Network design of cable modem systems for WWW applications

Abstract

The cable industry has begun testing and deployzng high speed cable modems f o r data delivery. However, practical network designs require the estzmatzon and predzctaon of performance under realzstic traffic models and must consader the domznant factors that affect packet loss probabzlaties and offered load.In this paptr we evaluate tht use of a stochastzc model of i4'It'H' client-server transactzons as a tool for netuork dFsign and analysis Speczfically, CI sensztzwty analysis of the model 15 performed to zdentzfy the tmpact uarious model parameters haor on predicted packet /os5 probabilities an an Internet access netuork uti1z:ing CATV transport.The traffic model used zs a self-simalar traffic model zn whtch the znter-arrival tzmes of document requests generated by each sourcc 2s based on U two-state 0.V-OFF SOUTCC modd descrzbcd an (11 and thf lcngth of each document is gzven b y a Pareto distrabutaon as described zn [2] W e investigate the results of uszng such a model an predzctzng a number of netuork performance param e t e rs t n clu dz ng buffer requ z rem e n t s a n d a eh z e v ed channel utilization. W e tdso evaluate the number of M' M' 1.I' users that a head-end can support for a specific bandwidth The effects of multaplexing, decreasing the znter-arrival times, ancreasang the length of the OAV period. changing the tad of the document size dastrabutton, and zncreaszng the buffer site are all conszdered. W e also zdentafy which parameters most affect the packet loss probabdzty and the offered load on the system. Such parameters wzll be the dominant factors that need to be used an network and capaczty planning for CATV data delioery systems.