RG               UP                       CP
            |Offline Request |                        |
           1|--------------->|                        |
            |                |    Relay the Offline   |
            |                |        Request         |
            |               2|------to CP via Si----->|
            |                |                        |
            |                |    Send the Offline    |
            |                |        Response        |
            |               3|<-----to UP via Si------|
            |Offline Response|                        |
           4|<---------------|                        |
            |                |     Session Delete     |
            |                |        Request         |
            |                |<--------via Ci---------|
            |                |     Session Delete     |
            |                |       Response         |
            |                |---------via Ci-------->|
            |                |                        |