ā01-28-2010 01:41 PM - edited ā03-15-2019 09:14 PM
ā02-01-2010 12:50 PM
Hello Steve,
That's interesting one for sure.
Though 'header-passing error-passthru' is a good catch but the thing is that CUBE/CME IP-to-IP code does not forward 488 response to the other call leg.
Instead 500 is sent and call is terminated.
There was an internal discussion about that issue and as far as I know this behaviour will be changed in 15M train.
If you want to know details you can contact your Cisco Account team and they will shed some light here.
Some things to consider/possible workaround:
- this behaviour will only happen in case CME/CUBE will forward T.38 re-INVITE between IP call legs and CUCM or other call agent will
reply with 488 message.
- as far as I understand this is conf call so no parties are able to terminate FAX call. You can define dial-peers so that no FAX capabilities
configured on CUBE for that call flow and 488 will be sent by CUBE itself and not forwarded by CUCM
- even if 488 response will be sent to the Service Provider - it's up to them how to treat that call further - whether they have a g711 fallback for such
calls or not
- the underlying problem behind this behaviour is that SIP does not have T.38 capabilities negotiation as H.323 does and thus any side can initial
switchover at any time during the call . With H.323 if there was no T.38 capabilities received during H.245 negotiation the party will not initiate switchover.
That's different with SIP and can't be changed but we have 488 response and party which receive it may process it so the call is not terminated.
Regards,
Vladimir.
ā02-02-2010 12:07 PM
Thanks for the feedback, what would be the best way to define dial-peers so that there are no FAX capabilities? I can give that a try.
ā02-02-2010 01:43 PM
Hello Steve,
To implement this change you will need:
1. disable FAX support on system level
voice service voip
fax proto none
2. disable FAX on dial-peers where it's not required
dial-peer voice X voip
fax proto none
3. enable FAX on dial-peers where it required
dial-peer voice Y voip
fax proto t38
Regards,
Vladimir.
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