Transcript Network and the internet

Network and the internet
Part eight
Introduction to computer, 2nd semester, 2009/2010
Mr.Nael Aburas [email protected]
Faculty of Information Technology
Islamic University of Gaza
TCP/IP protocol
TCP/IP protocol is a collection of protocols
standards used by the Internet to implement the
four-level communication hierarchy implemented
in the Internet.
 TCP/IP defines a version of the transport layer,
we say version because the TCP/IP provides fir
more than one way of implementing the
transport layer, one of the other options is UDP
(user Datagram Protocol).
 This means that the application layer might
choose to send data via a TCP or UDP version of
the transport layer (4.15)

Difference between TCP and UDP
1.
Before sending a message as requested by
the application layer, a transport layer based
on TCP sends its own message to the
transport layer at the destination telling
that a message is bout to be sent, then
waits for this message to be
acknowledged.( establish a connection
before sending a message). A transport
layer based on UDP does not establish such
a connection, it sends the message to the
address and forgets a bout it.
Figure 4.15 Choosing between TCP
and UDP
4-4
Difference between TCP and UDP
2.
3.
4.
TCP transport layer at the origin and destination work
together by means of acknowledge to assure that all
segments of the message are successfully transferred (TCP
is called a reliable protocol). UDP doesn't offer such
retransmission services (unreliable protocol).
TCP provide flow control, meaning that a TCP transport
layer at a message’s origin can reduce the rate at which it
transmits to keep from overwhelming its counter part at
the destination, as well as congestion control, can adjust its
transmission rate to alleviate congestion. UDP doesn't
support.
Transport layer based on UDP is more streamlined that
based on TCP
Usage of TCP and UDP

Usage of UDP:
◦ DNS lookup
◦ VOIP

Usage of TCP:
◦ Mail server
TCP/IP
IP is the Internet’s standard for
implementing the tasks assigned to the
network layer
 An interesting feature associated with
forwarding is that each time an IP network
layer at a message’s origin prepares a packet,
it appends a value called a hop count, or
time to live, t that packet
 This value is a limit to the number of times
the packet should be forwarded as it tries to
find its way through the Internet.
