Bridge

A bridge  operation sin both  physical  and data link  layer of OSI model. At physical  layer  it works  like  repeater as it regenerates the  signal  and performs  inter connection of different  physical  media  types  such as  coaxial cable, twisted  pair work  etc. Bridges technology supports  two data link  layer  protocols called LIC ( Logical Link Control)  MAC ( Media  Access Control). Bridges when work in data  link layer it can check the physical  (MAC) address  fro source and destination contain in a frame  and hence deciding  whether to forward  or discard the frame. For  example  it source  and destination are on the same  network  segment the bridge filters the frame. If  destination  is on a different  network  segment  the bridge  forwards the frame. Bridges  are made  to divide  a big network  into  smaller sub network  known  as  segments.

Bridges  are different  to repeaters as they  have filtering  capacity  which  is not  available with repeaters. Bridges sends  the data  frames  only to the  concerned segment thus preventing excess traffic. For e, g,  if a network  is divided in four  segments. Segments  i1 send  a frame destined  for  another  host on  segment  3 the bridge  forwards  the frame  only to segment  3 and not the  segment  2 and  4 thus blocking  unwanted traffic.