Retronetworking / BBS-Revival setup at #36C3

Harald Welte — Sat, 04 Jan 2020 16:00:00 GMT

After many years of being involved in various projects at the annual Chaos Communication Congress (starting from the audio/vidoe recording team at 15C3), I've finally also departed the GSM team, i.e. the people who operate (Osmocom based) cellular networks at CCC events.

The CCC Camp in August 2019 was slightly different: Instead of helping an Osmocom based 2G/3G network, I decided to put up a nextepc-based LTE network and make that use the 2G/3G HLR (osmo-hlr) via a newly-written DIAMETER-to-GSUP proxy. After lots of hacking on that proxy and fixing various bugs in nextepc (see my laforge/cccamp2019 branch here) this was working rather fine.

For 36C3 in December 2019 I had something different in mind: It was supposed to be the first actual demo of the retronetworking / bbs-revival setup I've been working on during past months. This setup in turn is sort-of a continuation of my talk at 34C3 two years ago: BBSs and early Intenet access in the 1990ies.

Rather than just talking about it, I wanted to be able to show people the real thing: Actual client PCs running (mainly) DOS, dialling over analog modems and phone lines as well as ISDN-TAs and ISDN lines into BBSs, together with early Interent access using SLIP and PPP over the same dial-up lines.

The actual setup can be seen at the Dialup Network In A Box wiki page, together with the 36C3 specific wiki page.

What took most of the time was - interestingly - mainly two topics:

A 1U rack-mount system with four E1 ports. I had lots of old Sangoma Quad-E1 cards in PCI form-factor available, but wanted to use a PC with a more modern/faster CPU than those old first-generation Atom boxes that still had actual PCI slots. Those new mainboards don't have PCI but PCIe. There are plenty of PCIe to PCI bridges and associated products on the market, which worked fine with virtually any PCI card I could find, but not with the Sangoma AFT PCI cards I wanted to use. Seconds to minutes after boot, the PCI-PCIe bridges would always forget their secondary bus number. I suspected excessive power consumption or glitches, but couldn't find anything wrong when looking at the power rails with a scope. Adding additional capacitors on every rail also didn't change it. The !RESET line is also clean. It remains a mystery. I then finally decided to but a new (expensive) DAHDI 4-port E1 PCIe card to move ahead. What a waste of money if you have tons of other E1 cards around.
Various trouble with FreeSWITCH. All I wanted/needed was some simple emulation of a PSTN/ISDN switch, operating in NT mode towards both the Livingston Portmaster 3 RAS and the Auerswald PBX. I would have used lcr, but it supports neither DAHDI nor Sangoma, but only mISDN - and there are no mISDN cards with four E1 ports :( So I decided to go for FreeSWITCH, knowing it has had a long history of ISDN/PRI/E1 support. However, it was a big disappointment. First, there were some segfaults due to a classic pointer deref before NULL-check. Next, libpri and FreeSWITCH have a different idea how channel (timeslot) numbers are structured, rendering any call attempt to fail. Finally, FreeSWITCH decided to blindly overwrite any bearer capabilities IE with 'speech', even if an ISDN dialup call (unrestricted digital information) was being handled. The FreeSWITCH documentation contains tons of references on channel input/output variables related to that - but it turns out their libpri integration doesn't set any of those, nor use any of them on the outbound side.

Anyway, after a lot more time than expected the setup was operational, and we could establish modem calls as well as ISDN dialup calls between the clients and the Portmaster3. The PM3 in turn then was configured to forward the dialup sessions via telnet to a variety of BBSs around the internet. Some exist still (or again) on the public internet. Some others were explicitly (re)created by 36C3 participants for this very BBS-Revival setup.

My personal favorite was finding ACiD Underworld 2.0, one of the few BBSs out there today who support RIPscrip, a protocol used to render vector graphics, text and even mouse-clickable UI via modem connection to a DOS/EGA client program called RIPterm. So we had one RIPterm installation on Novell DOS7 that was just used for dialling into ACiD Underworld 2.0.

Among other things we also tested interoperability between the 1980ies CCC DIY accoustic coupler "Datenklo" and the Portmaster, and confirmed that Windows 2000 could establish multilink-PPP not only over two B-channels (128 kbps) but also over 3 B-Channels (192).

Running this setup for four days meant 36C3 was a quite different experience than many previous CCC congresses:

I was less stressed as I wasn't involved in operating a service that many people would want to use (GSM).
I got engaged with many more people with whom I would normally not have entered a conversation, as they were watching the exhibits/demos and we got to chat about the technology involved and the 'good old days'.

So all in all, despite the last minute FreeSWITCH-patching, it was a much more relaxing and rewarding experience for me.

Special thanks to

Sylvain "tnt" Munaut for spending a lot of time with me at the retronetworking assembly. The fact that I had an E1 interface around was a good way for him to continue development on his ICE40 based bi-directional E1 wiretap. He also helped with setup and teardown.
miaoski and evanslify for reviving two of their old BBSs from Taiwan so we could use them at this event

The retronetworking setup is intended to operate at many other future events, whether CCC related, Vintage Computing or otherwise. It's relatively small and portable.

I'm very much looking forward to the next incarnations. Until then, I will hopefully have more software configured and operational, including a variety of local BBSs (running in VMs/containers), together with the respective networking (FTN, ZConnect, ...) and point software like CrossPoint.

If you are interested in helping out with this project: I'm very much looking for help. It doesn't matter if you're old and have had BBS experience back in the day, or if you're a younger person who wants to learn about communications history. Any help is appreciated. Please reach out to the bbs-revival@lists.osmocom.org mailing list, or directly to me via e-mail.

LaForge's home page (Posts about bbs)

Retronetworking / BBS-Revival setup at #36C3