RADIUS attribute from rfc5090
This attribute holds the user name used in the HTTP Digest calculation. The RADIUS server MUST use this attribute only for the purposes of calculating the digest. In order to determine the appropriate user credentials, the RADIUS serverMUST use the User-Name (1) Attribute, and MUST NOT use the Digest-Username Attribute. This attribute MUST only be used in Access-Request and Accounting-Request packets. Type 115 for Digest-Username Length >= 3 Text In Access-Requests, the RADIUS client takes the value of the username directive (username-value according to ) without surrounding quotes from the HTTP-style request it wants to authenticate.