Re: I-D ACTION:draft-rahman-rtg-router-alert-dangerous-00.txt

Hi Adrian,

Adrian Farrel wrote:
> I quoted from RFC 2113. The full and correct quote is...
> 
>   Routers that recognize this option shall
>   examine packets carrying it more closely (check the IP Protocol
>   field, for example) to determine whether or not further processing is
>   necessary.  Unrecognized value fields shall be silently ignored.
> 
> I don't see that it says that the examination has to be in the slow path.

Ok. But probably more difficult if the decision cannot be made by
looking at the RAO value alone, which was exactly my point:
The value should provide enough information for the decision whether
to pass it up or not (a general value like IPv4 RAO "0" doesn't make
much sense IMHO).

> I don't know what "silently ignored" was supposed to mean. It would be
> interesting to know how it has been implemented.
> 
> Recall that definining new behavior is well and good, but you have to be
> able to get packets through routers that are already deployed. It is no
> help if they drop them or pass them up to a higher protocol that barfs.
> Backward compatibility is a big part of this problem.

So obviously the whole thing has been messed up by imprecise
specifications and weird implementation behavior. The question
is really how to proceed now.
a) Work on an update of RFC 2113, fixing specification flaws.
   This may cause inconsistent behavior between old implementations
   and new implementations following the new spec/RFC.
b) Define a new RAO option type, this time with proper semantics,
   let alone existing implementations of the old RAO stuff.

Please see also the "I hate Router Alert" slides (slide 13-)
from Robert Hancock @IETF67 (Nov 2006):
http://www.ietf.org/proceedings/06nov/slides/nsis-1/nsis-1.ppt
So the issues of the last bullet on slide 25 are still unsolved
(except for the IANA issues).

Regards,
 Roland