Draft: draft-ietf-rtcweb-jsep

Commentary: a = ssrc and a = ssrc - group . 
 note I still assume you might receive a = ssrc because it might come from non - JSEP endpoints .  if you want that removed .
Paragraph (version A):
An "a=ssrc" line, as specified in RFC5576, Section 4.1, indicating
the SSRC to be used for sending media, along with the mandatory
"cname" source attribute, as specified in Section 6.1, indicating
the CNAME for the source.  The CNAME MUST be generated in
accordance with Section 4.9 of I-D.ietf-rtcweb-rtp-usage.
Paragraph (version A):
If FEC is supported for this media type, another "a=ssrc" line
with the FEC SSRC, and an "a=ssrc-group" line with semantics set
to "FEC-FR" and including the primary and FEC SSRCs, as specified
in RFC5956, section 4.3.  For simplicity, if both RTX and FEC are
supported, the FEC SSRC MUST be the same as the RTX SSRC.
Paragraph (version A):
If FEC is supported for this media type, another "a=ssrc" line
with the FEC SSRC, and an "a=ssrc-group" line with semantics
set to "FEC-FR" and including the primary and FEC SSRCs, as
specified in RFC5956, section 4.3.  For simplicity, if both RTX
and FEC are supported, the FEC SSRC MUST be the same as the RTX
SSRC.
Paragraph (version A):
If an RtpTransceiver has been stopped and is associated with an m=
section, and the m= section is not being recycled as described
above, an m= section MUST be generated for it with the port set to
zero and the "a=msid", "a=ssrc", and "a=ssrc-group" lines removed.
Paragraph (version A):
For RtpTransceivers that are not stopped, the "a=msid", "a=ssrc",
and "a=ssrc-group" lines MUST stay the same if they are present in
the current description.
Paragraph (version B):
If an RtpTransceiver has been stopped and is associated with an m=
section, and the m= section is not being recycled as described
above, an m= section MUST be generated for it with the port set to
zero and the "a=msid" line removed.
Paragraph (version B):
For RtpTransceivers that are not stopped, the "a=msid" line MUST
stay the same if they are present in the current description.
Paragraph (version A):
For RtpTransceivers that are still present, the "a=msid",
"a=ssrc", and "a=ssrc-group" lines MUST stay the same.
Paragraph (version B):
For RtpTransceivers that are still present, the "a=msid" line MUST
stay the same.
Paragraph (version A):
If any RtpTransceiver has been stopped, the port MUST be set to
zero and the "a=msid", "a=ssrc", and "a=ssrc-group" lines MUST be
removed.
Paragraph (version B):
If any RtpTransceiver has been stopped, the port MUST be set to
zero and the "a=msid" line MUST be removed.
Paragraph (version A):
If RTX has been negotiated for this m= section, another
"a=ssrc" line with the RTX SSRC, and an "a=ssrc-group" line, as
specified in RFC5576, section 4.2, with semantics set to "FID"
and including the primary and RTX SSRCs.
Paragraph (version A):
If FEC has been negotiated for this m= section, another
"a=ssrc" line with the FEC SSRC, and an "a=ssrc-group" line
with semantics set to "FEC-FR" and including the primary and
FEC SSRCs, as specified in RFC5956, section 4.3.  For
simplicity, if both RTX and FEC are supported, the FEC SSRC
MUST be the same as the RTX SSRC.
Paragraph (version A):
For RtpTransceivers that are not stopped, the "a=msid", "a=ssrc",
and "a=ssrc-group" lines MUST stay the same.
Paragraph (version B):
For RtpTransceivers that are not stopped, the "a=msid" line MUST
stay the same.