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MULTI-PATH ROUTING

MULTI-PATH ROUTING. A packet by packet multi-path routing approach. OVERVIEW. Multi-path routing (Benefits / Problems) Multi-Path routing Transport Protocol Per-hop Packet Distribution Simulation results. Benefits /Problems Multi-Path routing. Benefits:

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MULTI-PATH ROUTING

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  1. MULTI-PATH ROUTING A packet by packet multi-path routing approach

  2. OVERVIEW • Multi-path routing (Benefits / Problems) • Multi-Path routing Transport Protocol • Per-hop Packet Distribution • Simulation results

  3. Benefits /Problems Multi-Path routing • Benefits: • Enables Load balancing implementations • Simplifies algorithms if single flows can take multiple paths • Increases throughput • Decreases delay • Challenges: • Route Identification • Route Selection • Transport Protocols: Leads to persistent packet re-sequencing

  4. Multi-Path Transport Protocols • TCP is not effective in this environment • TCP uses windowing for error and congestion control • When packets are received out of order, DUPACKS are generated • DUPACKS typically decrease window size by 50% • DUPACKS cause sender to enter Fast Retransmit • Persistent DUPACKS reduce throughput while increasing traffic load

  5. Multi Path Transport Protocols • Eifel Algorithm • Uses time-stamp option to differentiate between transmissions and re-transmissions • Restores TCP congestion window to value prior to retransmit when packet received • DSACK • Uses DSACK option to communicate from receiver to sender • Dynamically manipulate dupthresh value • TCP Persistent Reordering • Ignores DUPACKS. Uses timers to identify packet loss

  6. Route Selection • Round Robin and pure load balancing not effective • Do not take network conditions into consideration • Minimum Delay Routing • As delay increases, the proportion of traffic distributed to that rout decreases

  7. A B A B 1 2 1 2 3 4 5 3 4 5 6 7 8 6 7 8 9 0 9 0 C D C D Route Selection • Minimum Delay Routing with dynamic service differentiation • In multi path routing, a greedy node can starve other nodes on the network

  8. A B A B 1 2 1 2 3 4 5 3 4 5 6 7 8 6 7 8 9 0 9 0 C D C D Route Selection • I experimented with Minimum Delay Routing with dynamic service differentiation • Traffic that is on a primary route is given priority over traffic on a secondary route

  9. Simulation Method • Developed Network Simulator software similar to the Click Router Platform • C++ objects represent Nodes and Links • Static Multi-Paths • RR, and Minimum Delay Routing as Route Selection methods • TCP-PR as transport protocol

  10. Simulation Topology A Green = 5 Mbps Red = 2 Mbps Black = 3 Mbps 1 4 2 3 C

  11. A B 1 2 4 3 5 6 7 8 C D Results Black = 8 Mbps Green = 5 Mbps Red = 1 Mbps

  12. References • S. Vutukury and J.J. Garcia-Luna-Aceves. A Simple Approximation to Minimum Delay Routing. Proc. of ACM SIGCOMM, Sept. 1999. • Stephan Bohacek, Joao Hespanha, Junsoo Lee, Chansook Lim, Katia Obraczka. A New TCP for Persistent Packet Reordering-TCP-PR, Accepted for Publication in Transactions on Networking, 2004 • S. Floyd, J. Mahdavi, M. Mathis, and M. Podolsky, “An extension to the selective acknowledgement (SACK) option for TCP.” RFC 2883, 2000. • R. Ludwig and R. Katz, “The Eifel algorithm: Making TCP robust against spurious retransmissions,” ACM Computer Communication Review, vol. 30, no. 1, 2000.

  13. TCP-PR QUESTIONS?

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