Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-channel-07.txt - Some editorial comments on section 5

[Michael Tuexen <[e-mail]>]

On Feb 11, 2014, at 7:12 PM, Christer Holmberg <[e-mail]> wrote:

> Hi,
> 
> Some editorial comments:
> 
> Q1:
> 
> Section 5 says:
> 
> 	"SCTP as specified in [RFC4960] MUST be used in
>   	combination with the extension defined in [RFC3758] and provides the
>   	following interesting features for transporting non-media data
>   	between browsers:"
> 
> I suggest to say:
> 
> 	"The SCTP extension defined in [RFC3758] MUST be supported, and
>     	provides the following features:
But this implies that the listed features are provided by the extension
defined in RFC 3758, which is not true. The features are provided by
the combination of RFC 4960 and RFC 3758.
> 
> 
> Q2:
> 
> Section 5 says:
> 
> 	"Each SCTP user message contains a so called Payload Protocol
>   	Identifier (PPID) that is passed..."
> 
> I suggest to remove "so called".
Removed.
> 
> 
> Q3:
> 
> Section 5 says:
> 
> 	"This value can be used to multiplex multiple protocols
>   	over a single SCTP association.  The sender provides for each
>   	protocol a specific PPID and the receiver can demultiplex the
>   	messages based on the received PPID."
> 
> I think we discussed this earlier. The PPID value CAN NOT (at least not as used by WebRTC) be used to multiplex multiple protocols over a single SCTP association. If you create multiple channels, for multiple protocols, the same PPID values may be used for each protocol.
> 
> The PPID CAN, however, be used within a data channel, e.g. to demultiplex the DCP from channel data.
I guess the problem is that I consider 'protocol' as something running on top of SCTP
like DCEP, Binary of String data, you consider 'protocol' as something running
on top of Binary of String data and the 'protocol' being identified in the JS protocol string.

What about using:

<t>Each SCTP user message contains a Payload Protocol Identifier (PPID)
that is passed to SCTP by its upper layer on the sending side and
provided to its upper layer on the receiving side.
The PPID can be used to multiplex/demultiplex multiple upper layers over
a single SCTP association.
In the WebRTP context, the PPID is used to distinguish between
UTF-8 encoded user data,
binary encoded userdata and
the Data Channel Establishment Protocol defined in
<xref target='I-D.ietf-rtcweb-data-protocol'/>.
Please note that the PPID is not accessable via the Javascript API.</t>

Does this address your issue?
> 
> 
> Q4:
> 
> Section 5 says:
> 
> 	"When using DTLS as the lower layer, only single homed SCTP
>   	associations MUST be used, since DTLS does not expose any address
>   	management to its upper layer."
> 
> I suggest to change "MUST be used" to "are supported".
OK.
> 
> 
> Q5:
> 
> Sometimes you say "SCTP" and sometimes "SCTP as defined in [RFC4960]".
> 
> I suggest to e.g. use the reference on the first occurrence, and then only use "SCTP".
I double checked:
SCTP as defined in [RFC4960] is used in
* In the Introduction (first occurrence) talking about SCTP / UDP
* In the Introduction to make sure which specifications are used: RFC 4960 and RFC 3758
* In section 5 when used with RFC 2119 language.
* In section 6 to make clear what relates to RFC 4960 and what to the NDATA extension.

All of these are intentional. Which one do you think is not necessary?
> 
> 
> Regards,
> 
> Christer
> 
> 
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