pop：很早就看见了。只是没有转过来，今天有人问我就写在这里了。学习一下吧。
来源：PHP China
新浪采用了ChinaCache做的CDN系统，ChinaCache在全国分布了四十多个点，同时采用基于动态DNS分配的全球服务器负载均衡技术。
从新浪的站点结构可以看出：
> www.sina.com.cn
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: libra.sina.com.cn
Addresses: 61.135.152.71, 61.135.152.72, 61.135.152.73,61.135.152.74 61.135.152.75, 61.135.152.76, 61.135.153.181,61.135.153.182, 61.135.53.183, 61.135.153.184, 61.135.152.65,61.135.152.66, 61.135.152.67, 61.135.12.68, 61.135.152.69, 61.135.152.70
Aliases: www.sina.com.cn, jupiter.sina.com.cn
在北京地区ChinaCache将www.sina.com.cn的网址解析到libra.sina.com.cn，然后libra.sina.com.cn做了DNS负载均衡，将libra.sina.com.cn解析到61.135.152.71等16个ip上，这16个ip分布在北京的多台前台缓存服务器上，使用squid做前台缓存。如果是在其它地区访问http://www.sina.com.cn可能解析刮..??的效果。
我们再看一个新浪其它频道是指到哪里的：
> news.sina.com.cn
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: libra.sina.com.cn
Addresses: 61.135.152.65, 61.135.152.66, 61.135.152.67,61.135.152.68 61.135.152.69, 61.135.152.70, 61.135.152.71,61.135.152.72, 61.135.152.73 61.135.153.178, 61.135.153.179,61.135.153.180, 61.135.153.181, 61.135.153.182 61.135.153.183,61.135.153.184
Aliases: news.sina.com.cn, jupiter.sina.com.cn
可以看出，各个频道的前台缓存集群与www.sina.com.cn的前台缓存集群是相同的。
2、搜狐
Sohu与新浪的原理差不多，下面是nslookup的结果：
> www.sohu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: pagegrp1.sohu.com
Addresses: 61.135.132.172, 61.135.132.173, 61.135.132.176,61.135.133.109 61.135.145.47, 61.135.150.65, 61.135.150.67,61.135.150.69, 61.135.150.74 61.135.150.75, 61.135.150.113,61.135.150.145, 61.135.131.73, 61.135.131.91 61.135.131.180,61.135.131.182, 61.135.131.183, 61.135.132.65, 61.135.
132.80
Aliases: www.sohu.com
只不过libra.sina.com.cn换成了pagegrp1.sohu.com
我们再来看一下sohu的频道：
> news.sohu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: pagegrp1.sohu.com
Addresses: 61.135.145.47, 61.135.150.65, 61.135.150.67,61.135.150.69 61.135.150.74, 61.135.150.75, 61.135.150.113,61.135.150.145, 61.135.131.73 61.135.131.91, 61.135.131.180,61.135.131.182, 61.135.131.183, 61.135.132.65 61.135.132.80,61.135.132.172, 61.135.132.173, 61.135.132.176, 61.135.133.109
Aliases: news.sohu.com
同新浪相同，用的是同样的服务器群，这可能是因为他们用的都是ChinaCache的服务吧，不过sohu的名字起的有点土，pagegrp1，没有libra，pavo好听，这名字听起来有点像法语，比较浪漫。
3、网易
网易似乎没用ChinaCache的服务，下面是nslookup结果：
> www.163.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.163.com
Addresses: 202.106.168.103, 202.106.168.104, 202.106.168.109,202.106.168.121 202.108.36.153, 202.108.36.155, 202.108.36.156,202.108.36.167, 202.108.36.172 202.108.36.196
直接在www.163.com 这个域名上做了DNS负载均衡。这样的话就要求服务器必须放的非常靠近主节点，才能保证各地的用户访问的速度。
但163不同的频道是放在不同的缓存集群上的，这与sina，sohu有些不同，等于sina，sohu是按照地区划分服务器集群，而网易按照频道划分服务器集群。
> 163.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: 163.com
Addresses: 202.108.36.205, 202.108.36.206, 202.108.36.207, 202.108.36.201 202.108.36.202, 202.108.36.203, 202.108.36.204
显然，这和www.163.com 不是一个集群，我们再来试一个：
> sports.163.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: channel.cache.163.com
Addresses: 202.108.36.136, 202.108.36.208, 202.108.36.209, 202.108.36.210 202.108.36.211, 202.108.36.212, 202.108.36.213
Aliases: sports.163.com
可以看出，和上面的集群也是不同的。
4、百度
百度的前台服务器就不是很多了：
> www.baidu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.baidu.com
Addresses: 202.108.250.249, 202.108.249.134
> baidu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: baidu.com
Address: 202.108.250.228
> mp3.baidu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: mp3.baidu.com
Address: 202.108.249.131
只有www.baidu.com做了两台服务器的集群，频道都用了一台服务器做前台
5、一搜
> yisou.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: yisou.com
Addresses: 202.165.102.114, 202.43.217.14, 202.43.217.15,202.43.217.16 202.43.217.17, 202.165.102.111, 202.165.102.112,202.165.102.113
> www.yisou.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.yisou.com
Addresses: 202.43.217.17, 202.165.102.111, 202.165.102.112,202.165.102.113 202.165.102.114, 202.43.217.14, 202.43.217.15,202.43.217.16
> mp3.yisou.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.yisou.com
Addresses: 202.165.102.113, 202.165.102.114, 202.43.217.14,202.43.217.15 202.43.217.16, 202.43.217.17, 202.165.102.111,22.165.102.112
Aliases: mp3.yisou.com
前台做了8台服务器的缓存集群，www.yisou.com和 yisou.com以及mp3.yisou.com是用的同一个集群。
通过前面的分析我们可以得到一个结论：sina和sohu使用了CDN与GSBL与DNS负载均衡技术，每个地区一组前台服务器群，网易，百度使用了DNS负载均衡技术，每个频道一组前台服务器，一搜使用了DNS负载技术，所有频道共用一组前台服务器集群。