A bandwidth control scheme for connectionless ATM traffic with multiple traffic classes

Abstract

A bandwidth control mechanism is proposed for A T M networks that can control of bandwidth usage in the presence of both connection-oriented and connectionless t r a f i c , as well as multiple classes of connectionless trafic. T h e bandwidth control mechanism operates at three levels. At the topmost level, bandwidth is dy- Figure 1 we illustrate the direct approach where two connectionless LANs access the ATM network through interworking units (IWU). Each IWU maintains a permanent virtual path (VP)to a CLS which is attached to an ATM switch. CLSs are endpoints of virtual paths in the ATM network, and each CLS is responsible for maintaining a permanent VP t o a t least one other CLS. When a local area network transmits connectionless traffic to a remote network, it actua,lly transmits a series of packets' t o its IWU. T h e IWU, in turn, relays the packets to a CLS, which then passes the packets to another CLS closer t o its destination.Any network protocol that implements the direct approach must address t,he issue of bandwidth allocation to connection-oriented and connectionless traffic. Obviously, a stat,ic allocat,ion of bandwidth to VPs "The work of Dehapriya Sarkar and J6rg Liebeherr was supported in part by the National Science Foundation under Grant No. ' We use the term 'packet' to denote a C L P D U ( = C o n n e ctaonless Protocol D a t a unit).carrying connectionless traffic will result in wastage of bandwidth during periods of low intensity of connectionless traffic, and in congestion during periods of high traffic intensity. A better alternative is t o vary the band.width allocation dynamically, using the actual connectionless traffic load as a heuristic for determining tlie bandwidth requirements. However, even if sufficient bandwidth is allocated t o connectionless traffic, one still has t o address the problem of distributing the available bandwidth t o a, possibly large, number of connectionless traffic flows'. In this paper we propose a multi-level bandwidth control scheme for managing connectionless traffic in an ATM network that operates a t three levels as shown in Figure 2: