Comparing DNS Resolvers in the Wild. DNS. Domain Name System Translates domain names into IP addresses Hierarchical distributed System Nodes are called as name servers What are resolvers?. Comparing DNS Resolvers in the Wild. DNS has evolved a lot over the years
We need to compare responsiveness of various DNS resolvers
Done by performing DNS queries to 10000 hosts.
Following information collected during the measurements
DNS relies on caching for efficiency
Selection done by mix of best and worst sites.
Download top 1,000,000 list of sites from Alexa
10,000 hosts selected as follows:
Most popular hosts which are likely to be in cache
Less likely in the cache
Web-pages containing flash content that browser may have to retrieve from different domain
Two hosts in same area can query DNS back to back
Response time will be shorter for the second host as the reply will be in cache
Compares response times between first and second query
Need to inspect timestamps in traces to find location
Traces need to be selected that do not interact
Generally, local DNS resolvers are used
Third party resolvers claim to provide advanced services that provide web site and phishing site blocking capability along with “suggestions” for failed lookups
Main problem in third party resolvers – larger response time
DNS performance depends of proximity of end hosts
Caching improves the latency with over 95% of second queries answered in less than 100ms
“good ISP”: response times for the second queries show only small variation and are consistently better than those for the first query.
“bad ISP”: scattered along a horizontal and vertical line, as well as the diagonal. We explain this behavior by a load balancing setup without a shared cache.