Traffic Engineering and Routing Hansen Bow Topics Traffic

Traffic Engineering and Routing Hansen Bow

Topics • • • Traffic Engineering with MPLS Issues Concerning Voice over IP Features of Netscope Qo. S Routing for High-Speed Networks Qo. S Routing for Multimedia

Traffic Engineering with MPLS: Methods • MPLS – multiprotocol label switching • Constraint-based routing • Enhanced link state IGP

MPLS-multiprotocol label switching • forwarding scheme • at ingress of MPLS network, IP packets are classified, tagged, and routed • at next router, tag is used to determine destination • before leaving, tag is removed

Constraint-Based Routing • computes bounded routes • reservable bandwidth of a link is an approximation • can be done online or offline

Enhanced Link State IGP (interior gateway protocol) • distribute link information • flood network to obtain information

Deploying MPLS System (Globe. Center) • Statistics Collection • Deploy LSP (label-switched path) with bandwidth constraint • Periodic update of LSP Bandwidth • Offline Constraint-Based Routing

Voice over IP Issues • modify capacity management and routing methods in IP to support IP telephony – delay less than 300 ms – loss rate <1% • First Model: RSVP • Second Model: voice service uses Virtual Private Network

RSVP Routing • Shortest Path First • Shortest Available Path First • Widest Available Path First

Virtual Private Networks • • • interconnects telephony switches Direct Path Only Success to the Top State-Dependent Routing Approximate State-Dependent Routing

Direct and Alternate Routing Policies

Differently Routed Calls with Trunk Reservation

Routing Policies with Integrated Services Model • not much difference between SPF, SAPF, WAPF • fewer blocked calls for a given network capacity because of better sharing of network capacity

Features of Netscope • traffic measurement and network modeling • provide global views of configuration and useage data

Utility of Netscope • • realizing customer SLAs tuning parameters of network components unite configuration experiment with possible solutions to variable complex traffic

Data • Network components • Modeling Traffic • Routing – multiple shortest paths

Visualization • • Objects Statistics Traffic and Links Changing Routes

Qo. S Routing Issues for High Speed Networks • Goals – satisfy Qo. S requirements for admitted connection – global efficiency • Classes – Source routing – Distributed routing – Hierarchical routing

Routing • Collection of State Information – local and global state – aggregated global state

Routing • Finding Feasible Path – Unicast • • link optimization link constrained path optimization path constrained – Dijkstra’s algorithm • http: //www. cs. uwa. edu. au/undergraduate/courses/230. 300/read ings/graphapplet/graph. html – Multicast • Steiner Tree

Routing Strategies • Source routing – centralized problem, loop-free – need global state, computation overhead • Distributed routing – routing response faster, scalable – need global state, more messages, loops • Hierarchical routing – scales well, computation shared – imprecision because aggregate state, complicated with constraints,

Future Directions • • Efficient Routing Algorithms Routing with imprecise state information Multipath Routing Rerouting

Qo. S Routing for Multimedia • Metric Selection – Efficient algorithms must exist for path computation – Reflect basic information of network – orthogonal • Multiple Metrics – additive, multiplicative, concave

Bandwidth and Delay as Metrics • finding path subject to two or more additive and multiplicative metrics is NP-complete • only feasible combination is bandwidth and, for example, delay

Path Computation Algorithms • Source Routing • Hop-by-hop – compute best path to every destination – shortest-widest path is free of loops

References • “Net. Scope: Traffic Engineering for IP Networks, ” A. Feldmann, A. Greenberg, C. Lund, N. Reingold, and J. Rexford, IEEE Network, Mar. /Apr. 2000, pp. 11 -19 • “Traffic Engineering with MPLS in the Internet, ” X. Xiao, A. Hannan, B. Bailey, and L. M. Ni, Ibid. , pp. 28 -33 • “Capacity Management and Routing Policies for Voice over IP Traffic, ” P. P. Mishra, and H. Saran, Ibid, pp. 20 -27 • “Quality-of-Service Routing for Supporting Multimedia Applications, ” Z. Wang, and J. Crowcroft, IEEE Journal on Selected Areas in Communications, Vol. 14, No. 7, Sept. 1996 • “An Overview of Quality of Service Routhing for Next-Generation High-Speed Networks: Problems and Solutions, ” S. Chen and K. Nahrstedt, IEEE Network, Nov. /Dec. 1998, pp. 64 -79