Fast IP Network Recovery Using Multiple Routing Configurations

Abstract

As the Internet takes an increasingly central role in our communications infrastructure, the slow convergence of routing protocols after a network failure becomes a growing problem. To assure fast recovery from link and node failures in IP networks, we present a new recovery scheme called Multiple Routing Configurations (MRC). MRC is based on keeping additional routing information in the routers, and allows packet forwarding to continue on an alternative output link immediately after the detection of a failure. Our proposed scheme guarantees recovery in all single failure scenarios, using a single mechanism to handle both link and node failures, and without knowing the root cause of the failure. MRC is strictly connectionless, and assumes only destination based hop-by-hop forwarding. It can be implemented with only minor changes to existing solutions. In this paper we present MRC, and analyze its performance with respect to scalability, backup path lengths, and load distribution after a failure. I. INTRODUCTIONIn recent years the Internet has been transformed from a special purpose network to an ubiquitous platform for a wide range of everyday communication services. The demands on Internet reliability and availability have increased accordingly. A disruption of a link in central parts of a network has the potential to affect hundreds of thousands of phone conversations or TCP connections, with obvious adverse effects.The ability to recover from failures has always been a central design goal in the Internet [1]. IP networks are intrinsically robust, since IGP routing protocols like OSPF are designed to update the forwarding information based on the changed topology after a failure. This re-convergence assumes full distribution of the new link state to all routers in the network domain. When the new state information is distributed, each router individually calculates new valid routing tables.This network-wide IP re-convergence is a time consuming process, and a link or node failure is typically followed by a period of routing instability. During this period, packets may be dropped due to invalid routes. This phenomenon has been studied in both IGP [2] and BGP context [3], and has an adverse effect on real-time applications [4]. Events leading to a re-convergence have been shown to occur frequently, and are often triggered by external routing protocols [5].Much effort has been devoted to optimizing the different steps of the convergence of IP routing, i.e., detection, dissemination of information and shortest path calculation, but the convergence time is still too large for applications with real time demands [6]. A key problem is that since most network

Balancing performance, robustness and flexibility in routing systems

“…From the table, we see that on average, robust optimization not only produces substantially fewer SLA violations across all failures (by factors ranging from 2 to 7 in most cases 10 ), but more importantly it yields drastic reductions when focusing on the "worst" top-10% of all failures, i.e., those with the highest number of SLA violations.…”

“…In the second category, [1,8,10] recently proposed to use MTR to improve network resiliency. Each routing protects against certain failure scenarios, with routers switching from one routing to another upon detecting failures.…”

“…When it comes to routing, this has triggered interest in solutions that compute paths according to different criteria as exemplified in the Multi-Topology Routing (MTR) extensions [18,17]. This added flexibility can be used to improve service differentiation for multiple performance criteria, e.g., [11], or improve robustness to failures, e.g., [10,8,1]. As detailed in Section 2, each of these issues is reasonably well understood in isolation.…”

Handling Transient Link Failures Using Alternate Next Hop Counters

“…Other proposed approaches that deal with link and/or node failures include Multiple Routing Configurations (MRC) [7], Resilient Overlay Network (RON) [8] and Failure-Carrying Packets (FCP) [9]. MRC computes a number of configurations for various failure scenarios such that for a given failure, one or more configurations can be used for bypassing.…”

Load-Balanced IP Fast Failure Recovery

“…A different approach for handling physical failures is Proactive Failure Recovery (PFR) ( [3]), in which routers compute and store backup paths for potential failures beforehand, and once a local link failure is detected, a router will redirect traffic to backup paths right away instead of waiting for the completion of network-wide routing convergence. PFR has short failure recovery time and reduces the overhead of both update propagation and path re-calculation.…”