MPLS backbone design

Service providers must take into account of several factors during design of their backbones. These factors are high performance, scalability and redundancy. During the design of the topology, it is not necessary only considering these factors if the backbone will run MPLS. If an MPLS backbone is being designed, logical protocols proccessing is also important. Interior gateway protocol to be implemented in the backbone can be either OSPF or IS-IS. Interior gateway protocol being used in the backbone is responsible of distributing logical addressing scheme to all routers in the backbone. On the other hand, BGP ?as an exterior gateway protocol- is necessary to communicate with other autonomous systems. Broadband remote access servers, which can be regarded as aggregation of the Internet traffic in the backbone will be connected to MPLS routers. In this case routers will learn Internet routes from BGP protocol. LDP protocols is responsible of distributing labelling information to MPLS routers in the backbone. LDP learns how to reach to IP subnets from OSPF protocol and with this information prepares LDP label bindings for these IP subnets. LDP has critical disadvantage by design. An LDP running router sends LABEL RELEASE message to upstream router if it losts connection to an IP subnet. LABEL RELEASE message does not have an acknowledgement. So the router that sends LABEL RELEASE message to upstream routers, deletes label bindings for this IP subnet without being sure whether upstream router get this message and deleted its label binding. In the solution proposed to this problem in this work, traffic for broadband remote access servers shoulsd be carried with static LSPs, those are protected with Fast Reroute mechanism. Since these static tunnels will be terminated at the core, RSVP will be used for these static LSPs and LDP will be used for dynamic LSPs. Therefore LDP disadvantage will be eliminated with this structure for the high volume traffics of broadband remote access servers.