Dear List

I'm currently facing an issue with a carrier whereby they are complaining that the via header branch parameter (sip.Via.branch == "z9hG4bKcydzigwkX") in the ACK messages is not unique which results in some calls being successful and some terminating after 20 seconds as their sip proxy determines it as a duplicate request. Is there a way to make the via header branch parameter in the ACK message unique across every transaction?

Thanking you in advance for your assistance.
Phillip