【正文】 and the dynamic bandwidth allocation are carried out based on the mercial software OPNET with some enhancement modules developed by the author. All the emulations are based on the finite state machine model. And a lot of emulation results are presented in this thesis. Several improvements in the protocols are also presented first time in this thesis based on these emulation results. And some suggestion is proposed. This paper first introduces the protocol and then focuses on the design, realization and simulation of the major functions in the protocol. Topdown design method is used in the project. The primary function of the system is divided into three blocks, data receiving, data transmitting and flow control and the inter block relationship is decrypted. Each block is then subdivided. At the end, the result is verified by simulation. The performance research of protocol based on OPNET introduces the principles and analysis the theories of . By using OPNET simulation platform, the work simulation model of the protocol is constructed. Based on analyzing the simulation results of channel throughout and utilization, the key conclusions and evaluations are drawn. So as to prove the feasibility of using OPNET software to improve and amend the protocol, and this is a new way to develop new work protocol in the future. Key words: OPNET, Simulation Software, III 目 錄 1 緒論 ....................................................................................................................................... 1 引言 .......................................................................................................................... 1 網(wǎng)絡(luò)仿真研究現(xiàn)狀 .................................................................................................. 2 擁塞控制的仿真 ........................................................................................... 3 對(duì)無(wú)線(xiàn)接入技術(shù)的仿真 ............................................................................... 4 對(duì)路由協(xié)議的仿真 ....................................................................................... 4 論文重點(diǎn)及結(jié)構(gòu)安排 .............................................................................................. 4 2 OPNET 概述 ......................................................................................................................... 6 網(wǎng)絡(luò)仿真的概念 ...................................................................................................... 6 OPNET Modeler 的體系結(jié)構(gòu) ................................................................................. 6 OPNET 的軟件結(jié)構(gòu) ..................................................................................... 7 OPNET 的功能 ............................................................................................. 7 OPNET 的仿真模型庫(kù) ................................................................................. 8 OPNET 的優(yōu)缺點(diǎn) ......................................................................................... 9 OPNET 核心函數(shù) .................................................................................................. 10 OPNET 的通信 仿真機(jī)制 ........................................................................... 10 OPNET 的核心函數(shù) ................................................................................... 10 OPNET Modeler 建模過(guò)程 ................................................................................... 11 OPNET Modeler 的仿真建模方法 ............................................................. 11 OPNET Modeler 建模流程 ......................................................................... 12 3 協(xié)議分析 .......................................................................................................... 13 以太網(wǎng)的發(fā)展歷史 ................................................................................................ 13 以太網(wǎng)核心思想 ......................................................................................... 13 以太網(wǎng)的標(biāo)準(zhǔn)化 ......................................................................................... 14 交換式和全雙工 以太網(wǎng) ............................................................................. 15 以太網(wǎng)的工作模式 ................................................................................................ 16 CSMA/CD 模型 .......................................................................................... 16 IV CSMA/CD 工作原理 .................................................................................. 17 CSMA/CD 算法 .......................................................................................... 19 協(xié)議 ..................................................................................................... 21 協(xié)議的物理層規(guī)范 ................................................................... 22 媒體訪(fǎng)問(wèn)控制 （ MAC） 層 ........................................................................ 23 媒體訪(fǎng)問(wèn)控制 （ MAC） 幀格式 ................................................................ 24 4 協(xié)議的仿真 ....................................................................................................... 26 模塊的劃分 ............................................................................................................ 26 數(shù)據(jù)發(fā)送模塊 ........................................................................................................ 26 綜合處理邏輯 ............................................................................................... 29 計(jì)數(shù)器模塊 ................................................................................................. 29 隨機(jī)數(shù)模塊 ................................................................................................. 30 CRC 模塊 .................................................................................................... 31 數(shù)據(jù)接收模塊 ........................................................................................................ 31 接收 MAC 的設(shè)計(jì) ................................