The first chapter web request process ... DNS: DNS 1. Check the browser cache have not resolve the domain name of the ip 2. cache does not have to look for the operating system hosts file configuration, and there is no operating system cache, there is use the operating system (for example, Baidu domain name set 127.0.0.1 will not be able to access Baidu) hosts file address C under win: \ Windows \ System32 \ drivers \ etc, win the operating system cache dns View command ipconfig / displaydns, refresh command ipconfig / flushdns so-called domain name hijacking is the domain name is resolved to ip hijackers set up 3. the front two are not after the domain name will be sent to LDNS (domain name server in the region: application vendors it will provide access to the Internet, namely Telecom or China Unicom also SPA), you can view the current dns server via nslookup 4. If ldns still did not go directly to the root server domain name server for resolution 5. root name server returns the local name server as a primary domain name server queries (gTLD server: international top-level domain servers ..com..cn..org), 6. local domain name server then request to server gTLD 7.gTLD query and This domain name back to the corresponding domain name server addresses (DNS task resolved by the need to provide their own domain name provider) 8. ip domain name and the domain name server mapping table queries stored, along with a TTL (DNS remain in the DNS server time) returns the value of the domain name server DNS server 9. the local domain name server to obtain ip resolution table and caching and TTL value is 10. the local server analysis results returned to the user according to the user the local caching system of TTL value Note: there may be multiple level domain name resolution or a GTM (Global Traffic Manager) load balancing control ... CDN: content distribution load balancing cdn = Mirror (Mirror) + Cache (Cache) + overall load balancing (the GSLB) ... http Analysis: browser, enter the URL, dns resolve the corresponding ip, access the corresponding server and initiate a get request, the server responds to the request processing
