The present disclosure describes methods and systems for establishing a Session Initiation Protocol Session. One method includes transmitting a first message requesting authentication configuration information; in response to the first message, receiving a second message that includes the authentication configuration information; transmitting a third message that includes authentication information based upon the received authentication configuration information; receiving an authentication challenge request that is formatted according to the second protocol; and in response to receiving the authentication challenge request, transmitting an authentication response to the second network node.