1. 1 Traffic Engineering By Kavitha Ganapa

2. 2 Introduction Traffic engineering is concerned with the issue of performance evaluation and optimization of operational IP networks Through carefully managing the traffic distribution inside a network Congestion hot spots can be reduced Resource utilization can be improved

3. 3 Need for Traffic engineering Need for service providers to efficiently provide and manage network resources to accommodate resource commitments To meet customer’s expectation of guaranteed and differentiated services To reduce cost of provisioning the services

4. 4 Fish problem Leads to extremely unbalanced traffic Poor utilization of network resources

5. 5 Fish problem in IP routing Fish problem is caused by primarily two properties IP routing is destination-based, all packets whose destination addresses share the same prefix have the same next hop Decision making in current routing is based on local optimization

6. 6 Traffic engineering solutions Fish problem is solved by going beyond current destination based routing and by providing mechanisms to explicitly manage the traffic inside network Overlay Model Peer Model

7. 7 Overlay Model Calculates the routes for traffic demands for edge nodes Service providers then set up MPLS explicit routes between edge routes and match traffic demands over them, creating a full-mesh network Suffers from N-square problem, problems with scalability

8. 8 Peer Model Achieves balanced traffic distribution by manipulating link weights in the OSPF routing protocol More scalable than Overlay Model Packets are forwarded based on longest- prefix match Eliminates N-square problem and reduces Reduces messaging overheads in setting up explicit routes

9. 9 Optimization objectives Minimizing congestion and packet losses in the network Network congestion is caused by Inadequate network resources (can be solved by new capacity or reduce demands) Unbalanced traffic distribution (can be addressed by better management of the resources in the network) Improving link Utilization Minimizing the total delay experienced by packets Increasing the number of customers with the current assets

10. 10 One objective To minimize the maximum of link utilization Why? Hot spots are the points with the highest link utilization Queuing delay increases nonlinearly as link utilization becomes higher By minimizing the maximum of link utilization traffic is spread and the resources are efficiently used

11. 11 Advantages of the Objective Reduces the total delay experienced by the packets Moves the traffic away from congested hot spots to less utilized parts of the network thus balanced traffic distribution Leaves more space for future traffic growth, the percentage of residual bandwidth is maximized by the minimizing the maximum link utilization

12. 12 Building blocks Data repository Topology and state discovery Traffic demand estimation Route computation (constraint-based routing) Network interface Graphic user interface Topology and state discovery and constraint based routing are two critical components of traffic engineering

13. 13 Topology and state discovery OSPF-based scheme Because OSPF is widely deployed Has the necessary mechanisms for distributing link status and constructing a topology database Extended link state information for traffic engineering Local and remote interface IP addresses Traffic engineering metric Maximum bandwidth Maximum reservable bandwidth Unreserved bandwidth Resource class

14. 14 Constraint-based routing Shortest path Minimum hop Minimize the total resource consumption per route Shortest widest path Avoids overloading by maximizing the residual capacity across the network Hybrid algorithm Combination of Shortest path/Minimum hop and shortest widest path

15. 15 Multipath load sharing Hashing based traffic splitting schemes Direct hashing Can split a load only into equal amounts Table-based hashing Can distribute the traffic as required

16. 16 Summary Traffic engineering is concerned with performance optimization of operational networks Provides a set of tools for efficiently provisioning and managing backbone networks Used to reduce congestion hot spots, improve overall utilization of networks and reduce the cost for meeting resource commitments to their customers

17. 17 Research work Our work includes the investigation of the QoS-based routing problem under two different frameworks: the traditionally used SPC-QRF The newly proposed SPD-QRF

18. 18 Acknowledgments The slides are prepared based on the information from Architectures and Mechanisms for Quality of Service by Zheng Wang