The JANET NRS (Name Registration Scheme) was a pseudo-hierarchical naming scheme used on British academic and research networks in the 1980s. It used a reverse domain name notation.


It was proposed in 1983 and used until the superficially similar Internet Domain Name System was fully adopted.[1][2][3][4]


The NRS "second-level domains" consisted of UK.AC (JANET academic and scientific sites), UK.CO (commercial) and UK.MOD (Ministry of Defence). Any organisations not falling into these categories were given their own "second-level" name, e.g. UK.BL (British Library) or UK.NEL (National Engineering Laboratory).

All NRS names had both a standard (long) and abbreviated (up to 18 characters) form. For example, UK.AC.CAMBRIDGE was the less widely used standard equivalent of the abbreviated name UK.AC.CAM.

For email, interoperability between the "Grey Book" email addressing style of user@UK.AC.SITE and ARPA and USENET addresses of the style was achieved by way of mail gateway at University College London.[2][3][5]

Comparison with DNSEdit

A principal difference with the Domain Name System was that the order of significance began with the most significant part (so called big-endian addresses). Also, NRS names were canonically written in upper case. For example, the University of Cambridge had the NRS name UK.AC.CAM, whereas its DNS domain is

After Internet country-code top-level domains were introduced from 1984, confusion was caused when the least significant part of an Internet address matched the most significant part of an NRS address and vice versa. The ccTLD ".cs" for Czechoslovakia came into use around 1990-2 until 1995. The classic joke was that e-mail intended for UK universities ended up in Czechoslovakia, since many JANET e-mail addresses were of the form user@UK.AC.universityname.CS, where "CS" stood for Computer Science (department).[2][3][5]

Another significant difference from the DNS was the concept of context to name lookups, e.g. 'mail' or 'file transfer'. This made the NRS more sophisticated than the DNS, permitting overloading of names.


JANET transitioned to using Internet protocols in 1991,[6] and by 1994 the DNS had become the de facto standard for domain names on JANET.[7] The final mail gateway was taken out of service by the end of 1997.[8]

The one remaining legacy of the NRS is the convention of using .uk for British DNS domains, rather than .gb as specified by ISO 3166.

See alsoEdit


  1. ^ Wells, Mike (1988-11-01). "JANET-the United Kingdom Joint Academic Network". Serials. 1 (3): 28–36. doi:10.1629/010328. ISSN 1475-3308.
  2. ^ a b c Houlder, Peter (January 19, 2007). "Starting the Commercial Internet in the UK" (PDF). 6th UK Network Operators' Forum. Retrieved 2020-02-12.
  3. ^ a b c Reid, Jim (April 3, 2007). "Networking in UK Academia ~25 Years Ago" (PDF). 7th UK Network Operators' Forum. Retrieved 2020-02-12.
  4. ^ The "Hidden" Prehistory of European Research Networking. Trafford Publishing. ISBN 978-1-4669-3935-6.
  5. ^ a b Mansell, Robin; Mansell, Dixons Chair in New Media and the Internet Interdepartmental Programme in Media and Communications Robin (2002). Inside the Communication Revolution: Evolving Patterns of Social and Technical Interaction. Oxford University Press. p. 208. ISBN 978-0-19-829656-0.
  6. ^ "FLAGSHIP". Central Computing Department Newsletter (16). September 1991.
  7. ^ Rutter, Dorian (2005). From Diversity to Convergence: British Computer Networks and the Internet, 1970-1995 (PDF) (Computer Science thesis). The University of Warwick.
  8. ^ "Janet(UK) Quarterly Report to the Janet Community: July 1997 to September 1997". Janet webarchive. 1997. Archived from the original on February 16, 2012.