IPv6 learning notes

Why from IPv4 Gradually transition to IPv6？

1、IPv4 Address exhaustion , The number of Chinese netizens is far greater than IP Number of addresses .

2、 because IPv4 The technology itself has the problem of wasting network address resources , When using A、B、C 3 After class addressing , Although convenient IP Address management , But wasted tens of millions of addresses , especially B Class address . for example , A need to 300 Companies with computers connected to the Internet , Use one C Class address （254 An address ） It's not enough. ; Use two C Class address will cause the routing table to explode , Thus, the performance of external routing protocols is affected ; Another option is to use a B Class address （65534 An address ）, But it was wasted 65234 An address .

IPv4 32 position 4,294,967,296 common 42 More than 100 million addresses

IPv6 128 position About equal to 1800 Billion addresses .

IPv6 advantage ：

IPv6 It's right IPv4 An important manifestation of thorough reform rather than repair , It's right Datagram header improvements , This is also IPv6 Significant improvements in other areas .IPv4 The header is of variable length and complex structure , Both host and router are difficult to improve processing efficiency .IPv6 Simplified basic header , Reduced processing complexity , Use and expand headers and improve adaptability .

IPv6 Transition technology

The transition mechanism can be basically divided into 3 class , namely ： Double stack （Dual Stack）, Tunnel （Tunnel）, translate （Translation）.3 Among the three basic transition technologies , Dual stack is the simplest and most acceptable transition method , Tunnel technology and translation technology are necessary technologies for specific occasions .

1、 Dual stack technology

Dual stack is defined in RFC 4213 in , It refers to the installation of both on terminal equipment and network nodes IPv4 And install IPv6 Protocol stack of , So as to realize the separation and IPv4 or IPv6 Information exchange between nodes . have IPv4/IPv6 Dual stack （ Pictured 4-1 Shown ） The node of is called double stack node for short , These nodes can send and receive IPv4 message , You can also send and receive IPv6 message . They can be used IPv4 And IPv4 Node interworking , It can also be used directly IPv6 And IPv6 Node interworking .

        Device interfaces configured as dual stacks can have one IPv4 Address or a IPv6 Address or both . meanwhile , The router contains two separate routing tables ： One for the IPv4 Addressing , Another one for IPv6 Addressing . Both tables reside in the same router .
        When the link layer of the dual stack node receives the data segment , Disassemble and check the packet header . If IPv4/IPv6 The first field in the header , namely IP The version number of the group is 4, The group is IPv4 Stack to handle ; If the version number is 6, By IPv6 Stack processing .
        For support IPv6 Routing learning , Dual stack router devices also need to run at the same time IPv6 The routing protocol of . If the current network is deployed OSPF, New support IPv6 Of OSPFv3; If the current network deployment is ISIS, Deploy in the network ISIS Multi Topology , To support the IPv6 Routing learning . Support IPv6 Of BGP4 + , Enable by configuration IPv6 Address family to support IPv6 Notification of route , Upgrade if necessary RR To support the IPv6 Route reflection function .

DS-Lite（Dual Stack Lite）： Lightweight dual stack
DS-Lite It is a lightweight dual stack solution , Only the home gateway is required for network deployment （B4） And newly deployed in the operator network AFTR（Address Family Translation Router） Double stack , Other network nodes only need to support IPv6 that will do . The operator is the home gateway （B4） Distribute private networks IPv4 Address and public network IPv6 Address . User access IPv6 Services can be provided through home gateway and IPv6 The man directly arrives at . about IPv4 Business , Through the home gateway （B4） And AFTR Establish between IPv4-in-IPv6 The tunnel , stay AFTR Realize the unpacking of tunnel on , And will IPv4 The private address is converted to IPv4 Public address , Send to IPv4 Business system . adopt DS-Lite Solution deployment , Operators can use a IPv6 The network also provides IPv4 And IPv6 service ,

2、 Tunnel technology

        Tunneling technology is a technology that encapsulates data packets of one protocol into data packets of another protocol for transmission , It is an effective way to connect isolated islands . There are many types of tunnels , Include 6PE、6vPE、 Manual Tunnel 、GRE、L2TP、6over4、4over6、6to4、ISATAP、Teredo etc. , Different types of tunnels can be used in different application scenarios . Tunnel technology has a big problem ： It is required that the equipment at both ends can be well interconnected .

3、 Address translation or protocol translation technology （NAT）

        There are two ways of address translation ：NAT and NAPT（Network Address and Port Translation）.NAT Mode only converts IP Address , Do not process port numbers . And take NAPT When the way ,NAT When the device performs address translation , Not only to IP The address in the message is converted , Also convert the port number in the message . But the application NAT when , Every private network IP You need a public address , It's a waste of address . therefore , It is often used in practical applications NAPT The way .

        NAT44 Is through the use of public / Private network address translation technology to conservatively extend IPv4 Method used , It is a relatively mature transition technology , It can solve the problem of insufficient address of operators . But the technology exists ALG The problem of 、 Scalability issues , Generally, try to avoid more than two levels NAT.
       NAT64 It's through IPv6/IPv4 Address translation technology to solve IPv6-only and IPv4-only The only way to communicate , Commonly used in IPv6 The end of acting technology .
        Translation techniques are used for IPv6-only The Internet and IPv4-only Network interworking . The translation device is located at the boundary of the two networks , It is necessary to translate IP The corresponding fields of the message header are forcibly converted . In addition, you also need to convert the address carried in the newspaper style . The latter is called ALG（Application Level Gateway）.

4、 contrast