ICANN Acronyms and Terms

ICANN has hundreds of acronyms and terms, which can be confusing. We created this multilingual tool to help explain what these terms mean and facilitate your work within the ICANN community.

ICANN Acronyms and Terms

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root hints file

A file that provides the names and Internet Protocol (IP) addresses of the 13 authoritative name servers in the root zone of the Domain Name System. Recursive resolvers consult this file when resolving domain names whose IP addresses are not in local cache. The root hints file is often installed with the resolver software. It is also available from the root/files">Internet Assigned Numbers Authority website.

root server

An authoritative name server that responds to queries about the contents of the root zone.

root server instance

An individual server that responds to Domain Name System queries that are directed to the Internet Protocol (IP) address of one of the servers that is authoritative for the root zone. For example, an “instance of the ICANN Managed Root Server" refers to a root server that answers queries sent to the IP address of the authoritative name server operated by ICANN.

Hundreds of root server instances exist around the world. When a resolver submits a query to a root server, anycast routing relays the query packet to the nearest (in terms of routing layout) root server instance. If a local instance is unavailable (perhaps due to a power outage or a network problem), routers automatically redirect the query to the next nearest instance.

Note: The term root server instance replaces root server mirror because it more accurately defines the technology that the Root Server System uses to provide the root service.

root server operator(RSO)

An organization responsible for managing the root service on the Internet Protocol (IP) addresses specified in the root zone and the root hints file.

Root Server System(RSS)

The set of root servers that collectively implement the root service.

Root Server System Advisory Committee(RSSAC)

The Advisory Committee that advises the ICANN Board and the ICANN community on matters relating to the operation, administration, security, and integrity of the Internet’s Root Server System. The RSSAC consists of representatives from the root server operator organizations and liaisons from other ICANN groups and the partner organizations involved in the technical and operational management of the root zone.

Root Server System Advisory Committee Caucus(RSSAC Caucus)

The group within the RSSAC that is responsible for the essential work of the RSSAC. The RSSAC Caucus produces advisories, reports, and other technical documents for approval by the RSSAC. The RSSAC Caucus consists of RSSAC members and individual Domain Name System and root server system experts appointed by the RSSAC.

root service

The collective services provided by all of the anycast instances managed by the root server operators. The root service responds to Domain Name System queries about the root zone. It does not matter which root server instance responds to a query. All root servers with the same version or edition of the root zone provide identical answers. Answers received from the root service can be validated using the Domain Name System Security Extensions.

root trust anchor

The authoritative key at the top of the chain of trust for the Domain Name System Security Extensions (DNSSEC). The authority of the root trust anchor is conferred through parameter settings on DNSSEC-aware resolvers. It is not derived from other keys.

The root trust anchor consists of a public-private key pair. The private key is used to sign the zone signing key (ZSK) for the root zone. DNSSEC-aware resolvers use the public key to verify the authenticity of data in the root zone.

root zone

The top of the Domain Name System hierarchy. The root zone contains all the information needed to find top-level domains. Each edition of the root zone has a unique serial number. All root servers are expected to have (and respond to queries about) the current edition of the root zone.

Root Zone Administrator(RZA)

The entity responsible for managing the data contained within the root zone. The Root Zone Administrator works with the operators of top-level domains (TLDs) and maintains technical and administrative details about the TLDs.

The RZA role is performed by Public Technical Identifiers (PTI) as part of its contracts with ICANN to perform the Internet Assigned Numbers Authority (IANA) functions. PTI is an affiliate of ICANN.

root zone distribution system

The collection of organizations, components, and procedures that provide a reliable and tamperproof means by which the latest version of the root zone can be acquired.

Root Zone Evolution Review Committee(RZERC)

The group that reviews proposed architecture changes to the contents of the Domain Name System root zone and makes recommendations regarding the changes to the ICANN Board. The RZERC consists of nine members:

root zone key signing key

The public-private key pair that is the secure entry point for the root zone and serves as the root trust anchor for the Domain Name System Security Extensions (DNSSEC). The root trust anchor uses its private key to digitally sign the zone signing key (ZSK) for the root zone. DNSSEC-aware resolvers use the root trust anchor’s public key to verify the authenticity of the data in the root zone.

Root Zone Key Signing Key Operator(RZ KSK Operator)

The entity that provides services related to the KSK for the Domain Name System as outlined in the DNSSEC Practice Statement for the Root Zone ZSK Operator.

The RZ KSK Operator is responsible for:

  • Generating and protecting the private component of the RZ KSK.
  • Securely importing public key component from the Root Zone Zone Signing Key Operator (RZ ZSK) Operator.
  • Authenticating and validating the public RZ ZSK keyset.
  • Securely signing the RZ ZSK keyset.
  • Securely transmitting the signed RZ ZSK key set to the RZ ZSK Operator.
  • Securely exporting the RZ KSK public key components.
  • Issuing an emergency key rollover within a reasonable time if any private key component associated with the zone is lost or suspected to be compromised.

The RZ KSK Operator role is performed by Public Technical Identifiers (PTI) as part of its contracts with ICANN to perform the Internet Assigned Numbers Authority (IANA) functions. PTI is an affiliate of ICANN.

root zone key signing key rollover(KSK rollover)

The process of retiring a root zone key signing key (KSK) and replacing it with a new key. The requirement for periodic rollovers of the KSK is specified in the DNSSEC Practice Statement for the Root Zone KSK Operator.

Root Zone Label Generation Rules(RZ-LGR)

A set of rules that determine valid top-level domain labels and their variant labels. The RZ-LGR includes a list of permissible code points and variant code point mappings (if any), along with a set of rules that act on these code points and mappings.

Root Zone Maintainer(RZM)

The entity that accepts root zone data from the Root Zone Administrator, cryptographically signs the root zone data using the zone signing key, and places the signed data in the root zone distribution system. The RZM also serves as the Zone Signing Key Operator for the root zone

Currently, Verisign serves as the RZM under contract with ICANN.

root zone management

The Internet Assigned Numbers Authority (IANA) function related to the stewardship of the root zone. Root zone management involves maintaining the authoritative registry of the top-level domains (TLDs), coordinating with the operators of the TLDs, and managing the root zone’s key signing key (KSK).

Like all IANA functions, root zone management is performed by Public Technical Identifiers, an affiliate of ICANN.