Bridge

BRIDGE:

In virtual cases, there is a need to interconnect different LANs and WANs in order to increase the network. For this purpose two approches are used( Bridge and Router).

The bridge is the simpler of these two and provide a mean of interconnection between similar LANs. While the router is more general purpose device capable of interconnecting a variety of LANs and WANs.

The bridge is a layer 2 device and designed for use between LANs that use same protocols. The bridge should contain enough buffer space to meet peak demand.

 

• Read all frames transmitted on LAN A and accept those addressed to any station on  LAN B.
• Using MAC protocol for  LAN B, retransmit each frame on B.
•  Do the same for B-to-A traffic.

 

BRIDGE PROTOCOL ARCHITECTURE:

Figure indicates the way in which data is encapsulated using a bridge. Data are provided by some user to LLC. The LLC entity appends a header and passes the resulting data unit to the MAC entity, which appends a header and a trailer to form a MAC frame. On the basis of the destination MAC address in the frame, it is captured by the bridge. The bridge does not strip off the MAC fields; its function is to relay the MAC frame intact to the destination LAN. Thus. the frame is deposited on the destination LAN and captured by the destination station.