Subject: Re: draft-helenius-ppp-subnet-00.txt

From: Vernon Schryver <[email-masked]>
Date: Wed, 15 Mar 2000 08:28:26 -0700 (MST)

> From: Rene Tio <[email-masked]>

> ...
> > Changing DHCP, if necesssary, surely would not be any more difficult
> > than changing IPCP.  Even if it were more difficult (and never mind
> > the recent blizzard of I-D's proposing changes to DHCP), the primary
> > criterion should be technical correctness, not political expediency
>
> I disagree with the first statement.  Ignoring the other arguments, changing
> IPCP to pass subnets is very simple.  Changing DHCP would require adding
> authorisation hooks into RADIUS to see if a user is allowed a particular
> sized subnets, or syncing the databases manually or via a new protocol so
> that if DHCP sees a particular address it knows it should hand out a
> particular subnet.  Then you need to add a new message so the server can
> unilaterally yank the address and subnet away from the current CPE and dole
> it out to someone else.

I don't see why you need to do any of that to DHCP:

   - you couldn't "yank the address and subnet away from the current CPE"
      with the proposed IPCP change

   - any synchronizing between RADIUS and DHCP that is needed would
      also be needed between PPP and RADIUS and DHCP.

   - how do RADIUS and DHCP current talk to each other when DHCP hands ou
      the correct IP address based on a RADIUS profile?

   - if DHCP does or does not now need authorization hooks for handing out
      host addresses, why would it need or not need authorization hooks
      for handing out network numbers

   - note the recent Internet-Drafts about authorization hooks in DHCP.

> While I agree that IPCP subnet is not the right way, especially given the
> many times it has been discarded, I don't see any other option currently
> solving this problem in a timely fashion.

Exactly what problem needs solving in a timely fashion?  

> ...
> > PPP is a point-to-point protocol.  The notion of netmask is unrelated
> > to the problems PPP is intended to address.  The IP address negotiated
> > by IPCP is related to other network interfaces on the point-to-point
> > router by at most convention, and today generally not even that (consider
> > NAT routers).  
> > It is as wrong to shove DNS into PPP as to push routing into PPP.
> > The netmask of other network than the PPP link simply does not belong
> > in PPP.
>
> Unfortunately that decision isn't in our hands.  I know of at least one
> vendor who already does this.

What do you mean by "this"?  Yes, I know of the Microsoft DNS garbage,
but do you mean that some others at some other vendor have shipped this
IP netmask nonsense?  Contrary to the to-be-determined blank for the
IPCP option number in the I-D?  If so, the IETF should finally put
its foot down, and refuse to publish this nonsense even as Informational,
because in view of the previous cycle of this discussion such an action
would have demonstrated bad faith on the part of those who did it.
The IETF has become too accomodating to the Microsoft style of 
trash-an-IETF-protocol-and-then--get-IETF-sanction.

And by the way, why was the draft not announced to the PPP mailinglist?

Vernon Schryver    [email-masked]

---

From: Rene Tio <[email-masked]>
Date: Wed, 15 Mar 2000 09:36:35 -0800

I'm going to have to make this my last email on the subject because (a) I no
longer do this stuff, and (b) I feel somewhat silly defending this in a
public forum, especially when the authors haven't spoken up, and when
neither I nor Redback had anything to do with the draft, nor do I/we
necessarily want to.  I'd just like to see the problem solved instead of
peter out like last time without a clear direction.

The implicit assumption in this model is that there is no DHCP server.
There is a RADIUS which contains the user record, including the size of the
users' subnet and most likely a static IP address.  Instead of a static IP,
there was thought to use a pool in the NAS, which hands out address in
increments according to a subnet size (different pools for different subnet
sizes).  I don't believe anyone is doing the latter today, since it
introduces other problems, however using a pool was seen as an advantage
since one could oversubscribe when deploying a not-always-on service, and
the NAS could regain addresses by taking down the CPE PPP connection.

Regarding the problem to be solved, it was autoconfiguration of the CPE home
ethernet segment, with autoconfiguration of other parameters a distant
second.  I cannot comment beyond this since I have not kept up with the
latest work in this area, although I would venture a guess that anything
which involves protocols other than RADIUS or DHCP would meet with great
resistance.  When this discussion popped up a year ago I believe several
vendors at least prototyped it.

Finally, I really don't know why the draft wasn't published on the PPP
mailing list since I was not part of it.

Rene

---

From: James Carlson <[email-masked]>
Date: 15 Mar 2000 14:01:14 -0500

[email-masked] (Vernon Schryver) writes:
> IP netmask nonsense?

Yes.  In fact, Juha Heinanen described using option 0x90 on this list
to do subnet assignment back in August last year.  He was told to do
DHCP back then as well.

As he described it, it was explicitly for ADSL.

Actually, his description of the option itself back then was different
from this draft.  I don't know why.  Here's what he wrote:

     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |     Type      |    Length     |             Mask
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Mask (cont)         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    where Type = 0x90 and Length = 0x06.

>  Contrary to the to-be-determined blank for the
> IPCP option number in the I-D?

Ayup.

>  If so, the IETF should finally put

Well, it *is* ADSL.  The same group that gave us PPPoE.  The pattern
is striking, isn't it?

> And by the way, why was the draft not announced to the PPP mailinglist?

Hey, anybody can publish a non-wg document ...

-- 
James Carlson, System Architect                     <[email-masked]>
IronBridge Networks / 55 Hayden Avenue   71.246W   Vox:  +1 781 372 8132
Lexington MA  02421-7996 / USA           42.423N   Fax:  +1 781 372 8090
"PPP Design and Debugging" --- http://people.ne.mediaone.net/carlson/ppp

---

From: James Carlson <[email-masked]>
Date: 15 Mar 2000 16:34:40 -0500

[email-masked] (James Carlson) blathers as though he
> Well, it *is* ADSL.  The same group that gave us PPPoE.  The pattern

As was quite graciously pointed out to me by one of the folks that I
just splattered for no good reason, my comment above is clearly way
out of line.  I apologize.

There is still a coordination problem here.  Some clearly IETF-related
work (like PPPoE and this new subnet option) are being done in an
unrelated forum.  The resulting efforts aren't being reviewed by the
folks nominally responsible for guiding PPP development.  It's
entirely possible that the working group consensus is misinformed and
needs some correction, but that won't happen without at least some
substantive and intentional debate on serious proposals.

This is bad for everyone.  The fundamental network design issues
aren't being addressed and the working group's role is reduced to just
publishing what's already being shipped.  That's not how interoperable
implementations are built.