It can also have a different path than the INVITE, if there are proxies that do not do record-route, so there can be less Via headers than in the INVITE.

By that I am wondering if the ACK relayed via tm module has the same Via branch as , expecting not to be. Maybe in the ACK for 300+ replies...

Cheers,
Daniel

ACK for successull response is a new transaction. It has to be different. May be it is better to point provider to this? 

On Mon, 10 Feb 2020, 14:26 Sebastian Damm, <damm@sipgate.de> wrote:

Hi,

I stumbled upon an interop problem with a carrier. We have the
following scenario:

Gateway --> Loadbalancer --> Carrier

The loadbalancer generates a Via header for each request. But since it
is stateless, the Via tag is generated for each request. As a
consequence, the Via tag in the ACK differs from the one in the
INVITE. And one carrier doesn't handle those ACKs if the Via tag
differs.

Is there a way to force the creation of a "deterministic" Via branch
tag? For example, building it from a hash over call-id and from-tag or
something like that?

Thanks in advance
Sebastian

--
Sebastian Damm
Voice Engineer
__________________________________________
sipgate GmbH

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