A fully qualified domain name (FQDN), sometimes also referred to as an absolute domain name,Cite error: A <ref> tag is missing the closing </ref> (see the
help page).
The topmost layer of every domain name is the
DNS root zone, which is expressed as an empty label and can be represented in an FQDN with a trailing dot, such as somehost.example.com.. A trailing dot is generally implied and often omitted by most applications. Trailing dots are required by the standard format for DNS
zone files, as well as to disambiguate cases where an FQDN does not contain any other label separators, such as the FQDNs for the root zone itself and any
top-level domain.
[1]
The length of each label must be between 1 and 63 octets, and the full domain name is limited to 255 octets, full stops included. [2]
Relative domain names
A relative domain name is a domain name which does not include all labels. [3] It may also be referred to as a partially-qualified domain name, or PQDN. [4] Hostnames can be used as relative domain names.
Usage
Dot-separated fully qualified domain names are the primarily used form for human-readable representations of a domain name. Dot-separated domain names are not used in the internal representation of labels in a DNS message [5] but are used to reference domains in some TXT records and can appear in resolver configurations, system hosts files, and URLs.
Web addresses typically use FQDNs to represent the host, as it ensures the address will be interpreted identically on any network. Relative hostnames are allowed by some protocols, including HTTP, but disallowed by others, such as the Simple Mail Transfer Protocol (SMTP). [6]
References
- ^ Fisher, Tim. "FQDN". About.com. Archived from the original on 3 April 2013. Retrieved 20 March 2013.
- ^ RFC 2181
- ^ Gavron, Ehud (October 1993). "A Security Problem and Proposed Correction With Widely Deployed DNS Software". Archived from the original on 2020-10-17. Retrieved 2020-10-01.
- ^ "Fully Qualified Domain Name (FQDN) and Partially Qualified Domain Name (PQDN)". Archived from the original on 2015-03-16. Retrieved 2015-03-23.
- ^ "Wireshark Q&A". osqa-ask.wireshark.org. Archived from the original on 13 April 2021. Retrieved 13 April 2021.
- ^ Klensin, John C. (1998-05-21). "Definition of domain names in Simple Mail Transfer Protocol". Tools.ietf.org. Archived from the original on 2013-12-30. Retrieved 2014-01-08.
External links
- RFC 1123: Requirements for Internet Hosts – application and support
- RFC 1535: A Security Problem and Proposed Correction With Widely Deployed DNS Software
- RFC 2181: Clarifications to the DNS specification
- RFC 4703: Resolution of Fully Qualified Domain Name (FQDN) Conflicts among Dynamic Host Configuration Protocol (DHCP) Clients
A fully qualified domain name (FQDN), sometimes also referred to as an absolute domain name,Cite error: A <ref> tag is missing the closing </ref> (see the
help page).
The topmost layer of every domain name is the
DNS root zone, which is expressed as an empty label and can be represented in an FQDN with a trailing dot, such as somehost.example.com.. A trailing dot is generally implied and often omitted by most applications. Trailing dots are required by the standard format for DNS
zone files, as well as to disambiguate cases where an FQDN does not contain any other label separators, such as the FQDNs for the root zone itself and any
top-level domain.
[1]
The length of each label must be between 1 and 63 octets, and the full domain name is limited to 255 octets, full stops included. [2]
Relative domain names
A relative domain name is a domain name which does not include all labels. [3] It may also be referred to as a partially-qualified domain name, or PQDN. [4] Hostnames can be used as relative domain names.
Usage
Dot-separated fully qualified domain names are the primarily used form for human-readable representations of a domain name. Dot-separated domain names are not used in the internal representation of labels in a DNS message [5] but are used to reference domains in some TXT records and can appear in resolver configurations, system hosts files, and URLs.
Web addresses typically use FQDNs to represent the host, as it ensures the address will be interpreted identically on any network. Relative hostnames are allowed by some protocols, including HTTP, but disallowed by others, such as the Simple Mail Transfer Protocol (SMTP). [6]
References
- ^ Fisher, Tim. "FQDN". About.com. Archived from the original on 3 April 2013. Retrieved 20 March 2013.
- ^ RFC 2181
- ^ Gavron, Ehud (October 1993). "A Security Problem and Proposed Correction With Widely Deployed DNS Software". Archived from the original on 2020-10-17. Retrieved 2020-10-01.
- ^ "Fully Qualified Domain Name (FQDN) and Partially Qualified Domain Name (PQDN)". Archived from the original on 2015-03-16. Retrieved 2015-03-23.
- ^ "Wireshark Q&A". osqa-ask.wireshark.org. Archived from the original on 13 April 2021. Retrieved 13 April 2021.
- ^ Klensin, John C. (1998-05-21). "Definition of domain names in Simple Mail Transfer Protocol". Tools.ietf.org. Archived from the original on 2013-12-30. Retrieved 2014-01-08.
External links
- RFC 1123: Requirements for Internet Hosts – application and support
- RFC 1535: A Security Problem and Proposed Correction With Widely Deployed DNS Software
- RFC 2181: Clarifications to the DNS specification
- RFC 4703: Resolution of Fully Qualified Domain Name (FQDN) Conflicts among Dynamic Host Configuration Protocol (DHCP) Clients