We present an approximate analytical method to compute efficiently the call-blocking probabilities in wavelength-routing networks with multiple classes of both unicast and multicast calls. Our approach involves the following steps. We start with an approximate solution to a linear single-class unicast network which we developed earlier. Next, all classes of calls on a particular route are aggregated to give an equivalent single-class model. We then extend the path decomposition algorithms that we have developed for single-class networks to handle mesh networks with multiple classes of calls. We show how to use these path decomposition algorithms to decompose large networks with multicast paths into smaller subsystems with only linear paths, which, in turn, are solved by the product-form approximation algorithm. We also consider a state-dependent Poisson arrival process for multicast calls which is more accurate in capturing the behavior of these calls.

This paper presents a closed-loop (demand-driven) approach towards VoD services, called multicast with caching (Mcache). Servers use multicast to reduce bandwidth usage by serving multiple requests using a single data stream. However, this requires clients to delay receiving the movie until the multicast starts. Using regional cache servers, Mcache removes initial playout delays at the clients, because the clients can receive the prefix of a requested clip from regional caches while waiting for the multicast to start. In addition, the multicast containing the later portion of the movie can wait until the prefix is played out. While this use of caches has been proposed before, the novelty of our scheme lies in that the requests coming after the multicast starts can still be batched together to be served by multicast patches without any playout delays. The use of patches has been proposed to be used either with unicast or with playout delays. Mcache effectively hires the idea of a multicast patch with caches to provide a truly adaptive VoD service whose bandwidth usage is up to par with the best known open-loop schemes under high request rates while using only minimal bandwidth under low request rates. In addition, efficient use of multicast and caches removes the need for a priori knowledge of client request rates and client disk storage requirements which some of the existing schemes assume. This makes Mcache ideal for the current heterogeneous Internet environments where those parameters are hard to predict.

A closed-loop (demand-driven) approach toward video-on-demand services, called multicast cache (Mcache), is discussed. Servers use multicast to reduce their bandwidth usage by allowing multiple requests to be served with a single data stream. However, this requires clients to delay receiving the movie until the multicast starts. Using regional cache servers deployed over many strategic locations, Mcache can remove the initial playout delays of clients in multicast-based video streaming. While requests are batched together for a multicast, clients can receive the prefix of a requested movie clip from caches located in their own regions. The multicast containing the later portion of the movie can wait until the prefix is played out. While this use of regional caches has been proposed previously, the novelty of our scheme lies in that the requests coming after the multicast starts can still be batched together to be served by multicast patches without any playout delays. The use of patches was proposed before, but they are used either with unicast or with playout delays. Mcache effectively hires the idea of a multicast patch with caches to provide a truly adaptive video-on demand service whose bandwidth usage is up to par with the best known open-loop schemes under high request rates while using only minimal bandwidth under low request rates. In addition, efficient use of multicast and caches removes the need for a priori knowledge of client disk storage requirements which some of the existing schemes assume. This makes Mcache ideal for the current heterogeneous Internet environments where those parameters are hard to predict. We further propose the Segmented Mcache (SMcache) scheme which is a generalized and improved version of Mcache where the clip is partitioned into several segments in order to preserve the advantages of the original Mcache scheme with nearly the same server bandwidth requirement as the open loop schemes under high request rates.

We analyze a multilayered queueing network that models a client-server system where clients and servers communicate via synchronous and asynchronous messages. The servers are organized in groups such that they form a multilayered hierarchical structure. The queueing network is approximately analyzed using a decomposition algorithm. Numerical tests show that the approximation algorithm has a good accuracy.

The cell loss priority (CLP) bit in the header of the ATM cell may be used either by the network to tag noncompliant cells, or by the application to declare two levels of quality-of-service (QoS) within the same virtual circuit (VC). We study the possibility of the use of this bit by the application alone. An application can offer two types of traffic streams to the network, namely, a precious traffic stream (with stringent QoS requirements, e.g., cell loss ratio (CLR) <10/sup -9/ and identified by the CLP bit=0) and a less precious stream (CLP=1 and less stringent QoS requirements, e.g., CLR <10/sup -4/). We study the performance of an ATM multiplexer with two traffic classes with different QoS requirements. The buffer priority schemes adopted are partial buffer sharing (PBS) and PBS+push-out (PO). We first obtain the engineering trade-off curves, between CLP=0 and CLP=1 traffic. To identify an operating point, we formulate a revenue optimization problem in which the constraints are the engineering trade-off curve and a simple model of the variation of CLP=1 demand with its price.