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The Delta Routing Project Low-loss Routing for Hybrid Private Networks

The Delta Routing Project Low-loss Routing for Hybrid Private Networks. George Porter (UCB) Minwen Ji, Ph.D. (SRC - HP Labs). Outline. Motivation/overview of corporate networks Problem Statement Architecture Two layers: Physical and Overlay The Delta Protocol The Delta+TM Protocol

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The Delta Routing Project Low-loss Routing for Hybrid Private Networks

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  1. The Delta Routing ProjectLow-loss Routing for Hybrid Private Networks George Porter (UCB) Minwen Ji, Ph.D. (SRC - HP Labs)

  2. Outline • Motivation/overview of corporate networks • Problem Statement • Architecture • Two layers: Physical and Overlay • The Delta Protocol • The Delta+TM Protocol • Evaluation • Conclusions

  3. Corporate Network ConstructionNetwork Layer • Distributed Locations connected by leased lines due to: • Need for predictable performance • Security • Management and control • Fixed initial cost, incremental additional cost due to traffic volume • Not necessarily overprovisioned • Reprovisioning on the timescale of days (or weeks) • Expensive (compared to ISP connectivity LON SEA OSPF NYC SF DC ALX LA DFW HOU

  4. Corporate Network ConstructionOverlay Layer ISP Connectivity • ISP Connectivity alreay at selected nodes to provide: • Web/Email access • VPN access to at-home or distance workers • Business services • Per-byte, ISP much cheaper than “Intranet” • But no QoS • Intranet corporate network with ISP links is called a ‘Hybrid Private Network’ LON SEA NYC SF DC ALX LA DFW HOU

  5. Problem of Congestion • Flash traffic (video, backup, data transfer) or steady corporate growth can lead to periodic congestion • Problem Statement: • Reduce congestion and packet loss on the Intranet by utilizing ISP connectivity while providing good end-to-end performance LON SEA NYC SF DC ALX LA DFW HOU

  6. Architecture

  7. Architecture • Overlay Layer: • Need to forward traffic around congested portions of the Intranet • Measurement-based path construction • Intermediate point may be better than “last hop” selection • Metric include measured latency and local queuing delay • Paths are selected on order of seconds or minutes • Physical (Intranet) Layer: • Single-domain routing protocol (OSPF) • Dijkstra • Forwarding decision: which packets go to Intranet and which go to the preselected overlay paths? (per packet)

  8. Physical Forwarding Algorithm • Ji, Minwen. Dial-controlled Hash: Reducing Path Oscillation in Multipath Networks. Proceedings of the International Conference on Computer Communications and Networks (ICCCN). Oct 2003. • Current Algorithm: • Prefer physical path, but if physical queue full send to overlay layer.

  9. Overlay Path Selection Algorithms • Static • Lasthop • Nexthop • Random • Dynamic • Delta • Minimize end-to-end delay • Delta+TM • Predict and avoid congestion by inferring global traffic matrix

  10. Delta Path Selection • Find path to minimize the sum of: • Local Queue delay + WAN delay + Intranet delay • Key feature is the use of locally obtained information

  11. Limitation of Delta Algorithm • Since Delta uses local information, it might send traffic to an overloaded link: congested • Can we avoid this?

  12. Delta+TM (Traffic Matrix) • Key idea: • Don’t choose paths that will subject the traffic to congestion • Use the original Delta algorithm (minimize end-to-end delay) but throw out paths that will subject packets to congestion • But how do we find out about remote congestion? • Given that message flooding will likely be inaccurate and might make the problem worse

  13. .3 .89 .6 1.2 1.3 .03 Traffic Matrix Estimation + = Topology Information • Each node measures flows that transit through it • Long-term averages are flooded to fill in the entries of the table that a node can’t directly measure

  14. Evaluation Simple Example Algorithm-antagonistic Topologies Large-scale Topology (PlanetLab-based)

  15. Linear Topology

  16. Congestion Event

  17. Congestion Event

  18. Evaluation Simple Example Algorithm-antagonistic Topologies Large-scale Topology (PlanetLab-based)

  19. Algorithm-antagonistic Topology • Simple topology with traffic flows that should expose a weakness to each topology

  20. Algorithm-antagonistic Topology

  21. Evaluation Simple Example Algorithm-antagonistic Topologies Large-scale Topology (PlanetLab-based)

  22. Planetlab as VPN-network source • Large, distributed testbed • We modelled the Overlay part of a fictional 43-node corporate network using traces taken over planetlab • The Intranet link topology was obtained from 2-level clustering and eyeballing • Traffic flows include a “measured flow” and a set of background and disruptive flows

  23. PlanetLab (UCLA->ac.uk) Packet Losses

  24. Conclusions • Utilizing ISP connectivity enables balancing packet loss rate –vs- end-to-end delays • Dynamic algorithms can adapt to a variety of wide-area conditions • Congestion prediction can help in certain environments, however local-only decision making works well • Certain “choke points” must be identified so that synchronization effects will not occur • Making better use of bandwidth can lower cost of deploying distributed corporate networks

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