Adding Custom Sip-Header to Active Call

[RossStevenson]

Hi all,

  Hoping someone can help me here and clear up if this is possible plus the best way to achieve it.

Basically I need to add a custom value to a call, so the third party can detect the call and apply a workaround their end.

We're having issues with the dreaded mid-call INVITE with a third party when a live call gets transferred, tried disabling it entirely, adding the sendrecv on the SIP trunk itself in call manager (which does fix it) but generally find it then has an adverse effect with something else.

So we now have another work around, but requires us to tag the call with a custom value so the third party can trace this and apply a fix their side.

I've been looking into SIP-Profiles on the CUBE and can choose a random sip-header I suspect isn't being used and add it with the following command

(using the Warning SIP-Header here as an example)

voice class sip-profiles 11
request INVITE sip-header Warning add “Custom Value Tag”

If I add this to the outbound dial-peer, would this actually amend the mid-call INVITE that gets sent out during the concurrent call when it gets transferred? Or because the call is live and isn't a new call, does this need applying elsewhere? i.e globally or on the inbound DP?

[b.winter]

In my opinion, thinking about it, I wouldn't see a possibility, how a system knows, if it's an INVITE (e.g. to start a call) or a mid-INVITE (e.g. for transfer).
Technically, there is no difference between them, except that both may contain different headers / values. But the message type is always "INVITE".
The technicians just call them like that, to express the context of the INVITE.
So you probably have to set a custom header for every INVITE, as I don't see how to distinguish between a normal and a mid-Invite.

And in general: You don't need to use standard SIP headers, to transport custom values. You can create and use custom headers as well e.g. "myCustomHeader: thisIsATestValue".

[RossStevenson]

Thanks for the response b.winter

I don't forsee it being an issue to add it to every INVITE, as long as its not disruptive. As long as I use a header that isn't used in an INVITE or even as you said, use a custom one, then there shouldn't be any harm in adding it in, right?

Also, any ideas on the placement for that sip-profile, would that be applied in the outbound dial-peer? Just confusing me as the original call would've been an inbound external call, but when the transfer happens, obviously its sending the INVITE back out to the third party. So would it need to be applied on the original inbound DP?

[b.winter]

No, it shouldn't do any harm.

About the placement: Depends, which system needs to "see" this header and in which direction?
If the header is processed by the third party server, then probably in CUBE in the outbound direction towards the third party.

[RossStevenson]

Yea, the external third party where the call originates from. I'll give it a shot and see how it goes.