IBM CTI 2572 manual Transmission Control Protocol TCP

IP

UDP headers are contained in IP
	IP		UDP
datagrams. Data is directed to a						DATA
	HEADER		HEADER
particular process by the use of a
port number. In essence, a port is a
message queue for the destination
	SOURCE	DESTINATION
application. Certain port numbers				LENGTH	CHECKSUM	DATA
	PORT	PORT
may be universally assigned and are
called well known ports. Echo,				UDP

Time, Nameserver, and SNMP
(Simple Network Management
Protocol) use well known ports.
The 2572 uses well known ports so	Figure 13 UDP Datagram
that other network nodes can access
2572 services. In other
applications, the port number may be negotiated by the application software.

The UDP protocol adds to IP only the ability to distinguish among multiple destinations within a given host. Therefore, like IP, it provides unreliable conectionless delivery service. The application program must segment data into packets and must perform any error detection and recovery services that may be required.

5.5 Transmission Control Protocol (TCP)

Like UDP, TCP uses the concept of a port number to identify a process within a host computer. Unlike UDP, TCP provides a reliable connection-orientedservice. TCP is usually used where large amounts of data are being transferred (such as file transfer).

As compared to UDP, TCP adds the following functionality:

1)Stream Orientation

Using UDP, the application program places a packet of data in a single datagram. Using TCP, applications send byte streams of data which TCP software may segment into several IP datagrams. Thus, TCP hides the packetizing of data from the application program. TCP buffers the data sent from the application and attempts to build packets of optimum size.

2)Connection-Oriented Communications

Using UDP, an application program simply launches a datagram to the desired destination. With TCP, a virtual connection is established between applications before data is actually transferred. Should the connection fail (e.g. network hardware problem),

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