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On 2020-02-27 15:00, Tom Herbert wrote:
On Thu, Feb 27, 2020 at 2:52 PM Joe Touch < touch@xxxxxxxxxxxxxx> 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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