opnet 14.5 包交换网络仿真教程

opnet 14.5中，详细的介绍了包交换网络仿真的全过程。包括每一步的操作与配置。
Getting Started There are several design concepts you should consider before you start building the network model Network topology and the physical communication medium The functions of the different node types The method the process model uses to determine which point-to-point transmitter addresses a particular peripheral node The role of peripheral nodes Network Topology The initial network will consist of four peripheral nodes connected to a hub node by point-to-point links Point-to-point links can either be simplex (unidirectional) or duplex(bidirectional). In this case, you will use custom duplex links to connect transmitter-receiver pairs. Looking only at the communications medium as represented the network would look like this Communications Medium of the network peripneral nodes hub node duplex point-to-point link - point-to-point receiver point-to-point transmitter Functions of the Different Node Types The purpose of the model is to simulate packets traveling from one peripheral node to another peripheral node through the packet switching hub node In the hub node, you can assume that packets containing destination addresses will arrive randomly on the four incoming links from the four peripheral nodes. the destination address is an integer value specifying a destination peripheral node. The hub node must contain a process model that can retrieve the incoming packets read the destination address and send the packets to the appropriate point-to-point transmitter Different Node Types peripheral nodes inode 1 ode 2 hub node hub node 0 node 3 The role of the hub node model Packet streams each have a unique index. the easiest method is to set up a direct association between the hub process outgoing packet stream indices and the peripheral destination address values. In a more adaptive model the hub process model could maintain a table for translating destination address values to transmitter stream indices. In this tutorial, a direct correspondence between designating addresses and packet stream Indices Is appropriate In summary, the hub node model will consist of a point-to-point transmitter/receiver pair for each peripheral node, and a process model used to relay packets from a receiver to the appropriate transmitter Hub node rovO xto rove xmt rCv xt2 rCv xmt The Role of Peripheral Nodes The peripheral node model must generate packets, assign destination addresses, and process received packets. The peripheral node model will use a generator module to create packets. It will use a user-defined process model to assign destination addresses to packets and send them to the node's point-to-point transmitter. This process model will retrieve packets arriving from the point-to-point receiver. Upon receiving a packet, the same process model will calculate the packet' s end-to-end delay and write the value to a global statistic(a global statistic is accessible to multiple processes throughout the system) Peripheral Node Ccv SCc proc P xmt Building the Models To build this network model, you must do the following steps. Building the Packet Switching Network Start Define packet format Define link mode Create hub node model Create peripheral node model Build network model Done Creating a New Packet Format The Packet Format Editor can create packets containing any number of different fields that affect packet size The packets in this network contain a single field with the destination address of the packet. after the packet format has been created it can be specified as an attribute in a generator so that packets created by the generator will be formatted accordingly To create a new packet 1 If not already running start the program 2 Close any open projects 3 Choose file new and select Packet Format from the pull-down list. Click OK 4 Click on the create new field tool button then move the cursor into the editor window 吕 5 Left-click to place a field in the editor window, then right-click to end the field creation operation ba new field is created in the editor window 10