, Average = 20ms \Users\jithesh_sathyan>arp -a Interface: 132.32.132.576 0xa Internet Address Physical Address 132.32.132.1 00-14-1b-e4-f4-00 dynamic 132.32.132.35 00-1e-68-0e-82-35 dynamic 132.32.132.98 00-1e-90-26-c2-a6 dynamic 224.0.0.252 01-00-5e-00-00-fc static 239.255.255.250 01-00-5e-7f-ff-fa static 255.255.255.255 ff-ff-ff-ff-ff-ff static C:\Users\jithesh_sathyan>telnet 132.32.132.57 Figure 26.1 Working with PING, ARP, and TELNET in MS-DOS (Microsoft disk operating system). Socket Communication that is to be debugged using telnet utility. Since most telnet clients facilitate the connection to ports other than default port 23, the telnet utility can also be used to investigate new TCP-based protocols. Most operating systems include telnet clients, SO telnet is rarely used programmatically. Address resolution protocol resolves IP addresses into their equivalent MAC addresses and routing information protocol helps to identify the number of hops to a destination. There are many more utility applications that can aid in network troubleshooting. 26.4 Client-Server Model The client-server model is the most common way by which an element requests services from another network element (see Figure 26.2). In a typical network like two computers connected through the Internet, the local computer (client) runs a program that requests a service from another program on the remote computer (server). There can be multiple clients in the network that request for service from a server. The communication channel between server and client could always be connected or the connection can terminate upon completion of service. Using the IP address of the client and the port address of the specific server program, a com- munication channel is established between the client and the server. Once a connection is established, the channel remains active and open for com- munication. After the completion of the service from the server, the communica- tion channel between the client and the server can be closed. The server program keeps 