An Enhanced Extension to Wilkinson's Equivalent Random Technique with Application to Traffic Engineering

In this paper we present an enhanced extension to Wilkinson's equivalent random technique that allows one to easily compute the different levels of blocking that various streams of traffic see using the same trunk group. This empirical extension is based on a regression analysis and is superior to a similar extension by Katz. An application of our extension to system sizing problems in AUTOVON is presented. Previous sizing methods in the AUTOVON access area did not properly account for the peakedness of overflow traffic and thereby violated desired grades of service. The methods presented here overcome this problem, and yield a lower cost solution using fewer two-way trunks.     

The DTX-240D digital circuit multiplication system

This paper describes the DTX-240D digital circuit multiplication system (DCMS) offered by ECI Telecom. It will accept up to 240 × 64 kb/s trunks carrying either 64 kb/s voice, voice band analogue non-speech signals, or digital data for transmission over a 2·048 Mb/s digital link. Over 1000 are currently ‘on-line’ and carrying traffic. The system comprises a pair of terminals, one on each side of the interterminal digital link (bearer). It will normally operate in the network at a concentration ratio of 5:1, in which case 150 × 64 kb/s trunks, carrying voice, voice band data or digital data can be concentrated into one 2·048 Mb/s bearer. The users are able to increase the number of trunks up to 240 per 2·048 Mb/s bearer, when time zone differences cause a spread of busy-hour traffic carried on a single system. Each terminal will normally be located at an international switching centre (ISC) but may also be located at an earth-station. The system uses a DSI (digital speech interpolation) stage providing a 2·5:1 multiplication, followed by an additional 2:1 multiplication by means of ADPCM (adaptive differential pulse code modulation). In addition, the VBR (variable bit rate) technique is used to prevent clipping, due to overload congestion. The system can also be used with 1·544 Mb/s digital bit streams (trunk side or bearer).     

大规模高速网络流量工程研究

主要讨论互联网主干上的流量工程。由于现在路由协议使网络的低效率和新的应用的出现，迫切要求发展新的技术、引进流量工程的观点来处理这些问题。介绍了MPLS等的新的IP交换技术及其相关的路由算法；讨论了在IP主干上电话传输技术。     

IP over WDM网中的策略路由算法

业务量工程允许管理者通过赋予业务主干不同的业务量工程属性来体现一定的管理策略,在为业务主干建立标记交换路径(LSP)时也应该考虑这些策略的影响,该文讨论了业务主干具有不同优先权属性时的 LSP建立问题,针对中断 LSP个数最少和中断业务量最小两种指标,分别提出不同的解决策略:最小连接数中断法(MCNIM)和最小连接带宽中断法(MCBIM),并在不同负载的动态业务下对所提算法进行了仿真研究,给出了仿真结果。     

A projection of future ATC data processing requirements

Forecast traffic growth for the 1980-1995 time period will exceed the capacity of the present airport and air traffic control automation system in high-density areas. If traffic growth is to be accommodated, higher levels of automation are required. The Department of Transportation Air Traffic Control Advisory Committee (September 1968-August 1969) established a computer sizing group to determine the feasibility of achieving the necessary level of automation within the projected technology. This paper presents a model of the future system, a summary of the functions automated, and estimates of the necessary computer instruction rate and storage requirements as developed by this computer sizing group.     

Computations of DSI (TASI) Overload as a Function of the Traffic Offered

This paper presents an analysis of the performance of a digital speech interpolation (DSI) system as a function of the traffic offered to the system. We assume that the DSI overload degradation occurs as clipping or freezeout. This is identical to TASI freezeout. Unlike conventional analysis, which assumes all of the trunks entering the DSI system are busy all the time, we calculate the freezeout fraction as a function of the traffic offered. In almost all practical situations the freezeout fraction, computed based on traffic assumptions, is considerably less than that computed assuming all trunks are busy. When a DSI system is used to compressNtrunks down intocchannels, there is always a tradeoff between the blocking probability in the trunk group and the degradation introduced by the DSI system. This tradeoff depends on the traffic offered and is explored in this paper.     

Wide-area Internet traffic patterns and characteristics

The Internet is rapidly growing in number of users, traffic levels, and topological complexity. At the same time it is increasingly driven by economic competition. These developments render the characterization of network usage and workloads more difficult, and yet more critical. Few recent studies have been published reporting Internet backbone traffic usage and characteristics. At MCI, we have implemented a high-performance, low-cost monitoring system that can capture traffic and perform analyses. We have deployed this monitoring tool on OC-3 trunks within the Internet MCI's backbone and also within the NSF-sponsored vBNS. This article presents observations on the patterns and characteristics of wide-area Internet traffic, as recorded by MCI's OC-3 traffic monitors. We report on measurements from two OC-3 trunks in MCI's commercial Internet backbone over two time ranges (24-hour and 7-day) in the presence of up to 240,000 flows. We reveal the characteristics of the traffic in terms of packet sizes, flow duration, volume, and percentage composition by protocol and application, as well as patterns seen over the two time scales     

Local Network Area Size Optimization

A foundation for economically optimizing the size of a local network area, defined as an area comprising a transit switch and a number of local switches homing on it, is obtained by introducing the concept of an "intra-area traffic ratio." The local network area radius is found to be optimal when the gradient of the intra-area traffic ratio relative to the area radius equals the ratio of the junction cost per kilometer to the cost per circuit for trunks going out of the area. An empirical formula for determining this intra-area traffic ratio is given.     

