Delayed Internet routing convergence

Abstract

This paper examines the latency in Internet path failure, failover, and repair due to the convergence properties of interdomain routing. Unlike circuit-switched paths which exhibit failover on the order of milliseconds, our experimental measurements show that interdomain routers in the packet-switched Internet may take tens of minutes to reach a consistent view of the network topology after a fault. These delays stem from temporary routing table fluctuations formed during the operation of the Border Gateway Protocol (BGP) path selection process on Internet backbone routers. During these periods of delayed convergence, we show that end-to-end Internet paths will experience intermittent loss of connectivity, as well as increased packet loss and latency. We present a two-year study of Internet routing convergence through the experimental instrumentation of key portions of the Internet infrastructure, including both passive data collection and fault-injection machines at major Internet exchange points. Based on data from the injection and measurement of several hundred thousand interdomain routing faults, we describe several unexpected properties of convergence and show that the measured upper bound on Internet interdomain routing convergence delay is an order of magnitude slower than previously thought. Our analysis also shows that the upper theoretic computational bound on the number of router states and control messages exchanged during the process of BGP convergence is factorial with respect to the number of autonomous systems in the Internet. Finally, we demonstrate that much of the observed convergence delay stems from specific router vendor implementation decisions and ambiguity in the BGP specification.

Characterizing user-perceived impairment events using end-to-end measurements

“…At the edge, where the end customer connects to its service provider, traffic cannot be routed around the failure and the outage persists until the problem is resolved. In the core, traffic can be routed around the failure but routing protocols take from several seconds to several minutes to converge [12]. In the meantime, routing errors occur, causing outages for the end-user.…”

“…Route changes can be caused by router or link failures or when a failed component recovers from a failure. Failures are often followed by a service disruption that lasts from a few seconds to a few minutes while routing protocols converge to the new route [12][13][14]. Restoration at Layer 2 is usually faster than restoration at Layer 3 [15].…”

Load-Balanced One-hop Overlay Multipath Routing with Path Diversity

“…The convergence time for routing protocols to route around these failures is often in the order of seconds or minutes [3] [4], during which certain end-to-end connections may experience seconds or minutes of outage [5]. Overlay routing has been proposed in recent years as an effective way to improve reliability and efficiency of the Internet without any changes in the Internet infrastructure.…”

Mathematical Model of the Relationship between BGP Convergence Delay and Network Topologies

“…However, it has been observed that in many cases, BGP routers explore a large number of pos-sible routes before converging on a new stable route. Labovitz et al (2001) found that the delay in Internet inter-domain path fail-over now averages 3 min and some non-trivial percentage of fail-overs trigger routing table oscillations lasting up to 15 min.…”

“…Researchers have been looking into it in different angle trying all to improve, understand or resolve BGP convergence problem. Labovitz et al (2001) examines the latency in internet path failure/failover and repair die to convergence properties of inter-domain routing. Pei et al (2002) shows that BGP can take hundreds of seconds to converge after failure, while the delay can be increased for large-scale failure.…”