Path vs Subpath vs Link Restoration for Fault

Path vs. Subpath vs. Link Restoration for Fault Management in IP-over-WDM Networks: Performance Comparisons Using GMPLS Control Signaling

Restoration techniques n WHEN A FIBER FAILS 1. The upstream end node of the failed sends an alarm message to the source node of the disrupted optical LSP 1. The downstream end node sends a teardown message to the destination node of the optical LSP 2. After the source node receives the alarm message, it tries to reestablish the optical LSP by sending a setup message to the destination node via a alternate path

Simulation platform n n n ns 2 optical cross-connect(OCX) module WDM link module Label Distribution Protocol module WDM specific Traffic Engineering module explicit route computation module

General philosophies and implement n 1. Contention Resolution n n When the LSP setup request follows too closely to a change the up-to date link state information may not be available at the source node of the new request. 1. All near requests come to a single node from a common source node. n n 2. When the source nodes are different. n n sol : To allow the source nodes to retry when the initial restoration effort fails. 2. Identification of the Restoration Optical LSPs n n sol : The common source node can increase its routing computation. When assigning identification to a restoration LSP. Should the retoration path use the same identification as the original one or not? 3. Loop Prevention n A loop in an LSP is defined as the LSP traversing a node for more than once.

Restoration performance results n Restoration success n n Restoration time n n the average repair time for all successfully restored paths. Availability n n the ration of the total number of successfully restored connections to the total number of disrupted connections. the ratio of the total uptime for an optical LSP to the total duration of the optical LSP. Blocking probability n the ration of the number of unsuccessful connection requests to the total number of connection requests in a network.

Performance comparison of the restoration techniques

Enhanced path restoration techniques

The effects of fault interarrival time n Failure frequency directly affects network availability, independent of whether the restoration success rate is high or low.