Networking and Internetworking - Guide to Cloud Computing for Business and Technology Managers - page 39

may sometimes lose packets. It allows the Internetworking of very different
networks that then act as one network.
The new protocol standards were known as the Transmission Control
Protocol (TCP) and the Internet protocol (IP). TCP details how information
is broken into packets and reassembled on delivery, whereas IP is focused
on sending the packet across the network. The protocol that resides at the
network layer in the TCP/IP protocol suite is called Internet Protocol (IP).
IP's primary function is to perform the routing necessary to move data pack-
ets across the Internet. IP is a connectionless protocol that does not concern
itself with keeping track of lost, duplicated, or delayed packets or packets
delivered out of order. Furthermore, the sender and receiver of these pack-
ets may not be informed that these problems have occurred. Thus, IP is also
referred to as an unreliable service. If an application requires a reliable ser-
vice, then the application needs to include a reliable transport service above
the connectionless, unreliable packet delivery service. The reliable trans-
port service is provided by software called Transmission Control Protocol,
which turns an unreliable network into a reliable one, free from lost and
duplicate packets. This combined service is known as TCP/IP. These stan-
dards allow users to send electronic mail or to transfer files electronically,
without needing to concern themselves with the physical differences in the
networks.
TCP/IP is a family or suite of protocols consisting of four layers.
a. Network interface layer: This layer is responsible for formatting
packets and placing them on to the underlying network. It is equiva-
lent to the physical and data link layers on OSI Model.
b. Internet layer: This layer is responsible for network addressing. It
includes the Internet protocol and the address resolution protocol. It
is equivalent to the network layer on the OSI Model.
c. Transport layer: This layer is concerned with data transport and is
implemented by TCP and the user datagram protocol (UDP). It is
equivalent to the transport and session layers in the OSI Model.
d. Application layer: This layer is responsible for liaising between user
applications and the transport layer. The applications include the
file transfer protocol (FTP), Telnet, domain name system (DNS), and
simple mail transfer protocol (SMTP). It is equivalent to the applica-
tion and presentation layers on the OSI Model.
The Internet protocol (IP) is a connectionless protocol that is responsible for
addressing and routing packets. It is responsible for breaking up and assem-
bling packets, with large packets broken down into smaller packets when
they are traveling through a network that supports smaller packets. A con-
nectionless protocol means that a session is not established before data are
exchanged. Packet delivery with IP is not guaranteed as packets may be lost