Question about Time Window in USM

Hello,

If I understand RFC3414 well, the Time Window for USM is a fix value and
equal to 150s. My questions are the following : 
-Is there a possibility to change this value (besides an
implementation-dependent way) remotely (of course with authentication) ? I
didn't find a MIB Object in the SNMP-USER-BASED-SM-MIB module who reflects
this Time Window object.
-Why RFC3414 proposes a value of 150s for this object ? In 150s a
read-request (for certain variables who are sensitive) can easily be
replayed by another non-authoritative SNMP engine. He doesn't need to change
anything in the SNMP message just change the source UDP address to get the
answer from the authoritative SNMP engine send back to him and so get the
value of variables normally only visible to authorized persons. (He doesn't
need to know the authorization key to see if the response is authentic
because he doesn't care). Or did I miss something ?

Thanks for your feedback,

Koen Kennes.

P.S. : If some questions look silly, I apologize because I'm a snmpv3
novice.


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