Route flapping

Abstract: A method of improving convergence in networks that use path vector protocols. In one embodiment using Border Gateway Protocol (BGP) for inter-domain route and reachability communication, nodes that need to remove routes using EBGP NLRI announcements send BGP WITHDRAW messages containing a new route originator attribute that identifies an originator of a specified withdrawn route. A receiving node removes the specified route from its routing information base (RIB), and matches the originator to other paths in the RIB. Matching paths are marked as ineligible for consideration in a best path computation, thereby preventing the use of routes that are unreachable but not yet withdrawn by an originating node. The approach causes faster BGP convergence, reduces unnecessary route flapping, and alleviates unnecessary route dampening.

Abstract: Although most studies of Internet routing treat each IP address block (or prefix) independently, the relationship between prefixes is important because routers ultimately forward packets based on the "longest-matching prefix." In fact, the most-specific prefix for a given destination address may change over time, as BGP routes are announced and withdrawn. Even if the most-specific route is withdrawn, routers may still be able to deliver packets to the destination using a less-specific route. In this paper, we analyze BGP update messages and Netflow traffic traces from a large ISP to characterize both the changes to the longest-matching prefix over time and the resulting effects on end-to-end reachability of the destination hosts. To drive our analysis, we design and implement an efficient online algorithm for tracking changes in the longest-matching prefix for each IP address. We analyze the BGP message traces to identify the reasons for prefix-match changes, including failures, route flapping, sub-prefix hijacking, and load-balancing policies. Our preliminary analysis of the Netflow data suggests that the relationship between BGP updates and IP reachability is sometimes counterintuitive.

Abstract: With the explosive growth of Internet, the low efficiency of BGP has seriously influenced its usability. In this work, a TLP (thread level parallelism) approach with local speculation is proposed to improve the BGP performance. The thread partition is locally performed on each separated sub-module at route processing, and the speculation strategy is implemented to guarantee the memory consistency and sequential commit. Experiments on Intel Quad-core server show that this approach reaches an average speedup of 1.46 under single peer, multi-peers and route flapping. It is also shown that the packet throughput can be improved greatly under multiple sessions by taking advantage of TLP.

Abstract: Developing optimized distributed protocols for large-scale networks is a challenging problem due to scalability and stability concerns. Scalability concerns can be naturally addressed by interpreting distributed protocols as a non-cooperative game of local protocol components attempting to maximize their individual utilities. One of the difficulties in implementing this approach is developing adaptive algorithms capable of learning of the expected utilities and adjusting the corresponding control actions for the purpose of approaching the solution to the corresponding game, and thus optimization of the global system performance. It is known that the best response by each component to its expected utility may result in unstable behavior and deterioration of the overall performance. On an example of cross-layer optimization of a TCP/IP network, this paper discusses the possibility of avoiding these undesirable effects by allowing the control actions occasionally deviate from their best response values. Using simulations, the paper suggests that (a) sufficient level of randomness in route selection improves the network performance by eliminating the route flapping instability, (b) the optimal level of randomness keeps the network within the stability region in close proximity to the border of this region, and (c) it may be possible to optimize the network performance by adjusting the level of randomness.