Re: [rtcweb] DataChannels API and external negotiation

[Randell Jesup <[e-mail]>]

On 4/3/2013 12:05 PM, Peter Thatcher wrote:
> I think moving protocol into the dictionary is a good idea.   In fact,
> I'd like to see label move there as well, but that's probably asking
> too much.
>
> And now for a little of my own bikeshedding:
>
> I don't understand way we have "stream" and "preset", since you can
> only set "stream" if "preset" is true.  Why not just make the rule "if
> stream is set, no in-band message is sent", and get rid of "preset"
> altogether?  I really don't like the word "stream" sneaking in, since
> it's so overloaded (MediaStream, RTP Stream, etc).  I'd prefer "sid"
> or just "id".

The reason was that I wanted a way to have the system select a stream to 
use (that you can then communicate externally to the other side); this 
avoids any chance of a collision with existing streams. If this is seen 
as not useful, then we can collapse it to a single entry.   (I also 
toyed with using stream 65535 as a flag to tell the system to allocate 
one; that seemed too hacky.)

Since this option was almost solely for those who understand the 
underlying SCTP-ness of this, I used "stream", but I'm fine with 
"streamId" or "id" (or "index" might be better than "id", which sounds 
like a label of some sort).  I dislike "sid" for similar reasons to 
disliking "rtx".

> I like the idea that reliable+ordered is the default, and both
> reliability and ordered can be set independently.  I also prefer
> "ordered" over "outOfOrderAllowed", and along with that I like the
> idea of a "reliable" flag that, if false, is the equivalent of either
> maxRetransmitNum:0 or maxRetransmitTime:0.  Finally, I think
> "maxRetransmitTime" should make its units clear, perhaps calling it
> "maxRetransmitMillis", and "maxRetransmitNum" could be shortened to
> simply "maxRetransmits".

Those seem reasonable (I'd use Millisec/MilliSec or perhaps MS instead 
of Millis -- how are millisecond time values in other HTML5 specs 
described?).  On "reliable:false" - is this just a shorthand for 
"ordered:false, maxRetransmits:0"?  If so, I'm probably ok with it - 
it's redundant, but makes it easy to use/read for a common case.

>
> So the dictionary for my bikeshed would be:
>
> dictionary DataChannelInit {
>    DOMString protocol;
>    unsigned short id;
>    boolean ordered;
>    boolean reliable;
>    unsigned short maxRetransmits;
>    unsigned short maxRetransmitMillis;
> };

-- 
Randell Jesup
[e-mail]