Re: [Int-area] New Version Notification for draft-bonica-intarea-lossless-pmtud-01.txt

[Fred Baker <[e-mail]>]

On Nov 1, 2019, at 12:39 AM, Joe Touch <[e-mail]> wrote:
> On Oct 31, 2019, at 5:07 PM, Erik Kline <[e-mail]> wrote:
>> 
>> It may be folly to try to modify IPv4 implementations at this point.   I have no objections if you wish to try pushing this big rock up hill, but I doubt you will be successful.
>> 
>> BTW, what *actually* prevents a middlebox from doing IPv6 fragmentation? 
> 
> Expecting it to work. That middlebox has no idea what packets are going through other middleboxes from the same endpoint. There’s no way it can pick IDs to avoid collision, the way the origin can. That’s why both IPv4 and IPv6 rely on the origin creating those IDs.
> 
> The result would either be significantly increased reassembly errors, sort of like accidental poisoning of the receiver’s cache, or potentially resulting in incorrect packets (the latter could be more likely in some cases, e.g., when the fragment happens to have a zero IP checksum).

I don't especially disagree with you, BUT...

Thinking about middlebox fragmentation. OK, suppose I am a company with N middleboxen. Suppose I configured the middleboxes to generate N disjoint ranges of IDs. If I have a datagram arriving at a middle box and being fragmented into two or more, and the ID generated is within the range assigned to the middle box, I don't think the results you predict actually transpire.

Note that I'm not writing a draft about that. I'm not sure I want anyone thinking it's a great idea and needs to be implemented.