Re: [BEHAVE] Fwd: IPv6 hosts sending <1280 byte packets

> -----Original Message-----
> From: behave-bounces@ietf.org 
> [mailto:behave-bounces@ietf.org] On Behalf Of Iljitsch van Beijnum
> Sent: Sunday, February 07, 2010 11:40 AM
> To: behave@ietf.org WG
> Subject: [BEHAVE] Fwd: IPv6 hosts sending <1280 byte packets
> 
> Ben Stasiewics has done some testing to see if hosts actually 
> respond with a fragment header after a < 1280 too big 
> message, and the results are surprising.
> 
> Looks like we can't depend on hosts implementing this correctly.

To be clear, Ben Stasiewicz's test does not determine if the problem is hosts
failing to implement the last paragraph of Section 5 of RFC2460 correctly, or
if host-/network-based firewalls are blocking ICMPv6 packet-too-big messages
or blocking IPv6 packets with the fragment header.

I recently received email from TAHI (http://www.tahi.org), which does IPv6
conformance testing.  Their test is listed at
http://www.ipv6ready.org/docs/Core_Conformance_Latest.pdf and its test
v6LC.4.1.6 ("Receiving MTU Below IPv6 Minimum Link MTU") which appears to have
been tested since 2005.  So any recipient of the IPv6 Ready certification will
implement things correctly.  And there may well be sysctl settings to tweak
this specific behavior.

But no matter the reason, I agree that a greater than 50% failure on the
Internet means the function is effectively broken.  In my view, Ben's testing
invalidates the consensus reached in the meeting at IETF76 (Hiroshima), and I
have asked authors of xlate and xlate-stateful to revise the documents
accordingly.

If anyone thinks we should keep the IETF76 consensus, please speak up now!

-d

> Begin forwarded message:
> 
> > From: Ben Stasiewicz <ben@wand.net.nz>
> > Date: 7 februari 2010 19:39:08 GMT+01:00
> > To: mtu@psc.edu
> > Cc: Matthew Luckie <mjl@wand.net.nz>
> > Subject: Re: IPv6 hosts sending <1280 byte packets [was RE: 
> RRG discussion of SEAL, IPTM - and my critique of RFC4821]
> 
> > On 29/01/10 08:40, Dan Wing wrote:
> >> Ben, would it be possible to conduct a test to see how 
> hosts react to PTB
> >> smaller than 1280?
> 
> > I conducted such a test and found that 299 (43.46%) of the 688
> > IPv6-capable web servers that I tested did include an IPv6 
> fragmentation
> > header in their response packets after they were sent an ICMPv6 PTB
> > message specifying an MTU < 1280 bytes. The other 389 
> (56.54%) did not.
> 
> > I am happy to answer any questions about the test.
> 
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