The Service Advertising Protocol provides the same function in IPX networks as SLP in IP networks. It registers information in a database and allows clients to query the database to find services.NetWare servers using IPX use SAP to advertise their services and network addresses. Routers gather this information and share it with other routers. Workstations on the network access the information provided by routers to determine which services are available on the network and to obtain the IPX address of the services. Workstations use this information to initiate a session with a service.SAP makes the process of adding and removing services on an internetwork dynamic. As servers start up, they use SAP to advertise their services; as they are brought down, they use SAP to indicate that their services are no longer available.As a router becomes aware of any change in the internetwork server layout, this information is broadcast immediately to all neighboring routers. SAP broadcast packets containing all server information known to the router are sent periodically---the default is every 60 seconds. These broadcasts keep all routers on the internetwork synchronized and provide a means of updating routing information when a router or server has become inaccessible since the last broadcast. A server might be inaccessible because a router went down, or because a router dropped a packet containing a notification that the route to the server is unreachable. Servers that are inaccessible do not appear in the SAP broadcast.