+-+--------------------+----------------------+---------------------+
| | Servers or proxies |      Access link     |             Clients |
+-+--------------------+----------------------+---------------------+
|0| DCTCP (existing)   |                      |    DCTCP (existing) |
+-+--------------------+----------------------+---------------------+
|1|                    |Add L4S AQM downstream|                     |
| |       WORKS DOWNSTREAM FOR CONTROLLED DEPLOYMENTS/TRIALS        |
+-+--------------------+----------------------+---------------------+
|2| Upgrade DCTCP to   |                      |Replace DCTCP feedb'k|
| | TCP Prague         |                      |         with AccECN |
| |                 FULLY     WORKS     DOWNSTREAM                  |
+-+--------------------+----------------------+---------------------+
| |                    |                      |    Upgrade DCTCP to |
|3|                    | Add L4S AQM upstream |          TCP Prague |
| |                    |                      |                     |
| |              FULLY WORKS UPSTREAM AND DOWNSTREAM                |
+-+--------------------+----------------------+---------------------+