3Com 10014299 manual Sap

372CHAPTER 24: CONFIGURING IPX

network routing information which can be sent to destination or needs to be forwarded, so that when a packet is received, the next router can be found to transmit the packet. The routing information here can be configured both statically and dynamically. In a router, collection and maintenance of dynamic routing information are realized by RIP.

RIP is an abbreviation for Routing Information Protocol. A router creates and maintains an inter-network routing information database (usually called router information table) through RIP. When the router starts, RIP begins exchange of routing information with external RIPs enabled hosts constantly. When creating a new path, RIP adds its routing information into the router information table, and when finding a faulty path, RIP deletes its routing information from the router information table. It can be seen that the router information table reacts flexibly to inter-network error and congestion. In case of error and congestion, the router information table can be modified dynamically to change the path. The following diagram describes the relation between main components of RIP.

Figure 135 Schematic diagram of the relation between main components of RIP

Router

Information Table

Routing Information

TimerTimer

RIP Process

	Periodic					Aging Process
Broadcast Process
		Socket			RIP Request/Response Packets
		0 x 453
				IPX Process
			NICs and Drivers

SAP

SAP is an abbreviation for Service Advertising Protocol. SAP allows providing various service nodes, such as file server, print server, NetWare access server and remote control console server, and broadcasting their service types and addresses. When servers start, they broadcast their services through SAP, and when serves are shut down, they indicate the termination of services through SAP.

Through SAP, a router creates and maintains an inter-network service information database, usually called service information table. It tells what services are provided by the network, and what inter-network addresses these servers have. This is an important function, for a workstation cannot establish session with file servers if it does not know their addresses.

A server that provides services will periodically broadcast its services and address to the adjacent sites. Clients cannot use such information directly, it is collected by SAP agents in different routers on the network, and saved in their server information tables. Since server information is often dynamically updated by SAP,