           +----------------+               +----------------+
           |      +------+  |               |      +------+  |
     |     |  *-->|  T1  |  |         |  +-------->|  T1  |  |
     |     |      +------+  |         |  |  |      +------+  |
---->|---->|================|    ---->|--+  |================|
     |     |      +------+  |         |  |  |      +------+  |
     |     |  *-->|  T2  |  |         |  +-------->|  T2  |  |
           |      +------+  |               |      +------+  |
           +----------------+               +----------------+
