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Optimized QoS Protection of Ethernet Trees

Optimized QoS Protection of Ethernet Trees. Tibor Cinkler, Andr á s Kern, Istv á n Moldov á n. Ethernet in Metro Access Networks. Ethernet is the most dominating LAN technology Cheap equipment + high speed (up to 10 Gbps) Switched Ethernet - Carrier grade properties are required:

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Optimized QoS Protection of Ethernet Trees

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  1. Optimized QoS Protection of Ethernet Trees Tibor Cinkler, András Kern, István Moldován

  2. Ethernet in Metro Access Networks • Ethernet is the most dominating LAN technology • Cheap equipment + high speed (up to 10 Gbps) • Switched Ethernet - Carrier grade properties are required: • Traffic Engineering • Resilience Ericsson, January 2006, Budapest

  3. Spanning Tree Protocol (STP) • Reverse learning + broadcast based packet switch • Tree–like topology desired • STP: • Defines loop-free logical packet forwarding topology • Spans a tree between the switches • Problems: • Slow convergence (improved by RSTP) • Bad network utilization Ericsson, January 2006, Budapest

  4. Multiple Spanning Tree Protocol • MORE VLAN based spanning trees • Multiple spanning tree instances • Each tree runs a separate RSTP instance • 1 VLAN  1 tree • Number of trees is decision of the operator • By default tree spanning is “Topology-Driven”: • Port costs based on topology and link capacities • Costs can be set manually (to obtain desired trees) Ericsson, January 2006, Budapest

  5. Protection switching • 802.3ad Link Aggregation • uses redundant links for load balancing and protection • Using MSTP • 2 MSTI trees, two paths: red and green • VLAN 1 -> MST 1, VLAN 2 -> MST 2 • A and B uses VLAN 1, in case of failure switch to VLAN 2 VLAN 1 MST 1 A LAN B VLAN 2 MST 2 (backup) Ericsson, January 2006, Budapest

  6. Model assumptions • Typical Metro Topology: • Aggregated traffic (demands) goes from the access to the edge nodes. • Root of the trees at Edges node one or more trees per edge node TrafficDestination TrafficSource Ericsson, January 2006, Budapest

  7. Optimization framework • Optimize the spanning trees • Goal is to minimize the used network resourcesto maximize network throughput • Provide 1:1 protection • To protect all traffic is expensive - protect only a part of the traffic: the prioritized traffic • Best Effort can use the protection paths Ericsson, January 2006, Budapest

  8. Formal description: ILP • Integer Linear Program is used • Result is a global optimal solution • Constraints • Total load does not exceed the link capacities and QoS limits • If a demand uses a link the assigned tree will also use it • Tree constraints (no cycles) • Backup paths must be disjoint Ericsson, January 2006, Budapest

  9. Evaluation Criteria • Maximal Throughput of the network • Scaling up the offered load • The allocated capacity for protection • Resilience vs. Throughput: the amount of traffic lost in case of failure • Complexity Ericsson, January 2006, Budapest

  10. Throughput gain Ericsson, January 2006, Budapest

  11. Throughput w/ protection Ericsson, January 2006, Budapest

  12. Capacities allocated Ericsson, January 2006, Budapest

  13. Heuristic • Decomposition: • Demand Routing (DR) • Based on Simulated Allocation (SAL) • Tree Assignment and Placement (TAP) • Tree construction algorithm • Results verified by simulations • comparison to ILP solution Ericsson, January 2006, Budapest

  14. Heuristic Results Ericsson, January 2006, Budapest

  15. Relative throughputs Ericsson, January 2006, Budapest

  16. Conclusion • We present an optimization TE Framework for QoS and protection • ILP – not scalable • Heuristics – scalable, close to optimal • We show that: • With optimization we can use redundant links • Throughput doubles compared to STP • Optimized 1:1 protection • The same throughput as STP but all protected • Protecting QoS traffic only is reasonable tradeoff Ericsson, January 2006, Budapest

  17. Thank you for your attention! Ericsson, January 2006, Budapest

  18. The End… Ericsson, January 2006, Budapest

  19. QoS model • Priority based scheduling: • Lower priority traffic is not served until there is higher priority traffic in the queue. • To ensure low delay for each QoS class:amount of higher priority traffic should be limited for each link • The ratios are examples, and should be determined individually for each operator 10% 20% 30% remaining Ericsson, January 2006, Budapest

  20. QoS provisioning • Preprovisioned VLAN based QoS pipes • Traffic engineered paths for VLAN pipes • Resources assigned to pipes • Optimization ensures that QoS requirements are met for each link • Edges: • Classification - VLANs • Admission control, policing • All nodes • Queuing, scheduling Ericsson, January 2006, Budapest

  21. Loss in case of failure • Throughput lossiscomparedto the network throughput without failure • losses are measured immediatelyafter the link failure, so the restoration capability of theSTP is not considered Ericsson, January 2006, Budapest

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