INTERNET WORKING
Definition - What does Internetworking mean?
Internetworking is the practice of connecting a computer
network with other networks through the use of gateways that provide a common
method of routing information packets between the networks. The resulting
system of interconnected networks is called an internetwork, or Internetworking is the process or technique of connecting
different networks by using intermediary devices such as routers or gateway
devices.
EXPLAINATION
Internetworking
is a term used by Cisco, BBN, and other providers of network products and services
as a comprehensive term for all the concepts, technologies, and generic devices
that allow people and their computers to communicate across different kinds of
networks.
The most notable example of internetworking is the Internet, a network of networks based
on many underlying hardware technologies, but unified by an internetworking protocol standard, the Internet Protocol Suite, often also
referred to asTCP/IP.
The smallest amount of effort to create an internet (an
internetwork, not the Internet), is to have two LANs of
computers connected to each other via a router. Simply using either a switch or a hub to connect two local area
networks together doesn't imply internetworking, it just expands the original
LAN.
Internetworking ensures data communication among networks owned
and operated by different entities using a common data communication and the
Internet Routing Protocol. The Internet is the largest pool of networks
geographically located throughout the world but these networks are interconnected
using the same protocol stack, TCP/IP. Internetworking is only possible when
the all the connected networks use the same protocol stack or communication
methodologies.
A computer network is
a set of different computers connected together using networking devices such
as switches and hubs. To enable communication, each individual network node or
segment is configured with similar protocol or communication logic, which
usually is TCP/IP. When a network communicates with another network having the
same or compatible communication procedures, it is known as Internetworking.
Internetworking is also implemented using internetworking devices such as
routers.These are physical hardware devices which have the ability to connect
different networks and ensure error free data communication. They are the core
devices enabling internetworking and are the backbone behind the Internet.
Interconnection of networks:-
Internetworking is stated as a way to connect disparate
types of networking technology, but it became widespread through the developing
need to connect two or more local area networks via some sort of wide area
network. The original term for an internetwork was catenet.
The definition of an internetwork today includes the
connection of other types of computer networks such as personal area networks.
The network elements used to connect individual networks in the ARPANET, the
predecessor of the Internet, were originally called gateways, but the term has
been deprecated in this context, because of possible confusion with
functionally different devices. Today the interconnecting gateways are called
Internet routers.
Another type of interconnection of networks often occurs
within enterprises at the Link Layer of the networking model, i.e. at the
hardware-centric layer below the level of the TCP/IP logical interfaces. Such
interconnection is accomplished with network bridges and network switches. This
is sometimes incorrectly termed internetworking, but the resulting system is
simply a larger, single subnetwork, and no internetworking protocol, such as
Internet Protocol, is required to traverse these devices. However, a single
computer network may be converted into an internetwork by dividing the network
into segments and logically dividing the segment traffic with routers. The
Internet Protocol is designed to provide an unreliable (not guaranteed) packet
service across the network. The architecture avoids intermediate network
elements maintaining any state of the network. Instead, this function is
assigned to the endpoints of each communication session. To transfer data
reliably, applications must utilize an appropriate Transport Layer protocol,
such as Transmission Control Protocol (TCP), which provides a reliable stream.
Some applications use a simpler, connection-less transport protocol, User
Datagram Protocol (UDP), for tasks which do not require reliable delivery of
data or that require real-time
Tunneling:-
:If they are two geographically separate networks, which wants to
communicate with each other, they may deploy a dedicated line between or they
have to pass their data through intermediate netwoks.
Tunneling is a mechanism by which two or more same networks
communicate with each other, by passing intermediate networking complexities.
Tunneling is configured at both ends.
[Image:
Tunneling]
Data when enters from one end of Tunnel, it is tagged. This tagged
data is then routed inside the intermediate or transit network to reach the
other end of Tunnel. When data exists the Tunnel its tag is removed and delivered
to the other part of the network.
Both ends feel as if they are directly connected and tagging makes
data travel through transit network without any modifications
Networking
models:-
Two architectural models are commonly used to describe the protocols
and methods used in internetworking.
The Open System
Interconnection (OSI) reference
model was developed under the auspices of the International
Organization for Standardization (ISO)
and provides a rigorous description for layering protocol functions from the
underlying hardware to the software interface concepts in user applications.
Internetworking is implemented in the Network
Layer (Layer 3) of the model.
The Internet
Protocol Suite, also called the TCP/IP model of the Internet was not designed
to conform to the OSI model and does not refer to it in any of the normative
specifications in Requests for
Comment and Internet standards. Despite similar
appearance as a layered model, it uses a much less rigorous, loosely defined
architecture that concerns itself only with the aspects of logical networking.
It does not discuss hardware-specific low-level interfaces, and assumes
availability of a Link Layer interface to the local network link to
which the host is connected. Internetworking is facilitated by the protocols of
itsInternet Layer.
Open Systems Interconnection
model (OSI):-
The Open Systems Interconnection model (OSI) is a conceptual model that characterizes and standardizes
the internal functions of a communication
system by partitioning it into abstraction layers. The model is a
product of theOpen Systems Interconnection project
at the International Organization
for Standardization (ISO),
maintained by the identification ISO/IEC 7498-1.
The model groups communication
functions into seven logical layers. A layer serves the layer above it and is
served by the layer below it. For example, a layer that provides error-free
communications across a network provides the path needed by applications above
it, while it calls the next lower layer to send and receive packets that make
up the contents of that path. Two instances at one layer are connected by a
horizontal connection on that layer
(Communication in the OSI-Model)
Internet protocol suite :-
The Internet protocol suite is the computer networking model and set ofcommunications
protocols used on the Internet and similar computer networks. It is
commonly known as TCP/IP,
because its most important protocols, the Transmission
Control Protocol (TCP) and the Internet Protocol(IP), were the first
networking protocols defined in this standard. Often also called the Internet model, it was
originally also known as the DoD
model, because the development of the networking model was funded by DARPA, an agency of the United States Department of Defense.
TCP/IP provides end-to-end
connectivity specifying how data should be packetized, addressed, transmitted, routed and received at the destination. This
functionality is organized into four abstraction layers which are used to sort
all related protocols according to the scope of networking involved.[1][2]From
lowest to highest, the layers are the link
layer, containing communication technologies for a single network segment
(link); the internet layer,
connecting hosts across independent networks, thus establishing internetworking; thetransport layer handling host-to-host communication; and
the application layer, which
provides process-to-process application data exchange.
The TCP/IP model and related
protocol models are maintained by the Internet
Engineering Task Force (IETF).