Communications In ATM Networks Research Articles

Real-time transport of MPEG video with a statistically guaranteed loss ratio in ATM networks

Unlike deterministic real-time communication in which excessive resources may be required for absolute performance guarantees, statistical real-time communication seeks to achieve both probabilistic performance guarantees and efficient resource sharing. This paper presents a framework for statistical real-time communication in ATM networks, providing delay-guaranteed transport of MPEG-coded video traffic with a statistically-guaranteed cell-loss ratio. Delay-guaranteed communication is achieved with a modified version of Traffic-Controlled Rate-Monotonic Priority Scheduling (TCRM). A set of statistical real-time channels that share similar traffic characteristics are multiplexed into a common macrochannel. Those statistical real-time channels which are multiplexed together share the resources of a macrochannel, and individual statistical real-time channels are given timeliness and probabilistic cell-loss guarantees. A macrochannel is serviced by the modified TCRM which improves link utilization and makes channel management simpler. Based on the analysis of an M/D/1/N queueing system, we propose a procedure for determining the transmission capacity of a macrochannel necessary to statistically guarantee a cell-loss ratio bound. Our extensive trace-driven simulation has shown the superiority of the proposed framework to the other approaches. The overall cell-loss ratios for multihop statistical real-time channels are shown to be smaller than the predetermined bounds, thus verifying our analytical results.

Real-Time Communications in ATM Networks

This dissertation examines issues concerning real-time communication in ATM LANs such as those used in Hard Real-Time (HRT) systems. Applications in such systems have stringent quality of service (QoS) requirements. Support of hard real-time applications in ATM LANs requires efficient traffic management functions. This work studies two such functions: connection admission control (CAC) algorithm and input traffic regulation. In hard real-time systems, the QoS requirements are specified in terms of end-to-end cell deadlines and no cell loss due to buffer overflow. A CAC algorithm must admit a new connection only if its QoS requirements can be met without violating that of the previously admitted connections. Hence, computation of the worst case end-to-end cell delays and buffer requirements are pivotal issues in CAC design. Arbitrary topology of the network complicates the problem as it might lead to cyclic dependencies among various connections, making the delay and buffer analysis difficult. The first major contribution of this work is the development of a general framework to efficiently analyze an ATM LAN. The efficiency of the end-to-end delay and buffer analysis depends on the effectiveness of the traffic descriptors used in the network. We propose a comprehensive traffic description function, $\Gamma$(I). $\Gamma$(I) provides adequate information about the worst case traffic behavior of connections anywhere in the network and its use simplifies the analysis of ATM LANS, even those which do not support internal traffic restoration mechanisms. Further, simple approximations of $\Gamma$(I), proposed in this work, alleviate the space and time constraints imposed by the network on the CAC. We use the proposed analysis methodology to design an effective and efficient CAC algorithm for ATM LANs with arbitrary topology. The second major contribution of this work is the use of traffic regulation as a technique to meet the delay requirements of connections. This is the first work which uses leaky bucket parameter selection as a means to guarantee the QoS of HRT connections. Leaky buckets provide simple and user-programmable means of traffic regulation. We design and analyze an efficient optimal algorithm for selecting the burst parameters of leaky buckets to meet connections' deadlines.

Performance Studies of Real-Time Communications in ATM Networks

This paper presents a performance study of ATM Network in support of realtime multi-media traffic. Multiple classes of traffic with different real-time requirement will be used in the study. The performance of the ATM switch is examined in terms of cell missing ratio due to deadline missing and cell loss ratio due to buffer overflow in both switch and gateway as well. A higher level of abstraction in terms of burst loss ratio will also be collected. The results indicated that first-come-first-serve scheduling algorithm is insufficient to handle real-time traffic. This paper presents a better method to improve the performance significantly especially when the virtual path bandwidth negotiated is conservative.

