You are required to simulate the behavior of a packet switching network inside the laboratory. The creation of a network will require using the packet and link editors; defining the collected statistics; and learning new Kernel procedures. Some other benefits that will be derived from the lab include learning the principles of model design; becoming familiar with the node and process models; learning how the node and process models function within a network model; carry out parametric studies of various statistics. The performance of a simple packet switching network is measured by the end-to-end delay experienced by traffic on the network (Copeland 1). The objective of this lesson is to enable a student to model a simple network in which four peripheral nodes generate traffic while a central hub node relays the traffic to the appropriate destination within the network.
A student will be required to consider several design concepts before he starts building the network model. These concepts include network topology and the physical communication medium; the functions of the different node types; the method used by the process model in the determination of which point-to-point transmitter addresses a particular peripheral node; and the role of peripheral nodes network topology. These concepts are further explained in the preceding paragraphs.
Network topology and the physical communication medium: the first network will contain four peripheral nodes connected to a hub node by point-to-point links. The point-to-point links can either be simplex or duplex. Simplex links are unidirectional whereas duplex links are bidirectional. Custom duplex links will be used to connect transmitter-receiver pairs in this initial network.
Functions of the different node types: the purpose of the model is to simulate the packets that are travelling from one peripheral node to another peripheral node through the packet switching hub node. At the hub node, there is an assumption that the packets containing destination addresses will arrive randomly through the four incoming links from the four peripheral nodes. The destination address is an integer value that specifies a destination peripheral node. It is mandatory for the hub node to contain a process model that is capable of retrieving the incoming packets, reading the destination address, and sending the packets to the appropriate point-to-point transmitter.
The role of the hub node model: each packet stream has a unique index. The easiest method involves the setting up of a direct association between the hub process outgoing packet stream indices and the peripheral destination address values. A more adaptive hub node model will ensure that the hub process model can maintain a table for translating destination addresses values to the transmitter stream indices. This tutorial highlights the appropriateness of having a direct correspondence between designating addresses and the packet stream indices. In other words, the hub node model will consist of a point-to-point transmitter/ receiver pair for each peripheral node and a process model that will be used to relay packets from a receiver to the appropriate transmitter.
The role of peripheral nodes: the peripheral node model has several duties that include generating packets; assigning destination addresses; and processing the received packets. The peripheral node model uses the generator module in the creation of packets. A user defined process model is used to assign the destination addresses to packets and then sending them to the node’s point-to-point transmitter. The process model retrieves the packets that arrive through the point-to-point receiver. After receiving the packets, the process model calculates the packets’ end-to-end delay and writes the value to a global statistic. The global statistic is made accessible to all the processes carried out within the system.
Works Cited
Copeland, Lee. Packet-Switched vs. Circuit-Switched Networks. 20 Mar. 2000. Web. 26 Apr. 2016. http://www.computerworld.com/article/2593382/networking/networking-packet-switched-vs-circuit-switched-networks.html
