Cloud Computing Learning Route course syllabus Courseware: about DNS

Cloud Computing Learning Route course outline Courseware: about DNS:

=

Name resolution:

NetBios name: tianyun localhost WINS hosts

FQDN: fully qualified domain name www.tianyun.com baidu.com www.126.com. Mail.qq.com hosts DNS Server

I. hosts file

Function: to achieve name resolution, mainly to provide fast resolution for local hostnames and cluster nodes

Database: plane structure, centralized database

2. Domain name service DNS

Purpose: name resolution (for example, host name resolution to IP)

Namespace name space: a mechanism for naming hosts on the Internet

DNS database Datebase: hierarchical, distributed database

Authoritative name server: stores and provides actual data for a zone, such as 126.com 's DNS server, which records the records of all hosts in the 126.com domain, such as:

Www.126.com. X.x.x.x

Ftp.126.com. Y.y.y.y

Authoritative name server types include:

Master: primary DNS server that contains data from the original zone

Slave: back up the DNS server and obtain a copy of the zone data from the Master server through (zone transfer)

Non-authoritative name server: does not store the actual data of a certain area, only caches the DNS server. Although the query can be provided, the content of the query is not authoritative.

DNS parsing process:

For example, the client parses www.126.com

The client queries its own cache (including records in hosts), if the query is not sent to the DNS server in / etc/resolv.conf

If the local DNS server is authoritative about the requested information, it sends (authoritative answer) to the client.

Otherwise (not authoritative), if the DNS server has requested information in its cache, it will send (non-authoritative answer) to the client

If the query information is not in the cache, the DNS server searches the authoritative DNS server to find the information:

a. Starting from the root zone, search down according to the DNS hierarchy until the name server, which has authority on the information, gets the answer for the client.

The DNS server passes the information to the client and keeps a copy in its cache for later search.

b. Forward to another DNS server