Alice                                            Bob
          |                     Offer                     |
          |---------------------------------------------->|
          |            Additional Candidates              |
          |---------------------------------------------->|
          |                     Answer                    |
          |<----------------------------------------------|
          |            Additional Candidates              |
          |<----------------------------------------------|
          | Additional Candidates and Connectivity Checks |
          |<--------------------------------------------->|
          |<========== CONNECTION ESTABLISHED ===========>|