OSI Model

 

• The full form of OSI is(Open System Interconnection


• control is passed from one layer to the next starting at the application in one station,proceeding to the bottom layer,over the channel to the next station and back up the hierarchy

Physical layer

• this layer conveys the bit stream elctrical impulse,light or radio signal,through the network at the electrical and mechanical level


• Fast Ethernet RS232, and ATM are protocols with physical layer components

Data link layer

• At this layer,data packets are encoded and decoded into bits


• It furnishes transmission protocol knowledge and management and handles errors in physical layer,


• flow control and frame synchronization
  
  
  
  • The data link layer is divided into 2 layer
    
    
    
    • Media access control layer(MAC)
    
    
    • Logical link control layer(LLC)
    
    
    
    
  
  
  • The MAC sub layer controls how a computer on the network gain access to the data permission to transmit 'd'.
  
  
  • The logical link control layer controls frame synchronization,flow control and error checking
  
  
  
  

Network layer

• The layer provides switching and routing technologies,creating,logical paths knows as virtual circuits,for transmitting data from node to node


• Routing and forwarding are function of this layer,as well as addressing,inter networking,error handling,congestion control and packet sequencing

Transport layer

• the layer provides transparent transfer data between end system or hosts and its responsibility for end to end error recovery and flow control

session layer

• This layer establishes manages and terminates connection between application


• the session layer setup co-ordinates and terminates conversation,exchange and dialogues between the application at each end


• It deals with session and connection co-ordiantion

Presentation layer

• this layer provides independence from difference in data representation by translating from application to network format and vice versa


• the presentation layer works to transform data into the form that the application layer can accept

Application layer

• This layer support application and end user process


• telnet and FTP are application that exist entirely in the application layer


• EXample
  
  
  
  • HTTP
  
  
  • SMTP
  
  
  • FTP