Multicast: Wired to Wireless Hrishikesh Gossain Carlos de Morais Cordeiro Dharma P. Agrawal IEEE Communication Magazine June 2002 資工所 蔡家楷

Outline

 Introduction  Multicast Support  Multicast in the Internet  Multicast in Wireless Mobile Environment  Conclusion & Future Direction 2

Introduction

  Provide efficient way of services for application  Real-time Class gaming 、 Multiplayer on line IPv4 reserved Class D address to support multicasting 3

Multicast Support

 Initial Support  Multicast-capable routers (MRouters)   Dedicated Tunnels Multicast backbone (MBone)  Presently   No need dedicated tunnels Native multicast 4

Multicast Support

 Multicast Group Membership  IP supports dynamic joining and leaving of a group by IGMP (Internet Group Management Protocol) 5

Multicast Support

 Packet Forwarding  Multicast forwarding algorithm  Source-based  Core-based 6

Source-based

 RPB – Reverse Path Broadcasting  Spanning tree is created for each (source,group) pair  TRPB – Truncated Reverse Path Broadcasting   Manage group by IGMP Prune non-leaf router Source Router Membership 7

Source-based

 RPM – Reverse Path Multicasting  Spans only to routers and subnetwork with group member 8

Core-based

 CBT - Core Based Tree   Build a single shred multicast tree with a core router All packets are forwarded through the core   Group managed by the core Receiver-oriented 9

Multicast in the Internet

 Routing Protocol  DVMRP – Distance Vector Multicast Routing Protocol  Source-based  First packet forward to entire interface  Prune message  Graft message 10

Multicast in the Internet

 Routing Protocol  MOSPF – Multicast Extensions to OSPF  Unicast routing information obtained from OSPF  Group membership obtained from IGMP  Build a multicast forwarding tree on demand for each (source,group) pair  Hierarchical routing – hosts are partitioned into autonomous system (ASs) 11

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Multicast in the Internet

 Routing Protocol  PIM-SM - Protocol-Interdependent Multicast-Sparse Mode  Support multicast independent of any underlying unicast routing protocol  For sparse distributed receiver on Internet 13

Multicast in the Internet

  RP – Rendezvous point  Forwarding packets destined for the multicast group DR – Designated router  Handles multicast group membership message in it’s domain Group S M DR M RP DR S M M 14

Multicast in Wireless Mobile Environment

 Issue in Mobile Environment  Multicast forwarding algorithm   Dense or sparse mode protocols QoS provisioning 15

Multicast in Wireless Mobile Environment  Proposals for multicast over MIP by IETF   Remote Subscription   An MH resubscribe to the multicast group each time it moves to a new foreign network Frequent resubscription may lead to lost packets Bidirectional Tunneling   Using unicast Mobile IP tunnels from their Has Requires the HA of an MH to be a multicast router 16

Multicast in Wireless Mobile Environment  Multicast support using Mobile IP (MoM)   Tunnel convergence problem  Select one HA as DMSP (Designated Multicast Service Provider) Packet loss when MH handoff  Select more than one DMSP 17

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Multicast in Wireless Mobile Environment  Multicast for Mobility Protocols (MMP)  Provide fast and efficient handoffs for MH  Combines Mobile IP and CBT  MIP for controls communication up to the foreign network  CBT for movement of hosts inside foreign network 19

Multicast in Wireless Mobile Environment  MMP working flow  BS send beacon include multicast CoA    According CoA, MH send join message to BS BS transmits a CBT join request to the Core The core request the HA of MH to replace the CoA to its own address 20

Multicast in Wireless Mobile Environment  MMP drawback   Assumes a large-scale deployment of multicast-capable routers in each domain Not protocol-indendpent 21

Reliable wireless Multicast Protocols   RMDP Protocol – Reliable Multicast Data Distribution Protocol    FEC (Forward error Control) & ARQ (Automatic Repeat Request) A data object to be transmitted is a file Split file into packets, and encoded to transmission Drawback: encoding/decoding done by software, affect performance 22

Reliable wireless Multicast Protocols  RM2 Protocol – Reliable Mobile Multicast  Used for both wired & wireless   Rely on  IGMP: to manage group membership  IETF’s Mobile IP to support CoA MADCAP – Multicast Address Dynamic Client Allocation Protocol 23

Reliable wireless Multicast Protocols  RM2 Protocol   NACK for request retransmitting  NACK: Negative acknowledgements RS manage retransmission for fixed/mobile user or mixture of them 24

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Conclusion & Future Direction  There is no one-size-fits-all protocol for multicast  Both wired & wireless multicast proposal designed to cope with specific scenario  QoS, Security and so on 26