Circuit Switched Telephony

Telephony from 1876 until ~ 1988
Analog voice circuit 300-3000 Hz
Dial-up connection between A and B party
Copper wires physically switched at intermediate telephone exchange
Voice signal possibly amplified in the path

Hardware

Telephone
Copper wire
Telephone Exchange

Accoustic Coupler

First devices to transmit bits as audible tones over telephone
User manually dialled phone number like voice call
After call was established, both sides put receiver into coupler

images/accoustic_coupler.jpg

Modems

Automatization of the accoustic coupler

Avoid speaker/micrphone path
directly generate/receive tones on phone line
directly dial the phone number / answer the line

images/Modems.jpg

Modem Speeds / Standards

Standard	Rate (bps)	Year created
V.21	300	1962*
V.22	1200	1980*
V.22bis	2400	1984*
V.32	9600	1984*
V.32bis	14400	1991
V.32ter	19200	1993
V.34	28000	1994
V.34bis	33600	1996
V.90	56000	1998

BBSs

What’s a BBS?

Computer with Modem accepting incoming calls
offering interactive service to users who dial in

Content

bulletin boards / message boards
live chat with sysop (or other users in multi-line BBS)
multi-user games (text based!)
file areas / downloads
ASCII / ANSI artwork

images/dosbox-telemate-login.png

Technology/Software

Both sides: Computer + Modem
BBS Side
- BBS Software
- often extended by "doors" (external programs, think of CGI for web)
User Side
- Terminal Program (e.g. TELIX, Telemate for DOS)

images/telemate.jpg

The "BBS Protocol Stack"

In the spirit of protocol stack diagrams…

images/bbs-protocol_stack.svg

Curiosity: Vector Graphics

BBSs were typically all Text, mostly ANSI CP437 charset
RIP (Remote Imaging Protocol) / RIPscrip introduced vector graphics
- RIPscrip introduced in 1992 (by TeleGrafix)
  - Commands like “!|w00001B0M10” to draw vector graphics over Modem
- RIPterm as terminal program for EGA (640x350)

images/Nouveau.png

Isolated BBSs

To participate in bulletin/message boards

Users log in at different times
BBS is busy while a user is logged in
Multiple modems / phone lines is one (expensive) option to scale
Time limit per User (minutes/day) often used

Points / Offline Messages

Users don’t read/write interactively during active modem call
Messages get written offline and compressed/batched during short call

Advantages:

lower cost (shorter phone calls, metered!)
shorter connection per user
BBS can scale to more users this way

images/xpmenu.gif

BBS networks (store + forward)

Idea: Replicate bulletin / message boards between independent BBSs, for

scalability in number of users
scalability in geographic scope
- most users will prefer least-expensive local calls to long-distance
efficient transport over long distance due to routing/forwarding of compressed batches

BBS network technology (examples)

FIDO (Netmail + Echomail)
- Othernets like TrekNet, GerNet using same FTN technology
Z-Netz (Mail + News)
- T-Netz, CL-Netz
UUCP (Usenet Mail + News)
- Often only way to access "Internet" before IP access was available
MausNet - Münster Apple User Service
- used by up to 120 BBSs in DE / AT / CH

Example: FIDOnet

Starts in 1984 with two BBSs
Initial limit of 250 nodes reached in 1985
Hierarchic, Regoinal routing/Adressing introduced in 1986
- Nodelist defines all nodes of the network + hierarchy
Addresses like "Harald Welte @ 2:2490/1343"
Up to 39,000 nodes in 1996, estimated 2 Million users world-wide

Example: Z-Netz

Started as Zerberus-Netz implemented in Zerberus Software
Later renamed to Z-Netz as the ZConnect protocol was implemented in other software
- Standards defined based on perceived complexity of RFCs and Usenet/UUCP
CrossPoint (DOS) most popular point software for ZConnect
Addresses like H.WELTE@SILVER, later H.WELTE@SILVER.zer

Example: UseNet

Established in 1980 in the US
Uses UUCP (Unix-to-Unix-Copy) as transport mechanism over Modmes
- UUCP was created in the 1970ies and used to copy files, including Internet Mal
Usenet News format (RFC850) designed very similar to Internet Mail (RFC822)
Hierarchy of News Groups that gets replicated / flooded accross the network
Routing defined in route maps

Curiosity: Floppy Poll/Point

Not everyone had a phone line in the 1990ies
- particularly Eastern Germany had big lack of phone lines
Some people thus exchanged daily floppies in evenlopes and mailed them as postal letters
Messages arrived about one day later, but with 1-2 days latency even inside the dial-up store-and-forward network, it hardly matters

images/floppy-disk-1219954_640.png

Internet

Early ways to access Internet:

Mail/News via UUCP (as stated earlier)
Dial-Up Modem to a TTY of a Unix machine connected to TCP/IP
- Often workstations at universities. You could then run FTP, IRC, telnet, Gopher on the test console
ftp-mailers
- a FTP client running on a remote machine, whose input/output is used by e-mail
- you send a mail with "ftp ftp.sun.com" and "ls"
- hours or days later you get the list of files
- you respond with cd / get / …
- hours later you get the file as batch of UUencoded mails

