Hi Patrick, as stated in other posts I'm not an expert in networks but,
being Italian, I'm an expert in workaround. :-)
Since you cannot controll fragmentation I suggested that forcing a service
level could also be the way to change the fragmentation level:
RFC 3168:
ECN-capable packets MAY have the DF (Don't Fragment) bit set.
Reassembly of a fragmented packet MUST NOT lose indications of
congestion. In other words, if any fragment of an IP packet to be
reassembled has the CE codepoint set, then one of two actions MUST be
taken:
* Set the CE codepoint on the reassembled packet. However, this
MUST NOT occur if any of the other fragments contributing to
this reassembly carries the Not-ECT codepoint.
* The packet is dropped, instead of being reassembled, for any
other reason.
If both actions are applicable, either MAY be chosen. Reassembly of
a fragmented packet MUST NOT change the ECN codepoint when all of the
fragments carry the same codepoint.
We would note that because RFC 2481 did not specify reassembly
behavior, older ECN implementations conformant with that Experimental
RFC do not necessarily perform reassembly correctly, in terms of
preserving the CE codepoint in a fragment. The sender could avoid
the consequences of this behavior by setting the DF bit in ECN-
Capable packets.
Situations may arise in which the above reassembly specification is
insufficiently precise. For example, if there is a malicious or
broken entity in the path at or after the fragmentation point, packet
fragments could carry a mixture of ECT(0), ECT(1), and/or Not-ECT
codepoints. The reassembly specification above does not place
requirements on reassembly of fragments in this case. In situations
where more precise reassembly behavior would be required, protocol
specifications SHOULD instead specify that DF MUST be set in all
ECN-capable packets sent by the protocol.
for the rest it is quite clear to me that the service levels do not
correspond to the fragmentation but sometimes you talk to the mother-in-law
to make the wife understand something.
Best regards
--
Marco Facchinetti
Mr S.r.l.
Tel. 035 962885
Cel. 393 9620498
Skype: facchinettimarco
Il giorno mer 4 mar 2026 alle ore 14:04 Patrik Schindler <poc@xxxxxxxxxx>
ha scritto:
Hello Marco,
Am 04.03.2026 um 13:37 schrieb Marco Facchinetti <
marco.facchinetti@xxxxxxxxx>:
I guess the TOS keyword is the closest one.
No, not the slightest. TOS is related to modifying transmission priority
flags of a packet and not related at all to packet fragmentation. See:
https://en.wikipedia.org/wiki/Type_of_service
vs.
https://en.wikipedia.org/wiki/IP_fragmentation
:wq! PoC
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