Alice                      Bob
                  |                         |
                  |     INVITE (Offer)      |
                  |------------------------>|
                  |      183 (Answer)       |
                  |<------------------------|
                  |  INFO/OK (+SRFLX Cand.) |
                  |------------------------>|
                  |                         |
                  |               +----------------------+
                  |               |Bob:  Now I know Alice|
                  |               | is ready. Send INFO! |
                  |               +----------------------+
                  |  INFO/OK (+SRFLX Cand.) |
                  |<------------------------|
                  |                         |
                  |    200/ACK (Answer)     |
                  |<------------------------|

          Note: "SRFLX" denotes server-reflexive candidates