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1-26
Chapter 1
Planning a Network Topology
the network layer and either TCP or UDP at the transport layer (see Figure
1-6). In fact,
the TCP/IP suite is named for the most commonly used combination of
protocols.
Transport Layer
Network Layer
F01pm06
Figure 1-6 TCP/IP network and transport layer protocols
IP is the key protocol of the TCP/IP suite. Almost all TCP/IP traffic is
carried using IP
packets called datagrams. An IP datagram is something like the envelope you
use to
mail a letter. The datagram has the address of the intended recipient and
the address of
the sender. As the packet travels across the network, computers read the
recipient’s
address and pass the packet along toward its intended destination. IP is
also responsi-
ble for routing packets across an internetwork.
Whether a network communication process uses IP with TCP or IP with UDP
depends
on the requirements of the application generating the network traffic. TCP
is a connec−
tion−
oriented protocol, which means that before two computers can communicate,
they exchange a series of messages that establish a connection between them.
In addi-
tion, the computers acknowledge the data packets they receive from each
other, ensur-
ing that the transmitted data arrives intact. Computers use TCP when they
have to
transmit relatively large amounts of data that must arrive intact at the
destination. The
drawback to using TCP is the additional traffic generated by the connection
establish-
ment and acknowledgment messages.
UDP is a connectionless protocol, which means that two computers can
communicate
without establishing a connection first, and they do not transmit dedicated
acknowl-
edgment messages. Computers typically use UDP for brief exchanges of data,
such as
request and response messages, or for data transmissions that can survive
the loss of an
occasional packet, such as streaming audio or video. The advantage of using
UDP is
that its overhead is much lower than that of TCP.
In addition to these three primary protocols, the TCP/IP suite includes many
others,
spanning the OSI reference model from the data-link to the application
layer, and pro-
viding a number of different administrative functions. When you configure a
computer
to use TCP/IP, you install the entire suite of protocols at once. In the
Windows Server
2003 operating system, the TCP/IP protocol suite takes the form of a single
module that
you install in the Network Connections tool. The process is similar in other
versions of
the Windows operating system.
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