nanog mailing list archives
Re: Question regarding anycasting in CDN setup
From: Charles Gucker <cgucker () onesc net>
Date: Wed, 1 Feb 2012 15:36:46 -0500
On Wed, Feb 1, 2012 at 3:25 PM, Anurag Bhatia <me () anuragbhatia com> wrote:
Hello everyone! I have a small question and was wondering if someone could help me with that. Question is - why companies like Google, Amazon are having partial anycasting in CDN setups? E.g if we pick a random hostname from url of Picasa picture - lh3.googleusercontent.com - this one is further a cname string and at the end you will find different A records when checked from different locations.
The simple answer for this is, Google cannot be expected to have a local cache of every image supplied to them globally on every server. So they use unicast servers behind a DNS based geo load balancer configuration. As for DNS, every anycasted node is expected to be able to resolve any DNS request that is made. It's all a matter of disk and acceptable delay in providing the data from the "closest" disk. charles
Current thread:
- Question regarding anycasting in CDN setup Anurag Bhatia (Feb 01)
- Re: Question regarding anycasting in CDN setup Charles Gucker (Feb 01)
- Re: Question regarding anycasting in CDN setup Jared Mauch (Feb 01)
- Re: Question regarding anycasting in CDN setup Mike Jones (Feb 01)
- Re: Question regarding anycasting in CDN setup Anurag Bhatia (Feb 08)
- Re: Question regarding anycasting in CDN setup Anurag Bhatia (Feb 08)
- Re: Question regarding anycasting in CDN setup Brett Watson (Feb 08)
- Re: Question regarding anycasting in CDN setup Joe Provo (Feb 08)
- Re: Question regarding anycasting in CDN setup Anurag Bhatia (Feb 23)
- Re: Question regarding anycasting in CDN setup Anurag Bhatia (Feb 08)