Code change:
elapsed time between the acknowledgements for specific TCP segments from a TCP receiver since TCP octet sequence numbers and acknowledgements for those sequence numbers are carried in the clear, <del> even if the TCP payload itself is encrypted.  See tcp-behavior for more information. </del> <ins> even if the TCP payload itself is encrypted.  See reliable-behavior for more information. </ins> As transport protocols evolve to encrypt their transport header fields, one side effect of increasing encryption is the kind of passive monitoring, or even "performance enhancement" (RFC3135) that was possible with the older transport protocols (UDP, described in <del> udp-behavior and TCP, described in tcp-behavior) is no longer possible with newer transport protocols such as QUIC (described in quic-behavior).  The IETF has specified a "latency spin bit" mechanism in Section 17.4 of RFC9000 to allow passive latency </del> <ins> unreliable-behavior and TCP, described in reliable-behavior) is no longer possible with newer transport protocols such as QUIC (described in quic-behavior).  The IETF has specified a "latency spin bit" mechanism in Section 17.4 of RFC9000 to allow passive latency </ins> monitoring from observation points on the network path throughout the duration of a connection, but currently chartered work in the IETF is focusing on endpoint monitoring and reporting, rather than on passive

Related discussion:
text: Section 5.5.2 Head-of-Line Blocking If Head-of-Line Blocking is indeed a relevant operational problem, it would be useful to add a corresponding reference (e.g., with measurements). Section 5.5.3. Wide and Rapid Variation in Path Capacity The statement "As many end devices have moved to wireless connectivity for the final hop (Wi-Fi, 5G, or LTE), new problems in bandwidth detction have emerged from radio interference and signal strength effects." could be moved to earlier parts of the document. Quite a bit of new computers apparently only have Wifi connectivity and no Ethernet port, i.e., Wifi may just be their default. Also, wireless may not only be used on the last hop, for instance in meshed setups. This may make the problem even harder. Section 6. Evolution of Transport Protocols and Transport Protocol Behaviors I really wonder whether UDP vs. TCP vs. QUIC is actually the relevant distinction. What may actually matter are the transport services provided by the protocol stack (e.g., RFC 8095). I fully agree to a related comment in the INTDIR review. Section 6.1. UDP and Its Behavior UDP is also used for encrypted tunnels (OpenVPN, Wireguard, etc.). Does encrypted tunneling really have no operational impact on streaming apps other than circuit breakers? (I am thinking about 4K streaming over OpenVPN and the like.) Section 6.2. TCP and Its Behavior This text should IMHO be presented and be discussed in TCPM. Personally, I am not convinced that this document is a good place for discussing the long history of TCP congestion control. If the objective of the document is to provide a tutorial, IMHO it would be more useful to briefly explain the state-of-the-art in year 2022. Some further specific comments on TCP congestion control: It is surprising that RFC 5681 is not referenced.793bis has normative statements regarding congestion control, and most stacks are compatible to what is written in 793bis. Several operating systems use CUBIC by default and support standard Reno. Another general good reference for TCP standards is RFC 7414.Does ECN, DCTCP, etc. really not matter at all, for instance, if a data center hosts video playout servers?