PPPoE vs. Bridged ADSL

Sean Donelan sean at donelan.com
Thu Oct 29 09:07:12 UTC 2009

On Wed, 28 Oct 2009, David E. Smith wrote:
> With PPPoE, however, the end-user can't just plug in and go - they'll have
> to configure their PC, or a DSL modem, or something. That means a phone call
> to your tech support, most likely. In many cases, DHCP can lead to
> plug-and-play simplicity, which means they don't have to call you, and you
> don't have to answer their calls. Everyone wins. :)

One of the reasons for UUNET's PPPOE design was to reduce phone calls and 
configuration hassles.  But in a different way.  In the "old" days, people 
thought there would be separation between the ISP and the wholesale 
network.  The idea that the provider could control/manage the CPE, like a 
cable set-top box, was probably more radical at the time than a dumb
modem and PPPOE client on the PC.

PPPOE can allow changing ISPs just by changing the username at domain, 
without needing to call wholesale provider's tech support and 
reconfiguring the circuit. You could even have multiple PC's sharing the 
same circuit, each connecting to different ISPs at the same time.  Or use 
PPPOE to "call" a business' DSLAM pool for work access, and then call 
AOL's DSLAM pool for personal use.  The concept of multiple "dialers" was 
well supported on most operating systems, and more familar to the public 
at the time than trying to set hostnames or read MAC addresses in DHCP 

In those days, VPN/IPSEC tunnel support wasn't very common. Businesses 
still had dial-up modem pools, X.25 PADs, and private 
PPP/PPPOE/PPPOA/PPPOx connections.  Compared to the overhead for other 
point-to-point and  tunneling protocols at the time, PPPOE's overhead 
didn't look that bad.  And since it was based on PPP, PPPOE made route 
addressing (and other routing stuff) easy.  Addressing a single host is
the simple case of the more general router PPP information.

As Milo used to say, with enough thrust you could get DHCP to do many of 
those same things too.  There were a lot of experiments, and not all of 
them worked well.

As they say, the world changed.

Ethernet won, vertically integrated ISPs won, VPN won, and yes DHCP 
(with lots of options) won too.  We can have a betamax/vhs-style argument 
of technical superiority; but the market made a choice.

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