Multicast Negative-Acknowledgment (NACK) Building Blocks
RFC 5401

Network Working Group                                         B. Adamson
Request for Comments: 5401                     Naval Research Laboratory
Obsoletes: 3941                                               C. Bormann
Category: Standards Track                        Universitaet Bremen TZI
                                                              M. Handley
                                               University College London
                                                               J. Macker
                                               Naval Research Laboratory
                                                           November 2008

        Multicast Negative-Acknowledgment (NACK) Building Blocks

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2008 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.

Abstract

   This document discusses the creation of reliable multicast protocols
   that utilize negative-acknowledgment (NACK) feedback.  The rationale
   for protocol design goals and assumptions are presented.  Technical
   challenges for NACK-based (and in some cases general) reliable
   multicast protocol operation are identified.  These goals and
   challenges are resolved into a set of functional "building blocks"
   that address different aspects of reliable multicast protocol
   operation.  It is anticipated that these building blocks will be
   useful in generating different instantiations of reliable multicast
   protocols.  This document obsoletes RFC 3941.

Adamson, et al.             Standards Track                     [Page 1]
RFC 5401                   Multicast NACK BB               November 2008

Table of Contents

   1. Introduction ....................................................2
      1.1. Requirements Language ......................................4
   2. Rationale .......................................................4
      2.1. Delivery Service Model .....................................5
      2.2. Group Membership Dynamics ..................................6
      2.3. Sender/Receiver Relationships ..............................6
      2.4. Group Size Scalability .....................................6
      2.5. Data Delivery Performance ..................................7
      2.6. Network Environments .......................................7
      2.7. Intermediate System Assistance .............................8
   3. Functionality ...................................................8
      3.1. Multicast Sender Transmission .............................11
      3.2. NACK Repair Process .......................................13
      3.3. Multicast Receiver Join Policies and Procedures ...........26
      3.4. Node (Member) Identification ..............................26
      3.5. Data Content Identification ...............................27
      3.6. Forward Error Correction (FEC) ............................28
      3.7. Round-Trip Timing Collection ..............................29
      3.8. Group Size Determination/Estimation .......................33
      3.9. Congestion Control Operation ..............................34
      3.10. Intermediate System Assistance ...........................34
   4. NACK-Based Reliable Multicast Applicability ....................35
   5. Security Considerations ........................................36
   6. Changes from RFC 3941 ..........................................38
   7. Acknowledgements ...............................................38
   8. References .....................................................39
      8.1. Normative References ......................................39
      8.2. Informative References ....................................39

1.  Introduction

   Reliable multicast transport is a desirable technology for efficient
   and reliable distribution of data to a group on the Internet.  The
   complexities of group communication paradigms necessitate different
   protocol types and instantiations to meet the range of performance
   and scalability requirements of different potential reliable