Re: [6man] #11 (rfc2460bis): HBH header handling

[Bob Hinden <[e-mail]>]

Hi,

This proposed change is to make the processing of HBH options optional.  To me this matches what we have in operational practice.  Making that change, reduces the need for the note about some nodes may not processing HBH options.

I support this change.

Comments?

Bob


> On Jun 12, 2016, at 11:34 AM, 6man issue tracker <[e-mail]> wrote:
> 
> #11: HBH header handling
> 
> 2460bis relaxes the must to a should. And incorporates a paragraph from
> 7045 giving performance considerations.
> The use of a _should_ process combined with a _may_ drop is not elegant.
> The second paragraph can also be read as a licence to drop.
> 
> After having thought about the text in draft-ietf-6man-hbh-header-
> handling, I propose the following instead:
> 
> OLD:
>   The exception referred to in the preceding paragraph is the Hop-by-
>   Hop Options header, which carries information that should be examined
>   and processed by every node along a packet's delivery path, including
>   the source and destination nodes.  The Hop-by-Hop Options header,
>   when present, must immediately follow the IPv6 header.  Its presence
>   is indicated by the value zero in the Next Header field of the IPv6
>   header.
> 
>   It should be noted that due to performance restrictions nodes may
>   ignore the Hop-by-Hop Option header, drop packets containing a hop-
>   by-hop option header, or assign packets containing a hop-by-hop
>   option header to a slow processing path.  Designers planning to use a
>   hop-by-hop option need to be aware of this likely behaviour.
> 
> NEW:
>   The exception referred to in the preceding paragraph is the Hop-by-
>   Hop Options header, which carries information that may be examined
>   and processed by nodes along a packet's delivery path, including the
>   source and destination nodes.  The Hop-by-Hop Options header, when
>   present, must immediately follow the IPv6 header.  Its presence is
>   indicated by the value zero in the Next Header field of the IPv6
>   header.
> 
>   NOTE: While RFC2460 required that all nodes must process the Hop-by-
>   Hop Options header, it is now expected that nodes only process the
>   Hop-by-Hop Options header if explicitly configured to do so.
> 
> 
> In short replace the should we a may, making HBH options header purely
> optional. Note that section 4.8 in 2460bis already uses a may.
> I also suggest we remove the 7045 paragraph on performance considerations,
> that's highly subjective.
> 
> 3. Section 4.3 HBH
> OLD:
>  The Hop-by-Hop Options header is used to carry optional information
>   that should be examined by every node along a packet's delivery path.
>   The Hop-by-Hop Options header is identified by a Next Header value of
>   0 in the IPv6 header, and has the following format:
> 
> NEW:
>   The Hop-by-Hop Options header is used to carry optional information
>   that may be examined by every node along a packet's delivery path.
>   The Hop-by-Hop Options header is identified by a Next Header value of
>   0 in the IPv6 header, and has the following format:
> 
> Same change as above.
> 
> --
> ----------------------------------+-----------------
> Reporter:  [e-mail]  |      Owner:
>     Type:  defect                |     Status:  new
> Priority:  major                 |  Milestone:
> Component:  rfc2460bis            |    Version:
> Severity:  In WG Last Call       |   Keywords:
> ----------------------------------+-----------------
> 
> Ticket URL: <https://tools.ietf.org/wg/6man/trac/ticket/11>
> 6man <https://tools.ietf.org/wg/6man/>
> 
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