Comment by klabb3
3 days ago
From what I understand the ”killer app” initially was because of mobile spotty networks. TCP is interface (and IP) specific, so if you switch from WiFi to LTE the conn breaks (or worse, degrades/times out slowly). QUIC has a logical conn id that continues to work even when a peer changes the path. Thus, your YouTube ads will not buffer.
Secondary you have the reduced RTT, multiple streams (prevents HOL blocking), datagrams (realtime video on same conn) and you can scale buffers (in userspace) to avoid BDP limits imposed by kernel. However.. I think in practice those haven’t gotten as much visibility and traction, so the original reason is still the main one from what I can tell.
MPTCP provides interface mobility. It's seen widespread deployment with the iPhone, so network support today is much better than one would assume. Unlike QUIC, the changes required by applications are minimal to none. And it's backward compatible; an application can request MPTCP, but if the other end doesn't support it, everything still works.