Multicast routing issues in ad hoc networks

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Multicast routing issues in ad hoc networks
Katia Obraczka Gene Tsudik
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Introduction

• A typical inter-network of the future will
  consist of a wired backbone and a collection of
  fixed infrastructure mobile and ad hoc networks.
  Multicast routing and packet forwarding protocols
  in ad hoc networks (AHN) must emphasize
• Robustness versus efficiency.
• Active adaptability.
• Unlimited mobility.
• Integrated multicast.

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Inter-network of the future
Mobile Networks
Ad Hoc Network
Ad Hoc Network
Ad Hoc Network
Ad Hoc Network switch
Wired link
Wireless link
Mobile host
Base station
Members of multicast group
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Mobile networks and mobility patterns

• Mobile networks with fixed infrastructure.
• Ad hoc networks.
• Inter-networking comprising wired fixed
  infrastructure and ad hoc networks.

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Issues in multicast routing in AHNs

• Fixed network multicast routing is based on state
  in routers it is unsuitable for an AHN
  environment.
• Host behavior completely independent of other
  hosts.
• No limit on host speed.
• No constraints on direction of movement.
• High probability of frequent, temporary network
  partitions.
• Storage capacity and power are severely limited.
• Robustness and high quantity of service.

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Hyper flooding a potential approach

• Maximum network diameter is assumed to be known.
• Maximum TTL (time-to-time) for a packet is
  known.
• Multicast packets carry hop counts as well as
  origination time stamps.
• Each host only keeps its own multicast group
  membership information.

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Hyper flooding a potential approach (continued)

• Every multicast packet is assigned a unique ID.
• Each host maintains a cache of IDs.
• A packet is re-forwarded by the host only on new
  neighbors.
• A packet is not forwarded if there are no new
  neighbors.

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Pruning unnecessary broadcasts
Time T1
Time T2
3
3
2
2
1
1
IDx
IDx
4
4
6
5
5
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Incomplete coverage
Time T1
Time T2
3
3
2
2
6
1
1
IDx
IDx
4
4
5
5
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Accommodating different AHNs

• Large, widely distributed AHN
• The AHN is partitioned in to clusters.
• Each cluster is assigned a cluster head.
• Intra-cluster multicast is performed with hyper
  flooding.
• Inter-cluster multicast is by traditional
  multicasting.

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Integration

• Design of mobile wired multicast
  gateway.
• Design of Ad-hoc wired multicast gateway.
• Mechanisms for active switching among different
  multicast routing mechanism.

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Summary

• Exploration of the design space of multicast
  routing algorithms suitable for AHNs.
• Development of multicast gateway.
• Prototyping and trial deployment.