An image example of the CDN principle

Recently want to understand the next CDN, from the Internet to find some documents looked under, and some with dig command interpretation is quite complicated, but the total feeling lacks some image examples for beginners to master. First, there are several concepts to be clear:

1, GSLB Global load balancing and IDNs intelligent DNS is a meaning, not two things. In the implementation of the way, there are F5 GTM and other mature manufacturers of products, you can also use open source software, such as bind to achieve.

2, CDN includes gslb+ cache, which also includes local load balancing (lvs/nginx/haproxy), cache server (squid or varnish) and other things, are open source software.

3, the current CDN mainly has blue flood and the net two mainland manufacturers, but the first-line internet companies also started to make their own CDN.

Any document introducing a CDN will mention the two core concepts of CDN:

1, according to a certain strategy to optimize the site access (the nearest visit is the most basic)

2, through the traditional DNS inside to accelerate the domain name NS or cname to GSLB, the implementation of the traditional DNS process takeover

OK, here's the question, how do we know if an Internet domain name is used for a CDN, and how many are deployed?

With www.163.com as an example analysis under:

Company intranet Broadband use is Shenzhen Telecom, we look at the results of Nslookup:

Server:dc01.delcomhk.com
address:192.168.1.26

Non-authoritative Answer:
Name:163.xdwscache.glb0.lxdns.com
addresses:113.107.112.214, 219.128.78.74, 113.107.56.96
Aliases:www.163.com, www.163.com.lxdns.com

Here the resolution of 3 addresses, it is easy to find that the three addresses belong to Guangdong Zhanjiang Telecom, Guangdong Foshan Telecom and Guangdong Jieyang Telecom.

These three cities are just across Guangdong province. Thus, NetEase in Guangdong Telecom CDN is in these three places.

We will then look at the production system of a Beijing Unicom computer room:

[ROOT@BJ-MSPRG-AP2/] #nslookup www.163.com
server:202.106.0.20
address:202.106.0.20#53

Non-authoritative Answer:
www.163.com canonical name = www.163.com.lxdns.com.
www.163.com.lxdns.com canonical name = 163.xdwscache.glb0.lxdns.com.
Name:163.xdwscache.glb0.lxdns.com
address:111.202.57.27
Name:163.xdwscache.glb0.lxdns.com
address:125.39.1.138

111.202.57.27 and 125.39.1.138, one is the address of Beijing Unicom, one is the address of Tianjin Unicom.

The three addresses that were resolved under Guangdong Telecom in the front are completely different, which realizes the so-called CDN near Access.

This article is from the "Memory Fragments" blog, so be sure to keep this source http://weikle.blog.51cto.com/3324327/1623232