[MMUSIC] Benjamin Kaduk's No Objection on draft-ietf-mmusic-rfc4566bis-35: (with COMMENT)
Benjamin Kaduk via Datatracker <noreply@ietf.org> Thu, 30 May 2019 14:34 UTC
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Date: Thu, 30 May 2019 07:34:23 -0700
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Subject: [MMUSIC] Benjamin Kaduk's No Objection on draft-ietf-mmusic-rfc4566bis-35: (with COMMENT)
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Benjamin Kaduk has entered the following ballot position for draft-ietf-mmusic-rfc4566bis-35: No Objection When responding, please keep the subject line intact and reply to all email addresses included in the To and CC lines. (Feel free to cut this introductory paragraph, however.) Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html for more information about IESG DISCUSS and COMMENT positions. The document, along with other ballot positions, can be found here: https://datatracker.ietf.org/doc/draft-ietf-mmusic-rfc4566bis/ ---------------------------------------------------------------------- COMMENT: ---------------------------------------------------------------------- I reviewed the diff from RFC 4566 but didn't make it quite all the way through the full document itself. What I did find in that partial read suggests that a full read-through by the authors may find some lingering stale language or minor internal inconsistencies. Another broad topic (with more comments throughout) is that an early and clear discussion of time representation may be helpful, and arguably does not need to refer to NTP time at all. (This is especially so when we refer to "NTP time format" and RFC 5905, which lists three formats, none of which have a straightforward translation to numeric strings without fraction part.) Section 4 SDP is primarily intended for use in an internetwork, although it is sufficiently general that it can describe multimedia conferences in other network environments. [...] nit(?): this verbiage ("internetwork") feels quite dated. Section 4.1 Some media types may redefine this behavior, but this is NOT RECOMMENDED since it complicates implementations (including middleboxes that must parse the addresses to open Network Address Translation (NAT) or firewall pinholes). (Similarly for "firewall pinholes".) Section 4.3 The usual security considerations about (potentially) referencing remote content would seem to apply. Perhaps a RFC 3986 reference (or more) would be appropriate. Section 4.6 Perhaps we should mention here that this categorization mechanism is deprecated/obsolete? Section 5 An SDP description is entirely textual. SDP field names and attribute names use only the US-ASCII subset of UTF-8 [RFC3629], but textual fields and attribute values MAY use the full ISO 10646 character set in UTF-8 encoding, or some other character set defined by the "a=charset:" attribute. [...] nit: here (and in Section 4.4 just above) may be the only times we include the colon when discussing an "a=" attribute; consistency would seem to suggest removing the colons. However, since SDP may be used in environments where the maximum permissible size of a session description is limited, the encoding is deliberately compact. Also, since descriptions may be transported via very unreliable means or damaged by an intermediate caching server, the encoding was designed with strict order and formatting rules so that most errors would result in malformed session descriptions that could be detected easily and discarded. This also allows rapid discarding of encrypted session descriptions for which a receiver does not have the correct key. I don't really see why the "rapid discarding" property follows from the compactness of the encoding, when the correct key for the encrypted description is not known. Section 5.x It's interesting to note that while the SDP attributes (Sections 6.x) got ABNF constructions for their values, the type descriptions here are still presented in a somewhat informal syntax (that, e.g., relies on implicitly stating that fields are whitespace-separated). Section 5.2 <sess-id> is a numeric string such that the tuple of <username>, <sess-id>, <nettype>, <addrtype>, and <unicast-address> forms a globally unique identifier for the session. The method of <sess- id> allocation is up to the creating tool, but it has been suggested that a Network Time Protocol (NTP) format timestamp be used to ensure uniqueness [RFC5905]. (et seq) There is not a single "NTP format timestamp"; RFC 5905 provides three different formats. If any of the three is fine, that should be stated, and if a single distinguished one is preferred, that should also be stated. Furthermore, the three formats all include multiple fields and not a rule for presenting them as a "numeric string" as described here, which on the face of it seems to exclude fractions. ("numeric string" does not seem to be specifically defined by this document.) Section 5.3 The "s=" line MUST NOT be empty and SHOULD contain ISO 10646 characters (but see also the "a=charset" attribute). [...] Is this perhaps intended to be "SHOULD only contain"? (Similarly in following subsections.) Section 5.9 The first and second sub-fields of the time-field give the start and stop times, respectively, for the session. These values are the decimal representation of Network Time Protocol (NTP) time values in seconds since 1900 [RFC5905]. To convert these values to UNIX time (UTC), subtract decimal 2208988800. Looking at the time formats listed in RFC 5905, one perhaps wonders if the values used by SDP are more appropriately described informally as just "seconds since the Unix epoch" without specific reference to NTP (both here and elsewhere in the document). NTP timestamps are elsewhere represented by 64-bit values, which wrap sometime in the year 2036. [...] I don't understand what this is referring to. Is this perhaps the "32 bits of seconds and 32 bits of fraction" format, which suffers from the y2038 (note '8', not '6') problem? Section 6.2 Perhaps "this was to assist" would be more fitting, given the obsolete nature of a=keywds. Section 6.9 This specifies the type of the multimedia conference. Suggested values are "broadcast", "meeting", "moderated", "test", and "H332". nit: I don't think these are "suggested" values; they are the only ones allowed by the ABNF. "recvonly" should be the default for "type:broadcast" sessions, "type:meeting" should imply "sendrecv", and "type:moderated" should indicate the use of a floor control tool and that the media tools are started so as to mute new sites joining the multimedia conference. There seems to be redundancy here with the "SHOULD" in Section 6.7 about "sendrecv" being the default for non-broadcast non-H322 sessions. Section 6.11 Is it intentional to lose the language about "order of importance" of multiple languages?
- [MMUSIC] Benjamin Kaduk's No Objection on draft-i… Benjamin Kaduk via Datatracker
- Re: [MMUSIC] Benjamin Kaduk's No Objection on dra… Paul Kyzivat
- Re: [MMUSIC] Benjamin Kaduk's No Objection on dra… Benjamin Kaduk
- Re: [MMUSIC] Benjamin Kaduk's No Objection on dra… Paul Kyzivat
- Re: [MMUSIC] Benjamin Kaduk's No Objection on dra… Paul Kyzivat