What is Protocol ?

Ø  It is the set of rules that every device has to follow in order to have proper communication.

Ø A protocol is a set of mutually accepted and implemented rules at both ends of the communications channel for the proper exchange of information. 

Ø  Protocols specify the standards for communication to define a method of exchanging data over a computer network, such as local area network, Internet, Intranet, etc. 

Ø  Each protocol has its own method of how data is formatted when sent and what to do with it once received, how that data is compressed, or how to check for errors in the data.

Ø  Network Protocols:

o   TCP/IP           (Department of Defence)    

o   IPx/SPx          (Novell)

o   AppleTalk      (Apple)                                                   

o   NetBIOS        (Microsoft)

o   OSI                 (ISO)

Ø  The key elements of a protocol are

Ø  Syntax- The term syntax refers to the structure or format of the data, For example, it is expected that the first 8 bits of data to be the address of the sender, the second 8 bits to be the address of the receiver, and the remaining stream of bits to be the message itself.

Ø  Semantics- The word semantics refers to the meaning of each section of bits. How  a particular pattern to be interpreted, and what action is to be taken based on that interpretation? For example, does an address identify the route to be taken or the final destination of the message? 

Ø   Timing- The term timing refers to two characteristics: when data should be sent and how fast they can be sent. For example, if a sender transmits data at 100 Mbps but the receiver can process data at only 1 Mbps, the transmission will overload the receiver and some data will be lost.

Ø  Some of the most common and well-known application layer protocols are as follows:

1)HTTP  :(Hypertext Transfer Protocol)

Ø  It is a protocol used to transmit data over the world wide web (Internet)-Browsing purpose. Used to access, send and receive Hypertext Mark-up Language(HTML) files on the internet  

2)SMTP :(Simple Mail Transfer Protocol)

Ø  This protocol is used for transferring emails between computers.It will use port number 25

3)FTP :(File Transfer Protocol)

Ø  It is responsible for allowing file to be copied from one device to another device

4)TCP :(Transmission Control Protocol)

Ø  This protocol ensures end to end transportation of data between multiple applications or services.

5)IP :(Internetworking Protocol)

Ø  This protocol is responsible for providing logical addressing called IP address to route the packet between networks.