So How Do We Handle This Link Failure?
You now see the chain of responsibility in action. A message is passed along the chain until it reaches an appropriate handler.
Recall that we have a link failure (Link 1 in Figure 1) in our network and we’re dropping data traffic. Some router vendors equip their devices with technology to automatically reroute LSPs in cases of error. If we assume we purchased our routers on Ebay or in a bargain basement sale, once the link failure occurs, the NMS must fix the problem! The fix might be to just create a new LSP that follows an alternative path. So, the last message in Listing 6 might include a high-priority message to another NMS component that is responsible for path computation. The further handling of the link failure is a matter for the policies and processes of the service provider.