Enhanced call: a paradigm for applications with dynamic client-membership and client-level binding in ATM networks

Abstract

Sophisticated applications in asynchronous transfer mode (ATM) networks require high-level quality-of-service (QoS) guarantees in conjunction with ATM QoS guarantees. We focus on applications that involve varying client-membership and client-level binding (i.e., dependence between current and future clients). Such applications include certain types of conferences, computer-supported cooperative work (CSCW), and client-server based applications. In a traditional call, these applications are set up with a known set of clients and newer clients are admitted via individual connection admission procedures. While this approach guarantees ATM QoS for every client admitted to the application, it cannot guarantee the addition of new clients to an existing application. Consequently, carried clients that depend on a new client can perceive a degraded service when the new client cannot be added because of lack of bandwidth. We refer to this degradation as client-level degradation. To guarantee an upper bound on client-level degradation, we propose a paradigm called enhanced call that statistically reserves virtual channel links (VCLs) for potential new client arrivals. The enhanced call specification encapsulates client descriptors and client-level QoS measures. We propose simple, scaleable, and practical client descriptors. Where possible, the descriptors are chosen in the same spirit as ATM descriptors. Given these descriptors, we develop an analytical framework to determine whether or not to admit an enhanced call. We also present an operational conformance definition that is enforced globally as well as locally.