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

       Note: "SRFLX" denotes server-reflexive candidates