Broadband public network and switch architecture

The authors present a view of public network and switch architecture evolution to broadband capabilities, driven by the applications evolutions and built on a synchronous fiber transmission infrastructure such as SONET (synchronous optical network). The scenario is based on the partitioning of broadband network functions between synchronous fiber transmission systems and cell-based transport. The first stage of evolution incorporates frame-based switching to support increasing data traffic for LAN (local area network) interconnections. Cell-based technology appears first in the form of point-to-point high-speed data trunks and then as switched high-speed access. Centralized cell switching will provide interconnect between cell-based trunks and shared access lines. Remote cell multipliers will provide traffic concentration when the number of customers further increases. Since cell transport will first be introduced in the network as an extension of frame transport to higher speed, interworking between cells and frames will be necessary     

Operational Evaluation of a Voice Concentrator Over AUTOVON Interswitch Trunks

This paper describes results of test and evaluation of a commercial voice concentrator applied to AUTOVON interswitch trunks between Feldberg, Germany and Ft. Detrick, MD. By virtue of time assignment speech interpolation (TASI) techniques, the voice concentrator provided approximately a 2-to-1 compression of voice channels onto trunks, with a configuration of 17 channels onto nine trunks selected for this AUTOVON application. Tests consisted of: 1) signaling performance characterization through the voice concentrator, 2) voice channel characterization of the nine selected trunks before and after cutover of the voice concentrator, 3) performance characterization of data signals operated through voice concentrator channels, 4) traffic data collection and analysis, and 5) user subjective evaluation. Test results indicated acceptable performance for the intended application, which was limited primarily to voice signals. Since completion of the testing and subsequent analysis, the Defense Communications Agency (DCA) has accepted the voice concentrator system for operational use with AUTOVON IST's in the Defense Communications System (DCS).     

On Cut-Off Limits of Delay-Loss Systems with Three Types of Traffic

In this paper, cut-off priority systems with a full access group of trunks (servers) are investigated which may be allocated to three groups of traffic sources. The total offered traffic will be divided into three traffic parts representing different types of services and will be served in a special order. The influence of these access priorities on characteristic traffic values like loss probability, delay-time and waiting probability will be investigated by means of an iterative calculation. Results are shown in examples and diagrams.     

Decomposition of Traffic in Loss Systems with Renewal Input

A method is proposed for the analysis of a teletraffic network with alternative routing. The approach used is to model a "general link" as a separate entity, being a first step towards analyzing the network in a link-by-link fashion. To this end the general link is considered to be a group of fully available trunks offered a number of separate streams of traffic. By considering the multivariate point process formed by the total stream of arriving calls, the individual streams of traffic overflowing from, and the individual streams of traffic carried on the common trunk, are distinguished. All streams of traffic in the network are considered to be well described by simple renewal processes. The validity of the method is illustrated with exact numerical results and by simulation.     

基于MPLS的流量工程——分布实时网络承载能力估计与分配模型

本文的主要工作是建立基于MPLS的流量工程模型.在商业运行的网络中,通过对已投资设施的充分利用获取竞争优势和商业回报的要求使得流量工程日益成为网络运营中不可缺少的手段.通过借鉴TCP和ATM的优点,结合面向连接和面向非连接两种处理方法的长处,建立一种基于MPLS的流量管理模型,该模型的特点是:管理功能模块边缘化,运输功能模块平面化,在高速,简单的运载核心上运行一个可管理的流量承载平台.模型的有效性通过两个方法得到评估.一是从形式上证明了模型运行状态的稳定性,完备性和对于时间轴的收敛性.二是使用Network Simulator建立模拟的网络环境验证对网络运行状态的优化结果.本文的工作基于以下重要概念:基于聚集的流量、流聚集、流量聚集点和流量分解点、扩充的链路耗费参数定义(承载能力占用率)、分布式公平队列等.     

