[bf1942] largedownloads DNS

Steve Getman steve at lightcubed.com
Sat Jul 16 17:54:58 EDT 2005

Correct.  The product is called Edgesuite.  Akamai has colocated servers 
with 1100 (as of six or so months ago so probably more now) physical 
locations.  Each colocation has a minimum of 3 load balanced servers.   
When a request is made for a file, their DNS entry points you at the 
nearest location (not necesarily geographically, it uses real time ping 
stats to choose the closest but in most cases that box will be in your 
upstream provider's datacenter.)  So if you're linked to the 'net 
through Comcast in Chicago, chances are you'll hit some boxes that are 
in the pop there.  Those boxes will look in their cache and see if the 
URI you are requesting is located on the local system.  If so, it serves 
it to you right from there and your traffic never even hits the public 
Internet.     If not, it makes a request to the origin server and stores 
the content for the next person.  Cache can be set to timeout at any 
time or forced to flush if you push something to the web site (process 
takes about 8 min or less to propagate).  Even when you do have to go to 
the origin server it uses a proprietary routing system which 
automatically routes around slow connections, theoretically giving you 
the fastest route to the host.  Lastly, the system uses compression on 
the last mile connection to shave a few more k off the transfer.  (Not 
all that useful in these cases since the files are already compressed.)

Over-all it's an impressive setup.  Allows the sites I manage to handle 
huge spikes in traffic without adding more boxes on our end. (i.e. we 
have handled a roadblock advertisement on Yahoo/MSN on three origin 
servers and existing network infrastructure without breaking a sweat, 
thousands of simultaneous users, 100s of mbps.)  It's not cheap but is 
better than having excess capacity sitting around.


> It's not round-robin. It seems to be geographical, using Akami. I 
> tried dig from several locations and got different answers. When I 
> couldn't reach the file on the server from one location, I just 
> plugged an IP from another location that worked into the hosts file 
> and got through.

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