Write notes on Frame Filtering Techniques.

Frame filtering:

The most valuable function performed through bridges is frame filtering. A bridge doesn't forward a frame unless essential. In particular, if a computer attached to individual segment sends a frame to a computer on similar segment, the bridge doesn't require forwarding a copy of the frame to the other segment.

To find out whether to forward a frame, a bridge utilizes the physical address found into the frame headers. While a frame arrives upon a segment, the bridge extracts and checks the destination address. If the bridge determines that the destination computer is attached to a segment over that the frame arrived, the destination will also have obtained a copy of the frame; therefore the bridge can discard a frame without forwarding a copy.

Most bridges are termed as adaptive or learning bridges since they learn the location of a computer automatically. The bridge utilizes the source address to automatically find out the location of the computer which sent a frame, and uses the destination address to find out whether to forward a frame.