So accessing the Jitsi Meet instance on my server (or indeed any old server) is no problem at all. Works a treat. Unless you're behind a firewall that blocks UDP.
Internet video and audio streaming typically requires using the UDP protocol, as it is low latency, as opposed to the TCP protocol used by Internet services that require reliable transmission of data. Reliability requires checking that you got all the data you asked for, uncorrupted, and in the order you asked for it, and asking for it again (and again, and…) if something went wrong, waiting a substantial fraction of a second for every missing or screwed up data packet. So reliability increases latency considerably.
Now recorded video can use TCP and work around that problem by buffering the video ahead of playback. This isn't a viable solution for real time conversations (because you haven't said what you said until you said it), so doing this involves using UDP and just tolerating lost/mangled data. This is why Zoom/Teams/whatever, despite the massive throughput of their data centres, still manages to be glitchy as hell on occasion.
The problem is that UDP is also used for all sorts of other applications that corporate networks regard as illegitimate, such as gaming or censorship evasion, and is also often used in malicious attacks. So corporate firewalls often simply block UDP access overall.
"But Katy", I hear you protest, "It's not the business of libraries to prohibit play, and certainly not to facilitate censorship!"
I quite agree, but the first priority of IT departments is arse-covering, and "Everybody else does it!" has been the default reason for pretty much everything IT departments do since time immemorial.
"But why then," you say, "Does Zoom and Microsoft Teams work perfectly well at my office and at the library?"
My, you're stroppy today! Is everything okay?
This is the fun part. Your office and library network whitelist Zoom, and Teams, and countless other big tech services, because they are either services they have explicitly invited into their organisation as a partner, or they are just so pervasive that they can't deny access to their users. These companies have the heft to demand that basically every other company on the planet reconfigure their network security to accommodate them.
So for every TCP or UDP port on every public-facing server of the tech giants, network administrators scramble to keep their long whitelists up to date. Because of course, servers are being added and removed all the time. Microsoft says it updates the list of it's TCP/UDP addresses and ports monthly.
Sources:
- Prepare your organization's network for Microsoft Teams
- Managing Microsoft 365 endpoints
- Zoom network firewall or proxy server settings
I read somewhere today (on a discussion board; dated; not trustworthy; seems plausible, though) that Google's not-at-all-creepy omniscient surveillance capabilities suggest a bit under 10% of Web traffic goes through a corporate firewall.
This is part of the dynamics that are breaking the Internet. Not only is this a huge barrier to market entry to a new online service that increases the market power of existing players, but it kills stone dead the idea of the Internet as a level playing field where the infrastructure is dumb and undiscriminating, and all the data and the services that use it are owned and controlled by users.
Even a quite large corporation doesn't want to pay someone just to keep on top of network security that operates on the sledgehammer principle of block everything not explicitly permitted such that now-critical third-party services don't regularly break. Which encouraging outsourcing this to companies like Cisco, who than use it as a "land and expand" opportunity to colonise the rest of the IT department.
Now is <10% of your audience (or whatever it is in reality) a showstopper for our purposes? I'm not sure, and in principle at least there is a sub-optimal workaround for UDP blocking that looks like a bit of a pain but worth evaluation. For conversations with people you know are not behind a firewall they do not themselves control (which could be at work, a library, cafe, pub, maybe a mobile data service, etc.) it's fine. For online events open to the general public, less fine.
Investigations continue.