Service Advertising Protocol (Sap); Sap Filtering - Intel ER8100STUS - Express 8100 Router Reference Manual

Service Advertising Protocol (SAP)

SAP functions
Service and Object types
How it works
Service advertising

SAP Filtering

Introduction
87
The Service Advertising Protocol (SAP) makes use of IPX and the medium-ac-
cess protocols for its transport. SAP provides the following functions:
initiates a workstation requests to get information about the name and
address of the nearest server of a certain kind
initiates a router requests to get information about the names and addresses
of either all servers, or all servers of a certain kind on the internetwork
sends responses to requests originating either from a router or a workstation
initiates periodic broadcasts by servers and routers
updates the accessible server information
SAP announces services and addresses of Novell NetWare networks. These ser-
vice advertisements are collected by a SAP agent in a Server Information Table.
A table indicates different kinds of services and associated objects that are cur-
rently known is given in Appendix F "Novell IPX Service Types", p.
Routers collect and exchange service information about all the services available
on the local network using SAP agents. Workstations that require information
about services available, send a broadcast, for example "get nearest server". The
local SAP agent then informs them about the nearest file server available.
SAP broadcasts are local broadcasts initiated by servers once a minute and re-
ceived by local SAP agents only. That is, the packets are not forwarded beyond
the local segments.
Novell services are offered from devices such as file servers (file transfer), print-
er servers (print service) and gateways (protocol conversion). Services are an-
nounced on the network. This service advertisement is not used directly by the
end systems, but instead collected by SAP agents located in file servers and rout-
ers. SAP agents exchange information with the same method as the Routing In-
formation Protocol and are therefore well informed about all active NetWare
servers on the internetwork. A SAP agent is part of an IPX router/server.
Service information entering and leaving a Intel Express 8100 Router can be fil-
tered to remove unwanted services. For example, this may be done to:
restrict access to servers from certain networks
reduce the amount of service information traffic
Novell IPX Routing
Service Advertising Protocol (SAP)
130.