[cisco-voip] Codec negotiation

[Scott Voll]

There was some talk a week or two ago, about ASA compatibility with CM and
having to keep them lock step.  Am I running into this kind of issue?  ASA
8.4.2 / CM 7.1.5?

Scott

On Wed, Dec 7, 2011 at 12:13 PM, Wes Sisk <wsisk at cisco.com> wrote:

> SCCP devices advertise capabilities on registration.  Those capabilities
> are never renegotiated unless video is added/removed/invoked.
>
> A little insight here -
> CM tells the phones the codec it *should* receive in the
> OpenReceiveChannel sent to the phone. However, the phones do not trust
> that.  The phone figures out the codec it is receiving based on the first
> few RTP packets received.
>
> If you are seeing ?? under codec I would be more suspecting of RTP not
> arriving at the phone.
>
>
> SIP and H.323 advertise codecs on a per-call basis.  MGCP advertises
> codecs once during registration.
>
> Regards,
> Wes
>
> On Dec 7, 2011, at 2:30 PM, Scott Voll wrote:
>
> can anyone tell me how Codec negotiation works?  Specifically what ports
> it works on?
>
> I have telecommuters using IPC 7.0.5 connecting with anyconnect (2.5)
> connecting to an ASA at the head end.  Calls to inside 7961's work fine.
>
> but I also have 881's doing site to site VPN with 7961 hanging off the
> back coming into the same ASA.  That phone can call internal 7961 also.
>
> The problem comes from IPC telecommuters calling 7961's behind the 881's.
>  When you place the call, it rings, they answer, the timer increments up.
>  But with a ?? it does not show a Codec.  It looks like we never negotiate
> the Codec.
>
> is this a Version problem?  CM is 7.1.5 and ASA is 8.4.2.  I THINK it
> worked with ASA version 8.2.4 (but I Can't downgrade to double check).
>
> Any other ideas?
>
> I have a TAC case with the ASA team and they are like ya, the vpn
> connections work.... open a new ticket with the voice team.  And before I
> did so, I figured you guys are really smart and probably have deal with
> these kinds of issues.
>
>
> Scott
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>
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