PPPoE vs. Bridged ADSL

Thu Oct 29 13:11:27 UTC 2009

This current draft

DHCP Authentication                 

http://www.ietf.org/id/draft-pruss-dhcp-auth-dsl-06.txt

Adds the username/password that PPP has to DHCP and I believe support IPv6.

Vince

-----Original Message-----
From: Sean Donelan [mailto:sean at donelan.com] 
Sent: Thursday, October 29, 2009 5:07 AM
To: nanog at nanog.org
Subject: Re: PPPoE vs. Bridged ADSL

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 configurations.

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.