The demand for IPv6 Domain Name System and Its Solution Method
Abstract: IPv6 protocol to replace IPv4 next-generation network protocol, it has many new features and functions. Domain Name System (DNS) is the Internet Infrastructure, IPv6 new features also require DNS support. Therefore, DNS is bound to be upgraded to meet the needs of IPv6. In this paper, IPv6 The address space, IPv6 address auto-configuration and plug and play, IPv6 mobility, IPv4 to IPv6 transition and other aspects of the IPv6 for DNS Needs and their solutions are analyzed and studied. Key words: IPv6; Domain Name System 1 Introduction IPv6 is the next generation network protocol, it has a huge address space; and address from the address structure, the distribution of support address aggregation, thereby greatly Reduce the routing table entries; has a network of convenient plug and play functionality; has good mobility support, and new features. Domain Name System (Domain Name System, referred to as DNS) through the main function of domain names and IP addresses corresponding relation between, to locate network resources that, according to domain name Query IP addresses, and vice versa. It is the Internet's infrastructure, a large number of network services (such as Http, Ftp, Email, etc.) are built Standing on top of DNS services. IPv6 network, DNS is very important, a number of new features and IPv6 support to DNS inseparable. In this paper, IPv6 address space, IPv6 Address Auto-configuration and plug and play, IPv6 mobility, IPv4 to IPv6 transition and other aspects of the new features of IPv6 for DNS needs and The solution was analyzed and studied. 2 IPv6 addresses Category IPv6 address length is 128 bits, the address in accordance with its transmission types are divided into three kinds [1]: Unicast address (Unicast Address): used to identify a single network interface. Destination address is the unicast address of the packet will be sent give
This address identifies the network interface. Anycast address (Anycast Address): used to identify a group of network interfaces (typically belonging to different nodes). Destination address is the anycast to The site where the data packets will be sent to the routing sense, the latest in a network interface. Multicast address (Multicast Address): used to identify the identity of a group of network interfaces (typically belonging to different nodes). Sent to multiple Multicast address packets sent to the group, all of the network interfaces. In IPv6 there is no broadcast address (Broadcast Address), with the Replaced by a multicast address. Among them, a single multicast address in accordance with the transmission range of addresses is divided into global address (Global Unicast Addresses), site-local addresses (Site-Local Have multiple addresses (including unicast addresses, anycast addresses, and multicast address). 3 IPv6 addresses with the DNS hierarchy IPv6 address space to provide up to 2128 addresses assigned to the Earth's surface an average of addresses per square meter in the number of Ge are 6.5 × 1023. So A huge address space enough to the future of mankind for a long time use. For the DNS is concerned, the need for resolution of the records are also the times than the IPv4 Greatly increased. However, IPv6 addresses are numerous, due to the structure and address the allocation of IPv6 addresses strict hierarchy, so the router Pressure not only did not increase but significantly reduced. IPv6 address hierarchy and methods of distribution are as follows: top-level address Aggregators TLA (that is, a large ISP or address of the governing body) was large Address, is responsible to the two addresses Aggregators NLA (small and medium-scale ISP) to assign addresses, NLA to the site-level Address Aggregation agencies SLA (subnet) And network users assigned addresses. IPv6 addresses in the DNS hierarchy through address chain technology can be a very good support. The following from the DNS Forward Address resolution and reverse address resolution analysis of two aspects. 3.1 Forward Address Resolution IPv4 address resource records are being resolved "A" record. IPv6 address being resolved at present, there are two resource
records, that is, "AAAA" And "A6" records. Which, "AAAA" proposed earlier [2], it is a "A" record a simple extension, due to IP addresses from 32-bit extensions to 128 Bit, expanded four-fold, so resource record from the "A" to expand into four "A". "AAAA" is used to indicate the corresponding domain names and IPv6 addresses the relationship between Does not support the address of the hierarchy. "A6" in RFC2874 [3] proposed, it is to an IPv6 address with multiple "A6" record to establish contacts, each "A6" records only Contains the IPv6 address as part of combination assembled into a complete IPv6 address. "A6" record to support a number of "AAAA" not available New features, such as address aggregation, change of address (Renumber) and so on. First of all, "A6" recording under the TLA, NLA, and SLA level, the distribution of the 128-bit addresses, IPv6 addresses decomposed into several levels Prefix and address of the suffix to form an address chain. Each address prefix and address of the address chain suffixes are part of a complete address of the chain of The formation of a IPv6 address. This idea in line with the hierarchy of IPv6 addresses to support address aggregation. Second, the user to change the ISP, you should change