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

From: Vernon Schryver <[email-masked]>
Date: Tue, 14 Mar 2000 12:17:29 -0700 (MST)

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

> ...
> As I recall, the last discussion petered out with the question that using
> DHCP may involve a change in the semantics of the DHCP subnet option.  I
> don't believe we (the group) answered that, nor did we answer how to resolve
> the issue that the DHCP and RADIUS information reside on if not two
> different machines then two different databases, which brings the question
> of how to authorise the remote end via RADIUS to use a particular subnet
> that is doled out via DHCP.

I don't recall the leading contender for the right place to put the
netmask.  Assuming it was DHCP, you already have DHCP and RADIUS involved
in most such PPP session.  Adding the IPCP state machine can only
exacerbate any problems with multiple databases.  DHCP and RADIUS
are not exactly strangers to PPP today.

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

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.

Vernon Schryver    [email-masked]

---

From: Rene Tio <[email-masked]>
Date: Tue, 14 Mar 2000 23:10:13 -0800

> 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.

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.

Note I have since passed on to another life, and have not kept up with new
developments.

> The netmask of other network than the PPP link simply does not belong

Unfortunately that decision isn't in our hands.  I know of at least one
vendor who already does this.

Rene