Surgery                       Expert
          |                             |
          |                             |
          |INVITE                       |
          |(offer basic                 |
          | audio&video&clue channels)  |
          |---------------------------->|
          |                             |
          |200 OK                       |
          |<----------------------------|
          |                             |
          |basic audio                  |
          |.............................|
          |                             |
          |basic video                  |
          |.............................|
          |                             |
          |CLUE channel                 |
          |.............................|
          |                             |
          |Advertisement                |
          |---------------------------->|
          |                             |
          |Advertisement                |
          |<----------------------------|
          |INVITE                       |
          |(to cover planned config)    |
          |<----------------------------|
          |INVITE                       |
          |(to cover planned config)    |
          |---------------------------->|
          |                             |
          |491 Request Pending          |
          |---------------------------->|
          |                             |
          |491 Request Pending          |
          |<----------------------------|
          |INVITE                       |
          |(to cover planned config)    |
          |<----------------------------|
          |                             |
          |200 OK                       |
          |---------------------------->|
          |                             |
          |Configure                    |
          |<----------------------------|
          |                             |
          |surgery audio->              |
          |.............................|
          |                             |
          |surgery video->              |
          |.............................|
          |                             |
          |surgery instrumentation video->
          |.............................|
          |                             |
          |surgery instrumentation audio->
          |.............................|
          |                             |
          |CLUE channel                 |
          |.............................|
          |                             |
          |(another OA unnecessary)     |
          |                             |
          |                             |
          |Config                       |
          |---------------------------->|
          |surgery audio->              |
          |<-expert audio               |
          |.............................|
          |surgery video->              |
          |<-expert video               |
          |.............................|
          |surgery instrumentation video->
          |<-expert presentation video  |
          |.............................|
          |                             |
          |surgery instrumentation audio->
          |.............................|
          |                             |
          |                             |
          |                             |