IBM Communication Controller Migration Guide

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

Internet.

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.

Applications

Transport

Internetwork

Network Interface

and

Hardware

Applications

TCP/UDP

ICMP

IP

ARP/RARP

Network Interface

and Hardware

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