Introduction
SAP Requests
Sometimes Clients will need to find out if a specific Server is available. This may occur immediately after a Client is brought up, and before it has received any SAP broadcasts. The Client (or a new Server) sends out a SAP Request broadcast asking for a specific Server. That Server, or a router with the best route to that Server, will respond to the Client (Server) making the request.
Server Types
There are many different types of Servers. Each type is defined and given a type code by Novell. When new types of Servers are invented they will be assigned a new Server type. Some common Servers are:
Type | Description |
0000 | Unknown |
0003 | Print Queue |
0004 | File Server |
0005 | Job Server |
0006 | Gateway |
0007 | Print Server |
0009 | Archive Server |
0024 | Remote Bridge Server |
0027 | TCP/IP Gateway |
Routing Information Protocol
The Novell Routing Information Protocol (RIP/X, where the X indicates IPX) is similar, but not identical, to the Routing Information Protocol used in IP routers. Novell RIP/X performs similar functions to IP RIP, in that RIP/X is used to communicate information about routes through routers to remote networks.
RIP/X Operation
The operation of RIP/X is, for all intents and purposes, identical to the operation of IP RIP. Routers send out broadcasts every 30 seconds containing the contents of that router’s route table (the list of best routes to known remote networks). When a router comes on line, the extent of its route tables will be its explicit route. In the case of a local router, it will be a route between the two networks to which the router is connected. In a pair of remote routers linked via a WAN connection, the first RIP broadcasts will contain only the route to the remote network. As time goes on, and assuming there are more routers in the network (and correspondingly more remote networks), the various routers will by way of RIP broadcasts inform each other of the various routes.
RIP/X Broadcasts
A RIP broadcast is sent out by IPX routers every 30 seconds or so. Each broadcast may contain information on up to 15 different routes (to 15 different networks; of course). If a router knows of more than 15 networks it will send out two (or more) broadcasts.
Note that to spread the network overhead a router will stagger the generation of RIP/X and SAP broadcasts. The router will send a RIP/X broadcast, followed 15 seconds later by a SAP broadcast, followed 15 seconds later by another RIP/X broadcast, etc., etc. The SAP and RIP/X broadcasts are sent every 30 seconds as required, but they are staggered by 15 seconds to spread the overhead.