Change:
tries to address:
We want a paragraph to say something about scope along the lines of: This document is for endpoints delivering streaming media traffic. This can include intermediaries like CDNs as well as content owners and end users, plus their device and player providers. We think this can help address a few issues from last call/iesg review, including: (more to be linked as we notice them)
Consider adding a subsection in the introduction about things that are out of scope, and (for extra credit), why they are out of scope.
From NAME (URL) Section 7. Streaming Encrypted Media As far as I know, streaming users sometimes use encrypted tunnels such as OpenVPN or WireGuard (or IPsec) to access video content. I may miss something, but it is unclear to me how that fits into the categories presented in Section (Seems closely related to URL )
The purpose of such tunneling is to circumvent geoblocks and access content from other regions - not to protect the media content. Encrypting the content is done by the content owner for its protection.
So, looking at , I'm seeing this text: I think this means that the effect is that the "transport-level information is opaque to intermediaries" effect described in the document applies, with the additional consideration that intermediaries can't see the IP addresses used inside the tunnel, either. I think the same applies to any IPsec-encrypted tunnel. Do we need to say that? And, if so - can we describe this without using product names and descriptions which may age badly in an RFC?
isn't as easy to read, but I think this is also the rough equivalent of IPsec, from a media operator perspective - all of the transport information and the IP addresses used inside the tunnel are obscured.
Just for the record, definitely worth checking as it is related to this discussion: URL
From NAME 's review (URL) (in Section 6.2. TCP and Its Behavior) Does ECN, DCTCP, etc. really not matter at all, for instance, if a data center hosts video playout servers?
This might be a scoping matter. I think this section was meant to be talking about delivery to end users, but maybe some discussion of datacenters is right to at least briefly mention somewhere? If so, maybe that gets a small section somewhere that mostly says the topic is out of scope as its own too-broad topic. Not sure if DCTCP/ECN needs a mention as it usually it wouldn't be required until you get below ultra low latency, but it can (presumably? I don't have ready measurements...) help with datacenter efficiency and reliability on your delay targets and maybe has some worthwhile references. Note: we dropped a bit of explanation about ECN (URL), and although we didn't really capture why in our notes IIRC the decision came from the low occurrence of marking in end user delivery.
From NAME (URL) (in Section 3.2.1. Recognizing Changes from an Expected Baseline) The text could also better distinguish between what matters to endpoints and considerations relevant only for middleboxes (such as passive monitors).
Up-leveling for this point - we need to include a scoping for this document. When we started this document, the scope was largely for content providers. If content providers have control of any middleboxes on the path or stats from middleboxes, that would be in scope. If CDNs own middleboxes like video transcoders, that would also be in scope. We want to exclude "middlebox" devices like ISP routers and tunnel endpoints. We'll revisit this comment when we have proposed text for scoping. Reviewer: Michael Scharf Review result: Ready with Issues This document has been reviewed as part of the transport area review team's ongoing effort to review key IETF documents. These comments were written primarily for the transport area directors, but are copied to the document's authors and WG to allow them to address any issues raised and also to the IETF discussion list for information. When done at the time of IETF Last Call, the authors should consider this review as part of the last-call comments they receive. Please always CC EMAIL if you reply to or forward this review. This informational document surveys network and transport protocol issues that affect quality of experience for streaming applications, in particular video. The overview covers many topics across different technologies. Readers may only be familiar with a subset of these topics and could therefore learn quite a bit from this kind of tutorial. Nonetheless, it remains somewhat unclear what the actual objective of some of the text is. For some topics, quite a bit of technical background is provided, but the discussion is not really comprehensive. In many sections, the document neither derives technical challenges, nor system/protocol requirements, nor practical usage guidance. It is just a kind of tutorial. Quite a bit of text also presents ongoing IETF work, and an RFC with this scope may thus get outdated soon. Section 6.2 deals with topics owned by TCPM. In similar past documents, I have asked for a TCPM presentation prior to an IETF last call in order to ensure that owners of running code are in the loop. I believe this strategy has worked well in the past. Having said this, as TSV-ART reviewer I don't strongly disagree with a publication. All these issues may just be OK for an informational