Transport Layer Protocols
This layer enhances the IP layer by
providing a mechanism by which the datagram can be directed to the appropriate APPLICATION
LAYER.
This
layer can also provide reliable streaming services to these applications using it.
The two
transport protocols are
Multiplexing and de-multiplexing
the data from many applications to and from the IP layer and directing the data to the
correct application is one of the responsibilities of the Transport Layer.
Application |
|
UDP |
TCP |
IP |
|
DATA LINK |
|
PHYSICAL |
Both UDP and TCP use port addresses
to deliver the information to the correct application layer service.
A port
is a 16-bit address. A number of these have been previously allocated for the most common
services. These ports are called as well known ports (0-255).
Look at a listing of the well-known port numbers.
A socket
is typically used with TCP/IP. A socket is a concatenation of the IP address and the port
number.
A socket can uniquely identify the
application layer service.
Note that well-known port numbers
are used only by server level application layer services.
Client program services select a
unique port number that has not been already used on their machine. This is done to ensure
that no two sessions use the same socket!
Maintained by Mohan Atreya , Last update April 8, 1999 First created on November 10, 1998 |