[cisco-voip] Strange behaviour of CME

[Cisco Voip]

Dear Sir, 

I dont have words to express my gratitude. Thanks alot

Just one thing, pls spare some time to help me clarify. When phone boots up, it 
will tell all the codec using capabilities exchange process. In my case R1 
already knew what IPC-1 is capable of. Same goes to R2 and IPC-2. So when IPC-1 
makes a call to IPC-2 (or vice versa), its upto R1 and R2 to negotiate which 
codec phones will use ? or will phones negotiate end to end which codecs they 
will use ? 





________________________________
From: Nick Matthews <matthnick at gmail.com>
To: Cisco Voip <cisco_newbie at yahoo.com>
Cc: ccieid1ot <ccieid1ot at gmail.com>; cisco-voip at puck.nether.net
Sent: Wed, January 26, 2011 7:49:11 PM
Subject: Re: [cisco-voip] Strange behaviour of CME

It's part of the negotiation that happens with SCCP.  The phone advertises every 
codec it is capable of, the gateway passes that information on, and once the 
call is ready to complete, each device chooses which of the available codecs 
they are going to use.  If one device advertises a list of codecs that doesn't 
match the other side, the call will not complete.  It would complete if there 
was a transcoder.

-nick


On Wed, Jan 26, 2011 at 1:20 AM, Cisco Voip <cisco_newbie at yahoo.com> wrote:

Ok i get my confusion.
>
>The codec between R1 and R2 was g729, while the default codec between R1 and 
>IPC-1 is g711. How did IPC knew that it has to use g729 instead of g711 ?
>
>Please clarify this
>
>
>
>
________________________________
From: Nick Matthews <matthnick at gmail.com>
>To: Cisco Voip <cisco_newbie at yahoo.com>
>Cc: ccieid1ot <ccieid1ot at gmail.com>; cisco-voip at puck.nether.net
>Sent: Wed, January  26, 2011 10:32:29 AM
>
>Subject: Re: [cisco-voip] Strange behaviour of CME
>
>
>The phone supports multiple codecs.  They simply have different priorities.  The 
>reason you always see g711 instead of g729 is because g711 has a higher 
>priority.  The modern phones (7942/7962 and above) support something like 7+ 
>codecs.
>
>-nick
>
>
>On Tue, Jan 25, 2011 at 11:37 PM, Cisco Voip <cisco_newbie at yahoo.com> wrote:
>
>Dear Sir, 
>>
>>As a followup, by default SCCP phones use codec g711. So did you mean that 
>>phones automatically switched to g729 ? i totally believe your point but for my 
>>further studies can you also refer me any cisco config guide to strengthen my 
>>concept 
>>
>>
>>Pls verify my above point
>>
>>
>>
>>
________________________________
From: Nick Matthews <matthnick at gmail.com>
>>To: ccieid1ot <ccieid1ot at gmail.com>
>>Cc: Cisco Voip <cisco_newbie at yahoo.com>; cisco-voip at puck.nether.net
>>Sent: Wed, January 26, 2011 5:10:12 AM
>>Subject: Re: [cisco-voip] Strange behaviour of CME
>>
>>
>>Transcoding is only required when there is a codec mismatch.  In this case it's 
>>something like:
>>
>>Phone 1:
>>g711ulaw
>>g711alaw
>>g729r8
>>g729br8
>>g722
>>...
>>etc
>>
>>GW1 to GW2:
>>g729r8
>>
>>Phone 2:
>>same as above phone 1
>>
>>
>>Since g729r8 is available by all, there is no need for transcoding.
>>
>>-nick
>>
>>
>>On Tue, Jan 25, 2011 at 2:47 PM, ccieid1ot <ccieid1ot at gmail.com> wrote:
>>
>>The phones has built in dsp to do the transcoding.
>>>duy
>>>ccie #27737 voice
>>>tmobile g2
>>>On Jan 25, 2011 10:03 AM, "Cisco Voip" <cisco_newbie at yahoo.com> wrote:
>>>> Hi all. 
>>>> 
>>>> I have setup the current setup in my lab
>>>> 
>>>> IPcommunicator-1 
>>>> 
------------------R1-GW-------------------R2-GW-------------IPcommunicator-2
>>>> 
>>>>                                SCCP (g711)                  default (g729)
>>>> 
>>>> On R1 i simply created a dial-peer voice 2141 voip, and defined the session 

>>>> target and destination pattern, and also codec to be g729r8. Now when i call 
>
>>>> from IPc-1 to IPc-2, the call is successful !!
>>>> 
>>>> I have set this up in dynamips and 2 IPcs are infact vmware machines. What i 
>
>>>> dont understand is, why there was no need for transcoding ? the default codec 
>>
>>>> between R1-GW and IPc-1 is g711, while between R1-GW and R2-GW, i set it to 

>>>> g729, so isnt transcoding needed here ?
>>>> 
>>>> 
>>>> 
>>>> 
>>>
>>>_______________________________________________
>>>cisco-voip mailing list
>>>cisco-voip at puck.nether.net
>>>https://puck.nether.net/mailman/listinfo/cisco-voip
>>>
>>>
>>
>>
>
>



      
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