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

181routers make decisions on LSP paths; label-distribution is downstream on-demand andordered; and resource management can be performed on the basis of LSPs [92]. MPLSbased flows are more restrictive than the SDN flow-abstraction; but it is fair to say thatflow-abstraction exists in some form in MPLS networks.We do not compare the SDN flow-abstraction to the MPLS datagram-based usagemodel(Sec. 5.1.1) for the following reasons: In the datagram-model, the only logicalassociation (or FEC or flow-definition) that matters network-wide is the IP-destinationaddress; forwarding decisions are still made independently router to router; and onecannot perform resource management at the flow level. However, even though the SDNflow-abstraction cannot (and should not) be compared to the MPLS datagram usagemodel;the former can still provide the service the latter enables – VPNs. We discuss thispoint in more detail in Sec. 5.4.5.2.2 MPLS and the Map-AbstractionWhen comparing MPLS network control with our control-architecture, it is important todistinguish between the map and the map-abstraction. We discuss them individually.Fig. 5.5 Network Maps in a) IP networks b) MPLS-TE networks c) SDNMaps: A map by our definition is an annotated graph of the network topology. Firstlet’s see how the maps themselves differ in different networks. In plain-vanilla IPnetworks, distributed routing protocols like OSPF and IS-IS distribute link state to each