Subject: Re: [rtcweb] Requesting "SDP or not SDP" debate to be re-opened
From: Roman Shpount <[email-masked]>
To: Silvia Pfeiffer <[email-masked]>
Cc: [email-masked], "[email-masked]" <[email-masked]>
Date: Fri, 21 Jun 2013 20:08:02 -0400
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>

On Fri, Jun 21, 2013 at 7:54 PM, Silvia Pfeiffer
<[email-masked]>wrote:

> Is it possible to continue using SDP but not do o/a ?
>

Neither SDP not O/A belongs in API.

The issue with SDP is that it creates an API surface which is using a
string blob. To make such API a standard you need to standardize the blob
format. Also, every time you add features you need to update the SDP format
and all the parsers that are dealing with it. Not sustainable long term.
Finally, SDP mixes multiple unrelated data items together, ie it specifies
transport parameters and media parameters at the same time. For a normal
API flow you need to control those separately.

O/A implies one model to negotiate media and transport parameters and
forces them to be negotiated at the same time. One other thing to keep in
mind that O/A compliant end points are not O/A internally. For instance you
can change the sending codec or sending codec parameters (like bitrate)
without going through offer/answer exchange. So, normally end points expose
offer/answer to the network, but use a different API internally to control
transport and media settings based on data received from O/A exchanges,
user input, and other factors (like detecting high packet loss and reducing
bandwidth or changing codec).
_____________
Roman Shpount