Bug 10688

Summary:	ISDN outgoing calls often fails when used on satellite systems
Product:	Drivers	Reporter:	Goudal Francois (francois)
Component:	ISDN	Assignee:	Karsten Keil (kernel)
Status:	CLOSED OBSOLETE
Severity:	enhancement	CC:	alan, francois
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.18.8	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	Proposed patch for workaround

Description Goudal Francois 2008-05-13 04:31:31 UTC

Latest working kernel version: none, as far as I know
Distribution: Debian 3.1
Hardware Environment: x86 machine + AVM Fritz! PCMCIA ISDN adapters
Problem Description:
When used on a satellite system, the I4L stack often fails to establish outgoing calls. This is due to timeouts in the I4L code that are more easily triggered because of the latency introduced by the satellite link. On an inmarsat system, I have faced more than 50% of failures, which is not really acceptable.

Steps to reproduce:
Buy an Inmarsat satcom system ;-) (Thrane M4, for example)
Connect your AVM Fritz ISDN card to it
Install the I4L driver (You probably prefer CAPI but you don't want the proprietary drivers from AVM so you don't have much choice)
Try to make linux dial a phone/dialup server on the ground using the satcom system.
Repeat the dialout several times, some of the attempts are probably going to fail.

Comment 1 Goudal Francois 2008-05-13 04:33:19 UTC

Created attachment 16123 [details]
Proposed patch for workaround

This patch proposes a workaround to the problem by multiplying by two the timeout values for the I4L subsystem.
This is proposed as a config option CONFIG_ISDN_SATELLITE.

Comment 2 Karsten Keil 2008-05-13 05:23:00 UTC

Yes this would be one possibility to address this. Maybe it would be better, if the general Dial timeout is configurable via a module parameter. I will have a look at this.