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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 protocol Multi-Path routing Transport Protocol Per-hop Packet Distribution Simulation results. Multi Path Routing.

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MULTI-PATH ROUTING

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  1. MULTI-PATH ROUTING A packet by packet multi-path routing approach Dennis Ippoliti 12/6/2004

  2. OVERVIEW • Multi-path routing (Benefits / Problems) • Multi-Path routing protocol • Multi-Path routing Transport Protocol • Per-hop Packet Distribution • Simulation results Dennis Ippoliti 12/6/2004

  3. Multi Path Routing • In a well connected network multiple paths exist With Multi-Path routing, traffic is diffused over several paths at the same time Typically, one path at a time is chosen and all traffic is sent over that path Dennis Ippoliti 12/6/2004

  4. Benefits of Multi-Path routing • Enables Load balancing implementations • Simplifies algorithms if single flows can take multiple paths • Increases throughput • Decreases delay • Takes advantage of considerable redundancy • 90% of all US Sprintlink POP pairs are connected by 4 or more paths • Increases Robustness to Eavesdropping • Attackers must sniff multiple links when traffic is diffused Dennis Ippoliti 12/6/2004

  5. Challenges in Multi-Path routing • Route Identification • Identifying available routes • Route Selection • Round Robin, Weighted Selection, Other • Metrics (Throughput / Delay / Drop rate) • Different subsets of routes will maximize/minimize different metrics • Leads to persistent packet re-sequencing • When multiple routes are used, the probability that packets are received out of sequence is high Dennis Ippoliti 12/6/2004

  6. Multi-Path Routing Algorithms • In a network G = (N, L) with N nodes and L links, MP Algorithms identify S(I,j) such that S(I,j) = the set of successor nodes to rout traffic from node I to node j. • Multi-path routing algorithms identify S(I,j) and rank order according to some minimum or maximum desired metric or combination of metrics Dennis Ippoliti 12/6/2004

  7. Multi-Path Routing Algorithms • Multi-Path Distance Vector (MPDV) • Multi-Path Link State (MPLS) • Enhanced Interior Gateway Routing Protocol Dennis Ippoliti 12/6/2004

  8. Multi-Path Transport Protocol • Multi-Path environment causes persistent packet reordering Dennis Ippoliti 12/6/2004

  9. 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 Dennis Ippoliti 12/6/2004

  10. 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 Dennis Ippoliti 12/6/2004

  11. 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 Dennis Ippoliti 12/6/2004

  12. 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 Dennis Ippoliti 12/6/2004

  13. 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 Dennis Ippoliti 12/6/2004

  14. Simulation Method • Developed Network Simulator software similar to the Click Router Platform • C++ objects represent Nodes and Links • Static Multi-Paths • RR, Load Balancing, and Minimum Delay Routing as Route Selection methods • TCP-PR as transport protocol Dennis Ippoliti 12/6/2004

  15. Results • TCP-PR 200% through-put over standard TCP • Round Robin, Load balancing, and Minimum delay route selection performed the same when link cost equal • Only Minimum Delay performed well when link cost was unequal • Dynamic service differentiation prevents starvation in the presence of greedy flows Dennis Ippoliti 12/6/2004

  16. TCP-PR QUESTIONS? Dennis Ippoliti 12/6/2004

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