[Users] sip trunking between carriers

[vallimamod abdullah]

Hello list,

I have an installation with openser connected to a PSTN gateway and I
am offering the possibility to my customers to rent a PSTN trunk to
forward long distance calls to a remote SIP carrier via my proxy.

My customer usually gets a sip normal account on from remote SIP
carrier and my proxy must use to authentificate all invites relayed to
this carrier.

So my question is: how can I authentificate my proxy to the remote
carrier with the credentials given by my customer ? Has anybody
already implemented a similar solution ?
I have checked the UAC module but it seems to give the ability to set
only a static credential on FAILURE_ROUTE.

Thanks,
-vma
.