[Serusers] Questions about domain field in Proxy-Authenticate

[Paul Belanger]

>From RFC3261:

20.27 Proxy-Authenticate

   A Proxy-Authenticate header field value contains an authentication
   challenge.

   The use of this header field is defined in [H14.33].  See Section
   22.3 for further details on its usage.

   Example:

      Proxy-Authenticate: Digest realm="atlanta.com",
       domain="sip:ss1.carrier.com", qop="auth",
       nonce="f84f1cec41e6cbe5aea9c8e88d359",
       opaque="", stale=FALSE, algorithm=MD5

My question revolves around the domain="sip:ss1.carrier.com" field.  I notice that SER does not
use the option, however I have another proxy that does.  I have searched for information about
this field, but not able to get the information I need.  Why would you use a realm and domain
field at the same time?  Is 1 preferred to another?  Should both be used?

Any help would be great.

PB