New network applications which i n volve transmission of continuous media data, such as audio and video conferencing, introduce immense challenges for the design of packet-switching internetworks. Existing ow and congestion control mechanisms have b e e n s h o wn to be ine ective for supporting the real-time requirements of continuous media data transfers. We propose a n o vel bandwidth regulation mechanism which improves the ability of the network to cope with multiple real-time and non real-time tra c classes. The mechanism achieves regulation of link bandwidth at two levels. At one level, bandwidth is dynamically regulated between di erent tra c classes. We i n troduce the concept of inter-class regulation which enforces that the bandwidth left unused by some tra c classes is assigned equally to tra c classes with high bandwidth demands. At the second level, bandwidth regulation is enforced on packet ows from the same class. Each end-to-end packet ow from the same class has identical bandwidth constraints if their routes share the link with the smallest capacity for this class. This concept is referred to as intra-class regulation. W e s h o w that a bandwidth assignment w h i c h p r o vides both intra-class and inter-class regulation without unnecessary waste of bandwidth is uniquely determined. We present a simple distributed protocol that achieves intra-class and inter-class regulation in a general internetwork. The protocol does not require network gateways to maintain state information on individual tra c ows, and adapts quickly to changes in the tra c load. The e ectiveness of the protocol is demonstrated by s i m ulation experiments.

A novel bandwidth regulation mechanism is proposed which improves the ability of a packet-switching network to cope with multiple real-time and non-real-time tra c classes. The mechanism achieves regulation of link bandwidth at two levels. At the rst level, bandwidth is dynamically regulated b etween di erent tra c classes. The concept of`inter-class regulation' i s i ntroduced which enforces that the bandwidth left unused by a tra c class is divided among tra c classes with high bandwidth demands. At the second level, bandwidth regulation is enforced on end-to-end tra c streams, socalled ows, such that ows from the same class with identical routes have the same throughput constraints. This concept is referred to as`intra-class regulation'. A simple distributed p r otocol is presented that achieves intra-class and inter-class regulation in a general internetwork. The e ectiveness of the protocol is demonstrated by simulation experiments.

We address the problem of routing connectionless trafc in an ATM network and propose an adaptive multipath routing scheme that enhances the routing methods employed at the Inter{Working Units (IWUs). We present a scheme that distributes packets among multiple Virtual Paths (VPs) according to the utilization of the links of these VPs. The utilization of the VPs is determined b y a f e edback mechanism. We present simulation studies to show the e ectiveness of the proposed adaptive multipath routing scheme.

This paper addresses the problem of routing connectionless tra c through an ATM network. A solution is proposed based on a per{ packet adaptive m ultipath routing scheme which is added to the routing algorithm implemented at the Inter{Working Units. A scheme is presented that distributes packets among multiple Virtual Paths (VPs) according to the utilization of the links on these VPs. The utilization of the VPs is determined by a periodic feedback m e c hanism. Simulation studies show the e ectiveness of the proposed adaptive m ultipath routing scheme.

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: