[cisco-voip] CF off net low audio issue

Mon Aug 31 17:20:19 EDT 2009

Hi Brandon,

This depends.

These cases will be converted into VOIP in a hairpin call:
-'no local-bypass' is configured under the 'voice-card x'
-One or more of the call legs is SCCP or MGCP
-The analog ports are on different routers

These cases the DSP will not be involved:
-Two analog ports on the same router that do not meet the above condition
-H323/SIP controlled ports on the same router that hairpin out two analog ports

In the scenario that we were talking about here, with 2 FXO ports that
come in and go back out - the DSPs will not typically be involved.
However - the analog attenuation that occurs naturally would still
occur.  The DSPs just wouldn't be there to amplify the stream.  You
could run into this scenario if you put input gain on the port, and
and now calls to users were fine, but calls that were hairpinned were
still silent.  You would actually want to configure 'no local-bypass'
on the voice-card so that you could still amplify the calls.

local-bypass is simply a mechanism to reduce the amount of DSPs
required on a platform by removing DSPs from a TDM-TDM call, and it's
on by default.

-nick

On Mon, Aug 31, 2009 at 4:50 PM, Zapp, Brandon D<bzapp at sisunet.org> wrote:
> That raises another question in my mind. Does anyone know if a POTs call comes in a router (2811 for example) and leaves that same via POTs does that router convert the call to VOIP or does it stay in the TDM world?
>
>
> Brandon Zapp
> Data Center Operations Analyst
> SISU Medical Systems
> bzapp at sisunet.org
>
>
>
> -----Original Message-----
> From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Countryman, Edward
> Sent: Saturday, August 29, 2009 9:32 PM
> To: Countryman, Edward; Dennis Heim; Nick Matthews
> Cc: cisco-voip at puck.nether.net
> Subject: Re: [cisco-voip] CF off net low audio issue
>
> How much do DSP's <on GW> matter?  The problem is after all, coming in POTs and sent right back out POTs, right?
>
> Reason for asking; problem sites have older "DSP-ware".  My newer and larger sites run a significantly newer version; 23.x compared to 9.x at problem sites.  Thoughts??
>
> -----Original Message-----
> From: cisco-voip-bounces at puck.nether.net [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Countryman, Edward
> Sent: Saturday, August 29, 2009 3:00 PM
> To: Dennis Heim; Nick Matthews
> Cc: cisco-voip at puck.nether.net
> Subject: Re: [cisco-voip] CF off net low audio issue
>
> Actually it is not.  I have the exact issue at 4 sites which the gain adjustment has improved.  The settings I ended up with are at the extreme ends of their respective ranges so not sure how staff will react come Monday morning.
>
> -----Original Message-----
> From: Dennis Heim [mailto:Dennis.Heim at cdw.com]
> Sent: Saturday, August 29, 2009 12:56 PM
> To: Countryman, Edward; Nick Matthews
> Cc: cisco-voip at puck.nether.net
> Subject: RE: [cisco-voip] CF off net low audio issue
>
> Is this site out in the middle of no man's land?
>
> Dennis Heim
> Network Voice Engineer
> CDW  Advanced Technology Services
> 11711 N. Meridian Street, Suite 225
> Carmel, IN  46032
>
> 317.569.4255 Office
> 317.569.4201 Fax
> 317.694.6070 Cell
> dennis.heim at cdw.com
> www.berbee.com
>
> -----Original Message-----
> From: Countryman, Edward [mailto:Edward.Countryman at provena.org]
> Sent: Saturday, August 29, 2009 1:10 PM
> To: Nick Matthews; Dennis Heim
> Cc: cisco-voip at puck.nether.net
> Subject: RE: [cisco-voip] CF off net low audio issue
>
> I was able to crank the input gain and bottom out the output attenuation.  Also required cranking the EC but was able to improve this significantly.
>
> There is now noticeable popping and hissing on the line but at least the caller can hear the audio.  I am going to also open an att (my carrier) trouble ticket.  Thank you!
>
> -----Original Message-----
> From: matthn at gmail.com [mailto:matthn at gmail.com] On Behalf Of Nick Matthews
> Sent: Thursday, August 27, 2009 6:17 PM
> To: Dennis Heim
> Cc: Countryman, Edward; cisco-voip at puck.nether.net
> Subject: Re: [cisco-voip] CF off net low audio issue
>
> We see a lot of these cases.
>
> This is generally the cause / scenario:
>
> The PSTN runs a long loop to a site.  At this site, the FXO has low
> volume.  IP phone users don't notice it, because they turn the volume
> up high on the IP phones to compensate.  Then, only call flows that do
> not go through the IP phones have the problem.  What will happen then
> is calls to voicemail, which do not have the IP phone gain configured,
> will be low volume (especially if played back in email and do not go
> back through the phone).  Plus, any calls that come in the system and
> go back out, will have the volume lowered.
>
> What is actually happening is the IP phone users are able to
> workaround the low volume issue themselves.  The real problem is the
> long loop to the router.  If you were to place an analog phone on the
> line instead of the router, you would have the same problem.
>
> The solution is to put input gain on the ports.
>
> voice-port 0/0/0
> input gain 6
>
> This can be done in the middle of a call (live change) to troubleshoot.
>
> The danger is if there is a low signal-to-noise ratio  If this is too
> low, turning up the volume on the line will also make the noise on the
> line very low.  The router has no way to enhance the SNR.  If this is
> the case, your best bet is to find a gain value that makes things as
> good as possible, finding a provider with a closer CO, or having the
> provider try re-running your loop (good luck).
>
>
> -nick
>
> On Thu, Aug 27, 2009 at 11:47 AM, Dennis Heim<Dennis.Heim at cdw.com> wrote:
>> I ended up opening a tac case. Tac has some special tools just for low level
>> analog trouble shooting.
>>
>>
>>
>> Dennis Heim
>> Network Voice Engineer
>> CDW  Advanced Technology Services
>> 11711 N. Meridian Street, Suite 225
>> Carmel, IN  46032
>>
>> 317.569.4255 Office
>> 317.569.4201 Fax
>> 317.694.6070 Cell
>>
>> dennis.heim at cdw.com
>> www.berbee.com
>>
>>
>>
>> From: Countryman, Edward [mailto:Edward.Countryman at provena.org]
>> Sent: Thursday, August 27, 2009 11:46 AM
>> To: Dennis Heim; cisco-voip at puck.nether.net
>> Subject: RE: CF off net low audio issue
>>
>>
>>
>> Do you if there is a Cisco job aid for this type of work;  is most of this
>> done in the router?  I don't necessary see anything on the CCM (mgcp) for
>> this.
>>
>>
>>
>> From: Dennis Heim [mailto:Dennis.Heim at cdw.com]
>> Sent: Thursday, August 27, 2009 10:37 AM
>> To: Countryman, Edward; cisco-voip at puck.nether.net
>> Subject: RE: CF off net low audio issue
>>
>>
>>
>> You will need to play with your input gain and output attenuation.
>> Additional, you may also need to do a tone sweep in order to get things like
>> impedance correctly tuned. Prepare to spend a lot of time to get those
>> analog lines tuned correctly.... Been there done that..
>>
>>
>>
>> Dennis Heim
>> Network Voice Engineer
>> CDW  Advanced Technology Services
>> 11711 N. Meridian Street, Suite 225
>> Carmel, IN  46032
>>
>> 317.569.4255 Office
>> 317.569.4201 Fax
>> 317.694.6070 Cell
>>
>> dennis.heim at cdw.com
>> www.berbee.com
>>
>>
>>
>> From: cisco-voip-bounces at puck.nether.net
>> [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Countryman, Edward
>> Sent: Thursday, August 27, 2009 9:50 AM
>> To: cisco-voip at puck.nether.net
>> Subject: [cisco-voip] CF off net low audio issue
>>
>>
>>
>> I have several smaller physician offices that will forward their main # to
>> an offsite answering service for after hours coverage.  The sites are all
>> trunked with POTS lines connected to FXO ports on 28xx series ISRs.  So the
>> incoming call on FXO port 1 effectively is sent back out on FXO port 2 etc.
>>
>>
>>
>> The problem I have is that the audio level the caller hears is greatly
>> attenuated; almost beyond discernment.  However if I call the far end
>> directly the call is very clear so it appears my router is the problem.
>>
>>
>>
>> Anyone have any thoughts on this?
>>
>>
>>
>> _______________________________________________
>> cisco-voip mailing list
>> cisco-voip at puck.nether.net
>> https://puck.nether.net/mailman/listinfo/cisco-voip
>>
>>
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