ATM LANs Research Articles

Admission control for hard real-time connections in ATM LANs

A connection admission control (CAC) algorithm must efficiently determine if a new connection can be admitted by verifying that its QoS requirements can be met without violating those of previously admitted connections. 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. To achieve these objectives a CAC algorithm must account for the traffic characteristics of connections. Furthermore, arbitrary topology of the network may lead to cyclic dependencies among various connections. An efficient CAC algorithm is presented that addresses these issues. The algorithm uses a traffic descriptor called the ‘maximum traffic rate function’ to effectively compute bounds on end-to-end delays of connections and buffer requirements within the network. The work differs from most previous work in that it does not require traffic restoration inside the network.

Efficient adaptive connection admission control algorithms for real-time ATM LANs

This study aims to provide adaptive communication services for real-time applications. In particular, how to admit adaptive real-time connections is addressed. Various search techniques in connection with admission control are investigated, and their tradeoffs under different performance criteria are assessed. The implementation and application of this new connection model in the NetEx system is also discussed.

Performance of integrated interlan telephony service over an ATM network

The demand for a seamless interconnection between the end subnetworks using ATM technology is steadily arising in the customer premises. A great demand also exists in enterprise networks for obtaining interLAN telephony service integrated with asynchronous data services. We determine the end-to-end performance of internetworked integrated services ATM LANs by using a simulation based approach. We further demonstrate the feasibility of providing interLAN telephony service integrated with asynchronous data services in internetworked ATM LANs. This entails the implementation of a crucial technique, which we have developed in the interworking units so as to segregate the voice data from the asynchronous data. The end subnetworks considered in case of the integrated services homogenous ATM LANs are IEEE 802.5 LANs, whereas the end subnetworks considered in case of integrated services heterogenous ATM LANs are IEEE 802.5 and the standardised 802.9 (isoEthernet) LANs. A significant issue addressed in this case is the internetworking of the packet based IEEE 802.5 LAN to the 802.9 LAN.

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.

Efficient Connection Admission Control Algorithms for Adaptive Real-Time Connections Over ATM LANs

In this paper, we present an adaptive real-time connection model. We address how to admit real-time connections under this new model and investigate various search techniques in connection admission and assess their tradeoffs under different performance criteria. We show new connection admission control algorithm with heuristic search techniques for increasing probability that a connection is admitted, and provide the best possible QoS to admitted connections.

Low-latency handover in a wireless ATM LAN

The micro- and picocellular architectures proposed for wireless ATM LANs lead to wireless terminals frequently changing their point of attachment to the network. Because ATM connections have quality of service (QoS) guarantees which must be maintained, handover must be as seamless as possible. We present a novel architecture and protocol which primarily aims to keep the interruption period due to handover low, rather than seeking to keep the process entirely lossless. We compare the tradeoffs made, with those in other schemes from the literature, and give quantitative results from an implementation of our scheme on a 10 Mbits/s/sup -1/ prototype wireless ATM LAN.

Performance Of An Input/output Buffered-type Atm Lan Switch With Back-pressure Function

An ATM switch with both input and output buffers provided with a back-pressure function has been proposed as a cost-effective switch architecture. The back-pressure function prohibits cell transmission from the input buffer to the corresponding output buffer to avoid cell loss at the output buffer due to a temporary congestion. Especially when this switch is applied to ATM LANs for data transfer services, its performance should be evaluated by taking into account bursty traffic. In this paper, we show the maximum throughput, the packet delay distribution, and the approximate packet loss probability of such an ATM switch for bursty traffic through an analytic method. In addition to a balanced traffic condition, an unbalanced traffic and a mixture of bursty and stream traffic are also analyzed. Through several numerical examples, we quantitatively show the effects of the average packet length and the output buffer size on its performance.

TMN-based customer network management for ATM networks

Effective end-to-end management of today's globalized heterogeneous corporate customer networks, a mixture of ATM WANs and ATM LANs, is essential for customers at the cutting edge of technology. ATM WAN and ATM LAN management systems generally have different management policies and management information models. Studies on the customer network management system (CNMS) to realize end-to-end customer network management have thus adopted the telecommunications management network (TMN) interoperability concept, which is based on CNM manager and agent interoperation. This article proposes an end-to-end customer network management method that realizes interoperation. In order to realize configuration management, fault management, and performance management, the CNM agent extracts the information needed by CNMS from the ATM transport network operations system and controls the operations system accordingly.

A unifying methodology for handovers of heterogeneous connections in wireless ATM networks

The aim of Wireless ATM is to provide multi-media services to mobile users. While existing research on Wireless ATM are focussed on handovers of unicast connections, handovers of multicast connections have not been investigated. While conventional multicast join and leave operations occur over the same path, this is not the case during mobile host migrations in a Wireless ATM network. In this paper, we reveal how handovers of multicast connections can be achieved in a manner irrespective of whether these multicast trees are source-, server- or core-based. More importantly, we demonstrate how the enhanced hybrid handover protocol incorporating crossover switch discovery can be used to support handovers of heterogeneous (i.e., unicast and multicast) connections in a uniform and unified manner, for Wireless ATM LANs employing either the centralised or distributed connection management scheme.

Architecture and Performance of MLAN: A Multimedia Local ATM Network

In this paper we present a Multimedia Local ATM Network (MLAN) protocol suitable for campus environment which (i)operates in the native ATM mode, (ii)does dynamic and fair bandwidth allocation as per desired criteria, (iii)guarantees continuous access to real time and high priority data traffic, and (iv)offers connectionless as well as connection-oriented service for MLAN-ATM network communication. The protocol has been designed for a bidirectional broadcast bus system topology. A new 'polling inactive customers only (PICO)' reservation technique exploits the characteristics of the multimedia traffic which enabled us to reduce the average overhead due to bus propagation delay. Also, new concepts of secondary polling and transmissions have been introduced to improve LAN throughput under low traffic conditious. The protocol performance has been determined analytically as well as by computer simulation using a multimedia traffic model developed in the paper. Results show that the protocol performance remains the same at all traffic compositions if the offered load does not change and is independent of the bit rate (R) when R≥50 Mbps. Based on the results, the proposed broadcast bus system MLAN architecture is well suited for designing high speed multimedia ATM LANs with a modest number of terminals over a 1 to 3 km bus.

IP on ATM local area networks

ATM offers increased bandwidth and greater flexibility and manageability. However, ATM's success as a LAN technology depends on its ability to provide LAN-like services compatible with existing protocols and applications. The authors address the various issues in the design and implementation of the Internet Protocol (IP) in the evolving ATM LANs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Protocol and Interface for ATM LANs

This paper describes the design and performance of a simple ATM host interface for a RISC workstation together with the MSNA protocol architecture. A feature of the MSNA architecture is that it can provide ATM virtual circuits directly to applications by demultiplexing to a degree normally associated with the transport layer of a protocol stack. We discuss implementations of the ATM adaptation layer of varying complexity and discuss the appropriate place for the adaptation layer to be terminated in a multimedia workstation.