[Blink] On re-invite ACK not reaching callee

[Adrian Georgescu]

Do you have the call id?


> On Aug 24, 2026, at 22:46, Robert Dyck <rob.dyck at telus.net> wrote:
> 
> Using latest flatpak for Linux.
> 
> Caller on sip2sip.info calls subscriber at a different domain. Callee answers and dialog is established. So far all good.
> 
> Caller does a re-invite ( hold ). The callee's UA sends 20OK. Caller's UA sends ACK. ACK never arrives. Callee's UA continues sending 200OK.
> 
> Callee is registered as GRUU. Incoming requests are normally translated by the local registrar and the request is forwarded to the callee's IP address. This also applies to re-INVITE and its ACK. The caller learns the registrar's address from the Contact it previously received in the initial 200OK.
> 
> Summary of in-dialog requests
> Initiial ACK - OK
> re-InVITE - OK
> second ACK - doesn't arrive
> Bye - doesn't arrive
> 
> An important detail - Registrar/Proxy is behind NAT. Router use DMZ forwarding.
> 
> The request URI of the ACK following re-INVITE is pointing at the external address of the registrar but the ACK was received at a private address. The ACK is forwarded to the external address. It never reaches the registrar because the router cannot hairpin the forwarded message.
> 
> ACK sip:8 at external-address:5060;gr=urn:uuid:38ee02db-f267-4dd9-9077-1b9d4fcfbf00 SIP/2.0 
>                                                            Record-Route: <sip:212.95.45.179;lr;ftag=803fbe29-6196-4af7-9771-db7d25007e6c> 
>                                                            Record-Route: <sip:174.142.205.46;r2=on;lr;ftag=803fbe29-6196-4af7-9771-db7d25007e6c> 
>                                                            Record-Route: <sip:174.142.205.46;transport=tcp;r2=on;lr;ftag=803fbe29-6196-4af7-9771-db7d25007e6c> 
>                                                            Via: SIP/2.0/UDP 212.95.45.179:5060;branch=z9hG4bK45c1.804d44d2.2 
>                                                            Via: SIP/2.0/UDP 174.142.205.46:5060;branch=z9hG4bK45c1.ab795fa4.2;i=d0969e07 
>                                                            Via: SIP/2.0/TCP 192.168.1.3:58491;received=external-address;rport=58491;branch=z9hG4bKPj62eb9faf-6eba-4f91-9539-8b2954cad94a;a
> lias
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