Traffic models are at the heart of any performance evaluation of telecommunications networks An accurate estimation of network performance is critical for the success of broadband networks Such networks need to guarantee an acceptable quality of service (QoS) level to the users Therefore, traffic models need to be accurate and able to capture the statistical characteristics of the actual traffic We survey and examine traffic models that are currently used in the literature Traditional short-range and non-traditional long-range dependent traffic models are presented The number of parameters needed, parameter estimation, analytical tractability, and ability of traffic models to capture marginal distribution and auto-correlation structure of the actual traffic are discussed

Traffic models in broadband networks

Many designs for integrated service networks offer a bounded delay packet delivery service to support real-time applications. To provide bounded delay service, networks must use admission control to regulate their load. Previous work on admission control mainly focused on algorithms that compute the worst case theoretical queueing delay to guarantee an absolute delay bound for all packets. In this paper we describe a measurement-based admission control algorithm for predictive service, which allows occasional delay violations. We have tested our algorithm through simulations on a wide variety of network topologies and driven with various source models, including some that exhibit long-range dependence, both in themselves and in their aggregation. Our simulation results suggest that, at least for the scenarios studied here, the measurement-based approach combined with the relaxed service commitment of predictive service enables us to achieve a high level of network utilization while still reliably meeting the delay bound.

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A measurement-based admission control algorithm for integrated services packet networks

In this study, a fuzzy autoregressive (fuzzy-AR) model is proposed to describe the traffic characteristics of high-speed networks. The fuzzy-AR model approximates a nonlinear time-variant process with a combination of several linear local AR processes using a fuzzy clustering method. We propose that the use of this fuzzy-AR model has greater potential for congestion control of packet network traffic. The parameter estimation problem in fuzzy-AR modeling is treated by a clustering algorithm developed from actual traffic data in high-speed networks. Based on the adaptive AR-prediction model and queueing theory, a simple congestion control scheme is proposed to provide an efficient traffic management for high-speed networks. Finally, using the actual Ethernet-LAN packet traffic data, several examples are given to demonstrate the validity of this proposed method for high-speed network traffic control.

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Traffic modeling, prediction, and congestion control for high-speed networks: a fuzzy AR approach

In this paper, we propose a video model to generate VBR MPEG video traffic based on the scene content description. Long sessions of nonhomogeneous video clips are decomposed into homogeneous video shots. The shots are then classified into different classes in terms of their texture and motion complexity. Each shot class was uniquely described with an autoregressive model. Transitions between the shots and their durations have been analyzed. Unlike many classical video source models, this model may be used to generate traffic of any type of video scenes ranging from a low complexity video conferencing to a highly active sport program. The performance of the model is evaluated by measuring the mean cell delay when the generated video traffic is fed to an ATM multiplex buffer.

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Content-based MPEG video traffic modeling

A virtual path connection (VPC) is a labelled path which can be used to transport a bundle of virtual channel connections (VCCs) and to manage the resources used by these connections. The virtual network is organized as a collection of VPCs which form a VPC, or logical, overlay network. If the VPCs are permanent or semi-permanent and have reserved capacity, establishing new VCCs requires simple connection admission decisions at the VPC terminators of existing VPCs. This would enable faster connection establishment since transit nodes are not involved in the connection setup. The virtual path concept also allows the possibility of segregating traffic types according to quality of service requirements. However, the extent to which VPC provisioning is able to improve network efficiency is dependent on the resource management decisions that determine the VPC topology and capacity allocations. The article surveys resource management using virtual paths in an ATM network. Of interest are techniques which modify the VPC topology and capacity assignments in order to adapt to changing traffic conditions and possible network failures. The resource management activities employed to facilitate such adaptation can be categorized by the timescale on which they operate. On the shortest timescale are strategies for dynamically making minor changes to the VPC topology or capacity assignments. On a somewhat longer timescale are strategies for making more widespread modifications to the VPC overlay network. This would be appropriate for traffic changes based on time of day and for recovering from network failures. Finally, on an even longer timescale, strategies may be employed to design a general VPC overlay network, to be used at startup or after major network upgrades. Solutions to VPC resource management for each of these timescales are discussed.

Resource management with virtual paths in ATM networks

The authors propose a new method for the modeling and call admission control (CAC) of variable bit rate video source, which come to the front of ATM networks as hot issues nowadays. First, the modeling of video source is accomplished using the three-state Markov chains including the effects of scene change at which the bit rate of video source is abruptly increased. Also, using two AR models, they improve the defects which an AR model has in modeling a video source. In addition, they represent the analytical model of a video source so that a network manager can acquire the information which is very important in managing the entire networks. CAC is accomplished using the previously defined analytical model. A routing manager calculates the cell loss probability of a chosen VP where a new call is connected so that the routing manager decides whether this new call is accepted or not. This calculation is accomplished through the GB/D/1-S queuing system. Using BIA (bandwidth increasing algorithm), they check whether the calls rejected by the routing manager could be accepted if possible. Finally, the applicable procedures to suitable allocate bandwidth to each VP on a link are presented in detail. >

Modeling and call admission control algorithm of variable bit rate video in ATM networks

Applications such as real-time video/voice service, distributed multimedia database access, and high-resolution image transfer require more bandwidth than is available today. These applications also require a large geographical span. To meet these requirements, we introduce the new protocol, MCDQDB, for a multi-channel dual-bus MAN which is the extension of a single channel DQDB MAN. MCDQDB can be easily implemented with the state-of-the-art WDM technology and conforms to the IEEE 802.6 standard, DQDB, with fairness and access delay improvement. The multiple channels of MCDQDB are made by WDM and the nodes of MCDQDB have fixed transmitters and receivers whose number is equal to the number of channels. Better fairness is obtained by distributing the head-end nodes. For an analysis, we compare MCDQDB with DQDB with a high speed channel. The simulation results show the advantage of MCDQDB in access delay and fairness, compared with the one channel original DQDB and the relation between the number of channels of MCDQDB and the channel speed of DQDB.

MCDQDB (Multi-channel DQDB) using WDM (wavelength division multiplexing)

We present a new ring protocol which is suitable for LAN/MAN compatible to the ATM network. The proposed ring protocol, Y-Ring protocol, resolves the fairness problems of ring networks. A key idea of the proposed Y-Ring protocol is to find the nodes that have more busy cells destined to it than other nodes. Since destination released cells have a great effect on the performance and unfairness of ring networks under heavy loads, the nodes that have many destination cells need to transfer a part of the released cells to the next node for fairness. Another key idea is that all operations of Y-Ring protocol are carried out on a independent ring in a decentralized manner without any control signals through an opposite ring.

Cheul Shim

Papers

Modeling and call admission control algorithm of variable bit rate video in ATM networks

MCDQDB (Multi-channel DQDB) using WDM (wavelength division multiplexing)

Ring protocol for ATM-LAN/MAN: Y-Ring protocol