Routing

1997

A recent trend in routing research is to avoid inefficiencies in network-level routing by allowing hosts to either choose routes themselves (e.g., source routing) or use overlay routing networks (e.g., Detour or RON). Such approaches result in selfish routing, because routing decisions are no longer based on system-wide criteria but are instead designed to optimize host-based or overlay-based metrics. A series of theoretical results showing that selfish routing can result in suboptimal system behavior have cast doubts on this approach. In this paper, we use a game-theoretic approach to investigate the performance of selfish routing in Internet-like environments based on realistic topologies and traffic demands in our simulations. We show that in contrast to theoretical worst cases, selfish routing achieves close to optimal average latency in such environments. However, such performance benefits come at the expense of significantly increased congestion on certain links. Moreover, the adaptive nature of selfish overlays can significantly reduce the effectiveness of traffic engineering by making network traffic less predictable.

The performance and reliability of the Internet depend, in large part, on the operation of the underlying routing protocols. Today's IP routing protocols compute paths based on the network topology and configuration parameters, without regard to the current traffic load on the routers and links. The responsibility for adapting the paths to the prevailing traffic falls to the network operators and management systems. This chapter discusses the modeling and computational challenges of optimizing the tunable parameters, starting with conventional intradomain routing protocols that compute shortest paths as the sum of configurable link weights. Then, we consider the problem of optimizing the interdomain routing policies that control the flow of traffic from one network to another. Optimization based on local search has proven quite effective in grappling with the complexity of the routing protocols and the diversity of the performance objectives, and tools based on local search are in wide use in today's large IP networks.

1997

In this paper we study the problem of on-line allocation of routes to virtual circuits (both point-to-point and multicast) where the goal is to route all requests while minimizing the required bandwidth. We concentrate on the case of permanent virtual circuits (i.e., once a circuit is established, it exists forever), and describe an algorithm that achieves an O(logn) competitive ratio with respect to maximum congestion, where n is the number of nodes in the network. Informally, our results show that instead of knowing all of the future requests, it is su cient to increase the bandwidth of the communication links by an O(logn) factor. We also show that this result is tight, i.e. for any on-line algorithm there exists a scenario in which (log n) increase in bandwidth is necessary in directed networks. We view virtual circuit routing as a generalization of an on-line load balancing problem, de ned as follows: jobs arrive on line and each job must be assigned to one of the machines immediately upon arrival. Assigning a job to a machine increases this machine's load by an amount that depends both on the job and on the machine. The goal is to minimize the maximum load. For the related machines case, we describe the rst algorithm that achieves constant competitive ratio. For the unrelated case (with n machines), we describe a new method that yields O(logn)-competitive algorithm. This stands in contrast to the natural greedy approach, whose competitive ratio is exactly n.

2001

This work addresses the problem of static routing complexity and performance for best effort traffic in a data network and more specifically an Internet network running an IGP (Interior Gateway protocol), and MPLS if necessary. We first give a short presentation of the various routing strategies (single-path and multi-path) and their possible realization in an IP intra domain network. We then briefly introduce the problem of the performance measurement of a routing pattern. We also define the complexity of a routing pattern as the number of MPLS tunnels needed for its realization. We show how the number of MPLS tunnels that are needed to enhance an IGP routing strategy can be minimized. We compare different routing strategies in IP networks from the two points of view: complexity and performance. We then propose two off-line Traffic Engineering methodologies for IP intra-domain network: the first one is based on an IGP/MPLS architecture; the second one is based only on the IGP routing using an optimized load balancing scheme. The algorithms used to compute the IGP metric and to optimize the routing patterns are also briefly described.

2004

Abstract Routing protocols for ad hoc wireless networks consider the path with the minimum number of hops as the optimal path to any given destination. However, this strategy does not balance the traffic load over the network, and may create congested areas. These congested areas greatly degrade the performance of the routing protocols. In this paper, we propose a routing scheme that balances the load over the network by selecting a path based on traffic sizes.

Computer Networks, 2004

QoS routing involves selection of paths for flows based on the knowledge at network nodes about the availability of resources along paths, and the QoS requirements of flows. Several QoS routing schemes have been proposed that differ in the way they gather information about the network state and select paths using this information. Most of these schemes can be categorized as best path routing where a source node selects the ''best'' path for each incoming flow based on its current view of the global network state. It has been shown that best path routing schemes require frequent exchange of network state, imposing both communication overhead on the network and processing overheads on the core routers. On the other hand, proportional routing schemes proportion incoming flows among a set of candidate paths. Two key questions that arise under proportional routing are how to select candidate paths and how to proportion flows among candidate paths. We propose a scheme that selects a few widest disjoint paths as candidates and equalizes the blocking probabilities of the candidate paths. We show that our proportional routing approach yields higher throughput with lower overhead than best path routing approach. Furthermore, we present a method for aggregating the state of an area and extend the proportional routing approach to provide hierarchical routing across multiple areas in a large network.

2009 17th IEEE International Conference on Network Protocols, 2009

1999

We present a new routing algorithm to compute paths within a network using dynamic link metrics. Dynamic link metrics are cost metrics that depend on a link's dynamic state, e.g., the congestion on the link. Our algorithm is destination-initiated: a destination initiates a global path computation to itself using dynamic link metrics. All other destinations that do not initiate this dynamic metric computation use paths that are calculated and maintained by a traditional routing algorithm using static link metrics. Analysis of Internet packet traces show that a high percentage of network traffic is destined for a small number of networks. Because our algorithm is destination-initiated, it achieves maximum performance at minimum cost when it only computes dynamic metric paths to these selected "hot" destination networks. This selective approach to route recomputation reduces many of the problems (principally route oscillations) associated with calculating all routes simultaneously. We compare the routing efficiency and end-to-end performance of our algorithm against those of traditional algorithms using dynamic link metrics. The results of our experiments show that our algorithm can provide higher network performance at a significantly lower routing cost under conditions that arise in real networks. The effectiveness of the algorithm stems from the independent, time-staggered recomputation of important paths using dynamic metrics, allowing for splits in congested traffic that cannot be made by traditional routing algorithms.