Reliable Multicast Transport (rmt)

Last modified: 2013-09-06


Transport Area Directors

Transport Area Advisor

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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 Correction.

The WG will carry out protocol standardization in general 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.

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 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

Submit design-space, building-blocks, and guidelines drafts for publication as Informational RFCs
Initial Drafts for the following building blocks: negative acknowledgments, forward error correction, a generic signaling mechanism for router assist, and transport protection
Submit Initial Drafts for the two protocol instantiations.
Submit Initial Draft for Congestion Control
Complete building-block drafts WG Last-Call and submit for publication as Proposed Standard
Complete building blocks and protocol instantiations for ALC and submit for publication as Experimental RFC
WG Decision on whether to pursue the router-assist building block work. These milestones may have to be modified accordingly
Submit WEBRC (congestion control building block) for publication as Experimental
Submit NACK building block and protocol instantiation for publication as Experimental
Evaluate when and how the RMT Experimental specifications will be submitted for publication as Proposed Standard, and update this charter accordingly
Submit remaining congestion control building blocks (TFMCC, PGMCC) for publication as Experimental
Submit all the RMT Eperimental Specifications published before July 05 for publication as Proposed Standard
Sep 2010
Submit FLUTE SDP document for publication
Sep 2010
Submit RMT Security documents for publication
Submit FCAST document for publication as Experimental
Submit RaptorQ FEC Scheme document for publication

No Internet-Drafts

Request for Comments

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