300 IBM Communication Controller Migration Guide
17.1 What is TCP/IP?
Although Transmission Control Protocol (TCP) and Internet Protocol (IP) are two
building blocks of a complete protocol suite, their relative importance gives rise to
the common name for this family of protocols: TCP/IP. TCP/IP follows the layering
approach, whereby protocol layers provide functionality to layers above and
make use of the functionality provided by layers below as illustrated in
Figure 17-1.
Figure 17-1 TCP/IP layering
In essence, the Internet Protocol allows for communication across multiple
heterogeneous networks. For example, it may be desirable to connect an
Ethernet network with an ATM network. Networks based on the TCP/IP suite are
called internetworks (or internets), the largest and most famous of which is the
IP provides a best-effort service of delivering data from one machine in an
internetwork to another. Transport functionality such as reliable data streaming,
congestion control, and flow control must be provided at a higher level, such as
TCP. Some applications leverage the reliable stream-oriented functionality
provided by TCP. Others, however, make use of the User Datagram Protocol
(UDP) which adds little functionality to basic IP besides the ability to demultiplex
data to multiple applications. Using UDP, the application is responsible for
ensuring reliability by perhaps retransmitting sent data or tolerating loss of data.
Network Interface
Network Interface
and Hardware

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