FreeSWITCH           Proxy               sip:1003          sip:1003
            +                 +                   +                  +
            |     Invite      |                   |                  |
            |---------------->|                   |                  |
            |                 |      Invite       |                  |
            |                 |+----------------> |                  |
            |                 |                   |    Invite        |
            |                 |+------------------|----------------->|
            |                 |                   |                  |
            |                 |    180 with 100rel|                  |
            |  180 with 100rel|<-----------------+|                  |
            |<---------------+|                   |                  |
            |                 |                   |                  |
            |   PRACK         |                   |                  |
            |+--------------> |                   |                  |
            |                 |    PRACK          |                  |
            |                 | +---------------> |                  |
            |  200 OK PRACK   |   200 OK PRACK    |                  |
            | <--------------+| <----------------+|                  |
            |                 |                   |                  |
            |                 |    180 without 100rel                |
            | <-----------------------------------------------------+|
            |                 |                   |                  |
            |                 |  200 OK to INVITE |                  |
            |<----------------|-------------------|-----------------+|
            |                 |                   |                  |
            | Orphan 200 Ok send ACK&BYE          |                  |
            |                 |                   |                  |
            |                 +                   +                  |
            +                                                        +