VPS + 2 providers + WEB + SIP. How to set everything up?

Question

linux

Good day. Can you tell me how to implement such a scheme and is it possible?
A VPS is rented on it, a redirect of WEB and SIP ports is configured, depending on which ISP provider works.
I tried to configure xinetd on the VPS, it redirects https, but gives a certificate error. Sip didn't work at all.
I do not even know where to start. IPTABLES? Xinetd? Any other solution?
Let me clarify a little. Can you suggest another solution. There is a server with services: WEB and SIP. 2 providers connected. One backup and only turns on when the main one falls. I thought to use two A records from the DNS provider, but the distribution of ip is roulette, because of this, plugging in the WEB. I also used SVR records for SIP, but some SIP phones switch normally, and some hang on a non-working IP and nothing helps, only an explicit indication of a working IP. In general, I initially thought to get by with only shamanism with DNS, but alas, "the stone flower does not come out."

Answer 1

Hmm... SIP is mostly UDP - just NAT. And it will work very hard.
https via nginx reverse proxy (having received automatic balancing and failover for free)
sip is better on a vps sip switch then it will just be a redirect of calls

Answer 2

VPN channel between the VPS and the server where the services are running.
Service connects to the VPN server, if a channel switch occurs, it reconnects. It doesn't care what the Service's IP is now.
And nginx on VPS solves the certificate problem, because DNS points to VPS