DLCETHER Name-Discovery Services

In addition to the standard IEEE 802.2 Common Logical Link Protocol support and address resolution services, Standard Ethernet data link control (DLCETHER) 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 request, the physical link is declared opened, and the name is assigned to the local port and SAP. If another port on the network has already added the name, a "name found" response is returned. The DLC_NAME_IN_USE result code indicates that the new attachment was unsuccessful and that 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. The only respondants to a find request are those ports that have listen attachments pending, receive colliding find requests, or are already attached to the requesting remote station.