Google Public DNS をちょっと見てみた。

google dns

  • アドレスが覚え易い
    • 8.8.8.8 と　8.8.4.4
  • 日本からは、海向こうになるが、40ms以内で応答している。（DNSサーバのパフォーマンスを考えると、許容範囲かな？）
  • Akamaiについて、download.windowsupdate.com で調べてみました。
    • なぜか、OCNのDNSサーバより、Google public DNSのほうが、早いサーバのアドレスを返しています。

　なぜだろう？

  • Google Public DNSの場合

> server 8.8.8.8
Default Server: google-public-dns-a.google.com
Address: 8.8.8.8

> download.windowsupdate.com
Server: google-public-dns-a.google.com
Address: 8.8.8.8

Non-authoritative answer:
Name: mscom-wui.vo.llnwd.net
Addresses: 117.121.254.221, 117.121.254.231
Aliases: download.windowsupdate.com, download.windowsupdate.nsatc.net


C:\>ping 117.121.254.221

Pinging 117.121.254.221 with 32 bytes of data:

Reply from 117.121.254.221: bytes=32 time=16ms TTL=51
Reply from 117.121.254.221: bytes=32 time=15ms TTL=51
Reply from 117.121.254.221: bytes=32 time=15ms TTL=51
Reply from 117.121.254.221: bytes=32 time=17ms TTL=51

Ping statistics for 117.121.254.221:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 15ms, Maximum = 17ms, Average = 15ms



  • OCNのDNSサーバの場合

> server 202.234.232.6
Default Server: nv-td501.ocn.ad.jp
Address: 202.234.232.6

> download.windowsupdate.com
Server: nv-td501.ocn.ad.jp
Address: 202.234.232.6

Non-authoritative answer:
Name: a26.ms.akamai.net
Addresses: 198.87.182.147, 198.87.182.136, 198.87.182.138
Aliases: download.windowsupdate.com, download.windowsupdate.nsatc.net
main.dl.wu.akadns.net, intl.dl.wu.akadns.net, dl.wu.ms.geo.akadns.net



C:\>ping 198.87.182.147

Pinging 198.87.182.147 with 32 bytes of data:

Reply from 198.87.182.147: bytes=32 time=109ms TTL=53
Reply from 198.87.182.147: bytes=32 time=111ms TTL=53
Reply from 198.87.182.147: bytes=32 time=108ms TTL=53
Reply from 198.87.182.147: bytes=32 time=106ms TTL=53

Ping statistics for 198.87.182.147:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 106ms, Maximum = 111ms, Average = 108ms