Improving the resilience in IP networks

Abstract

Quality of service issues of IP networks are mostly related to guaranteeing bandwidth for flows. However, many interactive real-time applications also require this bandwidth in an uninterrupted fashion. The paper describes how multipath routing and local failure reaction can be employed to provide uninterrupted QoS to applications. We show how multipath route sets can be found in reasonably meshed networks and how multipath routing can be used to save on the spare capacity required in case of link failures

Fast Local Rerouting for Handling Transient Link Failures

“…FIR imposes no such restrictions on weight assignment and assures loop-free forwarding to any reachable destinations in case of single link failures. An approach based on multiple alternate paths at every node to facilitate local failure reaction is proposed in [19]. This approach requires addition of "joker" links and increases the link loads in normal operation.…”

“…The final verification is done by building a tree rooted at covering all the nodes in without the link (line 16) and checking if it contains the edge (line 17). If so, link is included in the set of key links for all the nodes in that follow in the tree (lines [18][19]. The computation of forwarding tables is a relatively simple task once the key links are determined.…”

High Availability in the Future Internet

“…On the other hand, there are methods, which use explicit tunneling to avoid the failed components [7,17,36,6]. Proposals in [43,37] have topological requirements, whilst the mechanism proposed in [29] uses a central server to pre-compute forwarding decisions for common failure scenarios and download them into the routers. Accordingly, at the moment none of these proposals is available in IP routers, since they need modifications to the existing protocols, making LFA the only deployable option for ISPs.…”

Optimizing IGP link costs for improving IP-level resilience

“…Unfortunately, the former solution would allocate invaluable bits in the IP header, while the latter might cause painful packet fragmentation and time-consuming reassembly at the tunnel endpoint if the additional IP header does not fit into the MTU. Deflection routing for fast rerouting purposes is proposed in [20], while O2 routing, a resilient multi-path data forwarding method, is specified in [35]. Both require nonstandard IP forwarding functionality which at the moment are not available in routers.…”