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The Elements of IPX Routing 6-11
A workstation must first know a server’s network address before it can
initiate a session with a file server.
SAP Packet Structure
SAP uses IPX and the medium-access protocols for its transport. The packet
structure allows the following functions:
■ A workstation request for the name and address of the nearest server of a
certain type
■ A router request for the names and addresses of all the servers or of all the
servers of a certain type on the internetwork
■ A response to a workstation or a router request
■ Periodic broadcasts by servers and routers
■ Changed server information broadcasts
Figure 6-5 provides an overview of the SAP packet structure. Note that the
packet structure is encapsulated within the data area of IPX.
Figure 6-5 SAP Packet Structure
SAP Packet Structure
Operation (2 bytes)
Server Entry (1) (64 bytes)
Server Entry (n) (64 bytes)
(n <= 7)
.
.
.
Packet Type = 4
Socket = 452h
IPX Packet Format
IPX Header (30 bytes)
Data
Server Entry Structure
Service Type (2 bytes)
Server Name (48 bytes)
Network Address (4 bytes)
Node Address (6 bytes)
Socket Address (2 bytes)
Hops to Server (2 bytes)