CTI 2572 Technical Overview Manual
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UDP headers are contained in IP
datagrams. Data is directed to a
particular process by the use of a
port number. In essence, a port is a
message queue for the destination
application. Certain port numbers
may be universally assigned and are
called well known ports. Echo,
Time, Nameserver, and SNMP
(Simple Network Management
Protocol) use well known ports.
The 2572 uses well known ports so
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-oriented service. 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),
IP
HEADER
DATA
CHECKSUM
IP
G
SOURCE
PORT
DESTINATION
PORT
UDP
HEADER
LENGTH
DATA
UDP
G
Figure 13 UDP Datagram
