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myroslav
Asked: 2011-08-30 15:17:34 +0800 CST

DNS server request pattern optimization

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In a specific setup (Specific Website) DNS server is getting request for specific record (www.example.com) thus it's confident that the request will be followed by series of others (x.example.com, y.example.com, z.example.com).

Is it possible to gain reduction in these other requests if their RRs are included in additional section of DNS response (preemptive responding)? I.e. 

DNS QUERY
  www A

ANSWERS
  www A IN 11.22.33.44

AUTHORITATIVE NAMESERVERS
  NS IN ns1
  NS IN ns2

ADDITIONAL RECORDS
  x   A IN 55.66.77.88
  y   A IN 99.11.22.33
  z   A IN 44.55.66.77

The intention is to use such pre-populated responses:

  1. to speed up overall interaction with domain DNS server is serving (primary objective).
  2. to reduce DNS server load (secondary objective).

Is there any DNS service provider that is expert in this type of optimizations? Or let me know about argumented write-up on the topic and why the above is not possible.

domain-name-system

1 Answers

  1. It can never be confident of others. For example:

    website http://www.test.com/index.html (test.com is lookup one, then www.test.com is #2) has 20 images, all hosted on different sites.

    DNS can not predict this without loading the HTML first, but thats what the client is for. The client's browser will decode the HTML and request all the sources to the images, usually all at once.

    What if the page changes and they update all the links of images?

    BL: It's never going to be able to PREDICT dns requests, but it CAN cache prevoius requests.

    The TTL of the record (expiration time) will let the DNS server when to purge that record from the cache.

    That's just about it.

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