On Weds, 22 June 2011, Fernando Gont wrote:
On 06/16/2011 02:13 PM, Jean-Michel Combes wrote:
>> o draft-gont-6man-nd-extension-headers
>>
>> IMHO, this is not a good idea to forbid the use of IPv6 extension with
>> NDP messages, especially when the reason is partially based on
>> implementation issues (i.e. the implementation is not able to process
>> an IPv6 packet):
>
> Well, I'd argue that it is an operational issue, rather than an
> implementation issue. -- And chances are that if it is not possible to
> implement a simple solution for this concrete problem, some may start
> filtering *all* packets that include extension headers (in particular,
> those in which the uper layer protocol is not present in the first fragment)
I agree with Jean-Michel Combes and disagree with Fernando.
It absolutely is an implementation issue -- specifically it is
a "quality of implementation" issue, not a complexity issue.
More importantly, the implementation approach I described on the IPv6
list is neither complicated nor computationally expensive. In fact,
supporting the limited set of non-silly-for-ND-packet Extension Headers
has tiny incremental memory footprint and tiny increase in the
instruction count. The instruction count increase only applies if
an actual Extension Header is encountered, btw. The code for a L2
device to locate the IPv6 header, read that header, and read into
the ICMP message to determine that a packet is an ND packet *dwarfs*
the code to skip past the small set of reasonable Extension Headers
for ND packets.
Please (re-)read this previous note:
<http://www.ietf.org/mail-archive/web/ipv6/current/msg14241.html>
Yours,
Ran
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