1. Briefly describe the process of DNS domain name resolution
(1) Check the cache of the DNS server, if the requested address or name is found, a response message is sent to the client
(2) If it is not found, it will be searched in the database. If the requested address or name is found, a response message will be sent to the client.
(3) If it is not found, the request will be sent to the root domain DNS. server, and the top-level domain will be searched from the root domain in sequence, the top-level domain will be searched for the second-level domain, and the second-level domain will be searched for the third-level domain until the parsed one is found. Address or name, that is, send response information to the DNS server of the network where the client is located. After receiving the response, the DNS server stores it in the cache, and then sends the parsing result to the client. If it is not found, it returns an error message.
2. Please explain what DNS is and briefly summarize its role, what protocol does DNS use to transmit data, and which protocol does DNS use for data transmission under what circumstances?
(1) DNS provides domain name, IP correspondence
(2) DNS uses udp tcp two protocols during data transmission
(3) DNS uses TCP to transmit data during domain transmission. When DNS transmission data is larger than 512 bytes, tcp is used for data transmission, and when it is less than 512 bytes, udp is used for transmission.