Direction: Media Engine to Application

This value is set by the media engine to inform your app of one of the the following:

An incoming SIP mesage was received and the media engine wants to know if your app wants to challenge the message. In this case, the value of this member will be set to AUTHENTICATE_INCOMING_MESSAGE and the message type received will be specified by the MesageType member. If your app wants to challenge the SIP message, it should set the ChallengeMode and ChallengeType members to the appropriate values for your application. If your app does not want to challenge the SIP message, it should set the ChallengeMode to either WWW or proxy authentication, ChallengeType to CHALLENGE_TYPE_NONE. If your app challenges the SIP message, it also must specify a challenge algoritm that will be used by the media engine. It is recommended that the Algorithm member be set to CHALLENGE_ALGORITHM_MD5. The far end also requires a realm to challenge so your app must also set the ChallengeRealm member.

- OR -

An incoming SIP mesage was received that contains authorization credentials and the media engine is asking your application to validate the credentials. In this case, the value of this member will be set to AUTHENTICATE_VERIFY_CREDENTIALS. The ChallengeRealm member will contain the authorization realm the far end device specified and the hChallenge member will be a handle to internal challenge information the far end specified.