dscp markings on icmp request

Hi,
I have noticed doing some captures in my labs that when doing a ping
from a cisco router to another the dscp markings of icmp reply are
identical .For example if a ping from one CE to another CE with IPP=5
the reply comes back with IPP5. This with no special configuration .
I did test in real life pinging various sites from windows xp with
ping -v 136 for example (136 is the value of the TOS byte =>AF41 in
DSCP) . some sites reply with DSCP=0, others with same marking, others
with different marking.
Is any rule , rfc on icmp about his ? I did not find enaything pointing to this

br,
Ovidiu

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Received on Sun Jan 10 2010 - 18:08:20 ART