Netheads vs. bellheads redux: the strange victory of SIP over the
telephone network
by Hugo Landau, 2023-01-27
- https://www.devever.net/~hl/sip-victory

"How much do you know about how the PSTN (that is, the public
telephone network) works? At some point long long ago, it was
signalled using in-band frequencies, which facilitated the infamous
phreaking using so-called "blue boxes". This led to a switch to out
of band signalling, ultimately culminating in something known as
Signalling System 7 (SS7). SS7 traditionally was carried over
things like a T1/E1 or similar. The standards for SS7 are defined
by the ITU-T and have basically no "cultural" relation to the
Internet or IP. Ultimately, it defines a circuit switched
communications network based around separated signalling and
time-division-multiplexed (TDM) voice channels.
And then, of course, the internet happened. This led to an
interesting conflict between two fundamentally different cultures
of networking and associated visions. This has been popularly
documented as the "netheads vs. bellheads" phenomenon. The
difference between these worldviews is fundamental. The bellhead
view saw communications in terms of circuit switching, and viewed
applications as being integrated into a smart network and provided
by the telco.
It's actually interesting to note just how oblivious the bellhead
world was to its ultimate fate. Once upon a time, I flipped through
some old books about ISDN out of idle curiosity. One of the
striking things was the repeated use of the term "datacom", a term
which now seems basically extinct. The reason I found this striking
is because it implies that, to those working in the telco field at
the time, "datacom" was not the primary purpose of a network but a
kind of strange aside, a peculiar niche addition. From the modern
perspective this worldview seems almost comical; ironically, the
term datacom is no longer relevant because everything is "datacom".
" ...

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Am 29.03.2023 um 07:38:58 Uhr schrieb Computer Nerd Kev:

> "How much do you know about how the PSTN (that is, the public
> telephone network) works?

That was a long time ago. At least in Germany, they switched it off in
the 90s and completely replaced it by ISDN. Analog ports at the
telephone exchange were available for people who liked to continue
using the analog line.

> It's actually interesting to note just how oblivious the bellhead
> world was to its ultimate fate. Once upon a time, I flipped through
> some old books about ISDN out of idle curiosity. One of the
> striking things was the repeated use of the term "datacom", a term
> which now seems basically extinct. The reason I found this striking
> is because it implies that, to those working in the telco field at
> the time, "datacom" was not the primary purpose of a network but a
> kind of strange aside, a peculiar niche addition. From the modern
> perspective this worldview seems almost comical; ironically, the
> term datacom is no longer relevant because everything is "datacom".

ISDN is a concept from the 80s - fax machines were modern, connections
were expensive, Telex was still in broad use. The internet took over
and for most people VoIP via SIP/RTSP is fine.
Many young people don't have a "landline" phone anymore - they use
different apps on the smartphone to phone people. In school I rejected
to use them. People have to communicate with me via normal phone or email.

ISDN - at least in Germany - has been switched off. Analog lines are
still available via analog ports in MSAN (DSLAM), but are terminated to
VoIP.
Much cheaper for the ISP.
ATM is also being phased out, many ISPs here switched it off and
replaced it by Ethernet.

Computer Nerd Kev <not@telling.you.invalid> wrote:

> And then, of course, the internet happened. This led to an
> interesting conflict between two fundamentally different cultures
> of networking and associated visions. This has been popularly
> documented as the "netheads vs. bellheads" phenomenon. The
> difference between these worldviews is fundamental. The bellhead
> view saw communications in terms of circuit switching, and viewed
> applications as being integrated into a smart network and provided
> by the telco.

Today, with video and audio routed over the internet, the circuit
switching model's advantages come back. Being able to set up a virtual
circuit at the start of a video call, with predictable latency and
bandwidth, could go a long way towards making things work better. Not
that I think we're likely to see this change -- but it's an interesting
thought experiment about an internet that never was.

Alex Martini <alex.martini@icloud.com> wrote:
>Computer Nerd Kev <not@telling.you.invalid> wrote:
>
>> And then, of course, the internet happened. This led to an
>> interesting conflict between two fundamentally different cultures
>> of networking and associated visions. This has been popularly
>> documented as the "netheads vs. bellheads" phenomenon. The
>> difference between these worldviews is fundamental. The bellhead
>> view saw communications in terms of circuit switching, and viewed
>> applications as being integrated into a smart network and provided
>> by the telco.
>
>Today, with video and audio routed over the internet, the circuit
>switching model's advantages come back. Being able to set up a virtual
>circuit at the start of a video call, with predictable latency and
>bandwidth, could go a long way towards making things work better. Not
>that I think we're likely to see this change -- but it's an interesting
>thought experiment about an internet that never was.

The phone guys saw it coming and came out with ATM/Sonet which was designed
from top to bottom to allow circuit-switched connections and packet-switched
connections on the same network. But in the end, the cheapest possible
solution won out instad.

When I was a child, everyone predicted that when I grew up we would have
electricity that was too cheap to meter. That didn't happen, but we did
get long distance service that was too cheap to meter. Nobody ever predicted
that one.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."