* Pekka Savola:
If there is a transport protocol indication (either via ICMP or via a
refusal to send the datagram as in DCCP Section 14), then DTLS record
layer should inform the upper layer protocol of the error.
.. is this too weak? I've have thought that it would be natural that if
DTSLS record layer gets this notification (which, in the case of ICMP and
omitting information, is not necessarily given), it MUST pass this
information up. Note that the refusal to send could also apply to UDP
if packet is bigger than PMTU and DF bit is set or IPv6 is used.
What is the alternative if it doesn't? It would be fine if
the alternative is that the DTLS record layer react to that information
itself, but completely ignoring e.g. ICMP packet too big would lead to
communication failure.
ICMP packet too big is typically handled by the stack, not the
application. The stack updates the stored path MTU, the application
tries again, and this time, the stack produces smaller fragments.
AFAIUI, requiring ICMP processing in applications prescribes an
implementation model based on connected UDP sockets (in the
terminology of the BSD sockets API). This is not always desirable or
possible.
--
Florian Weimer <fweimer(_at_)bfk(_dot_)de>
BFK edv-consulting GmbH http://www.bfk.de/
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D-76133 Karlsruhe fax: +49-721-96201-99
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