strange ping and traceroute results

[Shachar Shemesh]

On 22/11/16 02:19, Amos Shapira wrote:
> On 21 November 2016 at 18:20, Shachar Shemesh <shachar at shemesh.biz
> <mailto:shachar at shemesh.biz>> wrote:
>
>     The DNS resolving google.com <http://google.com> guesses your
>     gegraphical location, and gives you an answer that is nearest
>     where you are. If you use another DNS to query the domain, you
>     will get a different IP:
>
>
> It's not always a "guess your geographic location". The smarter ones
> use Anycast to advertise the same IP address from multiple locations
> on the Internet and let BGP do its magic to route your packets to the
> nearest server, taking into account any congestion or other transient
> connection speed changes. This is how Google's DNS 8.8.8.8 works, or
> Akamai's CDN. The nice thing about it is that you get optimal response
> even at the host resolution stage. The DNS server can then take its
> knowledge of the DNS query source address into account when it decides
> which IP address to resolve to.
>
> It's pretty neat, personally I find it a fascinating trick:
> https://en.wikipedia.org/wiki/Anycast
>
It is, quite fascinating. It is not, unfortunately, as useful as you
make it out to be. Neither Google nor Akamai use it for web traffic, for
example.

The reason is twofold. First, anycast is poorly equipted to handle TCP
connections. There is a (remote) possibility that the handler of your IP
would change mid-request, which would not play nice with your connection.

The second, more pertinent, reason is that , at least for Akamai, they
would like to be able to control which server you reach when you make a
request. The would like to be able to re-route your in case something
bad happens to that server. DNS TTL can be set as low as 30 or 60
seconds. BGP routes have much longer settle times.

Shachar
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