I've been running it the last year or two to get e-mail to a vintage DOS BBS that had a UUCP package. I was pleasantly surprised it was out of the box usable on both CentOS and Debian, and Postfix still ships with example UUCP email config.
The key is to use a non-compressed codec such as G.711u/a-law, and disable echo and silence suppression. I can regularly get 28.8k-33.6k carrier speeds across the US when using an ITSP/VoIP provider and my modems connected to Grandstream/Linksys/Cisco analog telephone adapters.
I used the acme-dns server (https://github.com/joohoi/acme-dns) for this. It's basically a mini DNS server with a very basic API backed with sqlite. All of my acme.sh instances talk to it to publish TXT records, and accepts queries from the internet for those TXT records.
There's a NS record so *.acme-dns.example.com delegates requests to it, so each of my hosts that need a cert have a public CNAME like _acme-challenge.www.example.com CNAME asdfasf.acme-dns.example.com which points back to the acme-dns server.
When setting up a new hostname/certificate, a REST request is sent to acme-dns to register a new username/password/subdomain which is fed to acme.sh. Then every time acme.sh needs to issue/renew the certificate it sends the TXT info to the internal acme-dns server, which in turn makes it available to the world.
Back in the ISP days of the 90s, if you used the Microsoft Internet Explorer Administration Kit (IEAK) and wanted to distribute customized versions of IE to your customers, one of the requirements was to use IE-only elements on your main website to promote usage of IE. Marquee was one of the least obnoxious ways to do that compared to other options.
Qmodem was my favorite comm program during the BBS days, and it still is today when working with vintage computers. It was just nice to use. Its scripting language was the first I used and I find myself wishing there was a Linux comm program with scripting that worked that well. Long distance calls were expensive so I used a Qmodem script to call BBSs each morning to download my email before school.
Just the last several months I've been using Qmodem scripting to make thousands of modem calls over VoIP to test downloads to see which models and ATAs work best.
After I jumped back into the vintage BBS world I've been keeping an eye out for anything Qmodem. I recently just picked up a Qmodem manual on ebay that I wanted to scan and archive, because it's pretty rare to see.
Not too long ago I saw where John had posted to a FB group he was working on a new DOS version of Qmodem, my first interaction with him. I was excited to see it be worked on again and hoped to see the new version. Sad to see him go.
These were pretty decent, not too terrible, and could be set up to dial normal ISPs. They filled a niche with older customers and/those who had zero computer experience but wanted to check email and browse web pages back in the 90s. They didn't last long enough to bridge the gap to the tablet era, so I'm guessing a lot of people finally had to learn a computer.
I do remember playing some MIDI files on it and realizing how good it sounded compared to my basic SoundBlaster 16, which made me go out and get a SB AWE32.
I'm surprised there's no mention of QBasic that shipped with MS-DOS >= 5.0. This was built on top of EDIT.COM, and while it only ran a BASIC interpreter instead of compiling an executable like full-blown QuickBasic.
IIRC it had a rather extensive help lookup system for functions, data types, reference tables, error codes, and whatnot. You could step through your program, set debug points, all without exiting to DOS. It was my first ever exposure to an IDE, I thought it was pretty nice for what it was.
Traffic to vs through a router; both UDP and ICMP probes to a given hop will both go to the control plane which can be rate limited or handled by a general purpose CPU.
Probes to hops beyond will virtually always go through the fast data plane.
Usually this meant the new neighborhood was put behind a subscriber loop carrier (SLC) which added an extra analog/digital conversion. Voice calls were getting digitized locally, sent across a T1 (only 4 wires needed, instead of 96-192), and back to analog to the normal frame at the CO. The effect of this was the telltale sign of carrier speeds only hitting 26,400 bps.
To nitpick, the 53.3k limit only affected US Robotics' pre-V.90 standard called X2, due to how much power they would require, which violated FCC rules. K56Flex (the competing 56k protocol), and later the ratified V.90 standard didn't have this problem and you could achieve carrier speeds of 56,000 bps.
There's still a decent community of people running them either for nostalgia and/or bringing them into the Internet area. Some are telnet/ssh only, some have actual dial-up modems too.
I set up Wildcat! 4 (a DOS based BBS software) earlier this year and have had a blast with reliving the past. It was interesting to figure out how true to period vintage to run it vs letting some newness leak in, with 30 years of hardware and connectivity options to select from.
I wound up doing both dial-up and telnet access, and just last week got an UUCP gateway setup so it can dial out to a Raspberry Pi and send/receive internet email.
In my younger times I used to go to a lot of livestock auctions with the family. There was always a goat just casually standing by next to the egress gate of the arena to lead these panicked animals out, walk back in, and they would always follow it out
I recently tried this for making a YT video using an ATA with a USR Courier dialing into a ISP's POP in San Jose. V.92 flat out didn't work for me, but V.90 did. Surprisingly I was able get 50-53k downstream carrier rates, upstream was pretty lousy at 14.4-16.8k. The calls only lasted a couple of minutes before they were unable to renegotiate. 28.8k was much more reliable.
Most people tended to use their own ISP's mail servers back then. Hotmail, Yahoo, and AOL were the only third-party email services around, before the likes of Gmail took off. It would be trivial to go look at mail server logs to see if X login was connecting every X minutes.
Encryption was seldom used there for POP3/IMAP/SMTP because hey you're on the same ISP network and not crossing the Internet. Further it was pretty easy to hop on a terminal server like a Portmaster and do a debug/packet dump of individual dialup connections if somebody really wanted to see what somebody was doing.
As an small ISP owner in the 90s, there was no way to win. Incoming phone lines were a considerable hunk of your expenses so you wanted to have enough available at peak time in the evenings to not have busy signals. Smaller POPs may have only had a couple dozen phone lines. For the very vast majority of subscriber, they'd dial up for 2-6 hours, browse the web and whatnot, and disconnect. I hated the "unlimited" thing at the time because it was so shady for reasons like this. But, if you tried to sell "X hours per month" people really didn't like knowing they were on the clock, and if you tried to market it as "unmetered" then you got nailed by people saying "well what's the difference between unmetered and unlimited??" (I tried both). In retrospect I probably should've just played along with "unlimited" and fired/ran off my customers who kept connections nailed up for 20 hours a day.