In this testsuite, TRex is used to generate Uplink GTPU traffic on the RAN side
towards UPF on its 1st iface and which which should be sent back decapsulated (tunend) towards CN and received at TRex 2nd interface.

The GTPU traffic is generated by gtp_1pkt_simply.py profile passed to TRex,
which emulates <enb-ip-addr,TEID> sessions based on parameters passed through
trex-console when launching the test, and which should match those configured in
cpf/0.gtp_flood.vty used by osmo-upf-load-gen to allocated the sessions at the
UPF.

----
[trex-ran](172.16.32.{2-101})  ----GTPU--> ()[upf]
                                    |
[trex-cn](172.16.31.{100-200}) <----IP---- ()[upf]
----

See topoology.dot for a more detailed graph.