Limited Network Routing Using NBF

Multi-location networks, such as a wide area network (WAN), require routing capabilities, while single-location, small to medium-sized local area networks (LANs) generally do not require the overhead of a routing protocol.

NBF is not a routable protocol. It uses a single-part naming scheme that cannot be used to differentiate between computers belonging to multiple interconnected networks. NBF can provide a simple form of routing known as Token Ring source routing, which can only be implemented on Token Ring networks using bridges.

Token Ring source routing occurs when NBF broadcasts a NameQuery frame on a local Token Ring; if it does not receive a response in a set period of time, it enables source routing fields in the NameQueryRing frame that force source routing bridges to receive and process the frame. The source routing bridges add additional routing information to the frame and send it to all other rings to which the bridge is connected. When the name query frame reaches the desired computer, that computer sends its computer name in the return message frame, using the routing information from the query to send the message directly to the originating computer. The originating computer caches the routing information and uses the cache to address subsequent frames.