Shulou(Shulou.com)06/01 Report--

In the process of understanding CDN, many people find it difficult to understand too many terms. Today, I will give you an example to describe the concept of CDN. First of all, the content distribution network (Content Delivery Network, referred to as CDN) is a distributed network built and covered on the bearer network, which is composed of server groups of edge nodes distributed in different areas. CDN shares the pressure on the origin server, avoids network congestion, ensures that the distribution of website content is accelerated in different regions and different scenarios, and improves the speed of resource access.

1. GSLB global load balancing and iDNS intelligent DNS are the same meaning, not two things. In the way of implementation, there are mature factory products such as F5 GTM, or you can use open source software, such as bind.

2. CDN includes GSLB+ cache, which includes local load balancer (lvs/nginx/haproxy), cache server (squid or varnish) and other things, all of which are open source software.

3. At present, CDN mainly has two mainland manufacturers, Lanshun and Netcom, but first-line Internet companies have also begun to engage in CDN on their own.

Any document that introduces CDN will mention two core concepts of CDN:

1. Optimize website access according to certain policies (the nearest visit is the most basic)

2. Take over the traditional DNS process by transferring the accelerated domain name NS or CNAME to GSLB in the traditional DNS.

OK, the question is, how do we know if an Internet domain name uses CDN, how many are used, and where is it deployed?

Take www.163.com as an example to analyze:

The company's intranet broadband is used by Shenzhen Telecom. Let's take a look at the nslookup results:

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

Three addresses have been parsed here, and it is easy to find out that they belong to Guangdong Zhanjiang Telecom, Guangdong Foshan Telecom and Guangdong Jieyang Telecom.

These three prefecture-level cities span the whole of Guangdong Province. Thus it can be seen that NetEase's CDN in Guangdong Telecom is in these three places.

Let's take a 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 and the other is the address of Tianjin Unicom.

It is completely different from the three addresses parsed under Guangdong Telecom, which realizes the so-called CDN nearest access.

If there is anything else you don't understand, you can find our CDN technical engineer on the official website. CDN technical engineer has more than ten years of experience in the industry, so it will be more detailed and professional than the editor's answer. Official website link www.yisu.com

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