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advantages/disadvantages of kernel pppoe(4) vs userland pppoe(8)?



Hi,

I'm about to setup up ADSL at home for the first time, using the
following network topology:

ADSL        +-------+          +----------+         +----------+
to  <-----> |  DSL  |<-------> | firewall | <-----> | ethernet |
ISP         | modem |  pppoe   | + router |         |  switch  |
            +-------+          | + nat    |         +----------+
                               +----------+          |   |    |
                                                     V   V    V
                                                  to other computers

The firewall/router/nat box is (will be when I get this setup)
an old 486 laptop with 2 pcmcia ethernet cards, running 3.9-stable.
(Yes, I've ordered a CD; until it arrives I'm using 3.8-stable.)

I already have the (external) DSL modem, and from talking to other
Unix-savvy customers of my ISP (arcor.de), their setup is that the
DSL modem talks pppoe to me (in this case to my firewall/router/nat
box).  From looking at the FAQ section 6, it seems I have two basic
options available doing this in OpenBSD: pppoe(4) in the kernal, and
pppoe(8) in userland.  My question is, what are the relative
advantages/disadvantages of these?

The obvious tradeoff is performance: I expect pppoe(8) to be slower
due to the extra kernel/user-space crossings for each packet.  My
ADSL is 6M bits/sec downstream, 0.5M upstream.

But are there other significant differences in
* support for pppoe features?
* ease of configuration?
* reliability?

ciao,

--
-- "Jonathan Thornburg (remove -animal to reply)" <jthorn_(_at_)_aei_(_dot_)_mpg-zebra_(_dot_)_de>
   Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
   Golm, Germany, "Old Europe"     http://www.aei.mpg.de/~jthorn/home.html
   "Washing one's hands of the conflict between the powerful and the
    powerless means to side with the powerful, not to be neutral."
                                      -- quote by Freire / poster by Oxfam