Networking

I am starting of with the basics of networking and not divulging in to its huge and boring history, like who and how different models were made etc… such history hardly matter. I am writing this page to just give u all, the briefing of networkig concepts .

With the exponential advancement of technology in 1980s, many vendors used to make harware for a particular network . But as    there was no standard on which the harware was made internetwoking was not  possible . So International Organization for Standardization (ISO)  made some of the standards for all to follow . This standard was OSI model.
OSI has seven layer model.it includes :-

7.Application layer:- It interfaces directly to and performs common application services for the application    processes
6.Presentation layer :- Responsible for the delivery and formatting of information to the application layer for further processing or display.
5.Session layer :- provides the mechanism for opening, closing and managing a session between end-user application processes
4.Transport layer :-
3.Network layer :-Responsible for end to end(Source to destination) data delivery.Decides for the best path for packet to follow
2.Data link layer :-Responsible for node to node frame delivery.Deals directly with MAC address
1.Physical layer :- This provides for physical wiring and connections.

well for newbies its hard to remember all these , so there is a help u can get with mneumonics ….
I personally use :-

All People Seem To Need Data Processing

OSI model is rarely used nowdays, but is important to learn as  other derive from it , and osi is good for basics
Internet is based on TCP/IP model .

In TCP/IP(5 layered)following layers are made

5.Application layer
4.Transport layer.
3.Internet/Network layer
2.Data link layer
1.Physical layer

Each layer has its own function with a concept that a particular layer responds(or give service to) to the layer above and reequests service from the layer below .Now  i m gonna give a brief description of the fuctions of some layers.

3.Network Layer
Network layer  deals with transmitting data from source to destination. It is the most  important layer in the sense it decides for the best possible for the packet to follow .in short we can say network layer performs two functions :-

a)Forwarding :-Forwarding is the relaying of packets from one network segment to another by nodes in a computer network.
b)Routing :-Routing (or routeing – UK English) is the process of selecting paths in a network along which to send data or physical traffic. Routing is performed for many kinds of networks, including the telephone network, the Internet, and transport networks.Routing directs forwarding.

4.Transport layer :-
In tcp/ip model the transport layer is responsible  for delivering fata to the appropriate application process on the host computers . It functions to service request from the application layer and request service from networking layer
The transport layer is typically handled by processes in the host computer operational system, and not by routers and switches. The transport layer usually turns the unreliable and very basic service provided by the Network layer into a more powerful one.
Transport layer is basically implemented by TCP and UDP protocols, tcp being the most  popular
These two are the most widely used, tcp being the connetion oriented one and udp the connectionless

UDP or user datagram protocol is a very simple one . It is not a reliable protocol nor does provide for the services like vlan . Udp doesnot check for errors in the data transmission and hence is quite faster than tcp as it avoids all the overheads of error checking and data integrity .Hence udp is widely used in time-sensitive places , where occasional data loss is acceptable.UDP examples are like IPTV or VOIP
UDP also supports data broadcasting i.e. same data is to be sent to alll the recipients .

Transport layer provides many services which can be optionally added. its main services is like :- ports(part of session layer in osi model )

5.Application layer handles network servies,most notablly file and printing ,name resolution and redirector services .
name resolution is the process of mapping the ipaddresses to the human readable form .

Redirector services looks at your request and if it can be fulfilled locally then it is done so , else the request is forwarded to the another machine .This enables users to use files as if they were actually stored on the local machine .

*Note :- Packets in the networking cables are called frames.
Difference  betweeen tcp and udp……….actually many but udp allows message brodcasting,while tcp does not.

NOTE:-This page is not yet complete, due to time constraints . Please visit again for more updates .