Bridge

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Definition

Bridge is a networking device that connects two or more LAN's together.

Description

• Bridge is used when number of LANs starts increasing, the network traffic begins on overwhelming to available bandwidth.
• Reduces the network traffic of LAN by dividing it into segments.
• Operates at data link layer of OSI model.
• Can transfer data between two different protocols like Ethernet (802.3) and token bus (802.4).
• Checks the MAC address of the frame and decides to forward the frame or to discard the frame.

Types

Transparent bridge

• Source and destination devices are unaware of the bridge in between them, so called as transparent bridge.
• Accepts all incoming frames to the bridge.
• If the frame is unknown forward the frame to all LANs.
• If the frame is from the same LAN discard the frame from bridge.
• If the incoming frame is from different LAN accept it and forward it to particular LAN.

Source route bridge

• Used on token ring networks.
• Bridge derives the entire path of the frame embedded in the header of the frame and decides how to forward the frame through out the network till it reaches its destination.

Translational bridge

• Used when LANs have dissimilar protocols or speeds.
• Like Ethernet and token ring or Ethernet and FDDI.

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