Performance studies of real-time communications in ATM networks

This paper presents a performance study of ATM networks in support of multi-media traffic with different real-time requirements. The performance of the ATM switch is examined in terms of cell missing ratio due to missed deadlines, and cell loss ratio due to buffer overflows, in both switches and gateways. A higher level of abstraction in terms of burst loss ratio will also be included. The results indicate that a first-come-first-serve scheduling algorithm is insufficient to handle real-time traffic. This paper presents a better method, that significantly improves the performance, especially when the negotiated virtual path bandwidth is conservative.

Using special resources to support multimedia multiparty communications in ATM networks

This paper proposes a special resource based architecture to support multimedia, multiparty communications in ATM networks, and details it for the implementation of point-to-multipoint and multipoint-to-point ATM connections. The special resources are implemented by servers: these have a modular design and each of them provides the facilities specific to one special resource. Enhanced connection types are supported by a two level architecture: homogeneous servers are arranged into logical subnetworks that are accessed by the users by means of point-to-point switched connections. New algorithms are designed to route point-to-multipoint and multipoint-to-point ATM virtual connections inside the logical subnetworks. To this purpose, two classes of heuristics are considered: those that take into account only the link's spare capacity to identify a suitable and low cost routing; and those that attempt to minimize the number of resources assigned to a connection. The performance evaluation shows that the former have good connection blocking performance, are simpler and impose a lower load on the servers than the others.

New queueing strategies employing service interval-based priority for real-time communications in atm networks

In this paper, we propose queueing strategies employing the service interval-based priority (sip) which can provide delay-bounded, and loss-free services, while maximizing bandwidth utilization in the atm network. We also describe a variation of the sip, the residual service interval-based priority (rsip) which can achieve almost full utilization by assigning priorities dynamically on the basis of the residual service interval. We store the realtime cells belonging to different connections in logically separated queues, and for each queue, we set a parameter called service interval, during which only one cell is allowed to be transmitted. The sip server takes and transmits the head-of-line (hol) cell of the queue which has the smallest service interval, while the rsip server selects the queue with the smallest residual service interval. When there is no eligible real-time cell, it transmits non-real-time cell, thus enabling a maximized bandwidth utilization. Employing the above queueing strategies, we analyze the delay characteristics deterministically with the leaky bucket bounded input traffic and then dimension the optimal service interval. In dimensioning the service interval and buffer space of each real-time service queue, we consider burstiness of traffic in conjunction with delay constraints, so that bandwidth utilization can get maximized. In addition, we consider the issues of protection from malicious users, average bandwidth utilization, and coupling between the delay bound and the bandwidth allocation granularity.

Secure communications in ATM networks

High-speed networking technology and standards have progressed dramatically in the past few years and much attention is now focused on deployment efforts, such as the North Carolina Information Highway (NCIH) [7], and applications. With this shift in emphasis, concerns have been raised about information security. Examples of abuse of the Internet abound and unfortunately ATM networks are subject to many of these same abuses. This is of subtanstial concern when thinking about extending the reach of public data networking to broad segments of society.

VP dimensioning for high‐speed data communication in ATM networks

AbstractThis paper describes a VP bandwidth dimensioning method for dynamic connection admission control (CAC) in ATM networks. Dynamic CAC judges the admission of a connection by using the measured number of cells arriving at each VP as well as the source traffic descriptor. The bandwidth assignment can therefore reflect the actual traffic characteristics so that the dynamic CAC can compensate for the difference between the negotiated and the actual values of the descriptor. This kind of CAC is especially appropriate for a service for which users have difficulties specifying accurate values for the source traffic descriptor.The procedure for dimensioning the VP bandwidth is important for providing a service economically when the dynamic CAC is used. This paper develops the dimensioning method of the VP bandwidth for long‐term VP bandwidth management. The VP bandwidth management under dynamic CAC is difficult because this dimensioning method cannot use on‐line traffic measurement even though the CAC (the short‐term management) can. The dimensioning of the VP bandwidth is a key to making the service successful.