Re: [rtcweb] Plan A, respun

[Eric Rescorla <[e-mail]>]

On Thu, May 16, 2013 at 12:15 PM, Harald Alvestrand <[e-mail]>wrote:
>
>  If the true limit at which one has to change allocation strategy were to
>>> become 96, not 32, it actually strengthens my "falling off a cliff" argument
>>>
>>
>> And, to be clear, it's not a cliff. For any given session (without
>> a=ssrc:), you have to allocate ceiling(streams/96) ports. It's not like you
>> go from using one port to using 97 ports when you add the 97th stream. You
>> go from one port to two, which will handle 192 streams.
>>
>
> Going from one port to two ports is a cliff.
> We may have differing opinions on how tall it is.


Harald,

I am not following how this is a discriminating factor between Plan A and
Plan B.

In both Plan A and Plan B, any media stream which is intended to be
independently processable by a legacy endpoint must appear on its
own m-line. That means it must also have its own independent ports,
even if you are hoping to eventually be able to mux it via BUNDLE.

In both Plan A and Plan B, it is possible to indicate additional media
streams that are not processable by a legacy endpoint but that
will be processable by a new endpoint:

- In Plan A, this is done by marking them bundle-only
- In Plan B, this is done by having them be additional SSRCs on one
  of the extant m-lines.



Regardless of Plan A versus Plan B, bundle contemplates having
multiple media flows on the same media 5-tuple. Thus, it must
be possible to demux the flows somehow. As I read Plan A,
it proposes using both PT and SSRC to demux whereas plan B
only wants to use SSRC? So, the implication is that a Plan A
endpoint must:

1. Demux on both PT and SSRC (this is trivial, I think you will agree)
2. When acting as offerer, either always offer SSRC or conditionally
offer SSRC when the # of PTs is excessive.

I don't understand why you think that plan A means more ports than
plan B. Presumably we can simply specify that bundle requires
SSRC muxing, in which case plan A and plan B behave identically.

What am I missing?

-Ekr