IPv6 Foundation

One ,IPV6 Reasons for appearance ？

We all know IP The address is the unique identification of the host in the Internet ,IP It is also the core protocol in the Internet , But now use IPV4 yes 20 century 70 Designed in the late S , Up to now IPV4 The address is exhausted , That is to say, no new IP Address block , Therefore, this problem needs to be solved , It would not have been IPV6, Our teacher said , The amount of sand on earth is equivalent to IPV6 Number of addresses , so , This amount , But the future may also face the same crisis , This is not in the scope of our thinking

IPV6 Is a new version with a larger space address IP

Two ,IPV6

Message format

IPV6 and IPV4 The difference between

IPV6 Major changes introduced ：

• Larger address space ,IPV4 yes 32 position ,IPV6 yes 128 position
• The address hierarchy is extended , because IPV6 Increase in length , So it can be divided into larger levels
• Flexible header format ,IPV6 The first and IPV4 Header incompatible , And IPV6 Many optional extension headers are defined , It can not only provide more than IPV4 More features , It can also improve the processing efficiency of the router , The router does not handle the expansion header
• IPV6 The length of the head is fixed , Options in the payload ,IPV4 On the contrary
• IPV6 Protocol extensions can be allowed
• IPV6 Inspection and fields are cancelled , Increased router processing efficiency
• TTL Change to hop limit

Representation

One 、 It's divided into hexadecimal notation

The format is X:X:X:X:X:X:X:X, Each of them X Represents... In the address 16b, In hexadecimal , for example ：

ABCD:EF01:2345:6789:ABCD:EF01:2345:6789

In this representation , Every X The leader of 0 It can be omitted , for example ：

2001:0DB8:0000:0023:0008:0800:200C:417A→
2001:DB8:0:23:8:800:200C:417A

Two 、0 Bit compression representation

In some cases , One IPv6 The middle of the address may contain a long segment 0, You can put a continuous section of 0 Compress it into “::”. But to ensure the uniqueness of address resolution , In the address ”::” Only once , for example ：

FF01:0:0:0:0:0:0:1101 → FF01::1101

0:0:0:0:0:0:0:1 → ::1

0:0:0:0:0:0:0:0 → ::

3、 ... and 、 Embedded IPv4 Address representation

In order to achieve IPv4-IPv6 Interworking ,IPv4 The address will be embedded in IPv6 In the address , In this case, the address is often expressed as ：
X:X:X:X:X:X:d.d.d.d, front 96b It is expressed in hexadecimal , And finally 32b The address uses IPv4 Dot decimal representation of , for example ::192.168.0.1 And ::FFFF:192.168.0.1 These are two typical examples , Pay attention to the front 96b in , Compress 0 The bit method still works .

IPV6 Address type classification

1. unicast

Point to point communication

2. multicast

One to many broadcast communication

3. Anycast

A set of computers , But datagrams are only delivered to one of them , And it is usually the nearest

3、 ... and ,IPV4 towards IPV6 transition

1、IPv6/IPv4 Dual stack technology

Double stack mechanism is to make IPv6 The network node has a IPv4 Stack and a IPv6 Stack , Support at the same time IPv4 and IPv6 agreement .IPv6 and IPv4 It is a network layer protocol with similar functions , Both apply to the same physical platform , The transport layer is the same TCP or UDP, If one host supports IPv6 and IPv4 agreement , Then the host can and only support IPv4 or IPv6 Host communication protocol .

2、 Tunnel technology

The tunneling mechanism is that it will IPv6 Packets are encapsulated as data in IPv4 In the packet , send IPv6 Packets can be found in existing IPv4 infrastructure （ Mainly refers to IPv4 Router ） The mechanism of transmission on . With IPv6 The development of , There are some running problems IPv4 The backbone of the protocol is isolated from the local network IPv6 The Internet , In order to achieve these IPv6 Communication between networks , Tunnel technology must be used . The tunnel is transparent to the source site and the destination site , At the entrance to the tunnel , The router will IPv6 The data packets are encapsulated in IPv4 in , The IPv4 The source address and destination address of the packet are at the entrance and exit of the tunnel respectively IPv4 Address , At the tunnel exit , then IPv6 The packet is taken out and forwarded to the destination site . The advantage of tunnel technology lies in the transparency of the tunnel ,IPv6 The communication between hosts can ignore the existence of tunnels , The tunnel only acts as a physical channel . Tunnel technology in IPv4 towards IPv6 The initial application of evolution is very extensive . however , Tunnel technology cannot achieve IPv4 The host and IPv6 Communication between hosts

3、 Network address translation technology （NAT technology ）

Network address translation （Network Address Translator,NAT） Technology is to IPv4 Address and IPv6 Address is regarded as internal address and global address respectively , Or vice versa . for example , Inside IPv4 The host should communicate with the external IPv6 Host communication , stay NAT In the server IPv4 Address （ Equivalent to internal address ） Transform into IPv6 Address （ Equivalent to global address ）, The server maintains a IPv4 And IPv6 A map of addresses . conversely , When inside IPv6 Host and external IPv4 When the host is communicating , be IPv6 The host is mapped to an internal address ,IPv4 The host is mapped to a global address .NAT Technology can solve IPv4 The host and IPv6 Interworking between hosts