I know MPTCP has its own congestion control, such as "Coupled". However, MPTCP lies on the TCP layer. TCP already has original ones. Do these work duplicatedly together, or only MPTCP does independently?
In the case of together, it seems that HOL-Blocking problem occurrs, like the case of HTTP/2.
According to the phd thesis Implementation and Assessment of Modern Host-based Multipath Solutions of MPTCP developer Sebastien Barre the congestion control replaces traditional TCP congestion control, since the MPTCP congestion control was designed with the following principle:
“in multipath scenarios, to use only the less congested paths instead of spreading the traffic equally among the available paths”
and he states
"Another important difference between Multipath TCP and regular TCP is the congestion control scheme. Multipath TCP cannot use the standard TCP control scheme without being unfair to normal TCP flows."
MPTCP congestion control distributes the throughput to the TCP subflows by altering the congestion window, which would break traditional TCP congestion control if they ran concurrently, so I believe they do not run "duplicatedly together"