Internet with SLIP

if you had dial-up access to a Unix box
you could run SLIP on both sides, transporting IP over the modem line
- IP. At home. In your apartment !!1!
later superseded by PPP (auto-configuration, authentication, compression, …)

ISDN

Digital Circuit-Switched Telephony Network
- Transport of Digital Voice (PCM) audio and transparent digital data
Germany
- 1989 put in operation
- Until 1993 German 1TR6 system
- From 1994 European E-DSS1
- Hugely popularized from 1995 by subsidies

ISDN Terminal Adapter

ISDN is an all-digital network
No modulator / demodulator required
Instead, so-called terminal adapter
Speeds: 64000 (single B-channel) or 128000 (both B-channels)
V.110 as adaptation to do async serial over sync ISDN (1988)

images/isdn.jpg

How to get Internet Access?

Hard to access in early/mid 1990ies outside of academia
Almost no commercial ISPs (XLink, EUnet) - and very expensive
Grass-Roots groups of enthusiasts established themselves
Kommunikationsnetz Franken e.V. (KNF, franken.de) one of them
- dial-up UUCP and shortly later IP for personal, non-commercial users
- POPs in Nürnberg, Fürth, Erlangen, Forchheim, Würzburg, Regensburg, …
- Every user got 6 static IP addresses routed to wherever he dialed in (OSPF!)
- served ~ 800 users / members at peak

Individual Network (IN) e.V.

Umbrella Association established in 1992
- Goal to help regional member associations with negotiating framework contracts
- Actual technical access via WiN/DFN, XLink, EUnet
- Regional Member Associations include Oche, Augusta, Escape, IN-Berlin, Hanse, INKA, Toppoint, muc.de, IN-Passau, ThurNet, MAUS, CL-Net and many more
- IN members served more than 300,000 users at one point
- Dissolved in 2000, when
  - commercial ISPs were widespread, and
  - remaining IN member organizations could get decend connectivity with IN e.V.

Internet

With packet-switched TCP-IP

you just needed to dial one number
and then access systems world-wide

This brought new purpose to leased lines

Analog Leased Lines

Telephone operator permanently interconnects wires at exchange
No signaling (dialtone/ringtone etc)
Requires modems with special capabilities
- ATA without an incoming ring first
- ATD without a dialtone first
In Germany: "Analog G" of Post/Telekom
- I finally could afford one in 1998
- 900 DM installation cost
180 DM per month (60 DM per hop)

hub-nbg.franken.de, 1998

images/pict3_Lg.jpg

ISDN Leased Lines "SPV"

Not really a leased line
Basically only "flat rate calls" to one specific (fixed) destination
Available in national 1TR6 only

Abusing Analog Lines, Part 1

ICU-T
- inverse of ISDN NTBA
- ISDN BRI (2x64k + 16k) over 12km of telephone line
Special ISDN routers without signaling to use even 16k D-channel for data!

Easy upgrade to get performance of a leased ISDN line out of an Analog-G

Leased Lines at KNF, 1997/1998

hub-fue.franken.de, undated

images/hub-fue-03_Lg.jpg

Abusing Analog Lines, Part 2

When the first DSL modems became availale in the US

we imported some Ascend DSLpipe
with some fimrwares, they could be used back-to-back (without DSLAM)
suddenly we could get speeds of 2.3 MBps over analog lines
- if they were not too long
- if they didn’t have in-line inductors
soon less expensive alternatives came up Pairgain (2000)

images/ascend.jpg

From Online Bistro to Internet Cafe

Falken’s Maze was an Online Bistro established in the 1990ies
- I became a regular around 1994
initially had four DOS PCs, each with a Modem, dedicated phone line and a call charge meter
- you could go there, eat + drink and use the PCs to log into BBSs
quickly became preferred meeting point of various nerds, BBS users, SYSOP meetings, etc.
PCs were networked with 10base2 and NetWare (DOOM!)
people started to dial into CompuServe, AOL, etc.
Internet became more popluar, Falken’s Maze started subsidiary in Nuernberg
- ISDN SPV was used as Intenret uplink

EOF

End of File

BBSs and Early Internet Access in Germany

Circuit Switched Telephony

Hardware

Accoustic Coupler

Modems

Modem Speeds / Standards

BBSs

Content

Technology/Software

The "BBS Protocol Stack"

Curiosity: Vector Graphics

Isolated BBSs

Points / Offline Messages

BBS networks (store + forward)

BBS network technology (examples)

Example: FIDOnet

Example: Z-Netz

Example: UseNet

Curiosity: Floppy Poll/Point

Internet

Internet with SLIP

ISDN

ISDN Terminal Adapter

How to get Internet Access?

Individual Network (IN) e.V.

Internet

Analog Leased Lines

hub-nbg.franken.de, 1998

ISDN Leased Lines "SPV"

Abusing Analog Lines, Part 1

Leased Lines at KNF, 1997/1998

hub-fue.franken.de, undated

Abusing Analog Lines, Part 2

From Online Bistro to Internet Cafe

Further Reading

EOF