Pascal Thubert (pthubert) <[email protected]> wrote:
    > * Michael: Layer3 (meaning and above NOTNT) Only one per
    > packet. Payload is
    > already 1000 bytes layer 2 on every packet. not reduce layer 2 security,
    > repeat it on every fragment. Cannot eliminate in that layer.

To clarify.

If one has a 1000 byte CoAP packet, split up into 8 layer-2 fragments, the
layer-3 security will be applied once.  So the overhead of the layer-3
security may be much lower *on average* than the layer-2 security.

The layer-2 security will get repeated on each of the 8 layer-2 fragments.
It would be wonderful if that layer-3 security could be used to eliminate the
overhead of the layer-2 security, but that would open up our LLNs to being
used to carry bogus traffic.

(The OSCOAP layer-3 security can not be checked on a hop-by-hop basis without
sharing the session key everywhere)

Obviously, if one has an 80-byte CoAP packet, this calculation is not the
same.

--
Michael Richardson <[email protected]>, Sandelman Software Works
 -= IPv6 IoT consulting =-



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