DNS zone
This article may be too technical for most readers to understand.(October 2020) |
A DNS zone is a specific portion of the DNS namespace in the Domain Name System (DNS), which a specific organization or administrator manages. A DNS zone is an administrative space allowing more granular control of the DNS components, such as authoritative nameserver. The DNS is broken up into different zones, distinctly managed areas in the DNS namespace. DNS zones are not necessarily physically separated from one another; however, a DNS zone can contain multiple subdomains, and multiple zones can exist on the same server.
The domain namespace of the
A DNS zone is implemented in the configuration system of a
Domains and zones
Most top-level domain name registry operators offer their namespaces to the public or entities with the mandated geographic or otherwise scoped purpose for registering second-level domains. Similarly, an organization in charge of a lower-level domain may operate its namespace and subdivide its space.
Each registration or allocation of subdomain space obligates the registrant to maintain an administrative and technical infrastructure to manage the responsibility for its zone, including sub-delegation to lower-level domains. Each delegation confers essentially unrestricted technical autonomy over the allocated space. An area of one or more subdomains that have been delegated for management is called a DNS zone. A zone always starts at a domain boundary to include all leaf nodes (hosts) in the domain or ends at the boundary of another independently managed zone.
As each domain is further divided into sub-domains, each becoming a DNS zone with its own set of administrators and DNS servers, the tree grows with the largest number of leaf nodes at the bottom. At this lowest level, in the end-nodes or leaves of the tree, the term DNS zone becomes essentially synonymous with the term "domain", both in terms of use and administration. The term domain is used in the business functions of the entity assigned to it, and the term zone is usually used for the configuration of DNS services.
Forward DNS zones
DNS zones contain the records for mapping domain names to IP addresses or other information. The resolution of a domain name to its assigned information is also referred to as forward resolution, and the DNS zones associated with such processes are often referred to as forward zones.[2] The term arose as the opposite of reverse zones, which are used for the reverse process: finding the DNS name associated with an IP address. Such reverse zones are maintained in the Internet Address and Routing Parameter Area (domain arpa).
Another common use of the term forward zone refers to a specific configuration of DNS
Zones for Internet infrastructure
The top-level domain arpa serves as a delegation zone for various technical infrastructure aspects of DNS and the Internet, and does not implement the registration and delegation system of the country and generic domains. The name arpa is a remnant of the
Although the administrative structure of this domain and its sub-domains is different, the technical delegation into zones of responsibility is similar and the DNS tools and servers used are identical to any other zone. Sub-zones are delegated by components of the respective resources. For example, 8.8.2.5.5.2.2.0.0.8.1.e164.arpa., which might represent an E.164 telephone number in the
Example of zone authority in DNS queries
As an example of the DNS resolving process, consider the role of a recursive DNS resolver attempting to look up the address "en.wikipedia.org.". It begins with a list of addresses for the most authoritative name servers it knows about – the root zone name servers (indicated by the full stop or period), which contains name server information for all top-level domains (TLDs) of the Internet.
When querying one of the root name servers, it is possible that the
If the last name server queried did not contain authoritative data for the target of the CNAME, it would have issued the resolver with yet another referral, this time to the zone "text.wikimedia.org.". However, since the resolver had previously determined the authoritative name servers for the zone "org.", it does not need to begin the resolution process from scratch but instead start at zone "org.", thus avoiding another query to the root name servers.
There is no requirement that resolving should involve any referrals at all. Looking up "en.wikipedia.org." on the root name servers always results in referrals, but if an alternative DNS root is used which is set up to contain a record for "en.wikipedia.org.", then the record is returned on the first query.
See also
- Domain propagation
- DNS zone transfer
References
- ^ D.B.Terry, M. Painter, D.W.Riggle, S.Zhou, the University of California Berkeley, The Berkeley Internet Name Domain Server, Report No. UCB/CSD 84/182 (1984)
- ^ "What is Forward DNS (Or Forward DNS Lookup)? - Definition from Techopedia". 23 October 2012.
- ^ "Understanding Forward and Reverse Lookup Zones in DNS". 10 February 2019.