1. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 1/18

2. HELSINKI UNIVERSITY OF TECHNOLOGY Networking laboratory 2/18 Interior Gateway Protocol (IGP) Metric Based Traffic Engineering Visa Holopainen, visa@netlab.tkk.fivisa@netlab.tkk.fi Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma

3. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 3/18 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

4. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 4/18 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”

5. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 5/18 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.)

6. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 6/18 Some TE goals illustrated (1): Better throughput (Concept contd.)

7. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 7/18 Some TE goals illustrated (2): More equal link utilization (Concept contd.)

8. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 8/18 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 condition C –Action policy: if condition C then do action A

9. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 9/18 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 –…

10. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 10/18 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

11. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 11/18 ECMP TE (continued) ECMP is often considered to be sufficient TE method if both topology and traffic demands are symmetrical like in the figure Often not enough for complicated networks

12. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 12/18 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

13. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 13/18 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

14. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 14/18 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))

15. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 15/18 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

16. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 16/18 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

17. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 17/18 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%

18. HELSINKI UNIVERSITY OF TECHNOLOGY Visa Holopainen 18/18 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