Alice                      Bob
                  |                         |
                  |     INVITE (Offer)      |
                  |------------------------>|
                  |      183 (Answer)       |
                  |<------------------------|
                  |        PRACK/OK         |
                  |------------------------>|
                  |                         |
          +----------------------------------------+
          |Alice and Bob know that both can trickle|
          |and know that the dialog is in the early|
          |state. Send INFO!                       |
          +----------------------------------------+
                  |                         |
                  |  INFO/OK (+SRFLX Cand.) |
                  |------------------------>|
                  |  INFO/OK (+SRFLX Cand.) |
                  |<------------------------|
                  |                         |

        Note: "SRFLX" denotes server-reflexive candidates