25-09-2013, 04:26 PM
TCP/IP PROTOCOLS
AIM:
Study and use of common TCP/IP protocols and term viz. telnet rlogin ftp, ping,
finger, Socket, Port.
TCP/IP is actually a suite, or stack, of protocols that interconnect and work together to
provide for reliable and efficient data communications across an internetwork.
Application Layer Protocols
FTP
File Transfer Protocol (FTP) enables a file on one system to be copied to another system.
The user doesn't actually log in as a full user to the machine he or she wants to access, as
with Telnet, but instead uses the FTP program to enable access. Again, the correct
permissions are necessary to provide access to the files.
Once the connection to a remote machine has been established, FTP enables you to copy
one or more files to your machine. (The term transfer implies that the file is moved from
one system to another but the original is not affected. Files are copied.) FTP is a widely
used service on the Internet, as well as on many large LANs and WANs.
Telnet
The Telnet program provides a remote login capability. This lets a user on one machine
log onto another machine and act as though he or she were directly in front of the second
machine. The connection can be anywhere on the local network or on another network
anywhere in the world, as long as the user has permission to log onto the remote system.
You can use Telnet when you need to perform actions on a machine across the country.
This isn't often done except in a LAN or WAN context, but a few systems accessible
through the Internet allow Telnet sessions while users play around with a new application or
operating system.
Transport Layer Protocols
Network protocols are either connection-oriented or connectionless. Connection-oriented protocols - require that a direct connection be established between
two devices before data can begin to transfer between the devices. Packets are transferred
using a prescribed sequence of actions that include an acknowledgment to signal when a
packet arrives, and possibly resending the packet if there are errors. This method is reliable
and, as a result of its reliability and the overhead involved, much slower than connectionless
protocols.
Connectionless protocols - are largely based on your faith in the technology. Packets are
sent over the network without regard to whether they actually arrive at their destinations.
There are no acknowledgments or guarantees, but you can send a datagram to many
different destinations at the same time. Connectionless protocols are fast because no time is
used in establishing and tearing down connections. Connectionless protocols are also
referred to as best-effort protocols. A port (noun) is a "logical connection place" and
specifically, using the Internet's protocol, TCP/IP, the way a client program specifies a
particular server program on a computer in a network. Higher-level applications that use
TCP/IP such as the Web protocol, Hypertext Transfer Protocol, have ports with pre
assigned numbers. These are known as "well-known ports" that have been assigned by the
Internet Assigned Numbers Authority (IANA). Other application processes are given port
numbers dynamically for each connection. When a service (server program) initially is
started, it is said to bind to its designated port number.