scenario tests use the following environment.

diagram:

       ----------------------+--------------- tenant
                             |                network
                        +--------+
                        | router |
                        +--------+
                             |
       -----+----------------+--------------- provider
            |                |                network
       +---------+           |
       | dragent |           |
       +---------+           |
            |                |
            |                |
            |                |
            |                |
            +-----------+----+-------+-------
                        |            |
                   +---------+  +---------+
       docker      |   frr1  |  |  frr1   | ...
       container   +---------+  +---------+


docker container environment is provided by test tools with help of
python-docker library.
It has the following functions:
- run, stop and remove a container.
- some operations to frr container.
- get some information from frr container.
