When we visit a website, we simply enter the site's site and jump to the site page, and this process needs to be achievedDnsServersWillDomain name resolutionThis is an ip address, which will lead to data communications。
1 domain name analysis service (dns:domain name service)
1) listening port: udp/53, tcp/53
2) application: bind: bekerley internat name domain international domain name
2. Dns domain name structure
Icann (the internet corporation for assigned names and numbers)InternetThe name and digital address allocation agency is responsible for managing the internet generic top level domain (gtld) and national and regional top level domain (cctld) systems globally, as well as root server systems。
Root field
First level domain: com, edu, mi, gov, net, org, int, arpa
Organisation: . Com, . Org, . Net, . Mil, . Edu, . Gov, . Info, cc, . Me, . Tv
Country: . Cn, . Us, . Uk, jp, . Tw, . Hk, . Iq, ir
Inverse field: . In-addr. Arpa
Note: up to 127 level domain names
3, dns query type
1) recursive query
When a dns request is accepted by the server, if it falls within the server's jurisdiction, the higher server is requested to transmit the request sequentially and, in turn, to the host that sent the request。
2. Illustrative queries
Dns requests are accepted by the server and, if they are not within its jurisdiction, the client is given access to the root domain server and then informed to the client with the domain to access the lower level server until the final client has access to the server that controls the requested domain name。
3, dns resolution type
Dns server type:
1) main dns server: manage and maintain the server of the in-field resolver for the resolution; read and write
2) from the dns server: copy from the main server or from the server "replicate" (regional transfer) in the parsing library; read only
4. Inverse queries
Inverse queries are search domain names based on a resource record. This resource record may be a, cname or mx. In order to achieve reverse queries, dns has a special domain name, in-addr. Arpa, specifically for definition of reverse queries
5. Dns resolution process
The process through which a complete query is requested: clit (client) – >hosts file > dns service local cache (its own local cache) > dns server (recursion) > server cache (cache) > > organisation (overlay) > root > > top level domain name dns > level 2
Example: dns client query url flowchart
