This paper proposes a Versatile Network Architecture (V-NET) to support flexible delay guarantees for applications in real-time networks. Applications communicate over the V-NET by using end-to-end network connections which support real-time and reliability characteristics tailored to meet the application's specified requirements. V-NET differs from other proposed architectures in that, in addition to addressing the issue of quality of service (QoS) feasibility for a wide spectrum of real-time applications, it also provides a mechanism to determine a network state dependent range of feasible delay values at each switching node along the routing path. These delay ranges can be used to assign per-node delays that reflect the resource availability of the node, thereby reducing the likelihood of bottlenecks along the routing path. The V-NET delay guarantees are provided for a variety of packet scheduling algorithms and traffic policing mechanisms. This flexibility is an important design consideration as a real-time network architecture must accommodate existing and future multimedia applications, with hard-, soft-, and non-real-time traffic. The performance evaluation results demonstrate the efficiency of this scheme in handling different traffic scenarios and QoS requirements. We have shown that it is possible, and indeed efficient, to determine an upper-bound on the delay of real-time traffic, when using our per-node delay assignment policies.

A framework to support performance requirements for real-time applications in packet-switched networks is proposed. This framework is based on a network-level abstraction called alpha -channel. An alpha channel represents a simplex end-to-end communication channel characterized by a set of application-specific real-time performance values. Applications treat the alpha -channel as an end-to-end abstraction and specify their required performance characteristics in terms of the maximum end-to-end packet delay, the maximum number of packets that can be sent within that delay, and the on-time reliability. Based on specified parameters, the network verifies that it can guarantee the performance of the channel under any conditions baring hardware failures. The approach the framework uses to verify the feasibility of accepting an alpha -channel and the characteristics of the run-time environment to guarantee the applications' performance requirements are described. The results of a simulation experiment implementing the basic functionalities of the proposed scheme are also presented.>

The design of communication protocols to support guaranteed real-time communication for distributed multimedia systems is examined. A network level abstraction called phi -channel that supports the requirements of real-time applications is proposed. A phi -channel represents a fractional, simplex, end-to-end communication channel between a source and a destination. The channel is characterized by a set of specific performance parameters associated with its traffic. The required performance characteristics of a phi -channel are specified in terms of the packet maximum end-to-end delay and the maximum number of packets that can be sent over that delay. The primary attribute supported by the phi -channel is the on-time reliability. Based on the specified parameters, the underlying delivery system verifies the feasibility of supporting such a channel. The performance of an accepted phi -channel is guaranteed under any conditions, barring hardware failures. The basic scheme that the model uses to verify the feasibility of accepting a phi -channel and the run-time support used to guarantee its performance are described. The results of a simulation experiment implementing the basic functionalities of the proposed scheme are also presented.>

A network-level abstraction called phi -channel that supports the requirements of real-time applications is proposed. A phi -channel represents a simplex, end-to-end communication channel between a source and a destination. The channel is characterized by a set of specific performance parameters associated with its traffic, namely packet maximum end-to-end delay and the maximum number of packets that can be sent over that delay. The primary attribute supported by the phi -channel is on-time reliability. The basic scheme used to verify the feasibility of accepting a phi -channel, and the run-time support to guarantee its performance are described. The results of a simulation experiment implementing the basic functionalities of the proposed scheme are presented.>

Several transport protocols have been proposed for use in the Internet. The specifications of these protocols are based on the assumption that a general purpose transport protocol can be designed to be used by a variety of applications, including time-constrained applications. A widespread consensus among the researchers is that a general purpose transport protocol is not optimized for any applications, and thus cannot deliver the high performance required by real-time applications such as voice, motion and still video, and large file transfer. This paper investigates the validity of the above claim based on the gathering of empirical data. A generic 'protocol benchmark' is used to assess the real-time performance of a set of known transport protocols, and to analyze their suitability to handle the requirements of real-time applications.>