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DNS throttled query traffic RRS feed

  • Question

  • Hi,

    I have several VMs in a VNET (all in the same cloud service). The VMs talk to each other very frequently, for name resolution I use the azure provided name resolution.

    As for today I do not have any problems, But  I came across this article that made me a bit concern:

    https://msdn.microsoft.com/en-us/library/azure/jj156088.aspx#bkmk_IDNSfeatures

    On the last bulletin on the Considerations is says "If your application performs frequent DNS queries on multiple target names, it is possible that some queries may time out". What exactly does that mean in simple words? (-:  Each VM on my VNET frequently talks with other VMs on the VNET by using their names, do I need to worry about time outs?

    Thanks!

    Thursday, February 26, 2015 8:38 AM

Answers

  • Each VM is throttled at about 200 DNS queries per second. If you're doing very frequent DNS queries then you may hit this limit but most people don't. If you're using Windows then client side caching is turned on by default so repeat DNS queries mostly get resolved without the query leaving the VM at all.  Linux has various client side caching packages (such as dnsmasq) but most distros don't install them by default.

    Gareth

    Azure DNS

    • Marked as answer by nq_silverWeb Thursday, February 26, 2015 2:39 PM
    Thursday, February 26, 2015 10:29 AM

All replies

  • Each VM is throttled at about 200 DNS queries per second. If you're doing very frequent DNS queries then you may hit this limit but most people don't. If you're using Windows then client side caching is turned on by default so repeat DNS queries mostly get resolved without the query leaving the VM at all.  Linux has various client side caching packages (such as dnsmasq) but most distros don't install them by default.

    Gareth

    Azure DNS

    • Marked as answer by nq_silverWeb Thursday, February 26, 2015 2:39 PM
    Thursday, February 26, 2015 10:29 AM
  • Thank you very much gareth.

    200 per second is very fast, I think its enough for most applications.

    My VMs talks frequent but it's always with the same machines, so I guess the cache you talked about is used.

    Have a Great Weekend!!!

    Thursday, February 26, 2015 2:39 PM