Re: draft-macaulay-6man-packet-stain-00

On 12-04-08 3:10 AM, "Brian E Carpenter" <brian.e.carpenter@gmail.com>
wrote:

>On 2012-04-07 17:17, Joel jaeggli wrote:
>> I hesitate to suggest this because I'll probably turn into a pillar of
>> salt at some point for harping on it. however...
>
>Just don't look back (towards IPv4).
>
>> 
>> Getting new extension headers generally parsed is a high bar to get
>> over. 
>
>I have another concern; this draft appears to state that some
>middlebox inserts an extension header into a packet on the fly:
>  "IPv6 packet staining support consists of labeling datagrams with
>   security reputation information through the addition of an IPv6
>   destination option in the packet header by packet manipulation
>   devices (PMDs) in the carrier or enterprise network."
>
>I'm not aware of any provision in RFC 2460 allowing this, or of any
>other extension header that is inserted by a middlebox. The implications
>for MTU size and fragmentation are clear.

This point was brought up in the WG meeting which noted issues with
fragmentation.  I think it was clear based on numbers folks at the mic
that inserting an extension header mid-stream would result in negative
behaviours.

>
>> That said within one domain of control you might be able to fit a
>> subset of the information you're looking to carry into the  20 bits
>> available in flow label. 6437 probably provides enough cover/instruction
>> to allow for that.
>
>Given that the first paragraph of the Introduction to the draft is almost
>identical to the same paragraph in 6437, you may be on to something.
>However, it's only conformant if (a) the resulting values belong to a
>reasonably uniform distribution and are hard to predict and (b) the method
>MUST NOT be used for packets whose flow label is already non-zero.

The point of using the flow label seems valid.  The author will need to
re-evaluate the requirements as I believe it was noted in the WG
presentation that the Flow Label seemed to be too restrictive (size) for
this function (packet staining).  If the staining can be bounded by the
size of the flow label then perhaps the author can re-focus on using it
for this function (packet staining).

Victor K

>
>    Brian
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