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SCO Unix connectivity: Internet access via cable modem dropping

Posted on 2002-04-08
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Last Modified: 2013-12-23
Hi, not sure if this is right forum area for this but maybe someone can help or point me in the right forum direction:

I am working from home & connecting to a SCO unix server at work via my NTL cable modem, ie over the internet & I am using a VPN.

I don't have any trouble with any of the servers except one which insists on dropping my connection every time there is a pause in the network.  I have asked the techies at work to identify any timeouts set on the server but they don't know what they are looking for and are at a loss to help.  Waste of space actually.

Symptoms: All pc apps freeze for a short while (about 15-30secs) every so often at which time the sco box drops my connection.  All other servers, including another sco box do not.  

Anyone know what to look for so I can tell them in the office.  It's driving me crazy because as sods law would have it, it is the main server I use.

thanks
K

















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Question by:Kyliem
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14 Comments
 
LVL 38

Expert Comment

by:yuzh
ID: 6927306
Hi Kyliem,

   What type of modem are you using (make and model), do you know what type of modem is direct connected to your SCO box?

   You can type to set you modem run in the Hays compatible modem, and use lower speed to see what happen.
please tell me which version of SCO is running at your server if you can.

=====
yuzh
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LVL 16

Expert Comment

by:The--Captain
ID: 6927612
See http://pcunix.com/Bofcusm/1246.html - the person there had the opposite problem, but I think the proposed solution appears quite relevant to your situation.

Just a guess, but it sounds like your keepalive settings are incorrect.  Try adjusting them (or disabling tcp keepalives).

This is not a problem with your cable modem, since you only have a problem with one remote machine.  I'm not sure how yuzh thinks you are going to be able to readily adjust the speed of your cable modem, why he thinks it is directly connected, or what use hayes compatibility is (I'd make sure is was DOCSIS compliant, but like I said, the problem is not your cable modem)

-Jon

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LVL 38

Expert Comment

by:yuzh
ID: 6930097
Hi The--Captain,

    Just for your interested, you can adjust the speed of the modem, connection establish time, or which communication standard it support (eg, flex56, v90 etc), by changing the register values (us AT command set), please refer to your Modem Manual for details, as we play with UNIX, we should always buy a modem with manual. For a modem to talk with one attached to a SCO box, it should have hardware control enable, and software control disable, other setting are vary from the made and model of the modems.

   Kyliem, please try The--Captain's suggesttion first, it it work, great! If not, we will try to do something in a hard way.

========
 yuzh  
0
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Author Comment

by:Kyliem
ID: 6951835
Sorry guys, was called away unexpectedly last week.  Will get around to this once I've found my feet again and award points as necessary.  Thanks for the help, I wasn't ignoring you.

K
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Author Comment

by:Kyliem
ID: 6951920
Thought no time like present.  I checked the settings and keepalives are set to their default of 7200 secs (2hrs) for tcp_keepidle and 75 secs thereafter for tcp_keepintvl.

So seems ok in that respect alhtough I understand from the man pages that the application can override these settings.  Possible I guess, I'll have to run some normal sessions and a couple of sessions with application running to see if there is a noticeable difference.

Thanks
K
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LVL 16

Expert Comment

by:The--Captain
ID: 6955747
yuzh - since you apparently don't know what a cable modem is, please refrain from further participation in this discussion.

Kyliem - try turning that 75 figure wayyyy up (or maybe setting it to zero will disable it altogether), and see if the problem either lessens in frequency or disappears completely.

Thanks,
-Jon

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Author Comment

by:Kyliem
ID: 6955790
Ok, thanks Jon, won't be able to test until late next week as I have to go away on personal business.  Therefore question may appear on hold for a while but i am not ignoring anyone.  
Thanks
K
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LVL 16

Expert Comment

by:The--Captain
ID: 6956676
Also, good point about the app being able to override the setting - maybe a review of the telnet (or telnetd) docs on the SCO system will reveal an available adjustment...

-Jon
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LVL 38

Expert Comment

by:yuzh
ID: 6957514
Please tell me what type of modem are you using at both end.
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LVL 16

Expert Comment

by:The--Captain
ID: 6958322
Cable modem on one end, and (I'm guessing here) ethernet on the other (probably has net access via T1, DSL, etc).

I'll let Kyliem confirm (or deny) this...

-Jon
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LVL 16

Accepted Solution

by:
The--Captain earned 200 total points
ID: 6958329
Kyliem - if you have access to a packet sniffer on both ends, you may want to turn it on in order to see which side is transmitting packets during the hang.  Also, you may be accidentally forcing a disconnect if you keep typing during the hang - this may allow the IP subsystem to "notice" that the other end is not responding, and cause it to shut down.

I rarely have problems keeping sessions alive during momentary disconnects, but only if I don't try to type anything...  In the old days ('92), I used to be astonished that I could be completely disconnected by my ppp server for several minutes, reconnect, and still be connected to the same session (as long as I didn't try to use it when it was down).

Cheers,
-Jon

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Expert Comment

by:CleanupPing
ID: 9157222
Kyliem:
This old question needs to be finalized -- accept an answer, split points, or get a refund.  For information on your options, please click here-> http:/help/closing.jsp#1 
EXPERTS:
Post your closing recommendations!  No comment means you don't care.
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