Re: Ping TOS to test QOS...

Pavel,
        ..."expect the reply to be also marked with "...

I thought that this was dependent on the system that was replying.
I don't have a reference, but would have said that this was one
of the things nmap and others use to tell what OS is at the remote side.

-Carlos

Pavel Bykov @ 26/04/2009 4:55 -0200 dixit:
> Along with good pointers others are giving remember, that ICMP ECHO REPLY
> will be marked with the same DSCP ( and IPP and TOS*). So if you ping with
> DSCP EF (TOS 184), expect the reply to be also marked with EF/184
>
> *almost always, except for ECN marked traffic. If the incoming DS Field
> would have EC Capable and EC Congestion Experienced bits set, only one or
> none of the bits would be marked in backwards direction, based on device
> capability.
>
> On Wed, Apr 22, 2009 at 11:07 PM, Modular <modulartx_at_gmail.com> wrote:
>
>> I had a thought, (don't laugh, it happens), is it possible to use the TOS
>> setting
>> in extended Ping to test QOS classification? I did a little research on
>> conversion
>> of TOS byte setting to IPP or DSCP and the best I could come up with is
>> that
>> a TOS of 1 or 8 would convert to IPP 1 or DSCP 8? I played around with it
>> for awhile, setting up a policy-map to match DSCP 1, DSCP 8 and IPP 1
>> and then set to TOS in the extended ping on a different router to 1 and
>> none of the class maps in the policy map had packet counts greater than 0.
>>
>> Either I'm converting TOS to IPP/DSCP wrong or I'm completely off base with
>> this.?.?
>>
>>
>> Bryan R.
>>
>>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net