Central reverse-proxy ssh access

[TorhanPiper]

We have (many!) sites around the world, that we set up IPsec VPN to.However, some sites are behind ISPs that randomly block VPN.So ideally, we would like something that is not IPsec, and reaches out from a unix node at those sites, to a central server, and allows authorized authenticated people, to be able to (probably ssh) back in.

The one thing making it complicated, is that we have an existing VPN in place, and its probably not going away.Which means we probably cannot just replace our old VPN with some new, non IPsec one. The new connectivity has to exist in paralle with the old one.However, that makes routing conflicts a problem.Which I guess means we need some kind of central server, where people first connect to the server, then from the central server, they can connect to the various remote sites.

Suggestions?