CHAPTER 1: INTRODUCTION
The bridge is considered a node on the network and performs store and forward functions for packets on each network. This contrasts with a repeater which repeats the signal bit by bit from one side of the network to the other. The bridge actually reads each packet, checks the packet for accuracy, then decides whether the packet should be sent to the other network based on the destination address. If the other network is busy, it is the responsibility of the bridge to store the packet, for a reasonable time, until the transmission can be made.
The bridge is also responsible for handling collisions. If a collision happens as the bridge is transmitting onto the second network, the bridge is responsible for the back off and retransmission process. The original sending node is not made aware of the collision. It assumes the packet has been sent correctly. If the bridge is unable to send the packet to its final destination, the original sending station, expecting some response from the device it was attempting to contact, will “time out” and, depending on the protocol attempt retransmission.
1.6.1Filtering and Forwarding
The bridge decides whether to forward or filter a packet based on the physical location of the destination device with respect to the source device. A bridge dynamically learns the physical location of devices by logging the source addresses of each packet and the bridge port the packet was received on in a table called the Source Address Table (SAT).
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