LaForge's home page (Posts about retronetworking)

RetroNetCall: "Datex-L, the German CSPDN"

Harald Welte — Tue, 31 Jan 2023 16:00:00 GMT

I've presented about Datex-L, the German CSPDN (Circuit Switched Public Data Network) as part of the RetroNetCall talk series on retro-networking technology.

You can find the video recording at https://media.ccc.de/v/retronetcall-20230201-laforge-datex-l-cspdn

I've always been fascinated by "ancient" data communications - both the kind that I personally consciously witnessed from the late 1980s as well as the kind that I never experienced myself (like Datex-L).

I am not an expert in the subject by all means, as I was never involved in its design, implementation or even used it. However, given that there's very few public information online about Datex-L and/or other CSPDNs, I thought I could improve the situation by presenting about it.

RetroNetCall: "ISDN B-Channel protocols"

Harald Welte — Tue, 06 Dec 2022 16:00:00 GMT

I've presented about ISDN B-Channel protocols (X.75, V.120, V.110, T.70, ...) as part of the RetroNetCall talk series on retro-networking technology.

You can find the video recording at https://media.ccc.de/v/retronetcall-20221207-laforge-isdn-b-channel-protocols

Many people with some kind of telecom background are familiar with D-channel (signalling) protocols of ISDN, and you can find many publications on that topic. Surprisingly, much less publications are talking about the B-channel protocols used for data transmission, like VX.75, V.110, V.120, T.70, ...

RetroNetCall: "OCTOI project status update"

Harald Welte — Tue, 08 Nov 2022 16:00:00 GMT

I've presented an OCTOI project status update (Nov 2022) as part of the RetroNetCall talk series on retro-networking technology.

You can find the video recording at https://media.ccc.de/v/retronetcall-20221109-laforge-octoi-status-update

Deployment of future community TDMoIP hub

Harald Welte — Sun, 18 Sep 2022 16:00:00 GMT

I've mentioned some of my various retronetworking projects in some past blog posts. One of those projects is Osmocom Community TDM over IP (OCTOI). During the past 5 or so months, we have been using a number of GPS-synchronized open source icE1usb interconnected by a new, efficient but strill transparent TDMoIP protocol in order to run a distributed TDM/PDH network. This network is currently only used to provide ISDN services to retronetworking enthusiasts, but other uses like frame relay have also been validated.

So far, the central hub of this OCTOI network has been operating in the basement of my home, behind a consumer-grade DOCSIS cable modem connection. Given that TDMoIP is relatively sensitive to packet loss, this has been sub-optimal.

Luckily some of my old friends at noris.net have agreed to host a new OCTOI hub free of charge in one of their ultra-reliable co-location data centres. I'm already hosting some other machines there for 20+ years, and noris.net is a good fit given that they were - in their early days as an ISP - the driving force in the early 90s behind one of the Linux kernel ISDN stracks called u-isdn. So after many decades, ISDN returns to them in a very different way.

Side note: In case you're curious, a reconstructed partial release history of the u-isdn code can be found on gitea.osmocom.org

But I digress. So today, there was the installation of this new OCTOI hub setup. It has been prepared for several weeks in advance, and the hub contains two circuit boards designed entirely only for this use case. The most difficult challenge was the fact that this data centre has no existing GPS RF distribution, and the roof is ~ 100m of CAT5 cable (no fiber!) away from the roof. So we faced the challenge of passing the 1PPS (1 pulse per second) signal reliably through several steps of lightning/over-voltage protection into the icE1usb whose internal GPS-DO serves as a grandmaster clock for the TDM network.

The equipment deployed in this installation currently contains:

a rather beefy Supermicro 2U server with EPYC 7113P CPU and 4x PCIe, two of which are populated with Digium TE820 cards resulting in a total of 16 E1 ports
an icE1usb with RS422 interface board connected via 100m RS422 to an Ericsson GPS03 receiver. There's two layers of of over-voltage protection on the RS422 (each with gas discharge tubes and TVS) and two stages of over-voltage protection in the coaxial cable between antenna and GPS receiver.
a Livingston Portmaster3 RAS server
a Cisco AS5400 RAS server

For more details, see this wiki page and this ticket

Now that the physical deployment has been made, the next steps will be to migrate all the TDMoIP links from the existing user base over to the new hub. We hope the reliability and performance will be much better than behind DOCSIS.

