DLCTOKEN Name-Discovery Service

The token-ring data link control (DLCTOKEN) provides a name-discovery service that allows the operator to identify local and remote stations by name instead of by 6-byte physical addresses.

In addition to the standard IEEE 802.2 Common Logical Link Protocol support and address resolution services, token-ring data link control (DLCTOKEN) also provides a name-discovery service that allows the operator to identify local and remote stations by name instead of by 6-byte physical addresses. Each port must have a unique name of up to 20 characters on the network. 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 it is sent the specified number of times, 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, a name-found response is sent to the station that issued the find request. A result code (DLC_NAME_IN_USE) indicates that the new attachment was unsuccessful and 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 ports that have listen attachments pending, receive colliding find requests, or are already attached to the requesting remote station answer a find request.