Every host on the Internet has a unique address identifier called

Each host has a unique address identification called "IP address". The IP address is a unified address format provided by the IP protocol. It assigns a unique logical address to each network and each host on the Internet to shield the differences in physical addresses. Because of this unique address, it is ensured that users can efficiently and conveniently select the objects they need from thousands of computers when operating on connected computers.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

Every host on the Internet has a unique address identification, called an "IP address."

IP address (Internet Protocol Address) refers to the Internet Protocol address, also translated as Internet Protocol address.

The IP address is a unified address format provided by the IP protocol. It assigns a logical address to each network and each host on the Internet to shield the differences in physical addresses.

There is also a very important content in the IP protocol, which is that every computer and other device on the Internet is assigned a unique address, called an "IP address." Because of this unique address, it is ensured that users can efficiently and conveniently select the objects they need from thousands of computers when operating on connected computers.

The IP address is just like our home address. If you want to write to a person, you need to know his or her address so that the postman can deliver the letter. A computer sending information is like a postman. It must know the unique "home address" so as not to deliver the letter to the wrong person. It's just that our addresses are expressed in words, and the computer's address is expressed in binary numbers.

IP addresses are used to give computers on the Internet a number. What we see every day is that every connected PC needs an IP address in order to communicate normally. We can compare "personal computer" to "a telephone", then the "IP address" is equivalent to the "telephone number", and the router in the Internet is equivalent to the "program-controlled switch" of the telecommunications bureau.

The IP address is a 32-bit binary number, which is usually divided into 4 "8-bit binary numbers" (that is, 4 bytes). IP addresses are usually expressed in the form of (a.b.c.d) using "dotted decimal", where a, b, c, and d are all decimal integers between 0 and 255. Example: The dotted decimal IP address (100.4.5.6) is actually a 32-bit binary number (01100100.00000100.00000101.00000110).

Development History

The first IP address to appear is IPV4, which has only 4 segments of numbers, and each segment does not exceed 255. Due to the booming development of the Internet, the demand for IP addresses is increasing, making the issuance of IP addresses more stringent. Various data show that all global IPv4 addresses may be issued between 2005 and 2010 (the actual situation is that in 2019 The allocation of IPv4 addresses was completed on November 25, 2018). The lack of address space will definitely hinder the further development of the Internet. In order to expand the address space, it is planned to redefine the address space through IPv6. IPv6 uses a 128-bit address length. In the design process of IPv6, in addition to solving the address shortage problem once and for all, other problems that were not solved well in IPv4 were also considered.

The existing Internet runs on the basis of the IPv4 protocol. IPv6 is the next version of the Internet protocol, which can also be said to be the protocol of the next generation of Internet. It was originally proposed because with the rapid development of the Internet, the limited address space defined by IPv4 will be exhausted, and the shortage of address space will inevitably hinder the further development of the Internet. In order to expand the address space, it is planned to redefine the address space through IPv6. IPv4 uses a 32-bit address length, and there are only about 4.3 billion addresses, which are estimated to be allocated between 2005 and 2010, while IPv6 uses a 128-bit address length, which can provide almost unlimited addresses. According to a conservative estimate of the actual addresses that can be allocated to IPv6, more than 1,000 addresses can be allocated per square meter of the entire earth. In the design process of IPv6, in addition to solving the address shortage problem, other problems that were not solved well in IPv4 were also considered, mainly including end-to-end IP connection, quality of service (QoS), security, multicast, and mobility. , plug and play, etc.

With the rapid development of the Internet and the continuous improvement of Internet users' requirements for service levels, IPv6 will receive more and more attention around the world. In fact, there is no rush to promote IPv6. The problem of insufficient IPv4 addresses can be solved by simply extending 32 bits from 8 to 40 bits based on the existing IPv4. In this way, the number of available addresses is expanded by 256 times.

The difference between IPv4 and IPv6 protocols

1. The difference between protocol addresses

1) , Address length

IPv4 protocol has a 32-bit (4-byte) address length; IPv6 protocol has a 128-bit (16-byte) address length

2 ), address representation method

IPv4 address is a binary number expressed as a decimal. IPv6 addresses are binary numbers represented in hexadecimal notation.

3) Address configuration

The IPv4 protocol address can be configured manually or through DHCP. [Recommended related video tutorials: HTTP video tutorial]

The IPv4 protocol requires the use of Internet Control Message Protocol version 6 (ICMPv6) or DHCPv6 Stateless Address Autoconfiguration (SLAAC).

2. Differences in data packets

1) Packet size

IPv4 protocol data packets require 576 bytes, fragmentation is optional . The IPv6 protocol data packet requires 1280 bytes and will not be fragmented

2), the header

The length of the IPv4 protocol header is 20 bytes, and does not recognize data for QoS processing Packet stream, including checksum, containing options field of up to 40 bytes.

The IPv6 protocol header is 40 bytes in length and contains the Flow Label field of the packet flow specified for QoS processing, excluding checksum; the IPv6 protocol has no field, but the IPv6 extension header is available.

3) Packet fragmentation

IPv4 protocol packet fragmentation will be completed by the forwarding router and the sending host. Packet fragmentation of the IPv6 protocol is only done by the sending host.

Data packet

3. DNS record

IPv4 protocol address (A) record, mapping host name; pointer (PTR) record, IN-ADDR.ARPA DNS domain.

IPv6 protocol address (AAAA) record, mapped host name; pointer (PTR) record, IP6.ARPA DNS domain

4, IPSec support

IPSec support for the IPv4 protocol is only optional. The IPv4 protocol has built-in IPSec support.

5. Address Resolution Protocol

IPv4 Protocol: Address Resolution Protocol (ARP) can be used to map IPv4 addresses to MAC addresses.

IPv6 protocol: Address Resolution Protocol (ARP) is replaced by the functionality of Neighbor Discovery Protocol (NDP).

6. Authentication and encryption

Pv6 provides authentication and encryption, but IPv4 does not.

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