Mobile Ad Hoc Networks [manet] C. Perkins
Internet-Draft Futurewei
Intended status: Standards Track March 3, 2016
Expires: September 4, 2016

Using Layer 3 Multicast Suppression Protocols Above Layer 3


This document specifies how protocols operating at layers above layer 3 can use the multicast suppression algorithms, for instance the algorithms specified in RFC 6621.

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Table of Contents

1. Introduction

Limiting the number of multicast forwarders provides performance benefits when used with a protocol that relies on flooding messages throughout a network. Some good multicast suppression methods for limiting the number of multicast forwarders while maintaining complete network coverage are specified in RFC 6621 [RFC6621]. Routing protocols that use multicast can offer much greater performance using multicast suppression algorithms. Such algorithms do not affect the origination of multicast messages, but only determine whether a node needs to forward incoming multicast messages that are intended to flood the network. Enabling performance benefits for reactive manet routing protocols was a strong motivating factor in the development and publication of RFC 6621.

RFC 6621 multicast suppression algorithms are specified to operate at layer 3. Manet routing protocols use RFC 5444 [RFC5444] as a message bundling layer; they operate above layer 3. Such protocols specify that incoming multicast control messages have to be processed before regeneration; in other words, the incoming multicast message is not forwarded at all. Manet control messages are sent with the IP destination address set to the link-local multicast address LL-MANET-Routers [RFC5498] unless otherwise specified. This document specifies a way to use layer 3 multicast suppression algorithms at a layer above layer 3 so that algorithms that require network-wide flooding can reap the benefits of layer-3 multicast suppression algorithms.

2. Terminology

This document defines the following terminology:

Forwarding Node

A node that currently forwards incoming multicast messages to its neighbors, based on the results of running a multicast suppression algorithm.

Multicast Suppression Algorithm

An algorithm that determines which multicast routers are required for complete coverage of a multicast group; retransmission by other multicast routers for the multicast group is unnecessary.


Transmission of a message formed by processing and modification of an incoming message for an operation requiring the attention of members of a multicast group.

3. Use of multicast suppression algorithms above Layer 3

If the node is not currently a multicast forwarding node, then the node does not regenerate multicast messages even if the conditions for regeneration are satisfied.

For example, if an AODVv2 [I-D.ietf-manet-aodvv2] router is not currently a multicast forwarding node, then it does not regenerate multicast messages (e.g., RREQ or RERR) even if the conditions for regeneration are satisfied. This restriction only applies for regeneration, and does not apply for multicast RREQ or RERR messages originated by the node.

4. Security Considerations

This document does not introduce any security mechanisms, and does not have any impact on existing security mechanisms.

5. IANA Considerations

This document does not specify any IANA actions.

6. Informative References

[I-D.ietf-manet-aodvv2] Perkins, C., Ratliff, S., Dowdell, J., Steenbrink, L. and V. Mercieca, "Ad Hoc On-demand Distance Vector Version 2 (AODVv2) Routing", Internet-Draft draft-ietf-manet-aodvv2-13, January 2016.
[RFC5444] Clausen, T., Dearlove, C., Dean, J. and C. Adjih, "Generalized Mobile Ad Hoc Network (MANET) Packet/Message Format", RFC 5444, DOI 10.17487/RFC5444, February 2009.
[RFC5498] Chakeres, I., "IANA Allocations for Mobile Ad Hoc Network (MANET) Protocols", RFC 5498, DOI 10.17487/RFC5498, March 2009.
[RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621, DOI 10.17487/RFC6621, May 2012.

Author's Address

Charles E. Perkins Futurewei Inc. 2330 Central Expressway Santa Clara, CA 95050 USA Phone: +1-408-330-4586 EMail: