Subject: RE: [LL2]: Explicit Additional Mechanism to disable v4LL

From: "Christian Huitema" <[email-masked]>
Date: Wed, 19 Feb 2003 10:57:53 -0800

> From: Mika Liljeberg [mailto:[email-masked]]
> On Wed, 2003-02-19 at 18:06, Christian Huitema wrote:
> > I agree with KRE's assessment. This is not a security issue, but a
> > usability issue. Suppose a network in which, for whatever reason,
the
> > resident hosts have been configured not to interact with LL
addresses.
> > In such a network, the visiting host which configures an LL address
will
> > find out eventually that it cannot communicate with any other host.
> > Wouldn't it be better to have a way to learn that immediately?
> 
> You mean like put up a popup for the user rather than wait for him to
> try to connect to something? That sounds like a lot of fun waiting to
> happen...

The specific way in which information is conveyed to the user is
certainly out of scope for the IETF -- flashing red LED, red crossed
tray icon, pop up windows, whatever. The general idea is, if it won't
work, find it now. Maybe you can correct that through some action, e.g.
register the visiting host with some management service.

> Besides, if two such nodes are plugged in, wouldn't it be better to
have
> the communicate with each other even if the resident nodes refuse to
> communicate with them?

I guess you can argue that either way. It is certainly the case that if
they have link access today, no DHCP message will prevent two hosts from
communicating using, for example, IPX. So it is a bit hard to argue that
if a host has link access it should not be sending packets.

Maybe the whole LL2 issue is a tempest in a tea cup. After all, we
already have a way to determine that something is wrong: the host knows
that there is a DHCP server, but the DHCP server will not give an
address. This is probably enough to learn that "something is broken" and
display whatever red light is appropriate.

-- Christian Huitema

---

From: Mika Liljeberg <[email-masked]>
Date: 19 Feb 2003 21:11:42 +0200

> display whatever red light is appropriate.

This is my thinking as well.

If this is a usability issue, it should enough to tell the user that
DHCP is not giving out an address.

It surely cannot be a security issue, since any automated measure to
disable LL addressing would require the co-operation of the would-be
attacker.

My conclusion: reject LL2.

	MikaL