[atlas] Sudden increase in RTT to a.root-servers.net

On 11/5/11 9:38 PM, Daniel AJ Sokolov (lists) wrote:
> Hi,
>
> This is not urgent and probably not important.
>
> I have noticed that with the turn of the month (31st-> 1st) the RTT 
> from my probe (#1118) to a.root-servers.net has gone up a lot. It went 
> from ~32ms to ~115 ms (with a max of 494 ms).
>
> I checked the statistics of a few other public probes ("randomly" 
> picked) and could not find that pattern repeated there.
>
> So what does this tell me?Has my ISP downgraded one of their uplinks?
Such sudden steps in RTT are usually an indication of a probe reaching a 
different, more distant instance of an anycasted server.

The Atlas RTT map  (https://atlas.ripe.net/atlas/rtt_maps.html . 
selected measurement  'IPv4: a.root-servers.net')  shows all probes in 
the North Eastern US & Canada now have rather high round trip times to 
a.root-servers.net, 75ms is the lowest found. This is unusual; with 
global instances of the a root server in Ashburn, Virginia and New 
York[*] you would expect to see much lower RTTs on at least a good 
majority of these probes.

The public probe #338  (Culpeper, Virginia) sees ping times going up  to 
78ms at the same time yours increased to 115ms. [**]

So it's not your ISP downgrading the service. More likely something 
related to routing, somehow hosts in the east of the US now end up in 
the west of the US when talking to a.root-servers.net.

-- Rene

[*] http://www.root-servers.org/ lists six global sites for 
a.root-servers.net: two in the east, two in the west of the US, one in 
Germany and one in Hongkong

[**] 
http://zpm00.atlas.ripe.net/atlas/rrd.png?prb_id=338&msm_id=1009&type=weekly&end=last


**
>
> There is only three other probes here in Canada and they are not 
> public, so I can't check their numbers.
>
> Maybe one of you has a few moments to enlighten me. I try to 
> understand and learn from my probe's stats. :-)
>
> TNX
> Daniel AJ
>
>

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