George Bonser wrote:
> I am saying that MTU probing works just fine, even with a
> link in between that has a shorter MTU and doesn't pass
> ICMP.
And I have been saying your statement is unfounded.
> I actually have one of those.
I can't see any.
> It actively probes with packets of varying sizes and learns
> what the path MTU is.
First, it sets eff_pmtu to 1400B. OK?
> It does not rely on ICMP. Again, it actively probes with
> varying sizes of packets until it believes it has
> "converged".
> The initial value for search_high SHOULD be the largest possible
> packet that might be supported by the flow. This may be limited by
> the local interface MTU, by an explicit protocol mechanism such as
> the TCP MSS option,
OK, so, even with local MTU of 7500B and without ICMP PTB, if
local MTU of your peer is 1500B, TCP MSS makes search_high
1500B.
As eff_pmtu of 1400B is close enough to search_high, you are
done.
Eff_pmtu of 1400B will be used forever with no probe packets
sent.
> The timer for Linux is 5 minute by default but you can change it.
Timer timeouts do not affect TCP MSS.
Masataka Ohta
PS
Your lengthy quotation means you don't see the point.
