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Lesson 3
Selecting Network/Transport Layer Protocols
1-25
Lesson 3: Selecting Network/Transport Layer Protocols
Once you have selected a data-link layer protocol for your network, your
concerns for
the physical infrastructure are finished. It is now time to move upward in
the OSI ref-
erence model and select the protocols for the network and transport layers
and above.
There is no need to be concerned about protocol compatibility at this point,
because
all the data-link layer protocols in current use can function with any
network/transport
layer protocol combination.
After this lesson, you will be able to
■ Describe the circumstances under which you should use the three
network/transport
layer protocol options supported by Microsoft Windows operating systems
Estimated lesson time: 15 minutes
Windows Server 2003 (like all current Windows operating systems) includes
support
for three network/transport layer protocol combinations: TCP/IP,
Internetwork Packet
Exchange (IPX), and the NetBIOS Extended User Interface (NetBEUI). The
operating
systems can function with any or all of these protocols installed at the
same time. TCP/
IP and IPX are both collections of protocols (called protocol suites) that
function
together to provide services that span several layers of the OSI reference
model. Both
TCP/IP and IPX include network and transport layer protocols, and depending
on the
functions a computer is performing, the services provided by the protocol
suite can at
times run all the way up to the application layer. NetBEUI is a monolithic
protocol that
provides basic network functionality but is not nearly as flexible as TCP/IP
or IPX.
Using TCP/IP
TCP/IP is a large collection of protocols that provides a comprehensive
array of net-
working services in addition to basic Windows file sharing. For most network
design-
ers, the process of selecting protocols for the network and transport layers
is a brief
one, because TCP/IP is the only logical selection. Only TCP/IP provides the
flexibil-
ity, expandability, and Internet compatibility that most networks require.
The TCP/IP
protocols were designed in the 1970s to support the experimental
packet-switching
network that eventually became the Internet. Because this network consisted
of
many different types of computers, the protocols were designed to be
completely
hardware-independent. This is why the TCP/IP protocols have their own
indepen-
dent addressing system.
The two primary protocols in the TCP/IP suite are the Internet Protocol
(IP), which
operates at the network layer, and the Transmission Control Protocol (TCP),
which
operates at the transport layer. There is a second transport-layer protocol
called the User
Datagram Protocol (UDP). Virtually all TCP/IP communications use the IP
protocol at
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