DLC FDDI Name-Discovery Services

In addition to the standard IEEE 802.2 Common Logical Link Protocol support and address resolution services, the data link control (DLC) fiber distributed data interface (FDDI) also provides a name-discovery service that allows the operator to identify local and remote stations by name instead of by six-byte physical addresses. Each port must have a unique name on the network of up to 20 characters.

The character set used varies depending on the user's protocol. Systems Network Architecture (SNA), for example, requires character set A. Additionally, each new service access point (SAP) supported on a particular port can have a unique name if desired.

Each name is added to the network by broadcasting a find (local name) request when the new name is being introduced to a given network port. If no response other than an echo results from the find (local name) request after sending it the number of times specified, the physical link is declared opened. The name is then assigned to the local port and SAP. If another port on the network has already added the name or is in the process of adding a name, a name-found response is sent to the station that issued the find request, and the new attachment fails with a result code (DLC_NAME_IN_USE). The code indicates a different name must be chosen. Calls are established by broadcasting a find (remote name) request to the network and waiting for a response from the port with the specified name. Only those ports that have listen attachments pending, receive colliding find requests, or are already attached to the requesting remote station answer a find request.