Re: [Fecframe] comments on draft-ietf-fecframe-dvb-al-fec-02.txt

[zouzixuan <tendyntu at huawei.com>]

Hi, Ali
	Inline.
Zou ZiXuan, Senior Research Staff
Media & Communication Lab
HUAWEI TECHNOLOGIES CO.,LTD. 

Address: Huawei Industrial Base
Bantian Longgang
Shenzhen 518129, P.R.China
Tel: +86 0755 28789364
Fax: +86 0755 28788317
E-mail: tendyntu at huawei.com
www.huawei.com
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-----Original Message-----
From: Ali C. Begen (abegen) [mailto:abegen at cisco.com] 
Sent: Sunday, August 30, 2009 1:44 PM
To: zouzixuan; fecframe at ietf.org
Cc: Thomas Stockhammer
Subject: RE: [Fecframe] comments on draft-ietf-fecframe-dvb-al-fec-02.txt

Thanks for the review.

My comments are inline.

> -----Original Message-----
> From: fecframe-bounces at ietf.org [mailto:fecframe-bounces at ietf.org] On
Behalf Of zouzixuan
> Sent: Sunday, August 30, 2009 8:20 AM
> To: fecframe at ietf.org
> Cc: 'Ali C. Begen'; 'Thomas Stockhammer'
> Subject: [Fecframe] comments on draft-ietf-fecframe-dvb-al-fec-02.txt
> 
> 
> Hi, All
> 	The followings are my comments on
> draft-ietf-fecframe-dvb-al-fec-02.txt:
> 	Page 6, in SSRC item: " It is RECOMMENDED that the DVB AL-FEC
> protocol uses this mechanism for explicit SSRC signaling"
> 			Doe it make sense to use the keyword "RECOMMEDED"
> within the scope of IETF to guide the way of using SSRC for AL-FEC
protocol
> specified in DVB?

Using a deterministic SSRC=0 value is a special case, and is only acceptable
by RTP if it is signaled explicitly. 

Do you think we should say "MUST" or "SHOULD"? 

[zou] It seems that I lead to a misunderstanding. Sorry. I'm asking whether
it makes sense to stipulate in IETF the manner of a DVB standard by using
the IETF keywords "RECOMMENDED" or "MUST" whatever. Maybe a lowercase form
would be more proper. 

  
> 			".....the sender does not have to select a random
> initial sequence number for the FEC stream as suggested by [RFC3550]."
> 					Using a static sequence number
> certainly had no problem and is merely a implementation issue. So why not
> just let it be random to be fully compatible with RFC3550 . These words
> seems to be redundant.

Yes, RFC 3550 recommends using random initial seqnums, as does
[I-D.ietf-fecframe-interleaved-fec-scheme]. But, in AL-FEC, this behavior is
not really specified. This sentence emphasizes this point. We do not want to
specify anything that is not defined in the AL-FEC protocol.

 
> 	Page 9   "... Due to the lack of the format parameters, it is not
> possible to learn the FEC parameters from the SDP description. This
severely
> limits the ability of using multiple FEC streams that are generated with
> different settings. "
> 				Agree with this argument. This might be
> taken into account for more flexible usage if a new RTP profile for AL-FEC
> were brought up.

Right. A new RTP profile would resolve most of the outstanding issues.

-acbegen

 
> Best,
> Zou ZiXuan, Senior Research Staff
> Media & Communication Lab
> HUAWEI TECHNOLOGIES CO.,LTD.
> 
> Address: Huawei Industrial Base
> Bantian Longgang
> Shenzhen 518129, P.R.China
> Tel: +86 0755 28789364
> Fax: +86 0755 28788317
> E-mail: tendyntu at huawei.com
> www.huawei.com
>
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