Re: EMI/UCP bug

Hi Andreas

Did you get any further on this one?

Nisan
At 08:06 AM 10/23/02 +0200, you wrote:
>There's a bug in EMI which shows up under the following conditions:
>
>a) Kannel is under heavy load.
>b) the throughput of the EMI/UCP smsc is limited to a low value
>
>
>The effect occurs like this:
>
>The EMI/UCP SMSC does throttle to enforce the speed limitations. So the 
>ACK's/NACK's will not come in immediately but a bit later.
>For example if you have 5 messages a seconds set up, the EMI/UCP SMSC will 
>take 200msg to get you the ACK/NACK.
>
>Now Kannel does send additional packets down the same pipe because of 
>windowing. And they get delayed even further.
>The problem starts when those cumulated delays become larger than 60 
>seconds (or whatever timeout you define). Then Kannel presumes your SMS 
>didnt get there and sends it again. Usually it was getting there but no 
>ACK/NACk was received yet due to enforced speed limit of the SMSC. So the 
>result of all this is SMS duplications in masses.
>
>There's a speed limit factor in Kannel which lets it wait after a 
>submission a certain time. However this one doesn't work because new 
>incoming SMS on bearerbox do wake up the thread to continue. This is 
>relatively easy to fix.
>
>But ther's another issue. Windowing. Usually if you set windowing to 4 or 
>similar value, kannel should not submit more than 4 outstanding messages 
>and then wait for ACK/NACK. In this scenario, Kannel should never ever get 
>to the point where the ACK/NACK's cumulate to values above 60 seconds but 
>only to 4x the throughput delay, in our 5msg/sec example  with windowing 
>set to 4 that would be 0.8s.
>
>So there's definitively something wrong. We have seen this problem in our 
>setup and I've heard from other Kannel users having similar problems with 
>other SMSC's from other carriers.
>
>I will look into this bug more seriously now. If anyone has a few good 
>hints, let me know.
>
>
>
>Andreas Fink
>Global Networks, Inc.
>
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