[Mops] Comments on draft-ietf-mops-streaming-opcons-07

[Mike English <[e-mail]>]

Hello MOPS!

I finally carved out some time this morning to re-read the draft
"Operational Considerations for Streaming Media" with fresh eyes.

One thing that struck me on this read through is: the purpose of the
document is not very clearly defined. The lack of a clearly defined
purpose makes it difficult to evaluate whether the document succeeds
at its stated goals. I think it would be good to clarify this before
proceeding beyond the working group.

Here's what we have at the end of the introduction now:

   This document examines networking issues as they relate to quality of
   experience in internet video delivery.  The focus is on capturing
   characteristics of video delivery that have surprised network
   designers or transport experts without specific video expertise,
   since these highlight key differences between common assumptions in
   existing networking documents and observations of video delivery
   issues in practice.
<https://www.ietf.org/archive/id/draft-ietf-mops-streaming-opcons-07.html#section-1-8>

   Making specific recommendations on operational practices aimed at
   mitigating these issues 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 use in describing
   how new technologies address or avoid these existing observed
   problems.
<https://www.ietf.org/archive/id/draft-ietf-mops-streaming-opcons-07.html#section-1-9>

It seems like the document currently falls somewhere between a
description of current best practices and a set of problem statements
that could theoretically justify new protocol work within IETF, but
there's quite a bit of ambiguity remaining.

Another interpretation could be that this document intends to
primarily serve as a useful reference document for shared
terminology. In fact, the document does provide a definition for
"streaming" as well as definitions for several classes of latency.
Which brings me to my second observation: upon re-reading, the latency
categories defined by this draft seem somewhat arbitrary.

(See: "3. Latency Considerations")
<https://www.ietf.org/archive/id/draft-ietf-mops-streaming-opcons-07.html#name-latency-considerations>

If the intent is for this document to serve as a source for a shared
vocabulary, I wonder if we could try to ground these categories a bit
more firmly on specific qualitative differences between the different
categories. Either by reorienting around use cases or by seeking out
some specific latency thresholds, e.g. in human computer interaction
research.

Finally, I noticed that there are some passing references to real-time
communication in the document which imply but do not explicitly state
that real-time communication applications are considered outside of
the scope of the document. However, by the provided definition of
"streaming" it's hard to see how real-time communications applications
would not qualify:
   This document specifically focuses on the streaming applications and
   defines streaming as follows:
   *  Streaming is transmission of a continuous media from a server to a
      client and its simultaneous consumption by the client.
   *  Here, continuous media refers to media and associated streams such
      as video, audio, metadata, etc.  In this definition, the critical
      term is "simultaneous", as it is not considered streaming if one
      downloads a video file and plays it after the download is
      completed, which would be called download-and-play.

I think this document contains many useful concepts and explanations
relevant to IETF work exploring the development of new protocols or
protocol extensions, however, in my opinion, it suffers from a lack of
clarity of purpose, and I think that needs to be addressed.

What do others think?

Thanks!
-Mike