JANET NRS

The JANET NRS (Name Registration Scheme) was a pseudo-hierarchical naming scheme used on British academic and research networks until the superficially similar system used by the Internet DNS was fully established.

A principal difference 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 cam.ac.uk. 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.

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.

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).