[Bloat] Fw: Measuring Latency

[Alex Burr]

Oops, intended to CC the list...



> On Sunday, September 14, 2014 11:39 AM, Alex Burr <ajb44.geo at yahoo.com> wrote:
> > 
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> 
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> 
> On Sunday, September 14, 2014 12:32 AM, Jonathan Morton 
> <chromatix99 at gmail.com> wrote:
> 
> 
>> 
>> 
>>  To expand on this: to measure one-way delay, you would need finely 
> synchronised clocks (to within a 
>>  couple of ms) at both ends.  The average consumer doesn't have that 
> sort of setup - not even if they 
>>  happen to use NTP.  So it's not a goal worth pursuing at this level - 
> save it for scientific 
>>  Investigations, where the necessary effort and equipment can be made 
> available.
> 
> 
> This is true for absolute one way delay. But since we are interested in the 
> variation
> with load, it's actually easier. When you take the difference of two delays, 
> the synchronisation offset cancels out, so you are left with just the drift. 
> That may still be an insurmountable problem, but I would suggest at least 
> putting timestamps in the packets, even if you don't estimate one-way delay 
> up-front. That way people can try and get clever with clients later, without 
> having to change the server.
> 
> Alex 
>