5-12 CHAPTER 5: ROUTING WITH IPX
4=Get Nearest Server Response
■Server Entry — Each server entry includes information regarding a
particular server and consists of the following fields:
■Service Type — This field identifies the type of service the server
provides.
Although IPX routers use SAP, routers typically do not act as servers and
require no Server Type assignment.
■Server Name — This field contains the 48 byte character string name
that is assigned to a server. The Server Name, in combination with the
Service Type, uniquely identifies a server on an internetwork.
■Network Address — This field contains the server’s network address.
■Node Address — This field contains the server’s node address.
■Socket Address — This field contains the socket number the server
uses to receive service requests.
■Hops to Server — This field indicates the number of intermediate
networks that must be passed through to reach the server associated
with this field entry. Each time the packet passes through an
intermediate network, the field is incremented by one.
By using SAP, servers can advertise their services and addresses. The
information that these servers broadcast is not directly used by clients but is
collected by a SAP agent within each router on the server’s segment. The
SAP agents store this information in a server information table. If the agents
reside within a server, the information is also stored in their server’s bindery.
The clients can then contact the nearest router or file server SAP agent for
server information.
The SAP broadcasts that servers and routers send are local broadcasts and,
therefore, only received by SAP agents on their connected segments.
However, SAP agents periodically broadcast their server information so that
all SAP agents on the internetwork have information about all servers that
are active on the internetwork.