Dynamic Routing and Flow Control

Abstract

Abmuct-This is an expanded version of an earlier report, adding, new results. The first part introduces a simple analytic model showing that dynamic routing may increase network throughput or lower delay when trunks are moderately loaded, but will reduce throughput or increase delay at heavy trunk loads. The second part of the paper presents SimukttiOn results characterizing: 1) the operation of a network "Protected" by end-to-end flow control, 2) the operation of an ''unprotWted" network, 3) the transition between these two modes, 4) the effect of changing the update interval for the routing algorithms, 5) the effect Of Slow local loops, and 6 ) the effect of increasing the number of alternate paths available for dynamic routing.Overall, the results show that dynamic routing improves network performance only over a small parameter range, and should dynamic routing be used at all, it must be implemented with great care. INTRODUCTIONT HE overall congestion-control strategy of a packet-switched network specifies how that network protects itself from potential overload and how network resources are allocated to network users. In [ 11, it was suggested that congestion control has three component subareas: flow control, which prevents an unfair allocation of resources among competing users; routing, which strives to balance the load over equivalent network resources; and scheduling, which can reallocate network delay among various user classes.While the importance of congestion control is clear-a bad strategy will be very apparent to the user-the current understanding of congestion control is very limited. It is hoped that this paper which is an extension of an earlier paper [2] adds to this understanding.First, a simple analytic model is used to show where dynamic routing is useful. Second, the results of a simulation study show that dynamic routing may have adverse effects (worsen performance) in a network protected by flow control and that, at best, the performance of dynamic routing algorithms is quite sensitive to various parameters.Taken together, the results indicate that: 1) it is quite * dangerous to try to study flow control, routing, or scheduling as isolated mechanisms; and 2 ) before any conclusions can be drawn about the performance of a particular set of congestion control algorithms, the overall objectives of a particular network must be very carefully thought out. We shall see that minimization of delay or maximization of throughput require different congestion strategies.

Scalable and reconfigurable WDM network architecture

“…For example, the procedure of finding a route from node 1 to node 14@1.1.2 in Fig. 5 is as follows: after finding out CA(1, 14@1.1.2) = 1C1.1, we randomly choose a node, say 13, among [13,10,11,16] (which are located on the 2nd column of shuffle-net 1.1); then find a route from node 1 to node 13 in the shuffle-net 1.1 and inform node 13@21.1.2 to find a route to 14©1.1.2.…”

“…The static routing policy can cause congestion, especially in wide-area networks where traffic can be bursty and dynamic. Studies show routing and congestion control are closely related to each other [10]. Dynamic routing algorithms, such as the alternative path routing algorithm and the deflection routing algorithm [ 11] have been suggested to bridge between routing and congestion control.…”

MultiRoute - a congestion-aware multipath routing protocol

“…Currently, routing algorithms only consider shortest paths between networks, moreover there is a lack of cooperation between congestion control and routing. It has been shown that congestion control has a significant impact on routing [1], since packet loss will lower the overall performance of the network. Leveraging multiple paths has been a complex problem in Communication Systems, mainly due to out of order packet arrivals, but it has the potential to increase the overall network throughput significantly at a relatively low cost.…”

Performance optimization of integrated network control schemes in packet-switched networks

“…However, this separation does not reflect the behavior of real systems since the problems are closely related [21,10,11,23,14,241. In this paper, we view the control mechanisms from an integrated point of view that will include certain important strategies such as window flow control schemes and entry-to-exit routing schemes.…”