with the ISP to change its own IPv6 address. If you manually modify all the user sub-network The address registered in DNS, is a very complicated thing. While using "A6" records that the address of the chain, as long as the corresponding change of address prefixes ISP's name can be, we can greatly reduce the DNS resource records in the changes. And in the address near the bottom of the distribution level, and Vietnam, the need for more changes Less. In the example below, the node host.example.com address from example.com (SLA) distribution, example.com address from example1.net (NLA) distribution, while the example1.net address is from the ISP-A.net (TLA) distribution. The following records on the formation of more than a complete The chain of IPv6 DNS addresses. Example1.net change if the ISP, the need to change their DNS of the ISP address prefix,
and its network users example.com is no need to change the DNS settings. Example 1: IPv6DNS Address chain: $ ORIGIN example.com. host IN A6 64 0:0:0:0:42:: 1 company.example1.net. $ ORIGIN example1.net. company IN A6 32 0:0:201:1860:: SUBSCRIBER-X.ISP-A.net $ ORIGIN ISP-A.net. SUBSCRIBER-X IN A6 0 3ffe: 8050:: Example 2: the cases of one of the address translation into the "AAAA" records that the form of: $ ORIGIN example.com. host IN AAAA 3ffe: 8050:201:1860:0:0:0:0:42:: 1 3.2 Reverse Address Resolution IPv6 reverse lookup records and IPv4, as is the "PTR", but the address representation in two ways. One is to use "." Separated nibble 16 hexadecimal number format (Nibble Format), low address in the former, high address, the domain suffix is "IP6.INT.". The other is the binary String (Bit-string) format to "\ [" beginning of the 16 hex address (no separator, high front and low in the post) center, address, added, "]", The domain suffix is "IP6.ARPA.". Semi-byte format with 16 digits "AAAA" counterpart, is a simple extension of IPv4. Binary string format And "A6" records of correspondence, addresses such as "A6", as can be divided into multi-level address chain, said the authority at every level with the "DNAME" record. And "A6", as a binary string format also supports address-level features. In short, to address chain, expressed in the form of IPv6 address reflects the address of the hierarchy, support address aggregation and change of address. However, due to time The complete address resolution into multiple steps, need to follow the address allocation hierarchy to different DNS servers to query. All of the search Consultation had been successful to get the full analytic results. This is bound to extend the analysis time has also increased the chance of error. Thus, the need for further improvement of DNS Address chain function to improve the speed of domain name resolution in order to provide users with satisfactory service. 4 IPv6 Plug and Play features and DNS
IPv6 protocol support address auto-configuration [4] [5], which is a plug and play mechanism, without any human intervention, IPv6 network Interface to access the link local address, site local addresses and global addresses, and can prevent address duplication. IPv6 supports stateless address self Dynamic configuration and stateful address autoconfiguration in two ways. In the stateless address auto-configuration mode, you need to configure the network interface address of the first use of neighbor discovery mechanism to obtain a link-local address. Network Interface get the link-local address, and then accept the declaration of the address of the router prefix, combined with interface ID to get a global address. While Stateful address auto-configuration methods, such as DHCP (Dynamic Host Configuration Protocol), requires a DHCP server, through the client / server mode Type obtained from a DHCP server at address configuration information. IPv6 nodes through the address auto-configuration of IPv6 addresses and gateway address. However, the address auto-configuration of DNS servers does not include the self Fixed configuration. How to automatically discover the DNS server to provide resolution services is also a need to be resolved [6]. Under study DNS server Auto-discovery solution that can be divided into two types of non-state and the state. In the stateless mode, you need to subnet the internal DNS server is configured to site-wide anycast address. To conduct automatic configuration of nodes To the anycast address to send the server address for the purpose of discovery requests, ask DNS server addresses, domain names and search paths and other DNS information. This The request to reach the nearest DNS server, server, upon request, to answer unicast DNS server addresses, DNS domain names and search paths, etc. Information. Nodes in the server's response according to the local DNS configuration information, future DNS requests directly with the unicast address to send to the DNS server. Alternatively, you can not site-wide anycast address, while the use of site-wide multicast address or a link multicast address. Can also be a Direct use of site-wide anycast address as the DNS server
