On 2020-02-27 15:00, Tom Herbert wrote:
> On Thu, Feb 27, 2020 at 2:52 PM Joe Touch <[email protected]> wrote:
>
>> FWIW - there are separable issues here:
>>
>> - whether an IP header (or parts thereof) should be changed in transit
>>
>> AFAICT, the answer has always been yes, but limited to the hopcount/ttl in
>> the base header and hop-by-hop options in the options/extension headers.
>>
>> - whether an IP header length can change in transit
>>
>> I see no reason why it can't become smaller, but if it can become larger
>> then PMTUD and PLPMTUD don't work.
>>
>> So the question isn't just what is wanted, it's what is feasible.
> Joe,
>
> Per the problem about making packets larger in the network, I'd point
> out that this is already common due to in-network tunneling. In any
> case, it's really the only interesting case here (as opposed to making
> packets smaller).
Tunnels don't make packets bigger. They make a bigger packet at the
tunnel level. That then becomes the tunnel's problem to deal with (see
draft-intarea-tunnels).
Making the IP packet bigger itself creates a problem that cannot be
recovered that way.
I.e., same problem but very different consequences.
Joe
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