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SPX Watchdog Packets Keep ISDN Line Active

Article Number: P001
Article Type: Problem
Modified: November 11, 1998

SYMPTOMS

You have configured the Orbitor to perform connection management of an ISDN connection between two remote locations. Your application environment uses Novell's Netware and therefore, the Orbitor must perform IPX spoofing. It appears as though the ISDN Connection Management feature works properly most of the time, but on occasion, when certain client applications are started, the Orbitor doesn't seem to idle time-out (disconnect) the ISDN connection.

CAUSE

The application most probably uses Novell's SPX watchdog packets. Watchdog packets are sent only if there is an extended period where no traffic is detected on the session. The default WATCHDOG_TIMEOUT (the period between the last packet traffic on the session and the first watchdog packet) is normally 60 seconds (this is configurable by the SPX application through the Netware TLI interface). Any packet that arrives for a session will reset the Watchdog timer for that session. This includes any system packets as well as user data packets.

Watchdog Packets are used to detect idle and "lost" client sessions, but serve very little purpose otherwise. Novell no longer endorse the use of these packets, and recommend turning them off for most normal applicaton usage. However, there is no ability to turn them off without a system change on the server.

SOLUTION

SPXWDOG.NLM is a patch available from Novell that is used to disable SPX Watchdog packet generation. This is a workaround recommended by Novell to solve problems when using the SPX protocol in remote access applications and with products like the Orbitors.

SPX Watchdogs are not labeled and hence it becomes difficult to spoof them. Loading SPXWDOG.NLM will address this problem.

When this NLM is added to the system, it will add the following file server SET parameter to the configuration:

"set spx watchdogs=ON/OFF" The default is ON.

This NLM can be used for both Novell Netware 3.x and 4.x servers. To fully disable Watchdogs, the remote client/server should also disable the Watchdog generation. IPXODI V3.02 and IPX.NLM (32 bit IPX for the client) supports a NET.CFG parameter to disable SPX watchdogs. Patchman is not required for this patch since this program runs on all versions of the NW OS.

REFERENCES

SPXWDOG.NLM can be obtained from the Novell WEB site www.novell.com. Perform a search by clicking the Find it Now! Button. Under Search for Software Updates, Patches, and Drivers in Novell's File Finder enter the search string STRTL5.EXE. Follow the instructions under the long description for installation of the SPXWDOG.NLM.§

Copyright © 1998 Develcon Electronics Ltd.  All Rights Reserved.