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What is DNS?

DNS (Domain Name System) is a core service of the Internet. As a distributed database that can map domain names and IP addresses to each other, it can make it easier for people to access the Internet without having to remember the IP string that can be directly read by machines. DNS resolver is a server that points domain names to website space IP, allowing people to easily access websites through registered domain names. DNS consists of a resolver and a domain name server. The domain name server stores the domain names and corresponding IP addresses of all hosts in the network, and has the function of converting domain names into IP addresses. A domain name must correspond to an IP address. An IP address can correspond to multiple domain names at the same time, but an IP address does not necessarily have a domain name. The DNS protocol runs over the UDP protocol and uses port number 53. In the RFC document, RFC 2181 specifies DNS, RFC 2136 describes dynamic updates of DNS, and RFC 2308 describes reverse caching of DNS queries. Through DNS, you can find the URL you need to visit and send the information to your computer. There are two ways to query DNS: recursive query and iterative query. In a recursive query, if A requests B, then B, as the recipient of the request, must give A the answer he wants. In an iterative query, if recipient B does not have the exact content that requester A needs, recipient B will tell requester A how to obtain the content, but will not issue the request itself. When a user opens a Web browser, enters www.abc.com in the address bar, and presses the enter key to access, the computer will first access the host file local to the system. If the host file on the computer stores the IP address corresponding to domain name resolution, then the browser will directly access the website through the IP address. If the address corresponding to this domain name is not stored in the host file, the computer will first request the specified DNS server to query the ip address for this domain name resolution. If the DNS server caches this address, it will directly return the address to the computer. In general, DNS converts human-readable names (such as www.abc.com) into IP addresses (such as 192.0.0.1) that can be understood by computers, allowing users to access resources on the Internet through domain names rather than complex IP addresses.

What is IPv6?

IPv6 is version 6 of the Internet Protocol. It is a next-generation Internet core protocol designed by the International Internet Standardization Organization IETF to replace the current version of IPv4. IPv6 provides a large number of network addresses. In theory, the number of IP addresses that can be provided reaches 2 to the power of 128, which can "create a website for almost every grain of sand in the world." IPv6 has a much larger address space than IPv4, which can provide a technical foundation for network routing optimization and efficient traffic management and control. It is currently the only internationally recognized next-generation Internet commercial solution. IPv6 was introduced to solve the problem of IPv4 address exhaustion. With the development of technologies such as the Internet of Things and cloud computing, the demand for device networking has increased sharply, and IPv4 addresses can no longer meet the demand. IPv6 can provide an independent IP address for every Internet device in the world, including cars, street lights, fire hydrants, etc., which is centrally managed through the Internet of Things. IPv6 also provides many new features and functions, such as high security, strong mobility, and good quality of service. The IPv6 protocol family defines basic information about security, such as Datagram Encapsulation Security Protocol (ESP) and Sending Datagram Authentication (Authentication Header AH). IPsec is mandatory for all IPv6 nodes to ensure the security of end-to-end connections. In addition, IPv6 also supports automatic address configuration and mobile IP technology, allowing devices to obtain a care-of address anywhere and maintain communication connections while roaming between different networks. IPv6's extended header provides a large programmable space, which can be used to define performance requirements such as user type, service type, bandwidth, packet loss rate, latency, and jitter carried by IP packets, significantly reducing complexity and improving Accuracy and real-time. IPv6 also supports segmented routing (SRv6), which can establish VPN channels, organize broadband, low latency, low jitter and highly reliable channels on demand, and supports network slicing, multicast, broadcast and other functions. In general, IPv6 is an inevitable trend in the development of the Internet. It will seamlessly integrate with the new generation of information technology and support each other, providing a rare opportunity for independent innovation in network information technology.