addresses, all of the DNS resolution requests are sent to the anycast address. From the most The DNS server is responsible for recent resolution of this request, the analytical results obtained after a request to return the results to the node, rather than the practice of the DNS service Device unicast addresses, DNS domain names and search paths to disseminate information to the node. From the network scalability, security, usability and other aspects into account, the first A use of site-wide anycast address as the DNS server address ways relatively good. In a state of DNS server discovery mode, such as through a similar DHCP server to DNS server addresses, domain names and search DNS paths to disseminate information to the node. Of course, doing so requires additional servers. 5 IPv6 mobility and DNS Mobility IPv6 on a very good support, through local agents (home agent) and the binding update (binding update) and other technologies. Mobile host to reach a new subnet, the access to care-of address (care-of address), and registered with the local agent. To change the care-of address, the use Binding update message to the local agents and on the communication entities such as address update notification. For a domain name host, if the use of DNS technology, but also to some extent be able to support host mobility. In the mobile host location update At the same time, using dynamic DNS technology to modify the DNS in a timely manner corresponding to the address of the host domain name record, then you can get through the domain name resolution To the latest address of the mobile host and thus able to communicate with the mobile host. But because the DNS was designed primarily to support the static configuration, change Very low frequency of DNS data, it is difficult to adapt to the mobile host frequent change of address. This method is only suitable for mobile hosts is not very frequent, in the host Acquired a new address, regardless of whether the address is automatically configured care-of address or the address can be dynamic DNS technology to address
Notice of change is responsible for parsing the host primary DNS domain name servers. Master server to update and then notify the secondary servers to update, and to adjust the The cache valid time and avoid mistakes. Process shown in Figure 1. Figure 1 Schematic diagram with DNS support for mobility In short, the idea is to solve the mobility when the mobile node to change the address, to quickly and timely notification of communication such as communications agency or entity, To communicate each other in a timely manner with the host to continue to communicate the new location. And how to address when switching to maintain smooth communications, as well as Moving in the process of security, authentication and other mobility problems are to solve the focus. 6 IPv6 transition phase and the DNS In the IPv4 to IPv6 transition process, as the Internet infrastructure of the DNS service should support this network protocol upgrade and conversion. IPv4 and IPv6, DNS record format, etc. are different, in order to achieve the IPv4 network and IPv6 networks for DNS queries and responses can be To adopt the DNS-ALG Application Layer Gateway with NAT-PT method [7], in the IPv4 and IPv6 networks play a role in translation. For example, IPv4 address mapping using the domain name "A" record, and IPv6 use the "AAAA" or "A6" records. Well, IPv4 to IPv6 nodes to send The network DNS query request is "A" records, DNS-ALG put "A" be changed to "AAAA", and sent to the DNS in IPv6 networks The server. When the server's response when the DNS-ALG to reach, DNS-ALG amended answer to "AAAA" changed to "A", the IPv6 address change Into a DNS-ALG of the IPv4 address pool to convert addresses to the IPv4 addresses and IPv6 addresses conversion mapping between notification NAT-PT, And to convert this IPv4 address as the analytical results returned IPv4 host. IPv4 hosts to the IPv4 address as the destination address conversion and the actual The IPv6 hosts communicate through the NAT-PT. Indicate in Figure 2. Figure 2 DNS ALG diagram For dual-stack mode transition method, DNS server at the same time there is "A" records and "AAAA" (or "A6") records. As the node can handle both IPv4 protocol, but also can handle
the IPv6 protocol, so no conversion device similar to the DNS ALG. Regardless of DNS service Service device to answer "A" record or "AAAA" records, can communicate. 7 Summary With the continuous development of Internet technology, IPv6 has been away from us getting closer. DNS as the IPv4 era of network infrastructure services, Internet Plays an important role. In the coming IPv6 era, the new DNS protocol and functional requirements will no longer be provided only in the traditional sense of a simple capital Source location, but rather the one hand, similar to the IPv4 DNS to provide the basis for functionality, other new features with IPv6, and other agreements with organic Together, provide new features that make network configuration, maintenance, use become more simple and convenient, allowing users to feel the new technology has brought a new experience. References: [1] R. Hinden, RFC2373: "IP Version 6 Addressing Architecture", July 1998 [2] S. Thomson, RFC1886: "DNS Extensions to support IP version 6", December 1995 [3] M. Crawford, RFC2874: "DNS Extensions to Support IPv6 Address Aggregation and Renumbering", July 2000 [4] T. Narten, RFC2461: "Neighbor Discovery for IP Version 6 (IPv6)", December 1998 [5] S. Thomson, RFC2462: "IPv6 Stateless Address Autoconfiguration", December 1998 [6] Dave Thaler, draft-ietf-ipngwg-dns-discovery-analysis-00.txt, "Analysis of DNS Server Discovery Mechanisms for IPv6 ", July 2001 [7] G. Tsirtsis, RFC2766: "Network Address Translation Protocol Translation (NAT-PT)",