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 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

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

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

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

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

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

Simulation Topology Green = 5 Mbps Red = 2 Mbps Black = 3 Mbps 1 2 3 4 C Single Path routing 1, 2, C 3.4 Mbps Throughput Round Robin Multi-Path TCP 904 Kbps Throughput Round Robin Multi-Path TCP-PR 4.89 Mbps Throughput Minimal Delay Multi-Path TCP 5.88 Mbps Throughput Minimal Delay Multi-Path TCP-PR 10.48 Mbps Throughput

Results Black = 8 Mbps Green = 5 Mbps Red = 1 Mbps A->C Single Path 3 4 B C 6 7 D 2 5 8 Black = 8 Mbps Green = 5 Mbps Red = 1 Mbps A->C Single Path B->D Single Path A->C = 6.4 Mbps B-D = 2.2Mbps B-D Multi Path B-D = 4.2Mbps A->C Multi-Path A->C 10.4 Mbps B-D 2.4 Mbps A->C WTP Multi-Path B->D WTP Multi Path A->C 9.2 Mbps B-D 4.0 Mbps

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.

TCP-PR QUESTIONS?