The A+ Certification & PC Repair Handbook (Charles River Media Networking/Security)

As mentioned earlier in this chapter, network protocols are a common language or set of rules that computers use to communicate with one another. Protocols come in packages known as protocol stacks. Individual protocols reside at each layer of the OSI reference model in order to carry out specified functions. If the Core exam tests you on protocols, it will most likely focus on the TCP/IP and IPX/SPX protocol stacks. There are many network protocols in use. We will focus on the protocols you need to know for the Core exam.

TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP) is the most popular protocol in use today. It is the protocol of choice for the Internet. TCP/IP is commonly used with Ethernet, Token Ring, and Internet or network dial-up connections. Every computer on a TCP/IP network uses an IP address as a unique numeric identification. An IP address is a 32-bit numeric combination of four period-delimited octets, each of which can be a number from 0 to 255. An IP address can be up to 12 digits long.

An example of an IP address is 209.15.176.206. This IP address is associated with the domain name address that is provided by a domain name system (DNS) server of the publisher of this book, charlesriver.com. From a DOS prompt, you can use the TCP/IP ping utility to test a connection to the Charles River Media, Inc. Web site. Try it. Using Windows 2000, navigate to the DOS prompt. At the DOS prompt, type “Ping charlesriver.com.” You should receive an associated IP address of the Web site as well as four echo replies. Another popular TCP/IP utility is the tracert command. The tracert will tell the route you are using to establish a connection with a destination computer. In other words, it gives you all the TCP/IP addresses and domain names of the computers you are using to reach your final destination. Try the tracert command from the DOS prompt. Type “tracert charlesriver.com.” You will receive the IP addresses and domain names of the computers you are hitting to get to the Charles River Media, Inc. Web site. The time it takes for your request to go from each destination’s IP address is measured in units of time called hops. A subnet mask is used to specify which particular network a TCP/IP address belongs to.

You can check the IP configuration of your computer using two popular commands. If you are using Windows 95 or 98, type “winipcfg” at the DOS prompt. If you are using Windows NT, Me, 2000, or XP, type “ipconfig” or “ipconfig/all” at the DOS prompt. Your computer’s IP address, subnet mask, and default gateway settings will be displayed.

If your computer is unable to communicate with other computers on the network and all the other computers are functioning correctly, you should first check your computer’s IP address configuration settings. They may not be properly configured. If this is the case, your computer can only access itself.

IPX/SPX

Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) is a protocol stack used in Novell networks that supports routing. There are several versions of Novell operating systems in use today. When connecting a system to a Novell network, it is often necessary to bind a specific frame type to your NIC for connection to various Novell operating system versions. Frame type specifications are beyond our study focus; just remember that if you are having trouble connecting to a Novell network, you should first verify that the proper frame type is bound to your NIC.

NetBIOS

NetBIOS (Network Basic Input/Output System) is a program or API (Application Programming Interface) that allows application programs on separate computers to recognize and talk to each other. NetBIOS operates at both the session and transport layers of the OSI reference model. Operating systems such as DOS and Windows use a message format called SMB (Server Message Block) to assist with the sharing of folders, files, devices, and other tasks/tools. NetBIOS relies on and uses SMB format.

NetBIOS was originally created by IBM, and was later adopted and changed for use in operating systems that were created by Microsoft and Novell.

NetBIOS is not routable. This means that it, alone, does not allow communication between systems or programs that exist on separate networks (usually separated by routers). In other words, NetBIOS works well in LANs, not WANs. For WAN communication, you need TCP/IP.

NetBEUI

NetBEUI (NetBIOS Extended User Interface) is a nonroutable, small, efficient transport layer protocol meant for use in small networks with 1–200 workstations. NetBEUI does not have the overhead associated with larger protocols and is very efficient for workgroups or peer-to-peer networks.

In a nutshell, if you have a small workgroup that includes operating systems such as Windows 95, 98, Me, 2000, XP, or NT, installing NetBEUI will allow them to efficiently communicate with each other. According to Microsoft, the only configuration requirement needed for installing the NetBEUI protocol is a valid computer name.