3Com CoreBuilder 2500, User Manual

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IPX Routing in the NetWare Environment 6-3
Internet Packet
Exchange (IPX)
IPX is the primary protocol used for routing in a NetWare environment.
This connectionless, datagram protocol does not require an
acknowledgment for each packet sent. Protocols above IPX provide
packet acknowledgment or connection control.
IPX defines internetwork and intranode addressing schemes.
Internetwork addressing is based on network numbers that are assigned
to each interface in an IPX network. Intranode addressing is in the form
of socket numbers. Because several processes are normally operating
within a node, socket numbers provide a type of mail slot so that each
process can distinguish itself to IPX.
Routing Information
Protocol (RIP)
RIP allows the exchange of routing information on a NetWare network.
IPX routers use RIP to create and maintain their dynamic routing tables.
With RIP, one router exchanges routing information with a neighboring
router. When a router discovers any changes in the network layout, it
broadcasts this information to any neighboring routers. IPX routers also
send periodic RIP broadcast packets containing all of the routing
information that the router possesses. These broadcasts synchronize all
routers on the network and age those networks that might become
inaccessible if a router disconnects abnormally from the network.
Service Advertising
Protocol (SAP)
SAP provides routers and servers that contain SAP agents with a means of
exchanging network service information.
Through SAP, servers advertise their services and addresses. Routers
gather this information and share it with other routers. With this process,
routers dynamically create and maintain a database (called a server table)
of network service information. Clients on the network determine what
services are available and obtain the network address of the nodes
(servers) where they can access those services. Clients require this
information to initiate a session with a file server.
With SAP, a router exchanges information with neighboring SAP agents.
When a router’s SAP agent discovers a change in the network server
layout, it immediately broadcasts this information to neighboring SAP
agents. The router also periodically sends SAP broadcast packets that
contain all server information that the SAP agent possesses. These
broadcasts synchronize all servers on the network and age out any
routers or servers that become inaccessible due to abnormal shutdown.