RFC 1458 (rfc1458) - Page 2 of 19

Requirements for Multicast Protocols

RFC 1458          Requirements for Multicast Protocols          May 1993


   4.3.3 Multicast Routing Based on Quality of Service   . . . . . .  15
   4.3.4 Quality of Service Based Packet Loss  . . . . . . . . . . .  15
   5.    Interactions Among the Components: An Example   . . . . . .  15
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  18
   References  . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   Security Considerations   . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   Multicast protocols have been developed to support group
   communications.  These protocols use a one-to-many paradigm for
   transmission, typically using class D Internet Protocol (IP)
   addresses to specify specific multicast groups.  While designing
   network services for reliable transmission of very large imagery as
   part of the DARPA-sponsored ImNet program, we have reviewed existing
   multicast protocols and have determined that none meet all of the
   requirements of image communications [3].  This RFC reviews the
   current state of multicast protocols, highlights the missing
   features, and motivates the design and development of an enhanced
   multicast protocol.

   First, the requirements for network services and underlying protocols
   related to image communications are presented.  Existing protocols
   are then reviewed, and an analysis of each protocol against the
   requirements is presented.  The analyses identify the need for a new
   multicast protocol.  Finally, the features of an ideal reliable
   multicast protocol that adapts to network congestion in the
   transmission of large data volumes are presented.  Additional network
   components needed to fully support the new protocol, including a
   Multicast Group Authority and modifications to existing routing
   protocols, are also introduced.

2.  The Image Communications Problem

2.1 Scope

   Image management and communications systems are evolving from film-
   based systems toward an all-digital environment where imagery is
   acquired, transmitted, analyzed, and stored using digital computer
   and communications technologies.  The throughput required for
   communicating large numbers of very large images is extremely large,
   consisting of thousands of terabytes of imagery per day.  Temporal
   requirements for capture and dissemination of single images are
   stringent, ranging from seconds to at most several minutes.  Imagery
   will be viewed by hundreds of geographically distributed users who
   will require on-demand, interactive access to the data.




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