In this thesis, we have evaluated existing OAM mechanisms for MPLS backbone networks and compared these mechanisms to IP. This has shown that the MPLS OAM principles fully covers failure and reachability detection, avoidance of congested routers, SNMP features, fast rerouting and protection switching functions, traffic engineering and ad hoc mechanisms like Ping, We have also proposed the ITU-T LSP connectivity verification mechanism, fast rerouting and protection switching, and the use of MPLS MIB as recommended OAM mechanisms for large backbone networks. Also, we have three new ideas for OAM on MPLS in backbone networks.
Firstly, a new mechanism for classifying the traffic is provided by this thesis. It shows how one can use the MPLS technology to detect specific traffic behavior. This will make the MPLS backbone handle the traffic more logically. This mechanism gives the operators a better utilization of their backbone and simultaneously provides the customers with their required network performance. A patent on this mechanism is planned to be sent during this spring.
Secondly, we have found that the connectivity verification traffic load should be differentiated between the LSPs that need protection switching and those that do not. To achieve a better protection switching for detecting LSP errors faster, a shorter period between LSP connectivity verification packets than drafted by ITU-T is needed. This will result in an increased OAM bandwidth usage. At the same time, unnecessary OAM traffic needs to be removed to provide the best available bandwidth for working traffic. A well-thought differentiation of connectivity verification traffic will result in a reliable network while MPLS OAM traffic does not use unnecessary bandwidth.
Thirdly, a table describing the different proposed fast rerouting and protection switching mechanisms is provided. The table shows what layer that performs the failure detection, a gradation of their redundancy, if failure detection is needed and a gradation of their switching time. This will ease the operator’s choice of mechanisms to use in the large MPLS backbone networks.
Additionally, we have studied how MPLS has the possibility to detect different connectivity failures in respect to LSPs and nodes. When a failure is detected, it is possible to alert affected nodes both upstream and downstream to suppress alarm storms. This feature is important to reduce unnecessary OAM traffic, and to let only the failed LSP’s end point take appropriate action. In contrast to MPLS, where routers inside the backbone network handle the failures, IP let the source host outside the backbone handle the failures. The MPLS failure detection mechanisms seem to make MPLS a good choice for future backbone networks.
Further work should, as mentioned in Appendix D, test the algorithm presented and find optimal parameters for correct traffic classification. Also, further research has to find an appropriate interval for sending connectivity verification packets using testbeds. This must be done for achieving the best ratio between failure detection on LSPs for protection switching while limiting the OAM traffic on backbone networks.