6-12 CHAPTER 6: ROUTING WITH IPX
■ Socket address — A 2-byte field that contains the socket number
that the server uses to receive service requests
■ Hops to server — A 2-byte field that indicates the number of
intermediate networks that must be passed through to reach this
server. Each time a packet passes through an intermediate
network, this field is incremented by 1.
Client systems do not use this SAP information directly. Rather, SAP
agents within each router on the server’s network segment collect this
information. The SAP agents store this information in their server
information tables. If a server also contains a SAP agent, the server’s
bindery stores the SAP information. Client systems then contact the
nearest router or file server SAP agent to obtain server and service
information.
Server and router SAP broadcasts reach SAP agents only on directly
connected network segments. However, SAP agents periodically
broadcast their server information tables, so that all SAP agents on the
network know about all active servers. These server information tables
are described in the next section.
Server Information Tables
Server information tables contain data about all active servers on the
intranetwork. SAP agents use these tables to store information received
in SAP broadcasts.
Figure 6-6 shows a sample server information table.
Figure 6-6 Server Information Table
Server information table
Interface Name Type Network Node Socket Hops Age
1 LPX1102 4 45469f33 00-00-00-00-00-01 451 2 102
1 LPX1103 4 45469f44 00-00-00-00-00-01 451 5 65
2 LPX2001 4 45470001 00-00-00-00-00-01 451 4 33
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