CallManager 7.1.3.32900-4 and "Early Media" problem

Answered Question
Sep 28th, 2010

Hello.

We have this scenario:

IPPhone-(SCCP)-CallManager-(SIP)-PGW-(MGCP)-AS53XX-[PRI]-PSTN

When we make an outgoing call, for example, to a mobile phone that is turned off, we can't hear the "Early Media" message which informs that the call will be forwarded to the voice mail. We only hear the actual voice mail greeting.

What's wrong?

Best regards.

I have this problem too.
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Correct Answer by Chester Rieman about 6 years 3 months ago

Hard to tell from this little info but all portions must support early media (they should here)

and PRACK should be enabled in CUCM:

SIP Rel1XX Options

This field configures SIP Rel1XX, which determines whether all SIP provisional responses (other than 100 Trying messages) get sent reliably to the remote SIP endpoint. Valid values follow:

Disabled—Disables SIP Rel1XX.

Send PRACK if 1XX contains SDP—Acknowledges a 1XX message with PRACK, only if the 1XX message contains SDP.

Send PRACK for all 1XX messages—Acknowledges all1XX messages with PRACK.

If you set the RSVP Over SIP field to E2E, you cannot choose Disabled.

With early media cut through, a greeting gets played to the caller before the called party is alerted about the call. Trunks and gateways must support early media cut through for the greeting to get played in such a way. Cisco PRI/MGCP gateways, H.323 gateways and trunks support early media cut through. For SIP trunk to support early media cut through, you must enable PRACK. Be aware that a greeting may not get played if the device does not support early media cut through.

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Correct Answer
Chester Rieman Tue, 10/05/2010 - 09:58

Hard to tell from this little info but all portions must support early media (they should here)

and PRACK should be enabled in CUCM:

SIP Rel1XX Options

This field configures SIP Rel1XX, which determines whether all SIP provisional responses (other than 100 Trying messages) get sent reliably to the remote SIP endpoint. Valid values follow:

Disabled—Disables SIP Rel1XX.

Send PRACK if 1XX contains SDP—Acknowledges a 1XX message with PRACK, only if the 1XX message contains SDP.

Send PRACK for all 1XX messages—Acknowledges all1XX messages with PRACK.

If you set the RSVP Over SIP field to E2E, you cannot choose Disabled.

With early media cut through, a greeting gets played to the caller before the called party is alerted about the call. Trunks and gateways must support early media cut through for the greeting to get played in such a way. Cisco PRI/MGCP gateways, H.323 gateways and trunks support early media cut through. For SIP trunk to support early media cut through, you must enable PRACK. Be aware that a greeting may not get played if the device does not support early media cut through.

srsivara Tue, 10/05/2010 - 11:27

In addition to seting the SIP service parameters up, keep in mind that an MTP needs to be invoked to do Early Media on the SIP trunk.

- The 'Media Termination Point Required' checkbox on the SIP trunk config on CUCM has to be checked.

- Ensure that the MRGL on the SIP Trunk has access to an MTP

- Ensure that the region settings between the SIP trunk and MTP, and MTP and phone are set properly

- Reset the SIP trunk from CUCM admin, if you made any changes on the config page

You can test again and check if there's any difference in the call flow.

- Sriram

raziel78kain Fri, 10/08/2010 - 01:13

Dear crieman,

we have solved the problem.

We have made the following changes on the settings:

  • On the CallManager: SIP Rel1XX Enabled = Send PRACK if 1xx Contains SDP
  • On the PGW: SupportReliable100 = SUPPORTED

It hasn’t been necessary neither to reset the SIP trunk nor to activate the MTP.

Regards.

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