Service Advertising Protocol

The Service Advertising Protocol , or SAP for short , is a term from computer science and describes a protocol used in IPX networks for service discovery. Like IPX, it was originally developed by Novell Inc. for NetWare .

functionality

The SAP works on the broadcast - principle . Every server or host that offers a network service periodically sends an IPX broadcast to the network. The SAP packet contains the information about which service is offered, what the route to the host is and what MAC address the host that offers this service has. The clients cache this information locally so that, if required, they immediately know the corresponding network address from one of the services offered. Alternatively, there is also the possibility for the client to use a SAP request, also a broadcast, to inquire across the network whether a certain service is offered.

The specialty of SAP broadcasts is that they are routed and not, as is generally the case, limited to the respective local network segment.

criticism

When it was first introduced, the SAP was a good invention that represented a certain kind of plug and play , since you didn't have to worry about the configuration of the clients in an IPX network. Some time later, however, the problem that lay behind the principle of network-wide broadcasts also emerged. The standard period for a SAP broadcast was set by Novell at 60 seconds. In the ever-growing networks, there were soon real broadcast storms, as every network printer , every server, every router and sometimes also some clients offered services in the network. In later TCP / IP-supported versions of NetWare, SAP was therefore replaced by the Service Location Protocol (SLP).