Multicast Communication - Distributed Operating Systems - Lecture Slides, Slides of Operating Systems

Download Multicast Communication - Distributed Operating Systems - Lecture Slides and more Slides Operating Systems in PDF only on Docsity!

Communication

Multicast Communication

Unicast, Broadcast versus Multicast

• Unicast
  • One-to-one
  • Destination – unique receiver host address
• Broadcast
  • One-to-all
  • Destination – address of network
• Multicast
  • One-to-many
  • Multicast group must be identified
  • Destination – address of group Key: Unicast transfer Broadcast transfer Multicast transfer

IP multicast

• Highly efficient bandwidth usage Key Architectural Decision: Add support for multicast in IP layer Berkeley Gatech (^) Stanford CMU Routers with multicast support

So what is the big issue …

more than 20 years since proposal, but no wide area IP multicast

deployment

• Scalability (with number of groups) -- Routers maintain per-group state
• IP Multicast: best-effort multi-point delivery service -- Providing higher level features such as reliability, congestion control, flow control, and security has shown to be more difficult than in the unicast case Can we achieve efficient multi-point delivery without IP-layer support?

Pros and Cons

• Scalability
  • Routers do not maintain per-group state
  • End systems do, but they participate in very few groups
• Potentially simplify support for higher level functionality
  • Leverage computation and storage of end systems
  • Leverage solutions for unicast congestion, error and flow control
• Efficiency concerns
  • redundant traffic on physical links
  • increase in latency due to end-systems

Bandwidth Efficient Overlay Trees “ …three ways of organizing the root and the nodes into a distribution tree. ” 10 Mb/s R 1 2 R 1 2 R 1 2 R (^21)

The node addition algorithm R 5 5 7 1 10 2 10 3 8 R (^1 ) 3 Physical network substrate Overcast distribution tree

Client Joins

R 1 1 2 3 4 5 6 R 2 R 3 Key: Content query (multicast join) Query redirect Content delivery

Application level multicasting

• A survey on ALM