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Traffic Engineering With Traditional IP Routing Protocols by Bernard Fortz, Jennifer Rexford and Mikkle Thorup. Summary by Faisal Aslam Paper Achievement: It claims that Traditional IP (IGP) shortest path routing protocols are surprisingly effective for engineering the flow of traffic in large IP networks. It says that global optimization of link weights is more effective then other schemes. (This optimization is done outside the routers on some centralized location) Traffic Engineering (TE) Definition: Improving user performance and making more efficient use of network resources requires adopting the routing of traffic to the prevailing demands. This task is known as Traffic engineering. OSPF/IS-IS TE Extensions: Recent standards proposed TE extension to OSPF/IS-IS to incorporate traffic load in the link-state advertisements (LSA) and path selection decisions. However these extensions require modification to the routers to collect and disseminate the traffic statistics and establish path based on the load metrics. Instead this paper says that it is possible to select static link weights that are resilient to traffic fluctuation and link failures, allowing the use of the traditional incarnation of OSPF and IS-IS. Objective function: The simple performance objective function here is to minimize the maximum link load. Comparison between three approaches: The author have compared three approaches which are 1) initial configuration with unit weigthts 2) local change to the weight for congested link 3) Global optimization of the link weights. The comparison shows that using Global optimization of link weights one can get the best optimization. Advantages of Global optimization: The global optimization routing (centralized approach) has advantages like protocol stability (no unnecessary LSA generations) and diverse performance constraints (the selection of routing parameter can be depend on variety of performance constraints). Traffic Engineering Framework: The author’s framework has three main steps. 1) (Measure) The operator needs to measure the network topology and the offered traffic. 2) (Model) evaluating possible setting of the link weights requires a way to predict how they will affect the traffic. 3) After deciding on the values of the weights, an automated system or a human operator needs to change the IGP configurations. Author suggested AdvanceOSPF could handle 70% more demand than the InvCapOSPF (weight inverse to the capabilities) and UnitOSPF (each link have unit weight). Changing Traffic Demands: For example if the Day time traffic on and ISP is different then night time then in such case author suggest to have single optimization for both of the traffic demands. Few Changes to the link weights: Sometimes it is necessary to avoid link weight changes like situation where multiple link fails etc. But the author have analyzed that changing a single link weight is often quite effective.