13-17LESSON 1 CONFIGURING AND TROUBLESHOOTING TCP/IPTHE TCP/IP PROTOCO...

13-17Lesson 1 Configuring and Troubleshooting TCP/IP

The TCP/IP Protocol Suite

The TCP/IP suite of protocols provides a set of standards for how operating sys-

tems and applications communicate and how networks are interconnected. The

TCP/IP suite of protocols maps to a four-layer conceptual model known as the

Department of Defense (DoD) model. The four layers are as follows:

■

Network access layer The network access layer is responsible for placing

data on the network medium and receiving data off the network medium.

This layer contains physical devices such as network cables and network

adapters.

■

Internet layer The Internet layer is responsible for addressing, packaging,

and routing the data that is handed down to it from the transport layer. There

are four core protocols in this layer: IP, Address Resolution Protocol (ARP),

Internet Control Message Protocol (ICMP), and Internet Group Management

Protocol (IGMP).

■

Transport layer The transport layer protocols provide communication

sessions between computers. The desired method of data delivery deter-

mines the transport protocol. The two transport layer protocols are TCP and

User Datagram Protocol (UDP).

■

Application layer At the top of the model is the application layer, in

which applications gain access to the network. There are many standard

TCP/IP tools and services in the application layer, such as File Transfer Pro-

tocol (FTP), Telnet, Simple Network Management Protocol (SNMP), DNS,

and so on.

The purpose of this layering is to provide a level of abstraction between an appli-

cation or protocol in one layer and the functioning of the entire network. For

example, an application in the application layer needs to know only where to

pass information into the transport layer (and how to format that information); it

does not need to take into account any specific network configuration beyond

that point. Packets of data are passed down the layers on the sending host and

back up the layers on the receiving host.

If you are interested in learning more about how layering works, you should view

two multimedia presentations: “OSI Model” and “TCP/IP Protocol Suite.” Both

presentations are available in the Multimedia folder on the CD-ROM accompany-

ing this book.

Practice: Configuring and Troubleshooting TCP/IP

In this practice, you will use two TCP/IP tools to verify your computer’s configuration.

Then you will configure your computer to use a static IP address and verify your com-

puter’s new configuration. Next, you will configure your computer to use a DHCP server

to automatically assign an IP address to your computer (whether or not there is a DHCP

server available on your network). Finally, you will test the APIPA feature in Windows XP

Professional by disabling the DHCP server, if there is one on your network.

If your computer is part of an existing network, use the following table to record the

IP address, subnet mask, and default gateway that your network administrator provides

for you to use during this practice. Ask your network administrator whether there is

another computer that you can use to test your computer’s connectivity and record the

IP address of that computer as well. If you are not on a network, you can use the sug-

gested values.

Variable Value Suggested Value Your Value

Static IP address 192.168.1.201

Subnet mask 255.255.0.0

Default gateway (if required) None

Computer to test connectivity N/A