Frame Relay Applications: Novell IPX & IBM SNA - Page 2

By Cisco Press | Posted Feb 1, 2002
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Novell SAP
Novell SAP traffic can consume an adverse amount of WAN bandwidth. The router will send, without delay, a SAP update when a change is detected. It is recommended that you modify the SAP delay timer to "slow down" these delays, enabling more user traffic to get through the WAN.

The Cisco IOS command ipx output-sap-delay 55 will send SAP packets with a 55 ms delay between packets. Without a delay, all packets in the update are sent immediately, and the Frame Relay router consumes all available buffer space. With no bandwidth or buffer space available, user traffic will be dropped, requiring retransmission.

The ipx output-sap-delay command causes the router to grab only one buffer a time, leaving the remaining buffer space available to queue user traffic for transmission across the WAN.

The ipx sap-interval and ipx update-interval IOS commands can be used to change the frequency of the updates between IPX-enabled devices. All IPX-enabled devices (routers) interconnected across the Frame Relay WAN must be set to the same update interval. Otherwise, updates will not be synchronized, resulting in phantom routes--routes that appear and disappear with each update.

In a multipoint Frame Relay "broadcast" environment, in which message traffic is propagated to all sites and subinterfaces are not employed, SAP advertisements will be propagated to all sites as well.


NOTE:   The absence of the broadcast parameter in the Frame Relay map configuration will prevent both IPX RIP and SAP advertisements from being propagated.

Whereas point-to-point Frame Relay WAN links do not employ a map statement, IPX RIP and SAP updates will be propagated at will between each site. It is recommended that you use IPX RIP and SAP filters in this configuration to minimize the Frame Relay WAN traffic.

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