Subject: CEP: RTP not mandatory

From: "Ron Cohen" <[email-masked]>
Date: Sat, 12 Jun 2004 05:09:23 -0700

Hi,

There is one more change I propose before sending the SONET/SDH CEP
emulation draft to IESG.

I would like to change RTP encapsulation to optional. 

CEP control word is mandatory and carries both a sequence number and
pointer adjustment indications (N,P bits). 

All information required for delivery of timing (synchronization)
information is therefore contained with the control word and RTP is not
required as mandatory encapsulation.

If there is no common clock between Pes the RTP time stamp advance
together with the sequence number and adds no information. If common
clock is available to both Pes the native service method for conveying
the difference between service clock and the common clock should be used
(N,P). 

If there are no objections within a week I will prepare another version
of the draft with RTP as optional encapsulation.

Thanks
Ron

Ron Cohen
CTO
Lycium Networks 
Mobile: 650.823.7672
Mobile:  +972.55.245.104
Tel:  650.234.4010
Fax:  650.854.8183

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From: "Yaakov Stein" <[email-masked]>
Date: Sun, 13 Jun 2004 08:15:24 +0300

> I would like to change RTP encapsulation to optional. 

I fully support this.

We have done the same in SAToP, TDMoIP and Y.1413.

The only portion of the RTP overhead that can potentially
add anything is the timestamp, and it only helps in the common clock
case. 
Even in the common clock case one needs to choose the common clock rate 
wisely; and even then there are much better methods of clocking (as you
note).

In addition, there are complications in placement of the
RTP header, with IP and MPLS cases being treated differently.

So I believe that we should leave the RTP header only in those
places where it has already been implemented (e.g. CESoPSN)
and remove it entirely everywhere else.
As a compromise we can leave it as an option that no-one
will ever implement.

Y(J)S