Subject: UNH problems

From: Richard Draves <[email-masked]>
Date: Thu, 10 Jun 1999 11:32:49 -0700

Reviewing our latest UNH test results, there are a couple failures reported
where it looks to me like the test is wrong.

I believe we've already discussed one of them. The NUT (node under test) is
sending a packet via a default router, but the packet is queued while the
NUT performs Neighbor Discovery to resolve the router's link-layer address.
When the NUT receives the Neighbor Advertisement for the router, it
discovers that the router is actually not a router any more (IsRouter is
false). This causes the router to be removed from the NUT's default router
list. However our implementation proceeds to send the packet that was
pending ND. UNH says this is wrong.

The other failure concerns section 6.3.5 in the ND spec. The NUT has a
prefix in the on-link prefix list, and it has created a Destination Cache
Entry based on the on-link prefix. When the on-link prefix is removed
(either because its lifetime goes to zero, or because an RA is received
setting its lifetime to zero), can the Destination Cache Entry immediately
be purged, so subsequent packets to the destination will create a new DCE
using a default router? Section 6.3.5 notes that the DCE "need not" be
purged, because NUD will correct the situation if the destination address is
in fact no longer on-link. However there is no MUST in section 6.3.5 to
mandate this behavior. It happens to be convenient for our implementation to
purge the DCE immediately but UNH says this is wrong.

Any comments on these tests?

Thanks,
Rich
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From: Francis Dupont <[email-masked]>
Date: Fri, 11 Jun 1999 10:23:36 +0200

In your previous mail you wrote:

=> I believe MSR IPv6 behavior is correct even not optimal
(ie. problems lay between SHOULD and MAY). I don't know
if there is a Neighbor Discovery perfect implementation
somewhere, especially for marginal events.

[email-masked]

PS: look at Richard's message for the description of the two issues.

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From: "John F. Leser" <[email-masked]>
Date: Tue, 15 Jun 1999 09:35:10 -0400

> Any comments on these tests?

These tests check for optimal behavior, above and beyond what is
strictly required by the specifications.  Failure does not indicate a
failure to conform to the specification or to interoperate with other
implementations; it does indicate that there is another, possibly better
way to handle the test situation.  I say possibly because there may be a
cost associated with an optimization that makes it not worthwhile.
       
We will be making changes to how we report test results to indicate the
requirement level for each test, in order to eliminate this kind of
confusion.

***************************************************************** 
John Leser                            InterOperability Lab 
IP/Routing Consortium Engineer        University of New Hampshire
                                      7 Leavitt Lane, Room 106
Tel:   (603) 862-0090                 Durham, NH 03824-3525
Fax:   (603) 862-4181
Email: [email-masked]                Web: http://www.iol.unh.edu