What is Bridge?
In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the sameĀ protocolĀ (for example,Ā Ethernet orĀ token ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street. A bridge examines each message on a LAN, "passing" those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs).
In bridging networks, computer orĀ node addresses have no specific relationship to location. For this reason, messages are sent out to every address on the network and accepted only by the intended destination node. Bridges learn which addresses are on which network and develop aĀ learning tableĀ so that subsequent messages can be forwarded to the right network.
Bridging networks are generally always interconnected local area networks since broadcasting every message to all possible destinations would flood a larger network with unnecessary traffic. For this reason,Ā routerĀ networks such as the Internet use a scheme that assigns addresses to nodes so that a message or packet can be forwarded only in one general direction rather than forwarded in all directions.
A bridge works at the data-link (physical network) level of a network, copying a data frameĀ from one network to the next network along the communications path.
