IMcast: A PlugandPlay Multicast Routing Protocol

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IMcast A Plug-and-Play Multicast Routing
Protocol

• T.Venketesan and Wu-Hon F. Leung
• Illinois Institute of Technology, Chicago,

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Inroduction

• IP multicast deployment has been slow
• Less than 5 of the autonomous systems (AS) in
  the Internet are multicast enabled
• inter-working with legacy routers
• all immediate neighboring routers must be IP
  multicast enabled, or via tunnels
• address allocation scheme, MAAA
• TOO MUCH TO DO MANUALY .

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Recursive unicast trees

• Multicast data messages carry unicast destination
  addresses
• Multicast aware routers create copies with
  modified destination addresses to forward packets
  along the multicast tree
• Problem need to set up a tree
• Solution Hop-by-Hop (HBH), REUNITE,

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IMcast overview

• Features
• Automatic tunneling
• Efficient routing tree
• Independent address space
• Hierarchical address structure that enable a
  allocation mechanism like CIDR

IMcast Router
IMcast Router
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Automatic tunneling

• Use the protocol number field to intercept
  control messages. An IMcast router check it for
  each and every packet it receives
• Carry the group address in a separate 4 byte
  header on top of the IPv4 header of the data
  message, this is called the IMcast data header.
• IMcast control header, also carried on top of the
  IPv4 header in control messages
• All IMcast packets have unicast destination
  address.

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IMcast control header

• Type join, tree, fusion or leave.
• group_address multicast group id
• multicast_src_address root of the tree
• source_address originator of the control message
• Destination_address Destination node of the
  control message
• Fusioned_nodes is valid for fusion message and is
  an array of next hop addresses that exist in the
  routing table of a branching router. Fusion
  messages are of the form fusion(Ri Rj ..,
  S-gtD) where Ri, Rj are fusioned nodes, S is the
  source of the fusion message and D the
  destination.

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IMcast routing
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IMCast routing
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Hierarchical multicast addressing
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Hierarchical multicast addressing
What about port numbers?
Why only 32 bits?
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Evaluation
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Other comments

• No router support, but new router must be
  deployed?
• Firewall support?
• Host stack changes necessary (see section 2.3)?
• Compatibility with existing applications?
• Then, why not in the application-layer instead of
  the network layer?