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SubjectRe: IPSEC transport mode w/2.2.x kernels and large packets
Date
Hello!

> The IPv4 minimum MTU is 68 bytes. Its probably safe to throw away reports
> for < 128 bytes (NetROM).

BTW do you know that rfc1122 prohibits advertising MSS < 536. 8)

Fragmentation is less expensive than pure TCP in such cases.


> The minimum IPv6 MTU is high enough that the
> performance hit for current networks is acceptable worst case. So its simply
> not worth trying that prank on an IPv6 network

Seems, you did not understand me. Again, pmtu discovery is used
to increase packet size, rather than reduce. Turning it off
leaves us with mtu 576 (or 1280 for IPv6).

If we agreed with this, no problems exist and nothing to discuss.
Actually, if we rejected IP frames of size > 576, we also would
be right. Nobody is allowed to send them to use without our permission.
But we are not in children garden yet.
Nobody takes seriously the fact that IP is supposed to work over links
with mtu 68. We just fragment in this case.

Alexey

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