Chapter 5 Introducing SDN Control in MPLS Networks - High ...

193different customer’s traffic differently is not possible with Auto-Route. If a differentapproach is required, then the network-operator has to fall back on static-routes and PBR,to supersede the decisions taken by SPF and Auto-Route. But while such mechanisms areflexible, they are not automated. They require human-intervention typically through theCLI in multiple routers along a path for each packet-flow that the operator may wish toroute differently.SDN approach to Auto-Route: SDN allows both flexibility and automation in itsapproach to routing. Together these attributes present a programmatic solution.In contrast to Fig. 5.8a, with SDN we take the approach shown in Fig. 5.9. Thenetwork-map allows full visibility to node and link state. To this state (which comes fromthe switches), we add the link-state attributes we need for traffic engineering such asmax-reservable-bandwidth, unreserved-bandwidth, priorities and other operator-definedattributes. TE routing of LSPs (tunnels) can be performed by an application on this map,and the resulting tunnels are introduced as unidirectional links in another map.Fig. 5.9 Auto-Route in SDNThis latter map is used for routing packet-flows. We can simultaneously routedifferent kinds of packet-flows differently – for example, traffic can be routed on thebasis of the type of end-user application it supports (voip, web, video etc.); or it can berouted differently for different customers or services; all other traffic can use default IP