GeoIP: Getting content close to you

Content delivery networks (CDNs) utilize a number of technologies that assist in getting your content to your users quickly. CDN nodes located at points of presence (PoP), or high-traffic intersections on the Internet, cache data from large web applications and are primarily responsible for serving multimedia content and other flat content that doesn’t require rendering.
GeoIP, or geolocation, is another technology that CDNs often utilize to improve streaming performance. Geolocation is an addition to the domain name service (DNS) that allows it to return IP addresses associated with a geographic region.

GeoIP: How does it work?
Every time you stream media from a service like Netflix or Vudu, your requests are affixed with an Internet protocol (IP) address to identify you. Your IP address and corresponding resolvable host name contains a number of facts about you. Anyone can determine what general location you’re attempting to stream media from, and which Internet service provider (ISP) you’re using. Some ISPs even encode more location-based detail into their host names and IP addresses.
Based on your IP address, Netflix’s DNS server — using GeoIP technology — can determine where you are in the world and return the IP address of the nearest host providing the desired media. Streaming data from a CDN close to you cuts down transit time significantly and generally improves overall application functionality.

GeoIP and anycasting: What’s the difference?
GeoIP and anycasting can actually perform the same functions, or even work together. Anycasting will allow multiple nodes to exist with the same public-facing IP address. Routing algorithms will determine which CDN node you stream content from. The routing algorithm used most often routes you to nodes closest to your location on your provider’s network.
Many businesses choose to use GeoIP and anycasting together for reliability, with GeoIP specifying larger geographic zones of presence and anycasting making deep-down routing decisions.
Image source: Wikimedia Commons.