Rehoming Strategies for a Relief Toll Machine

When an existing toll machine exhausts and a relief toll machine is added, rehoming of existing trunk groups is necessary. The intent of this paper is to determine rehoming programs whereby the present worth of the total trunk rearrangement cost is minimized while the total number of trunks to be rearranged at any stage of the program is constrained to lie within specified lower and upper limits. The rehoming program will specify the amounts of trunks to be rearranged and their corresponding timings for the rearrangements to take place. It is found that the choice of a proper rehoming strategy is critically dependent on the relative magnitude of the monetary discount rate compared to the traffic growth rate. When the discount rate matches the growth rate, any feasible rehoming strategy for any type of existing and relief machines is appropriate. If the discount rate is lower than the growth rate, it is more economical to rehome the maximum allowable amount of trunks as early as possible. On the other hand, if the discount rate is higher than the growth rate, the rehoming strategy is completely reversed. This case calls for a delay of as much rehoming as possible. However, the number of trunks to be rearranged during each stage of the rehoming program is bounded by the specified minimum allowable limit.     

蜂窝无线网络话务承载能力评估比较算法研究

针对传统GSM蜂窝无线网络蜂窝分析理论的极限性,提出了无线网络话务承载能力增益的新概念及其相关算法,用于比较不同频率方案对无线网络综合性能的改善程度。通过采集不同阶段无线网络的相关测量数据,应用该算法进行分析能实时准确地反映无线网络采用不同频率方案导致的无线网络综合性能的客观变化情况。     

Empirical study of traffic trunking in Linux‐based MPLS test‐bed

The thrust of this study is to construct an MPLS test‐bed using open hardware and software and later use this test‐bed for experimenting with various traffic engineering options available with MPLS. We have constructed a test‐bed using Pentium PCs and Linux and used this test‐bed to try a well‐known MPLS traffic engineering feature of separating flows into multiple trunks. The purpose of this separation is to experimentally assess the quality of service benefits we can expect from MPLS networks. Copyright © 2003 John Wiley &Sons, Ltd.     

Performance evaluation of 10Base-T and 100Base-T Ethernets carryingmultimedia traffic

The performance of 10Base-T and 100Base-T Ethernet segments carrying audio/video traffic is presented. End-to-end delay requirements suitable for a wide range of multimedia applications are considered (ranging from 20-500 ms). Given the specific nature of the network considered and the maximum latency requirement, some data is lost. Data loss at the receiver causes quality degradations in the displayed video in the form of discontinuities, referred to as glitches. We define various quantities characterizing the glitches, namely, the total amount of information lost in glitches, their duration, and the rate at which glitches occur. We study these quantities for various network and traffic scenarios, using a computer simulation model driven by real video traffic generated by encoding video sequences. We also determine the maximum number of video streams that can be supported for given maximum delay requirement and glitch rate. We consider various types of video contents (video conferencing, motion pictures, commercials), two encoding schemes (H.261 and MPEG-1), and two encoder control schemes [constant bit rate (CBR) and constant-quality variable bit rate (CQ-VBR)] and compare their results. Furthermore, we consider scenarios with mixtures of video and data traffic (with various degrees of burstiness), and determine the effect of one traffic type over the other     

Product network as a traffic concentrator

The traffic capacity of product networks based on the Cartesian product of complete graphs has previously been investigated in terms of final selection for 2nd-order products. Traffic concentration has not, however, been previously considered, and, as a first step, the letter considers concentration using single-link connections. A preferred method of connecting trunks to the network is also indicated.     

Designing multi-hour hierarchical communications networks with fixed charge and piecewise linear costs

An algorithm is presented for the problem of sizing link capacities in an alternate routing telecommunications network with time-varying demands. Several algorithms have been developed since 1977 for this problem, where costs are linear and the existing network is ignored. We consider the case of per-trunk (communications channel) costs for adding and disconnecting trunks from an existing network, and fixed costs for the first trunk added or disconnected on each link. A branch and bound procedure is developed to solve the problem. Lower bounds in the search tree are obtained through the use of Lagrangian relaxation and subgradient optimization. Several tests are employed to detect infeasibility of subproblems generated in the tree search. Computational results are presented, including comparisons of results using different tolerances for pruning the search tree.     

Analysis on Partial Overflow Queueing Systems with Two Kinds of Calls

In this paper, the traffic model of one kind of the partial overflow system is presented and theoretically analyzed, which has remained unsolved up to today. In the partial overflow systems, the considered overflow traffic stream is a part of the traffic stream overflowing from a common trunks group with multiinput calls. The systems with two kinds of calls are treated. Both of the two input traffic streams are assumed to follow the Poisson process and the holding times of the calls are assumed to be identical and follow an exponential distribution. Under these assumptions, analytical formulas are derived to calculate the individual traffic characteristics for both the loss-loss partial overflow system and the wait-loss partial overflow system. With these results, the accuracy of the well-used equivalent random theory in approximating the traffic model offered with partial overflow stream is investigated. The two-input model is a general one and can be used for analyzing the model with more than two inputs. It is expected that the formulas derived in this paper can be Used to improve the accuracy of ERT method as well as used directly.