CAIP: a restoration routing architecture for DiffServ aware MPLS traffic engineering

The authors proposed an architecture for MPLS restoration routing of DiffServ traffic. This architecture, namely per class aggregate information with preemption (CAIP), facilitates provisioning of two key QoS features for multimedia traffic: prioritized guaranteed bandwidth and fast restoration in the event of an element failure. The CAIP architecture is scalable and requires propagating only per-class aggregate link usage information; such information can be readily piggybacked on link state routing packets using traffic engineering extensions to link state routing protocols (Katz et. al). CAIP results in improved bandwidth sharing compared to simple aggregate information scenario (SAIS), resulting in fewer LSP rejected requests and a greater amount of active bandwidth placed on the network. On average, CAIP rejects 881 LSP requests compared to 1010 rejected LSP requests in SAIS for a typical ISP network. Similarly, CAIP is able to place 220 units of bandwidth compared to 180 units of bandwidth placed in SAIS, thus showing an average improvement of about 22%. CAIP allows precise computation of preemptable bandwidth for an arbitrary set of prioritization requirements put forth by the service providers. A case study of service provider requirements and computation of preemptable bandwidth for those requirements were presented. CAIP can be integrated with those restoration routing schemes that make use of propagating aggregate link usage information. Furthermore, existing preemption schemes can be used with CAIP in order to decide the actual LSPs which need to be preempted.