XMPP Server-to-server SASL handshake

Question

I am trying to connect a server to a XMPP server, using the MD5 Digest SASL handshake. But the XMPP server always rejects my response to the challenge. The RFC says the response should look like:

username="example.org",realm="somerealm",\
nonce="OA6MG9tEQGm2hh",cnonce="OA6MHXh6VqTrRk",\
nc=00000001,qop=auth,digest-uri="xmpp/example.org",\
response=d388dad90d4bbd760a152321f2143af7,charset=utf-8

But the value of response (which I have correctly generated based on the inputs) relies on the username and password. For server-to-server communication, which username and password should it be using? The example.org username in the spec doesnt seem right..