Current Meeting Report

2.7.13 Reliable Multicast Transport (rmt)

NOTE: This charter is a snapshot of the 53rd IETF Meeting in Minneapolis, MN USA. It may now be out-of-date. Last Modified: 11-Feb-02
Roger Kermode <>
L Vicisano <>
Transport Area Director(s):
Scott Bradner <>
Allison Mankin <>
Transport Area Advisor:
Allison Mankin <>
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Description of Working Group:
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The purpose of this WG is to standardize reliable multicast transport.

Initial efforts will focus 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 expects to initially standardize three protocol instantiations, one each from the the following three families:

1) A NACK-based protocol 2) A Tree-based ACK protocol 3) An "Asynchronous Layered Coding protocol that uses Forward Error Correction

The WG will carry out protocol standardization by composing 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 arguments.

- 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.

To assist in this standardization process, the WG will also complete work on three documents. The first describes the design-space in which the three one-to-many transport protocols will be developed. The second explains the concepts of building-blocks and protocol instantiations. The third provides guidelines to authors of drafts that specify building-blocks and protocol instantiations. These three documents will be initially submitted as WG drafts and subsequently proposed as Informational RFC.

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

The WG will also standardize and generate RFCs for the following three protocol instantiations: A NACK-based protocol, A Tree-based ACK protocol and an Open Loop protocol that uses Forward Error Correction.

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 deliverables.

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 three protocol instantiations.
Done   Review drafts at the Adelaide IETF
Done   Submit Initial Draft for Congestion Control
Done   Complete building-block drafts WG Last-Call and submit for publication as Proposed Standard
Jun 00   Protocol instantiations drafts submitted for publication as Proposed Standard.
Dec 01   Congestion control draft submitted for publication as Proposed Standard.