A LAN provides local services based on the 48-bit address of the network interface card (NIC) attached to the computer. In particular, maintenance operations protocol (MOP)—which is required for booting cluster satellites, print servers, and terminal servers—is offered by LAN. LAN also supports cluster monitoring and management functions provided with SYSMAN and MONITOR.
MOP is also included in DECnet, so LAN is unnecessary when DECnet is installed. On the other hand, DECnet is a separately licensed product, and LAN is included in the OpenVMS license, so if DECnet is not required, LAN can support MOP and cluster needs.
LAN is managed with LANCP and LANACP. The LAN Control Program (LANCP) is used to examine and modify the network device database, to manage performance, to control LANACP, and to initiate MOP messages. For this purpose, LANCP supports about 20 commands. For instance, to show information about a device, the following command will produce a display similar to the following:
LANCP> SHOW DEVICE/COUNTERS EXA0: Device Counters EXA0: Value Counter ----- ------- 259225 Seconds since last zeroed 5890496 Data blocks received 4801439 Multicast blocks received 131074 Receive failure 764348985 Bytes received 543019961 Multicast bytes received 3 Data overrun 1533610 Data blocks sent 115568 Multicast packets transmitted 122578 Blocks sent, multiple collisions 86000 Blocks sent, single collision 189039 Blocks sent, initially deferred 198120720 Bytes sent 13232578 Multicast bytes transmitted 7274529 Send failure 0 Collision detect check failure 0 Unrecognized frame destination 0 System buffer unavailable 0 User buffer unavailable
The LAN Auxiliary Control Program (LANACP) is the server (or symbiont or daemon) that receives messages from other nodes.