What is measured?
How are the measurements presented?
What are the benefits of these measurements?
What is not measured?
How to navigate the site.
DNS queries are sent approximately once per minute to DNS root and TLD name servers. The queries are sent from about 60 locations worldwide, with the main concentration of queries coming from the RIPE Region. The elapsed time from sending the query to receiving the answer is measured.
Click here to view the most recent map.
The query types used in our measurements are not typically applied in real name resolution. However both the capability and the time to answer these queries are very similar to the referral queries used in name resolution. The server has to be running and correctly configured to answer our test queries.
Graphs are provided to depict the measurements from three separate views:
'Probe' view:
The 'Probe' view shows a number of
graphs, one to each server as seen from the Test Box that you select. You can
use this view to look at DNS root and TLD service quality at one particular
location . Because name servers are well-connected and geographically
dispersed, this view can also be helpful as an indicator of connectivity
between the Test Box location and the rest of the world.
'Server' view:
The 'Server' view shows
measurements from all locations to a particular server. You can use this to
assess the quality of the service provided by this particular server.
'Domain' view:
The 'Domain' view shows a number
of graphs for each domain, one for the root and each monitored TLD as seen from
almost all locations. You can use this view to assess the generic DNS root and
TLD service quality provided to the collective pool of TTM Test Boxes.
The DNS Monitoring Service provides a good assessment of the DNS root and TLD service at each TTM Test Box location. You can work out which name servers serve a particular location better than others, and what the typical delay is. You can also see what effect problems with the servers and/or the network infrastructure have on general DNS service quality.
The measurements allow you to rapidly evaluate any past or present DNS problem, and to work out if the problem is caused by poor root or TLD name service. By looking at measurements from all locations to a particular server, you can estimate the service quality of that instance. This comprehensive view lets you offset most local influences on metrics. This will give you a more complete picture than if the measurements were only from a single point on the Internet. It is possible to see if the server itself or the network infrastructure is behind poor quality service. You can also assess how 'close' any network infrastructure problems are to a given server.
'Global' DNS root and TLD service quality
We
measure from around 60 specific points. While this is much more accurate than
inferring DNS quality using only measurements from a single point, it is by no
means comprehensive. Our measurement locations are concentrated in the RIPE NCC Service Region. This provides a
reasonably accurate view of service quality in this region with some locations
outside the region for comparison.
The general quality of DNS name resolution
There
are many additional factors to take into account like DNS caching, service
quality of lower level DNS servers, their network connectivity and the quality
of DNS implementations. For instance, due to caching only a tiny fraction of
all DNS name resolutions are directly affected by the quality of DNS root
service.
Effects that last less than a minute
This is the
interval between queries sent from Test Boxes to name servers.
Notes on IP anycasting:
The scope of our
measurements is the DNS service provided at each particular Test Box location
from each particular name server address. Some name server operators provide
service at their address from different locations by means of IP anycasting.
Our measurements do differentiate between the different instances of such a
server by querying every minute for 'hostname.bind' or 'id.server'. The
instance can naturally only be determined when there is a valid reply from the
server. Currently, we are working on presentational aspects of this data. Watch
this space for notes on progress.
You can get around the DNSMON site by using the menu that is at the top of each page. each option will take you to a different part of the site and will also be the place to go if you need help at any time.
If you select domains, servers or probes, you will see a second level menu appear.
Each second level menu is specific the view that you selected. On
overview pages they let you select another overview (as shown above). When you
have chosen the overview that you want to see from the pull down menu, you must
click on the 'show' button.
On the third level invidual plot pages, you can select the time interval to plot and configure the plot (see above).