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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
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Introduction
 Provide efficient way
of services for
application

Real-time Class、
Multiplayer on line
gaming
 IPv4 reserved Class
D address to support
multicasting
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Multicast Support
 Initial Support



Multicast-capable routers (MRouters)
Dedicated Tunnels
Multicast backbone (MBone)
 Presently


No need dedicated tunnels
Native multicast
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Multicast Support
 Multicast Group Membership

IP supports dynamic joining and leaving of a
group by IGMP (Internet Group
Management Protocol)
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Multicast Support
 Packet Forwarding

Multicast forwarding algorithm
Source-based
 Core-based

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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
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Source-based
 RPM – Reverse Path Multicasting

Spans only to routers and subnetwork with
group member
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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
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Multicast in the Internet
 Routing Protocol

DVMRP – Distance Vector Multicast Routing
Protocol
Source-based
 First packet forward to entire interface
 Prune message
 Graft message

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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)

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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

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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
S
Group
M
DR
M
RP
DR
S
M
M
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Multicast in Wireless Mobile
Environment
 Issue in Mobile Environment



Multicast forwarding algorithm
Dense or sparse mode protocols
QoS provisioning
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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

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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
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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

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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
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Multicast in Wireless Mobile
Environment
 MMP drawback


Assumes a large-scale deployment of
multicast-capable routers in each domain
Not protocol-indendpent
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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
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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
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Reliable wireless Multicast
Protocols
 RM2 Protocol

NACK for request retransmitting


NACK: Negative acknowledgements
RS manage retransmission for fixed/mobile
user or mixture of them
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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
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