MTD calls cannot be put on hold

[Former Member]

Hi there, I'm quite in the dark regarding SIP protocol, maybe someone here can help me with this.

The problem is, as the title says, that MTD call cannot be put on hold. Why I think this is related to SIP signalling?

• When using legacy call gateways everything worked. Now, using IMS, it doesn't.
• The problem must be with IMS then! Well maybe not - using a dedicated call logging application the problem seems to be here:

The scheme shows that the re-invite containing the hold signal coming from the MTD phone hits the system's SIP bridge, receives an ack and then suddenly the system sends out a reinvite containing "sendrecv" as if it wants to cancel the hold.
This is an error, system is notified of this and it drops the call.

"Use cd-controlled transfers" is enabled and I tried disabling it - made no difference. The system is a SP 9 instance.

Does anyone have any ideas what to try?

Best wishes,
Jaanus

[alexander_kupke]

Hi Jaanus,

two questions to start with.

Do you try to put the call on hold from MTD device (by the way, is this a SIP device registered to contact center or some external device?) or out of the CDT?

Which holding method do you have set in the trunk configuration?
I just recently learned that the hold Format "IP Address Set to 0" seems to be seen as deprecated by some parties and sometimes is not supported any more. Depending on you IMS it might be the other way round as well. Also the checkbox "Add 'user=phone' to SIP URI"  might be required in some situations.

Regards

Alexander

[Former Member]

Oh, forgot to mention that specifically - the MTD device is a VOIP phone but not registered in this CCtr instance. It is also the source of the hold.

The trunk settings have "Inactive/Send-only-Receive-only" set as the hold format and I'll give the "Add 'user=phone' to SIP URI" a try.