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Interior Gateway Protocol (IGP) Metric Based Traffic Engineering

Interior Gateway Protocol (IGP) Metric Based Traffic Engineering. Visa Holopainen, visa@netlab.tkk.fi Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma. Contents. Concept of Traffic Engineering (TE)...…………………..4 Requirements for TE: Policy System……………………8

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Interior Gateway Protocol (IGP) Metric Based Traffic Engineering

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  1. Interior Gateway Protocol (IGP) Metric Based Traffic Engineering Visa Holopainen, visa@netlab.tkk.fi Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma

  2. Contents Concept of Traffic Engineering (TE)...…………………..4 Requirements for TE: Policy System……………………8 TE method classification………………………………….9 TE method 1: ECMP TE……………….........................10 TE method 2: MPLS TE…………………………………12 TE method 3: IGP Metric Based TE….........................13 Own contribution: Testing Strategic IGP Metric-Based TE in real networks……………………………………17 Summary/Conclusions…….…………………………….18

  3. Concept of Traffic Engineering (TE) • Traffic Engineering (TE) is a field of communications engineering that tries to make network operations more effective and reliable while at the same time optimizing resource utilization • “Application of technology and scientific principles to the measurement, characterization, modeling, and control of Internet traffic”

  4. Some problems that TE tries to solve (Concept contd.) • Effective bandwidth utilization within an Autonomous System • Optimal policy usage between Autonomous Systems (BGP TE) • Fast connectivity restoration after a component breakdown (IGP Fast Convergence, MPLS Fast Re-Route, etc.)

  5. Some TE goals illustrated (1): Better throughput (Concept contd.)

  6. Some TE goals illustrated (2): More equal link utilization (Concept contd.)

  7. Requirements for TE: Policy System • TE systems consist of a set of rules (Policy) that are propagated to enforcement points • Hierarchical policy systems possible • Business policy: f(High responsiveness) ->Response time must be < 2s • Utility function policy: f(Response time must be < 2s) -> condition C • Action policy: if condition C then do action A

  8. TE method classification • TE methods can be classified in many ways: • Short term vs. Long term TE • Intra-domain vs.Inter-domain TE • Centralized vs. Distributed TE • On-line vs. Off-line TE • Perfomance optimizing vs. Availability maximizing TE • Host-based vs. Network-based TE • …

  9. TE method 1: ECMP TE • Equal Cost Multipath (ECMP) balances load for all equal cost paths towards a destination • Every router performs a hash on received packets to determine which one of the paths should be used for the packet • The hash may be a function of source address, destination address, source port, destination port etc. and can be static or dynamic • The hashing can be performed separately for each packet or based on flows • Medium term, Intra-domain, Distributed, (Off-line), Network-based, Availability maximizing

  10. ECMP TE (continued) • ECMPis often considered to be sufficientTE method if both topology and traffic demands are symmetrical like in the figure • Often not enough for complicated networks

  11. TE method 2: MPLS TE • MPLS TE enables explicit (source) routing, which is quite significant, since it makes unequal-cost load sharing possible • In the figure, traffic load is divided evenly to unequal-cost router-paths x->y->z and x->k->v->z • MPLS TE is somewhat complicated to deploy but when correctly configured, it is very effective

  12. TE method 3: IGP Metric Based TE • Tactical IGP Metric Based TE tries to alter link costs in some specific points of congestion • Often only shifts the point of congestion

  13. IGP Metric Based TE (continued) • Strategic IGP Metric-Based TE tries to find an optimal link weight setting for the network (using some optimization goal(s))

  14. IGP Metric Based TE (continued) • The main idea in strategic IGP Metric Based TE is to 1) obtain topology and traffic information from the network, 2) feed this data to an optimization algorithm, and 3) send the optimal link weights back to the network • The routers calculate routes based on the optimal weights and traffic gets forwarded to optimal paths

  15. Optimization tool (IGP-WO) • Tries to find a link (interface) cost setting that balances load in the network • Uses iterative search and a utility function to discover near-optimal interface costs for SPF routing • Iterative search methods have the risk of visiting old solutions again (cycling) • Tabu-search meta-heuristic used to prevent this

  16. Own contribution: Testing Strategic IGP Metric-Based TE in real networks • TE-server uses IGP-WO to determine near-optimal interface costs dynamically based on topology discovery and measured traffic matrix • TE algorithm assumes that routers aren’t the bottleneck (-> not so useful if they are) • Network’s throughput improved about 15%

  17. Summary/Conclusions • Traffic Engineering (TE) methods try to make network operations more effective and reliable while at the same time optimizing resource utilization • Our measurements show that Strategic IGP Metric-Based TE improves throughput of real networks under certain conditions • Future work: making the optimal cost discovery faster by using a mapping system

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