What Is a Content Delivery Network (CDN)?

by on February 20, 2009 · 0 comments· LAST UPDATED February 20, 2011

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A CDN (also known as content distribution network) is nothing but a group of servers (system of computers) spread across the globe. The main is to optimizing the flow of digital content (such as css, images, JavaScript, video) and speed up web application to end-users. CDN utilizes advanced software, DNS, storage and networking technologies for organizing your data.

CDN distributes your content to geographically diverse servers (also knows as nodes) and then servers the content from closest node to the end users. In other words, users accesses a copy of the data near to the client, as opposed to all clients accessing the same central server, so as to avoid bottlenecks near that server. For example, www.cyberciti.biz servers the content from a central server located in USA (please note that the host command (DNS lookup utility) available under Apple OS X, Linux and UNIX like operating system. MS-Windows user should use the nslookup command):
$ host www.cyberciti.biz
Sample outputs:

www.cyberciti.biz has address 75.126.153.206
www.cyberciti.biz has IPv6 address 2607:f0d0:1002:51::4

On other hand files.cyberciti.biz servers the content using geographically diverse CDN based nodes. In other words contents from files.cyberciti.biz severed from closest node to the end users. This will result into increased speed and efficiency. For example, files.cyberciti.biz returns the following IP for all UK and European visitors:
$ host files.cyberciti.biz
Sample outputs:

files.cyberciti.biz is an alias for wac.3032.edgecastcdn.net.
wac.3032.edgecastcdn.net is an alias for gs1.wac.edgecastcdn.net.
gs1.wac.edgecastcdn.net has address 93.184.220.20

A query from North America returns different IP address, enter:
$ host files.cyberciti.biz
Sample outputs:

 host files.cyberciti.biz
files.cyberciti.biz is an alias for wac.3032.edgecastcdn.net.
wac.3032.edgecastcdn.net is an alias for gs1.wac.edgecastcdn.net.
gs1.wac.edgecastcdn.net has address 93.184.216.229

You can send ICMP ECHO_REQUEST to network using the ping command to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer. The ping command displays whether the destination responded and how long it took to receive a reply. The following ping test was done from our USA based server:
$ ping -c 4 files.cyberciti.biz
Sample outputs:

PING gs1.wac.edgecastcdn.net (93.184.216.229) 56(84) bytes of data.
64 bytes from 93.184.216.229: icmp_seq=1 ttl=60 time=0.377 ms
64 bytes from 93.184.216.229: icmp_seq=2 ttl=60 time=0.398 ms
64 bytes from 93.184.216.229: icmp_seq=3 ttl=60 time=0.374 ms
64 bytes from 93.184.216.229: icmp_seq=4 ttl=60 time=0.560 ms
--- gs1.wac.edgecastcdn.net ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3000ms
rtt min/avg/max/mdev = 0.374/0.427/0.560/0.078 ms

The following ping test was done from UK based server:
$ ping -c4 files.cyberciti.biz
Sample outputs:

PING gs1.wac.edgecastcdn.net (93.184.220.20) 56(84) bytes of data.
64 bytes from 93.184.220.20: icmp_seq=1 ttl=60 time=2.88 ms
64 bytes from 93.184.220.20: icmp_seq=2 ttl=60 time=3.04 ms
64 bytes from 93.184.220.20: icmp_seq=3 ttl=60 time=3.42 ms
64 bytes from 93.184.220.20: icmp_seq=4 ttl=60 time=2.79 ms
--- gs1.wac.edgecastcdn.net ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3000ms
rtt min/avg/max/mdev = 2.795/3.036/3.420/0.239 ms

Summary

In short Content Delivery Network is:

  • Global content delivery platform which is created created using smart software and network technology.
  • It can speed up your website and scale up web applications.
  • It can reduce buffering or jitters while watching HD video or audio content.
  • It can increases speed and decreases latency for large file downloads.
  • It can increases security for your web application.
  • Users get content from whichever server (node) is close to them or has a good network connection speed.
  • All CDN nodes are connected to high speed network links, which will result into faster download times and less vulnerability to network congestion.
  • Faster and reliable page loads means better user experience.
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