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890 pri to audiocodes mediant 800: css errors

We have an adtran 890 with a quad PRI card.  Port one of this card is going back to our service provider and the system clock is being set to this clock source.

Port 2 is going to an AudioCodes Mediant 800 SIP gateway.  The mediant 800 is set to use a recovered clock (i.e. adtran 890)

We see a lot of es and css errors on the mediant PRI.  Calls can still be placed through the mediant 800, but we have dropped audio and audio quality issues.  The LEC PRI looks clean.

Any suggestions on troubleshooting/fixing this?


Update to this issue:  We replaced the mediant 800 and that resolved the issue.

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Re: 890 pri to audiocodes mediant 800: css errors

CSS errors are "Controlled Slip Seconds" (also known as "clock slips" or "timing slips"). If there is a CSS error, there will also be an ES (errored second). This indicates there is a timing/clocking issue between the ATLAS and the Mediant 800. The Mediant 800 should get its clocking from the ATLAS, but the signal the ATLAS is receiving from the Mediant is not matching that clock.

I suggest verifying the Mediant is taking clock from the ATLAS, and possibly even changing the clock source, and then changing it back to the ATLAS. You can also try changing the PRIMARY TIMING SOURCE in the ATLAS to take timing from the Mediant 800. If the Network PRI doesn't show as many errors with that configuration, then you can run with it - otherwise change back to taking timing from the network PRI.

Hope this helps,


New Contributor

Re: 890 pri to audiocodes mediant 800: css errors

Thank you, we did try changing the clock source on the mediant and switching it back; we also tried all new L1 connections.  The mediant may be faulty and we are looking to see if we can  find a replacement.  Thank you for the advice and for confirming the nature of the issue.