In any case, this new setup for sure has a lot of capacity to connect many more more users to this network. At this point we can still only offer E1 PRI interfaces. I expect that at some point during the coming winter the project for remote TDMoIP BRI (S/T, S0-Bus) connectivity will become available.

Acknowledgements

I'd like to thank anyone helping this effort, specifically * Sylvain "tnt" Munaut for his work on the RS422 interface board (+ gateware/firmware) * noris.net for sponsoring the co-location * sysmocom for sponsoring the EPYC server hardware

Progress on the ITU-T V5 access network front

Harald Welte — Thu, 08 Sep 2022 16:00:00 GMT

Almost one year after my post regarding first steps towards a V5 implementation, some friends and I were finally able to visit Wobcom, a small German city carrier and pick up a lot of decommissioned POTS/ISDN/PDH/SDH equipment, primarily V5 access networks.

This means that a number of retronetworking enthusiasts now have a chance to play with Siemens Fastlink, Nokia EKSOS and DeTeWe ALIAN access networks/multiplexers.

My primary interest is in Nokia EKSOS, which looks like an rather easy, low-complexity target. As one of the first steps, I took PCB photographs of the various modules/cards in the shelf, take note of the main chip designations and started to search for the related data sheets.

The results can be found in the Osmocom retronetworking wiki, with https://osmocom.org/projects/retronetworking/wiki/Nokia_EKSOS being the main entry page, and sub-pages about

In short: Unsurprisingly, a lot of Infineon analog and digital ICs for the POTS and ISDN ports, as well as a number of Motorola M68k based QUICC32 microprocessors and several unknown ASICs.

So with V5 hardware at my disposal, I've slowly re-started my efforts to implement the LE (local exchange) side of the V5 protocol stack, with the goal of eventually being able to interface those V5 AN with the Osmocom Community TDM over IP network. Once that is in place, we should also be able to offer real ISDN Uk0 (BRI) and POTS lines at retrocomputing events or hacker camps in the coming years.

Retronetworking at VCFB 2022

Harald Welte — Thu, 08 Sep 2022 16:00:00 GMT

I'm happy to announce active participation at the Vintage Computing Festival Berlin 2022 in two ways:

Running a retronetworking exhibit on Modem and ISDN dial-up
Giving a talk on the Osmocom Community TDMoIP netwokr

The exhibit will be similar to the exhibit at the retrocomputing village of the last CCC congress (36C3): A digital telephony network with ISDN BRI and POTS lines providing services to a number of laptops with Modems and ISDN terminal adapters.

We plan to demo the following things: * analog modem and ISDN dial-up into BBSs ** text / ANSI interfaces via Telix, Telemate, Terminate ** RIPterm graphical interfaces * analog modem and ISDN dial-up IP/internet * ISDN video telephony

The client computers will be contemporary 486/Pentium machines wit DOS, Windows 3.11 and OS/2.

OsmoDevCall: "Retronetworking: V5 interfaces in ISDN/PSTN"

Harald Welte — Mon, 27 Dec 2021 16:00:00 GMT

I've presented on Retronetworking: V5 interfaces in ISDN/PSTN as part of the OsmoDevCall talk series on Osmocom and related technology.

You can find the video recording at https://media.ccc.de/v/osmodevcall-20211228-laforge-retro-isdn-v5

OsmoDevCall: "E1, TDM, PDH, SDH, Basics"

Harald Welte — Thu, 11 Nov 2021 16:00:00 GMT

I've presented on E1, TDM, PDH, SDH, Basics as part of the OsmoDevCall talk series on Osmocom and related technology.

You can find the video recording at https://media.ccc.de/v/osmodevcall-20211112-laforge-tdm