Designing a New Routing Simulator for DiffServ MPLS Networks

1. TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY Designing a New Routing Simulator for DiffServ MPLS Networks Peng Zhang Zhansong Ma Raimo Kantola {pgzhang, zhansong, kantola}@tct.hut.fi http://www.tct.hut.fi/u/pgzhang/QRS/index.html SCSC 2001 International Symposium on Performance Evaluationof Computer and Telecommunication Systems Orlando, Florida, July

2. Contents TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • DiffServ MPLS network functions • QoS Routing Performance and Cost • Enhanced QoS Routing Simulator • Link State Update Algorithms • Simulation Study of LSU Algorithms

3. DiffServ Architecture TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY Customer Services Operation, management and provision QoS signaling DS Domain Ingress node Egress node Interior node Classifying, marking shaping Forwarding PHB

4. DS Traffic Engineering Functions TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY Ingress node meter classifier marker dropper queuer Interior node dropper queuer marker dropper queuer Egress node

5. Dropping and Queuing TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY EF queue WRED1 AF1 queue WRED1 AF2 queue WRED1 AF3 queue WRED1 AF4 queue BE queue You can set: buffer size, serving rate, wred parameters etc...

6. Feasibility of QoS Routing TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • QoS Routing • finds paths that are subject to QoS requirements while achieving efficiency in network resource utilization • Benefits of QoS Routing • enables creation of virtual circuit-like services • improves user satisfaction • improves network utilization and increases network thruput • Benefits do not come free • cost of deploying QoS routing protocol • cost of processing overhead • cost of storage overhead • added complexity of routers • ... • Whether or not the benefits are worth the cost ?

7. Link State Update Algorithms TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • Period based (PB) • timeout T • an update is sent when timeout T expires, T is restarted. • Threshold based (TB) • threshold th, last advertised value bwio and current value bwic • updates when (|bwio - bwic| / bwio)> th for bwio 0, • bwic >0 for bwio 0 • Equal class based (ECB) • base class B, classes: (0,B),(B,2B),(2B,3B),…,etc • updating when available bandwidth changes across a class boundary • Unequal class based (UCB) • base class B and factor f(f>1) , classes: (0,B), (B,(f+1)B), ((f+1)B, (f2+f+1)B), ((f2+f+1)B,(f3+f2+f+1)B),…, etc • updating when available bandwidth changes across a class boundary

8. Multi-path QoS Routing TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • Motivation • The development of MPLS and DiffServ • The development of QoS routing (e.g., QOSPF) • The development of multi-path (QoS) routing in legacy networks • E.g., ATM networks • Content • Find multiple disjoint paths between a pair of nodes that satisfy QoS requirements (e.g., bandwidth, delay) • Link disjoint paths or node disjoint paths • For example, two link disjoint paths have no common links • Fully disjoint paths and partly disjoint paths • Fully disjoint paths have no common links/nodes • Partly disjoint paths have common links/nodes but not all • On-line or off-line path computation • On-line computation uses simple algorithms • Off-line may use complex algorithms • Combination: Once link failures happen, the on-line computation is used first for fast restoration and the off-line computation is used later for path optimization

9. Multi-path QoS Routing (cont’d) TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • Benefits • Enhance network reliability and survivability • If one or more paths fail, other paths are available • If one or more paths fail, users’ traffic are not interrupted • Minimize network delay • Improve network resource utilization • Satisfy users’ traffic requirements • Metrics • Simplicity • There lack simple and efficient multi-path routing algorithms • There are few multi-path QoS routing algorithms • Stability • Routing algorithms should efficiently work in various network environment, e.g., various network topologies, various traffic. • …

10. Multi-path QoS Routing (cont’d) TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • Considerations in QRS • Implement simple multi-path (QoS) routing algorithms • Inherit single path (QoS) routing algorithms of QRS • I.e., lowest cost (LC) and widest bandwidth (WB) • Based on link state schema (e.g., OSPF) • Algorithms in QRS • Two-step-link-disjoint-lowest-cost • The first step: find a lowest cost path that satisfies the bandwidth requirement • The second step: prune the links used in the first path and then calculate the lowest cost path in the residue topology • Two-step-node-disjoint-lowest-cost • Two-step-link-disjoint-widest-bandwidth • Two-step-node-disjoint-widest-bandwidth • Current work • Implement more multi-path QoS routing algorithms • Evaluate the performance of these algorithms and their impact on the network traffic • …

11. Enhanced QoS Routing Simulator TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY RM Realtime Traffic Source/Sink ERSVP QOSPF NODE(Classifier, marker) LINK(dropper, queuer) http://www.tct.hut.fi/~pgzhang/QRS/index.htm This version supports DiffServ and MPLS

12. ISP Topology TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY Minimum cut is 5*6Mb/s = 30 Mb/s Shortest path algorithm is able to use 3 of 5 alternative links. Link Bandwidth = 6Mb/s

13. Simulations with UCB TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY

14. Summary TEKNILLINEN KORKEAKOULU HELSINKI UNIVERSITY OF TECHNOLOGY • We have implemented a QoS Routing Simulator that supports IntServ, DiffServ and MPLS. • It can be used to study dynamics, stability, cost and performance and scalability of QoS routing. • We demonstrated the use of the Simulator for Unequal Class Based (UCB) link state updates. In UCB, the performance and cost are affected by two variables, by setting suitable values, this algorithm can produce a good combination of performance and cost. • Most recently two multi-path QoS routing algorithms have been added to the Simulator. • The Simulator is available for download on our www-site.