RFC. Some more specific comments: Section 3.2.1. Recognizing Changes from an Expected Baseline This section apparently assumes relatively static path properties, e.g., fixed network connectivity. It would be more useful to analyze the impact of Wifi and 4G/5G networks in one place. Some of this follows later in sections 3.2.1 and Yet, the split between these three sections is unclear. Having a discussion about today's Internet path characteristics and the dynamics at one place could be more useful. The text could also better distinguish between what matters to endpoints and considerations relevant only for middleboxes (such as passive monitors). Section 3.3 Path Requirements The statement "to find the bandwidth requirements for a router on the delivery path" may assume that the bottleneck on the path will be routers. Yet, on a path the bottlenecks could also be a link layer device (e.g., an Ethernet Switch, a Wifi access point, etc.). RFC 6077 (specifically Section 3.1.3) also explains that issue. A better wording may be "to find the bandwidth requirements for a delivery path". Section 3.6. Unpredictable Usage Profiles / Section 3.7. Extremely Unpredictable Usage Profiles I am not fully convinced by the distinction between "unpredictable" and "extremely unpredictable". To me, these two sections could be merged and maybe also be shortened. More specifically, Section 3.7 lists a lot of statistics from the past. What is IMHO a bit missing in Section 3.7 are actual operational considerations. For instance, are there any lessons learnt for the future? Note that Section 3.6 has a reasonable conclusion at the end. Section 4. Latency Considerations and Section 4.1. Ultra Low-Latency I am surprised by the definition "ultra low-latency (less than 1 second)", as well as some of the other numbers. For other real-time communication use cases, "ultra low-latency" would probably imply a latency requirement of the order of one millisecond. For instance, isochronous traffic for motion control in industrial networks may require a latency of 1 ms, and such "ultra-low latency" requirements are discussed elsewhere, e.g., in the DetNet WG. The terminology in this section should be better explained to readers dealing with networked systems with much harder latency requirements. And a reference should be added for these definitions in the context of video streaming. 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? Section 6.3. QUIC and Its Behavior As already noted, the discussion about head-of-line-blocking would really benefit from backing by a reference. Section 7. Streaming Encrypted Media As far as I know, streaming users sometimes use encrypted tunnels such as OpenVPN or WireGuard (or IPsec) to access video content. I may miss something, but it is unclear to me how that fits into the categories presented in Section

Discussion:
Several pointers for further reading on this rapidly changing subject (further). <del> Making specific recommendations on operational practices to mitigate the issues described in this document is out of scope, though some existing mitigations are mentioned in passing.  The intent is to provide a point of reference for future solution proposals to describe how new technologies address or avoid existing problems. </del> 1.1. <ins> A full review of all streaming media considerations is too wide a topic to cover comprehensively in a single document. This document focuses chiefly on large-scale delivery of streaming media to end users and related issues.  It is primarily intended for those controlling endpoints involved in delivering streaming media traffic.  This can include origin servers publishing content, intermediaries like content delivery networks (CDNs), and providers for client devices and media players. Topics outside this scope include: in-depth examination of real-time interactive media, such as video conferencing; although we touch lightly on topics in this space, the intent is to let readers know that for more in-depth coverage they'll need to look to other documents, since the techniques and issues for interactive real-time media differ so dramatically from those in large-scale one-way delivery of streaming media. specific recommendations on operational practices to mitigate issues described in this document; although some known mitigations are mentioned in passing, the primary intent is to provide a point of reference for future solution proposals to describe how new technologies address or avoid existing problems. generalized network performance techniques; while things like datacenter design and transit network design can be crucial dependencies for a performant streaming media service, these are considered independent topics better addressed by other documents. transparent tunnels; while tunnels can have an impact on streaming media via issues like the round trip time and the maximum transmission unit (MTU) of packets carried over tunnels, for the purposes of this document they're considered network path properties 1.2. </ins> Note to RFC Editor: Please remove this section and its subsections before publication. This section is to provide references to make it easier to review the development and discussion on the draft so far. <del> 1.1.1. </del> <ins> 1.2.1. </ins> This document is in the GitHub repository at: