Automatic Configuration of IPv6 stateless addresses

IPv6 is the core protocol of the Next Generation Internet. It solves many defects exposed by the IPv4 protocol, such as address scarcity, large route tables, and insufficient support for mobile devices. IPv6 supports automatic Address Configuration of network nodes, which greatly simplifies the work of network administrators.

1. IPv6 address format and address configuration method

　
A typical IPv6 host Unicast address consists of three parts: Global route prefix, subnet ID, and interface ID (64-bit ). Global
The routing prefix is used to identify an address range allocated to a site. A subnet ID is also called a subnet prefix.
A link is associated to identify a link in the site. The Interface ID is used to identify an interface on a link. It is unique on the link.

IPv6 address configuration can be divided into manual Address Configuration
And automatic address configuration. The automatic address configuration method can be divided into stateless address automatic configuration and stateful address automatic configuration. When the Stateless Address is automatically configured, the network interface receives the router Declaration
The global address prefix of the rule, and then obtain a global unicast address that can be clustered with the interface ID. The Dynamic Host Configuration Protocol (DHCP) is used in the automatic configuration of stateful addresses.
DHCP server. The Network Interface obtains address configuration information from the DHCP server in Client/Server mode.

2. generate an interface ID

In the stateless
The Interface ID can be obtained through the eui64 conversion algorithm in the automatic configuration mode. The Interface ID is converted from a 48-bit MAC address. Eui64 is a 64-bit
Extends the unique identifier. It is a combination of the IEEE-designated public 24-digit manufacturer identification and the 40-digit value specified by the manufacturer for the product. In an IPv6 address, the length of the Interface ID is 64 bits, which consists of 48 bits
Ethernet MAC address conversion. The eui64 conversion algorithm is introduced below.

The format of the 48-bit Ethernet MAC address is fixed as follows:

The C-bit indicates the vendor ID, the M-bit indicates the vendor ID, and the G-bit indicates a single host or a group. The conversion algorithm needs to reverse the first digit of the G bit and insert two fffe bytes between the C-bit and M-bit (3rd and 4th bytes of the MAC address, the Interface ID is:

Example 1 of automatic host address configuration in Windows XP.

(1) The linklayer address is the MAC address (0007951a0669 ).

(2) preferred linklocal obtains the local address of the host link through automatic configuration. Fe80 is the fixed prefix of the local link address. 207: 95ff: fe1a: 669 is the interface ID obtained from the MAC address conversion.

　　3. Obtain the global route prefix

A network node sends a router request RS (rolic solic itation) message to the router connected to it to obtain its global route prefix, as shown in vro Request Message 2 captured on the network.

The RS Message Type field value is 133, indicating that this is a router request message. The source address of the message is the local link address of the network node. Because this is a router request message, the destination address is ff02:: 2 (all vrouters multicast addresses ).

　
After the router receives the RS message from the network node, it returns the router to the node and declares the RA (Router Advertisement) elimination.
. RA Message 3 is shown. The source address of the RA message is the IPv6 address of the router, and the destination address is the local address of the network node.
Link address. The message type field value is 134, indicating that this is a route advertised message. The Message option field provides the global
Route prefix 1 ::. After obtaining the global route prefix, the network node combines with the interface ID to form its Global IPv6 address. At this point, the stateless address of the network node is automatically configured.

4 Conclusion

The Interface ID obtained by using the Eui 64 conversion algorithm is fixed by the random device hardware and globally unique. This algorithm is easy to implement and is an important algorithm for Automatically Generating interface IDs. Currently, in Windows and Linux operating systems, the Eui 64 conversion algorithm is used when generating interface IDs for hosts. As an improvement to this algorithm, rfc3041 introduces a random address mechanism, which includes a set of random numbers instead of the Interface ID converted from the MAC address. The address has a certain life cycle. After the life cycle ends, the address will be automatically changed, which effectively solves the problem of Internet access activity tracking on the node.

References

[1] Zhou Xun. Core of IPv6 next-generation Internet [M]. Beijing: Electronics Industry Press, 2003.

[2] rfc2460 Internet protocol, version 6 (IPv6) specification [s].

[3] IP consorrenttest suite, Internet Protocol version 6 Technical Document, 2002-01, University of New Hampshire, interperablity lab.

[4] IP version 6 group (IPv6) http://www.ietf.org/html.charters/ipv6arter.html.2003-9-25.

[5] rfc2463 Internet Control Message Protocol (ICMPv6) for the IPv6 specification.

[6] Silvia Hagen. essence of IPv6 [M]., translated. Beijing: Tsinghua University Press, 2004.

Author: Song Xiaoyu, Qiu Zeyang (Lanzhou Jiaotong University, Lanzhou 730070, China)