Hello,
I haven't heard there is any public SIP
interconnect offered by Zoom,
Not "public", but they're offering traditional phone interconnect
services. If you ask nicely you can get them to set up a BYOC link
(Bring Your Own Carrier) which is basically encrypted SIP and RTP.
Reportedly, the ability for customers to set up such interconnects via
the admin webpage is in the works.
I've since figured out that the solution to my problem is to radically
limit the crypto algorithms (offered to them *and* accepted from them)
via SDP. Apparently there's a somewhat-hairy bug in their gateway's
negotiation setup.
No usable reaction from Zoom support yet, let alone a fix that'd allow
me to remove that hack; as usual for companies of that size and/or rate
of growth, their front line support leaves much to be desired.
--
-- mit freundlichen Grüßen
--
-- Matthias Urlichs