Should QoS routing algorithms prefer shortest paths?

Abstract

Abstract-Multimedia traffic and real-time e-commerce applications can experience quality degradation in traditional networks such as the Internet. These difficulties can be overcome in networks which feature dynamically set up paths with bandwidth and delay guarantees. The problem of selecting such constrained paths is the task of Quality of Service (QoS) routing. This paper considers link-state routing, and the choice of cost metric used to implement QoS routing.There are two schools of thought regarding the choice of link cost. It is commonly assumed that QoS routing algorithms should limit hop count so as to conserve resources for future connections. Others advocate load balancing mechanisms so as to increase overall network utilisation. This paper investigates which of these approaches gives the better performance. We show that there is no one general answer to this question. We also point out the dangers of drawing general conclusions about routing algorithm performance based on the study of only a limited set of network topologies.

Connectivity aware routing - a method for finding bandwidth constrained paths over a variety of network topologies

“…In [9] we show that this statement is not always true and that for networks with low connectivity, the LD approach is in general much better solution than RC algorithms, even if the network load is high. On the other hand, at the low loads in highly connected networks, the resource conserving approach performs as well as load balancing does.…”

“…This often makes link cost expressed strictly as a function of link utilisation less attractive than the constant value used in minhop path computation. However, as our previous results show [9], for many networks with low connectivity only the load balancing approach of existing algorithms, can fully utilise available resources.…”

“…Such definitions result in the pure LD or RC approaches. In [9] we have shown that the performance of these two approaches depends on the level of network connectivity. This suggests that the primary link cost metric should be a combination of these two approaches, with their relative weighting set according to the level of network connectivity.…”

“…We think that the value of bias should increase with the level of network connectivity, because LD methods are beneficial for networks with low connectivity, and for highly connected networks they are outperformed by RC algorithms [9].…”

“…In [9] we have shown that, the performance of load distributing (LD) approach and approach performing resource conservation (RC) depend strongly on the level of network connectivity. Our findings suggest that QoS routing algorithms should be aware of this connectivity, to provide improvements comparing to static routing over a wide range of topologies.…”