1、DNS
When we visit a website, we usually don't use an IP address, but use a string consisting of Roman characters and dots. Ordinary users do not use IP addresses when using TCP/IP to communicate. This is possible because the DNS (Domain Name System) function is supported. DNS can automatically convert the string into a specific IP address.
This DNS applies not only to IPv4 but also to IPv6.
2、ARP
As long as the IP address is determined, IP datagrams can be sent to this target address. However, in the underlying data link layer, it is necessary to know the corresponding MAC address of each IP address in actual communication.
ARP is a protocol to solve the address problem. Taking the target IP address as a clue, it is used to locate the MAC address corresponding to the next network device that should receive data subcontracting. But ARP only applies to IPv4, not to IPv6. In IPv6, ICMPv6 can be used instead of ARP to send neighbor discovery messages.
RARP is a reverse ARP protocol, which locates IP addresses from MAC addresses.
3、ICMP
The main functions of ICMP include confirming whether the IP packet has been successfully delivered to the destination address, telling the specific reasons why the IP packet was discarded in the sending process, and improving the network settings.
ICMP in IPv4 only supports IPv4 as an auxiliary function. That is to say, in the period of IPv4, even without ICMP, IP communication can still be realized. However, in IPv6, the role of ICMP has expanded. Without ICMPv6, IPv6 cannot communicate normally.
4、DHCP
Setting IP addresses for each host one by one will be very cumbersome. Especially when using mobile devices such as laptops, terminals and tablets, you must reset your IP address every time you move.