[sf-lug] tcptraceroute, traceroute, Westell, ... Got router? / Where *is* that ("other") router? (linuxmafia.com)

[Rick Moen]

Quoting Justin Noor (justinnoor.io at gmail.com):

> I meet a lot of people who’ve had issues with AT&T modems. Of course there
> are too many variables to name, but could there ever be an open source DSL
> modem for AT&T?

To clarify again, these are usually described as 'ADSL modems', but 
are only vaguely similar to traditional modems.  On a network 
level, they are merely network bridges as deployed by me and Michael.
Which is to say, the two models discussed upthread are capable of
operating in a non-bridge mode where they have various router
& related capabilities, but are being used in this context _just_ 
in bridged mode, with that other stuff deliberately disabled.

The device modulates high-frequency tones for transmission to a digital
subscriber line access multiplexer (DSLAM), and receives and demodulates
them from the DSLAM.  (Which is the way in which they're kinda-sorta the
same as old-school modems.)

IIRC, one of these boxen consists of:

o  PSU, connector hardware widgets, chassis, and like that
o  a digital data pump chip
o  an analog chip, and a line driver
o  a bitty little microcontroller
o  a line filter

All of this is doubtless initialised and run by custom firmware.

Could someone write replacement open-source firmware?  Sure, could
happen.  Not likely, though.  Nobody wrote open-source firmware for your 
modem back in the 1980s and 1990s, either.


I'll also mention -- reiterate -- that neither Michael nor I uses AT&T.
We use Raw Bandwidth Communications, which is a CLEC, a competitive
local exchange carrier.  AT&T's role is an unfortunately unavoidable but
incidental one, of being the ILEC, the incumbent local exchange carrier
-- the asshats who own (in my case) the local exchange 'central office'
(CO) in downtown Menlo Park and the ~2 miles of copper twisted pair
wiring underneath Menlo Park streets connecting the CO westwards to my
house in University Heights, unincorporated San Mateo County.  The
ILEC's job, by law, in this connection, is to stay out of way of the
various CLECs, serve as a neutral connection point for them to connect
to their customers (sharing the ILEC's copper cable), and avoid shooting
the CLEC and the CLEC's customers in the foot.

In the latter area, staying out of the way and not shooting a
competitive carrier in the foot, AT&T screwed up and didn't bother to
fix its problem (whatever that problem was) for about 2 days and 7
hours.

Remember, when you decide whom to do business with, that this is a firm
that behaves that way.  I certainly will.