Re: [aqm] [Bloat] ping loss "considered harmful"

Wesley Eddy <wes@mti-systems.com> Tue, 03 March 2015 17:29 UTC

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Date: Tue, 03 Mar 2015 12:29:31 -0500
From: Wesley Eddy <wes@mti-systems.com>
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To: "Fred Baker (fred)" <fred@cisco.com>, Dave Taht <dave.taht@gmail.com>
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Subject: Re: [aqm] [Bloat] ping loss "considered harmful"
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On 3/3/2015 12:20 PM, Fred Baker (fred) wrote:
> 
>> On Mar 1, 2015, at 7:57 PM, Dave Taht <dave.taht@gmail.com
>> <mailto:dave.taht@gmail.com>> wrote:
>>
>> How can we fix this user perception, short of re-prioritizing ping in
>> sqm-scripts?
> 
> IMHO, ping should go at the same priority as general traffic - the
> default class, DSCP=0. When I send one, I am asking whether a random
> packet can get to a given address and get a response back. I can imagine
> having a command-line parameter to set the DSCP to another value of my
> choosing.
> 


I generally agree, however ...

The DSCP of the response isn't controllable though, and likely the DSCP
that is ultimately received will not be the one that was sent, so it
can't be as simple as echoing back the same one.  Ping doesn't tell you
latency components in the forward or return path (some other protocols
can do this though).

So, setting the DSCP on the outgoing request may not be all that useful,
depending on what the measurement is really for.

-- 
Wes Eddy
MTI Systems