[cisco-voip] Call Failure

[Aman Chugh]

Thanks Wes.

I would look at H.323 service parameters.

Regards,
Aman

On Thu, May 28, 2009 at 8:39 PM, Wes Sisk <wsisk at cisco.com> wrote:

>  If call preservation were enabled for the call then the phone would stay
> offhook until the user initiated a disconnect.  This leads me to 2 thoughts:
>
> 1. The call does not have call preservation enabled to begin with.  If this
> is true then as soon as the phone loses CM registration it will clear the
> call.  This is possible depending on the type of call (conference, transfer,
> mtp, internal, external) and the signaling protocols involved in the call
> (h323,cti call preservation disabled by default.  h323 can be enabled with
> service parameter).  Possibly the easiest way to verify this is to setup a
> call between 2 phones in india and then flap the WAN connection.  The call
> should stay up as SCCP endpoints always have call preservation enabled.  The
> most likely culprit here is the gateway signaling protocol. If h.323 then
> change CM service parameter/enterprise parameter to enable h.323 call
> preservation.
>
> 2. If call preservation is enabled and the call still automatically clears
> I only know of 1 thing that would cause this - ICMP messages on the
> network.  Gateways and phones both look for ICMP unreachable messages and
> terminate preserved calls if a threshold number of ICMP messages are
> received.  When your WAN flaps does it flap in such a way that the endpoints
> (gateway,phone) would receive ICMP messages?  I do not know of any way to
> change the ICMP behavior on endpoints.  However, you could creative in the
> network and have ICMPs suppressed for RTP streams.   This would allow the
> endpoints to continue to preserve the call.  Be careful though, this can
> also lead to orphaned call legs.
>
> While these may be technically viable what are the chances your external
> callers and users will hang on the line through 10 seconds of no audio?
>
> /Wes
>
>
> On Thursday, May 28, 2009 9:06:31 AM, Aman Chugh <aman.chugh at gmail.com><aman.chugh at gmail.com>wrote:
>
>
> I have a remote location which registers to the CCM at the central site ,
> all the PSTN traffic exits out of the central site gateway and we do not
> have any PSTN link at this remote site. This site is an extension of my
> central site. I have situation here as the my data link to this site flaps
> for 10 seconds resulting in all active calls to drop.
>
> I am using CCM 6 at the central site. Is there any way I can keep the call
> up when the link flaps. I know the call survives only when IP Phone losses
> it's link with CCM  but in my case the entire data link goes down.
>
> I know it is not possible as the entire data link goes down but out of
> curiosity want to know if this is remotely possible.
>
> TIA,
> Aman
>
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