Thanks to the authors for a well-written document. It is structured clearly, and explains the space nicely.

I have a few nit comments that could improve the document further (written as an IntArea review, but with some general nits as well):

- Section 3.2.1 says, "There are many reasons why path characteristics might change suddenly...". It may be good to mention MTU changes as part of the path changes, since changes in the maximum packet sizes supported by paths can be disruptive to traffic (requiring new PMTUD, etc).

- There are places that could benefit from more citations. For example, Section 3.5 says, "Historical data shows that users consume more videos and at a higher bit rate than they did in the past..." but does not explain what data this is.

- In Section 6.1 (on UDP), DNS queries are described as follows: "DNS, which is often used to send a single-packet request to look up the IP address for a DNS name, and return a single-packet response containing the IP address." I'm not sure how valuable this example is for explaining UDP, but if it is kept, please say that *multiple* packets are sent to get *multiple* addresses. With IPv6 and IPv4, clients query for both A and AAAA records, and handle multiple addresses, especially for IPv6.

- As a bit of transport commentary, I don't find the setup of Section 6 compelling. While UDP is a transport in a technical sense, for the purpose of media, it is almost always a layer upon which the protocol doing the congestion control work runs. To that end, QUIC is just another more standardized case of this, just like SCTP over UDP. Rather than talking about "UDP's behavior" vs "TCP's behavior", I suggest talking about how applications over UDP for media behave vs applications over TCP for media behave.