[v6ops] draft-elkins-6man-ipv6-diagnostic-header (Was: draft minutes ietf 81, 3 meetings...)

[Carlos Pignataro <[e-mail]>]

Hi,

I believe there was one further point raised in regards to
draft-elkins-6man-ipv6-diagnostic-header (though I don't recall if it
was at the mike by Andrew Y., in a corridor, or only in my head): the
Heisenbug principle -- if this is used in debugging (and diagnostics),
the issue being studied or attempted to reproduce alters its behavior or
goes away when modifying the packet (like compiling with different -o).
I think this is one of the most important arguments against this
proposal. The use of fragment header is interesting, a new header could
show much more pronounced deviation of observed behaviour than without it.

For completeness, I did ask some services escalation engineers about how
they use the ip-id in IPv4 for troubleshooting, and basically got two
main uses for very corner case situations in: i. identify middleboxes
and their characteristics (by check IP ID increment patterns, find if
packets generated by the same box), and ii. track set of packets along
different points in the network (e.g., back-to-back packets and see
rate, drops, out of order). But it's built into the v4 header.

Thanks,

-- Carlos.

On 8/2/2011 1:24 PM, Joel Jaeggli wrote:
> * Presentation - RFC for IPv6 IP identification field (header) - Mike Ackerman
> 	     http://tools.ietf.org/agenda/81/slides/v6ops-7.ppt
> 	     http://tools.ietf.org/html/draft-elkins-6man-ipv6-diagnostic-header
> 
> Fred B - Question for the group, do you use the IPID in ipv4? (no
> respondants other than presenters)
> 
> Weg G - We use it all the time? I've never heard of it...
> 
> Francis D - it's potentially a covert channel, also why not use the
> fregmentation header?
> 
> Bob H - We diefintently want to hear if this is useful. I don't know
> who puts this header in the packet?
> 
> Nalini ? - The host clearly
> 
> Andrei Y - typical use case for this header would be to see if a
> middle box is modifying the packet. 
> 
> Fred B - What I'm out of this discussion is that the application isn't
> a bad one, it could be simulated in a fregment.
> 
> Fred Baker - Meeting complete, go to Lunch