Layer 3 THE NETWORK LAYER

unit : datagram

Virtual circuit network:

it represented for incomming/outgoing interface in logic on each port of source

example one packet can come from multiple interface on a router.After that the router send out another interface with other VC number

+virtual circuit table

Inside a Router

+router_architecture

Input port processing

in this place. Router decapsultation, lookup/forwarding or queing to switch fabric ( prepare next step)

switch fabric

in his point . there are 3 way to Router can switch message from input to output

+switching techniques

  1. via memory . it is controled by processor . speed quite slow from milisecond -> hundred milisecond
  2. via bus . hardware with configuration by software before . quicker than type one but bus can service 1 message at a time
  3. crossbar . conenct input and output with many intersection => have more way one message can go from SRC to DES quickest this technique support send parallel multiple message in case all of them differ DES

Output processing

At this point. Router selecting and de-queueing packet for tranmission and performing the needed link-layer and physical-layer transmission functions