RFC 1458 (rfc1458) - Page 2 of 19
Requirements for Multicast Protocols
Alternative Format: Original Text Document
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.
Braudes & Zabele