[Megaco] 3GPP [RTCP-MUX] / ITU-T [H.248.57, H.248.RTPMUX] RTCP port allocation rules in case of RTP transport multiplexing

["Schwarz, Albrecht (Albrecht)" <[e-mail]>]

Dear All,
we spent some time in the meanwhile how H.248.57 could be upgraded. The proceeding isn’t straightforward because we need to decide on some rule interaction issues.
Our discussion and change proposals are now available (as part of ITU-T Q.3/16 March meeting):

AVD-4489

H.248.57: RTCP port allocation rules in context of RTP transport multiplexing - Discussion


AVD-4490

H.248.57: RTCP port allocation rules in context of RTP transport multiplexing - Change proposal for a revised H.248.57

Download:
http://wftp3.itu.int/av-arch/avc-site/2013-2016/1403_Gen/AVD-4489.zip
http://wftp3.itu.int/av-arch/avc-site/2013-2016/1403_Gen/AVD-4490.zip

The results of the Q.3/16 discussions will be the baseline for our 3GPP [RTCP-MUX] CRs for Iq (April meeting).

Any feedback would be appreciated,
Jürgen & Albrecht


From: Schwarz, Albrecht (Albrecht) [mailto:[e-mail]]
Sent: Sonntag, 10. November 2013 15:38
To: Nevenka Biondic; Kall, Jan (NSN - FI/Espoo); Tommy Young; Belling, Thomas (NSN - DE/Munich); LANDAIS, BRUNO (BRUNO); [e-mail]
Cc: DRAGE, Keith (Keith); [e-mail]; Arturo Martin De Nicolas; 박주영; Shaikh, Viqar A
Subject: [H.248.57, H.248.RTPMUX] RTCP port allocation rules in case of RTP transport multiplexing


Dear All,



the addition of SDP „a=rtcp-mux” to H.248 Iq profile (23.334/29.334) leads to RTCP port allocation rules which are not yet defined (due to the fact that Iq supports also “a=rtcp” besides the rsb property).

NOTE: Iq allows “a=rtcp” only in the H.248 RD, not in the H.248 LD, but there remains still open semantics.



Normative baseline is Table 1/H.248.57 (in case of “a=rtcp” support).

You know that the consideration of “a=rtcp-mux” is still an open action for H.248.57.



Like to recall again that there are four principal connection endpoints for RTP transport multiplexing: the LS, LD, RS and RD connection endpoints:



…

H.248.57/Figure 1 – Connection endpoint naming conventions – the four
RTCP ports of a bidirectional RTP/RTCP session



Please find attach an evaluation of additional support of “a=rtcp-mux”, extending Table 1/H.248.57 by additional cells.



NOTE: RFC 5761 is NOT EXPLICIT on the usage of “a=rtcp” together with “a=rtcp-mux”! It’s mentioned twice in the text. My INTERPRETATION of RFC 5761: there is an IMPLICIT assumption that the SDP Offerer/Answerer SHALL NOT use both SDP attributes together. However, a different interpretation is that the parallel usage is allowed, and the receiving side is then applying “semantic of ignore”. Both interpretations might be valid. However, would prefer rather an explicit specification.



Any comments, proposals?

Albrecht