The SAP allows service-providing nodes such as file servers, print servers, gateway servers, and client workstations to advertise services and addresses. The SAP makes adding and removing services on an internetwork dynamic. As servers are booted, they advertise services to other nodes through the SAP; when they are brought down, they use the SAP to indicate that services are no longer available.
Through the SAP, clients on the network can determine what services are available on the network, and obtain the internetwork address of the nodes where they can access those services. This is an important function since a workstation cannot initiate a session with a file server without the server address.
A gateway server, for instance, will broadcast a SAP packet periodically (usually every 60 seconds, the period defined for all servers advertising with the SAP) onto the network segment to which it is connected. The SAP agent in each router on that segment copies the information contained in the SAP packet into an internal table called the Server Information table. Because the SAP agent in each router keeps up-to-date information on available servers, a client wanting to locate the gateway server can access a nearby router for the correct internetwork address.
When setting up NetWare, you will need to turn SAP on and enter the number of services you will be advertising to use this feature.