With in the Avalo Voice Platform, SIP Realms are used as part of the device authentication statement, and function as part of the digest stack.
The AVP automatically generates a resolvable Realm in the format of a hostname (ie: 2sfs1ff.avpnet.us). The realm is mapped to the Primary SIP address with in the Geo proximity anycast DNS zone. This means that at a minimum a Realm can be used both as part of the authentication statement and as the hostname for the registration and/or proxy server address.