Introduction to Protocol

In computer Networks, communication occurs between two entities in different systems. 

o  Entity is anything sending and receiving information
o  SYSTEM is a physical object containing more than one entities
 Now, two entities in different systems cannot just send data and expect to be understood.
For communication to occur, these entities must agree on a PROTOCOL

PROTOCOLS
As discussed earlier, “Protocol is a set of rules governing communication”

o  Two computers cannot just send bit streams to each other and expect to be
understood
o  Entities must agree on a PROTOCOL

9  Same Example French and German

Protocol defines:
 What is Communicated?  

How it is Communicated?  

When it is Communicated?


KEY elements of a PROTOCOL
™  Syntax:

  Represents the Structure or the format of the Data
  Meaning the order in which data is presented

For Example
9  First eight bits to be Sender address
9  Next eight to be Receiver’s Address
9  The Rest to be Data

™  Semantics:

  Refer to the Meaning of each section of bits
  How is a particular pattern to be interpreted?
  What action should be taken based on interpretation?

For Example
9  Does an address identify the route to be taken or the final destination of the message?

™  Timing

Refers to 2 characteristics:
When data should be sent?
 How fast it should be sent?

For Example
9  If sender produces data at 100 Mbps
9  But Receiver can only process data at 1 Mbps 
9  The TX. will overload receiver and data will be lost