Perle Systems IOLINK-PRO IOLINK-520 - Manual (Page 12)

Introduction
IOLINK-PRO & 520 Reference Manua — 1.11
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.