Editing RADIUS (section)

===Realms===
A realm is commonly appended to a user's user name and delimited with an '@' sign, resembling an email address domain name. This is known as ''postfix'' notation for the realm. Another common usage is ''prefix'' notation, which involves prepending the realm to the username and using '\' as a delimiter.
Modern RADIUS servers allow any character to be used as a realm delimiter, although in practice '@' and '\' are usually used.

Realms can also be compounded using both prefix and postfix notation, to allow for complicated roaming scenarios; for example, somedomain.com\username@anotherdomain.com could be a valid username with two realms.

Although realms often resemble domains, it is important to note that realms are in fact arbitrary text and need not contain real domain names. Realm formats are standardized in RFC 4282, which defines a Network Access Identifier (NAI)  in the form of 'user@realm'. In that specification, the 'realm' portion is required to be a domain name. However, this practice is not always followed.  RFC 7542<ref>{{cite web |title=The Network Access Identifier |url=https://tools.ietf.org/html/rfc7542 |publisher=Internet Engineering Task Force (IETF) |access-date=8 May 2021 |date=May 2015|doi=10.17487/RFC7542 |last1=Dekok |first1=A. |doi-access=free }}</ref> replaced RFC 4282 in May 2015.