Geodns

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Geodns is a patch for BIND to allow geographical split horizon (different responses for different requesters) based on MaxMind's geoip (commercial) or geolite (free) databases.

The objective is where a website has, for example, a server in France and one in the US, and a user looks up the name of the website in DNS, if the user is in Europe, the user gets the IP address of the French server, whereas a user in the US gets the IP address of the US server. This can make access faster and lower costs compared to directing all users worldwide to the same server or to multiple servers round robin.

As it is DNS based, it is much easier to deploy than BGP anycast. It does not require any support from the ISP and will not break existing connections when the server selected for a particular client changes. However, as it is not intimately tied into the network infrastructure it is likely to be less accurate at sending data to the nearest server.

The requester that the resolving DNS server sees is typically not the end user, but the DNS server of the user's ISP doing a recursive lookup, and the recursive DNS server caches the result. As ISPs typically arrange for users to use DNS servers geographically near them, the system works nonetheless.

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