E1 controller clocking

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Feb 12th, 2008
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This is the part of the output of "sh controllers E1" on h323 gateway - Framing is CRC4, Line code is HDB3, Clock source is Line...


This means that clock rate has been configured correctly, I guess. Can someone please help?

Correct Answer by paolo bevilacqua about 9 years 2 months ago

That is, disabling modem relay, and relying on g711 codec plus perfect ip network with low latency and jitter, to carry modem signals of moderate speeds from one endpoint to another.


thanks for the nice rating and good luck!

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paolo bevilacqua Tue, 02/12/2008 - 04:02
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It's configured correctly if the connected device or circuit is supplying clock. If not, you need clock source internal.


In addition to that, on ISR routers, you need "network-clock-participate" commands to avoid slips.


Hope this helps, please rate post if it does!

UCBNOCWAN Tue, 02/12/2008 - 05:02
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Hi Paolo,

Good afternoon.

Thanks a lot for your reply. Really helps a lot. could you please tell me what is the function of Modem Passthrough configuration?

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paolo bevilacqua Tue, 02/12/2008 - 05:08
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That is, disabling modem relay, and relying on g711 codec plus perfect ip network with low latency and jitter, to carry modem signals of moderate speeds from one endpoint to another.


thanks for the nice rating and good luck!

UCBNOCWAN Tue, 02/12/2008 - 05:28
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Paolo,

Thanks for your reply. Just one more query though - what is to be gained by disabling modem relay & passing it over IP ?


Thanks...

paolo bevilacqua Tue, 02/12/2008 - 06:01
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You gain nothing, in fact it makes the transmission slower and more unreliable.


UCBNOCWAN Tue, 02/12/2008 - 07:09
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Then why apply the command at all? Seems very peculiar to me, I am doing it since it's a customer request.

Does this command work on pots dial-peers?

paolo bevilacqua Tue, 02/12/2008 - 07:30
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Well, if customers knew what they're doing, they would be the system integrators, and we would be doing something else.

So I would inform him that cisco recommends modem relay, then yhey still want modem pass-trough there is small chapter about it in the documentation.

UCBNOCWAN Tue, 02/12/2008 - 07:42
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Thanks Paolo, actually the customer request read like this - " could you please put codec G-711 A-law on these pots dial-peers? "

I was guessing that they were requesting modem passthrough. Or is there something else involved?

paolo bevilacqua Tue, 02/12/2008 - 07:53
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Ask what they want to do in practice, and we can suggest accordingly.

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