Fast emergency paths schema to overcome transient link failures in ospf routing

A reliable network infrastructure must be able to sustain traffic flows, even when a failure occurs and changes the network topology. During the occurrence of a failure, routing protocols, like OSPF, take from hundreds of milliseconds to various seconds in order to converge. During this convergence period, packets might traverse a longer path or even a loop. An even worse transient behaviour is that packets are dropped even though destinations are reachable. In this context, this paper describes a proactive fast rerouting approach, named Fast Emergency Paths Schema (FEP-S), to overcome problems originating from transient link failures in OSPF routing. Extensive experiments were done using several network topologies with different dimensionality degrees. Results show that the recovery paths, obtained by FEPS, are shorter than those from other rerouting approaches and can improve the network reliability by reducing the packet loss rate during the routing protocols convergence caused by a failure.Comment: 18 page

IP Fast Reroute in Networks with Shared Risk Links

Abstract. IP fast reroute is a mechanism that is used to reroute packets around a failed link as soon as the link fails. Most of the IP fast reroute mechanisms, that have been proposed so far, focus on single or dual link failures but can not handle Shared Risk Link Group (SRLG) failures when several links fail at the same time because of some common underlying component failure. Furthermore, most of current work is based on the assumption that each node in the network has access to some global topology information of the network. In this paper, we present the first IP fast reroute mechanism for SRLG failures that is not based on the assumption that the nodes in the network have global topology information of the network. In our mechanism, nodes in the network use "relay bits" to identify themselves as "relay nodes" for a reroute link in a fully distributed mannner. Through simulation, we show that our mechanism succeeds in rerouting around SRLG failures alomst 100% of the time, with average length of a reroute path about 1.5 times the re-converged shortest path

Resilient routing in the internet

Although it is widely known that the Internet is not prone to random failures, unplanned failures due to attacks can be very damaging. This prevents many organisations from deploying beneficial operations through the Internet. In general, the data is delivered from a source to a destination via a series of routers (i.e routing path). These routers employ routing protocols to compute best paths based on routing information they possess. However, when a failure occurs, the routers must re-construct their routing tables, which may take several seconds to complete. Evidently, most losses occur during this period. IP Fast Re-Route (IPFRR), Multi-Topology (MT) routing, and overlays are examples of solutions proposed to handle network failures. These techniques alleviate the packet losses to different extents, yet none have provided optimal solutions. This thesis focuses on identifying the fundamental routing problem due to convergence process. It describes the mechanisms of each existing technique as well as its pros and cons. Furthermore, it presents new techniques for fast re-routing as follows. Enhanced Loop-Free Alternates (E-LFAs) increase the repair coverage of the existing techniques, Loop-Free Alternates (LFAs). In addition, two techniques namely, Full Fast Failure Recovery (F3R) and fast re-route using Alternate Next Hop Counters (ANHC), offer full protection against any single link failures. Nevertheless, the former technique requires significantly higher computational overheads and incurs longer backup routes. Both techniques are proved to be complete and correct while ANHC neither requires any major modifications to the traditional routing paradigm nor incurs significant overheads. Furthermore, in the presence of failures, ANHC does not jeopardise other operable parts of the network. As emerging applications require higher reliability, multiple failures scenarios cannot be ignored. Most existing fast re-route techniques are able to handle only single or dual failures cases. This thesis provides an insight on a novel approach known as Packet Re-cycling (PR), which is capable of handling any number of failures in an oriented network. That is, packets can be forwarded successfully as long as a path between a source and a destination is available. Since the Internet-based services and applications continue to advance, improving the network resilience will be a challenging research topic for the decades to come

On Improving the Efficiency and Manageability of NotVia

This paper presents techniques that improve the efficiency and manageability of an intra-domain IP Fast Reroute (IPFRR) technique called NotVia. NotVia provides IP fast reroute service upon any single link or node failure for all destinations in an intra-domain network. However, it has a significant computational cost to restore its state upon topology changes, which slows the recovery of the IPFRR service itself upon a topology change. NotVia also increases the intra-domain forwarding table sizes, and poses potential obstacles for network management, as routers are unaware of the links (hence the amount of traffic) that they actually protect. This paper proposes techniques that can reduce both the computational costs and the forwarding table entries dedicated to NotVia addresses and that improve the manageability of NotVia. We use simulations to evaluate these techniques on real ISP topologies as well as randomly generated topologies using BRITE. The results show that the computational costs and the forwarding table size increments dedicated to restore the NotVia state are reduced to a fraction of their previous values for large topologies, suggesting that the techniques proposed in this paper make NotVia a more efficient and easy-to-manage technique for practical deployment