IPv6 domain name resolution service Basics

The Root Domain Name Server of the Internet has been improved to support both IPv6 and IPv4. Therefore, you do not need to create an independent Domain Name System for IPv6 domain name resolution. The IPv6 Domain Name System can be combined with the traditional IPv4 domain name system. Now the most common domain name service software BIND on the Internet has implemented support for IPv6 addresses, so the ing between IPv6 addresses and host names is easy to solve.

To support the IPv6 domain name resolution service system, you must support the following new features:

The type of the IPv6 address. the domain name server that recognizes the new features above can provide services for IPv6 address-name resolution.

1) forward IPv6 domain name resolution

The resource record for IPv4 address forward resolution is "A", while there are currently two resource records for IPv6 domain name resolution forward resolution, namely "AAAA" and "A6. "AAAA" was proposed earlier. It is A simple extension of IPv4 protocol "A". Because the IP address is increased from 32 to 128 bits, it is increased by four times, therefore, resource records are expanded from "A" to four "". However, "AAAA" is used to indicate the ing between the domain name and IPv6 address, and does not support hierarchical address.

The AAAA resource record type is used to resolve A valid domain name to an IPv6 address. It is compatible with the resource record type used by IPv4. The new resource record type is named AAAA because the 128-bit IPv6 address is exactly four times the 32-bit IPv4 address. Below is an AAAA resource record instance:

Host1.microsoft. comINAAAAFEC0: 2AA: FF: FE3F: 2A1C

"A6" is proposed based on RFC2874. It establishes a connection between an IPv6 address and multiple "A6" records. Each "A6" record only contains part of the IPv6 address, after integration, it is assembled into a complete IPv6 address. The "A6" record supports some new features not available in "AAAA", such as Address Aggregation and address change Renumber.

The "A6" record splits 128-bit IPv6 addresses into several levels based on the allocation levels of TLA, NLA, and SLA projects in the clustered global unicast addresses, constitute an address chain. Each address prefix and suffix are a part of the address chain. A complete address chain forms an IPv6 address. This idea conforms to the IPv6 address hierarchy and supports Address Aggregation.

At the same time, when you change the ISP, you need to change its IPv6 address as the ISP changes. It is very cumbersome to manually modify all the addresses registered in DNS in the user subnet. In the address chain represented by the "A6" record, you only need to change the ISP name corresponding to the address prefix, which can greatly reduce the modification of resource records in DNS. In addition, the Address Allocation layer is closer to the underlying layer, and less changes are required.

2) reverse IPv6 domain name resolution

The reverse resolution record of IPv6 domain name resolution is the same as that of IPv4, which is "PTR", but there are two address representations. One is the half-byte hexadecimal numeric format separated by ".". The low-byte address is in front, the high-byte address is in front, and the domain suffix is "IP6.INT .". The other is the binary string Bit-string format, starting with "\ [". The hexadecimal address has no separator, and the high position is in front and the low position is in the back, add "]" after the address, and the domain suffix is "IP6.ARPA. ". The half-byte hexadecimal numeric format corresponds to "AAAA" and is a simple extension of IPv4. The binary string format corresponds to the "A6" record, and the address is similar to "A6". It can be divided into multi-level address chains, and "DNAME" is used for each level of authorization. Like A6, the binary string format also supports the address hierarchy feature.

The IP6.INT domain is used to provide the Reverse Address to the host name resolution service for IPv6. Reverse retrieval, also known as pointer retrieval, determines the host name based on the IP address. To create a namespace for reverse search, all 32-bit hexadecimal numbers in the IPv6 address are in reverse order in the IP6.INT domain. For example, if the full expression for the address FEC0: 2AA: FF: FE3F: 2A1C is: FEC0: 0000: 0000: 0000: 02AA: 00FF: FE3F: 2A1C, in the IP6.INT domain: C.1.A. 2. f.3.E. f. f. f.0.0.A. a.2.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.c. e. f. IP6.INT.

In short, IPv6 addresses in the form of address chains reflect address hierarchy and support Address Aggregation and address change. However, since a complete address resolution is divided into multiple steps, you need to query different DNS servers according to the address allocation level, all the queries are successful to obtain the complete resolution results. This will inevitably prolong the resolution time and increase the chance of errors. Therefore, in terms of technology, IPv6 needs to further improve the DNS address chain function and improve the speed of IPv6 domain name resolution in order to provide users with ideal services.