Networking Guide
Chapter 4, Administering SCO IPX/SPX

Server information administration

Server information administration

When a file server or, in the case of SCO IPX/SPX, SAPD is first brought up, its internal SAP agent:

  1. Places the name of the server in the agent's server information table.

  2. Sends a SAP broadcast to each of its directly connected segments to inform the SAP agents on those segments that a new server has become available.

  3. Broadcasts a request to each of its directly connected segments for information about other servers that exist on the network. These requests are responded to by all the SAP agents on these directly connected segments.

  4. Places the information received in these responses in its server information table.

  5. Performs broadcasts about the servers that it is aware of every 60 seconds (except on asynchronous and X.25 links).

Figure 4-13 illustrates these initial and periodic broadcasts. 

Figure 4-13 Sequence used to build and maintain the server information table

As with routing information broadcasts, all server information broadcasts are local broadcasts and are subject to the best information algorithm. Any changes in server information are passed on immediately to ensure current information across the network. The router applies the aging process to its server information table entries in case any servers become unavailable. Finally, if the router is brought down, it will indicate to its directly connected segments that the servers the router has been advertising will no longer be available.