77th IETF Meeting in Anaheim, California USA. It may now be out-of-date.

Last Modified: 2008-08-21


Brian Adamson <adamson@itd.nrl.navy.mil>
Lorenzo Vicisano <lorenzo@vicisano.net>

Transport Area Director(s):

David Harrington <ietfdbh@comcast.net>
Lars Eggert <lars.eggert@nokia.com>

Transport Area Advisor:

David Harrington <ietfdbh@comcast.net>

Mailing Lists:

General Discussion: rmt@ietf.org
To Subscribe: rmt-request@ietf.org
In Body: subscribe
Archive: http://www.ietf.org/mail-archive/web/rmt/index.html

Description of Working Group:

The purpose of this WG is to standardize reliable multicast transport.

Initial efforts have focused solely on the standardization of the
one-to-many transport of large amounts of data. Due to the large
number of applications that fall into this category, and the sometimes
orthogonal requirements these applications exhibit, it is believed
that a "one size fits all" protocol will be unable to meet the
requirements of all applications. In recognition of this observation,
this working group will standardize two protocol instantiations,
initially as Experimental protocols, and then as warranted, in the
standards track, from the following families:

1) A NACK-based protocol.
2) An "Asynchronous Layered Coding protocol that uses Forward Error

The WG will carry out protocol standardization in general by composing
a a set of RFCs that specify

- building blocks: A set of easily-separable coarse-grained modular
components that are common to multiple protocols along with abstract
APIs that define a building block's access methods and their

- protocol instantiations: Specifications that define the necessary
gluing logic and minimal additional functionality required to realize
a working protocol from one or more building blocks. These
specifications will also include an abstract API that defines the
interface between the protocol implementation and an application.

The WG has previously completed work on three documents to assist in
the standardization process. RFC2887 describes the design-space in
which the one-to-many transport protocols will be developed. RFC3048
explains the concepts of building-blocks and protocol
instantiations. RFC3269 provides guidelines to authors of drafts that
specify building-blocks and protocol instantiations.

The WG will generate and submit for standardization drafts of the
following building-blocks for use in the construction of the two
protocols: congestion control, negative acknowledgments, forward error
correction, and to address the RFC 2357 security requirements.

Generic mechanisms for router assist are also considered for an
additional building block. Initial work on the framework for
router-assist has already been performed, the WG will evaluate whether
to complete this task basing on available resource and interest.

The WG will also standardize and generate RFCs for the following two
protocol instantiations: A NACK-based protocol, and an Asynchronous
Layered Coding (ALC) protocol that uses Forward Error Correction.
RFC 3450 is the Experimental RFC of the ALC protocol instantiation.

If new requirements are identified that cannot be satisfied with the
building-blocks and protocol instantiations described above, the Area
Directors in consultation with the IESG may add additional
building-blocks and protocol instantiations to the working group

This working group will work closely with the Internet Research Task
Force (IRTF) groups on Reliable Multicast (RMRG) and
Secure Multicast (SMUG), especially for meeting the congestion control
and security requirements mandated by RFC 2357. This working group may
work with the Area Directors to recharter to standardize reliable
multicast for additional scenarios beyond the one-to-many transport of
bulk data once they are sufficiently well understood.

Goals and Milestones:

Done  Submit design-space, building-blocks, and guidelines drafts for publication as Informational RFCs
Done  Initial Drafts for the following building blocks: negative acknowledgments, forward error correction, a generic signaling mechanism for router assist, and transport protection
Done  Submit Initial Drafts for the two protocol instantiations.
Done  Submit Initial Draft for Congestion Control
Done  Complete building-block drafts WG Last-Call and submit for publication as Proposed Standard
Done  Complete building blocks and protocol instantiations for ALC and submit for publication as Experimental RFC
Done  WG Decision on whether to pursue the router-assist building block work. These milestones may have to be modified accordingly
Done  Submit WEBRC (congestion control building block) for publication as Experimental
Done  Submit NACK building block and protocol instantiation for publication as Experimental
Done  Evaluate when and how the RMT Experimental specifications will be submitted for publication as Proposed Standard, and update this charter accordingly
Sep 2005  Submit remaining congestion control building blocks (TFMCC, PGMCC) for publication as Experimental
Dec 2005  Submit all the RMT Eperimental Specifications published before July 05 for publication as Proposed Standard
Apr 2006  Submit all remaining RMT Eperimental Specifications for publication as Proposed Standard


  • draft-ietf-rmt-flute-revised-11.txt
  • draft-ietf-rmt-sec-discussion-05.txt
  • draft-ietf-rmt-fcast-00.txt
  • draft-ietf-rmt-bb-fec-raptorq-02.txt

    Request For Comments:

    RFC2887 I The Reliable Multicast Design Space for Bulk Data Transfer
    RFC3048 I Reliable Multicast Transport Building Blocks for One-to-Many Bulk-Data Transfer
    RFC3269 I Author Guidelines for RMT Building Blocks and Protocol Instantiation documents
    RFC3450 E Asynchronous Layered Coding protocol instantiation
    RFC3451 E Layered Coding Transport (LCT) Building Block
    RFC3452 E Forward Error Correction Building Block
    RFC3453 I The use of Forward Error Correction in Reliable Multicast
    RFC3695 E Compact Forward Error Correction (FEC) Schemes
    RFC3738 E Wave and Equation Based Rate Control building block
    RFC3926 E FLUTE - File Delivery over Unidirectional Transport
    RFC3940 E NACK-Oriented Reliable Multicast Protocol (NORM)
    RFC3941 E NACK-Oriented Reliable Multicast (NORM) Building Blocks
    RFC4654 E TCP-Friendly Multicast Congestion Control (TFMCC): Protocol Specification
    RFC5052 PS Forward Error Correction (FEC) Building Block
    RFC5053 PS Raptor Forward Error Correction Scheme for Object Delivery
    RFC5170 PS Low Density Parity Check (LDPC) Staircase and Triangle Forward Error Correction (FEC) Schemes
    RFC5401 PS Multicast Negative-Acknowledgment (NACK) Building Blocks
    RFC5445 PS Basic Forward Error Correction (FEC) Schemes
    RFC5510 PS Reed-Solomon Forward Error Correction (FEC) Schemes
    RFC5651 PS Layered Coding Transport (LCT) Building Block
    RFC5740 PS NACK-Oriented Reliable Multicast (NORM) Transport Protocol
    RFC5775 PS Asynchronous Layered Coding (ALC) Protocol Instantiation

    Meeting Minutes


    RMT Working Group Status
    FLUTE Update
    RaptorQ Update