A small box at a branch office joins its phones to the main office over one encrypted link.
An office with a second location should not need a second phone system.
The usual choices, and why we did not like them
- A phone system at each site. Twice the work, and transferring a call between sites becomes a project.
- Branch phones connecting straight to the main office over the internet. It works until the branch's router gets in the way, and it exposes the main system to the whole internet.
- A site-to-site VPN. Fine if you already run one, and one more thing to break if you do not.
A small box at the branch
So we have started on Kahevo Hākuʻi: a small computer at the branch. The branch's phones connect to the box, on their own network. The box keeps one encrypted link back to the main office.
To the main system, a branch phone looks like any other phone. Nothing about calls, voicemail or menus has to know that branches exist.
One port, opened in one place
The branch always calls the main office, never the other way round. That has three useful results:
- Nothing is opened on the branch's router.
- The branch's internet address can change as often as it likes.
- The main office opens exactly one port for all of its branches.
A branch is known by its key, never by where it is connecting from.
Enrolling a box
An administrator adds the site and gets a one-time code. Type the code into the box. The box makes its own key, and the main office shows a short fingerprint to compare against the one the box shows on its own page before approving it. Until it is approved, nothing is carried in either direction.
Quiet to strangers
The main office does not reply to anyone it does not know. A scan of the internet sees nothing there.
Next
The link is built. Next, the calls.