draft-ietf-fecframe-dvb-al-fec-01.txt   draft-ietf-fecframe-dvb-al-fec-02.txt 
FEC Framework A. Begen FEC Framework A. Begen
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Informational T. Stockhammer Intended status: Informational T. Stockhammer
Expires: July 31, 2009 Digital Fountain Expires: February 12, 2010 Nomor Research
January 27, 2009 August 11, 2009
DVB Application-Layer Hybrid FEC Protection DVB Application-Layer Hybrid FEC Protection
draft-ietf-fecframe-dvb-al-fec-01 draft-ietf-fecframe-dvb-al-fec-02
Status of this Memo Status of this Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Copyright Notice Copyright Notice
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to this document.
Abstract Abstract
This document describes the Application-layer Forward Error This document describes the Application-layer Forward Error
Correction (FEC) protocol that was developed by the Digital Video Correction (FEC) protocol that was developed by the Digital Video
Broadcasting (DVB) consortium for the protection of media streams Broadcasting (DVB) consortium for the protection of media streams
over IP networks. The DVB AL-FEC protocol uses two layers for FEC over IP networks. The DVB AL-FEC protocol uses two layers for FEC
protection. The first (base) layer is based on the 1-D interleaved protection. The first (base) layer is based on the 1-D interleaved
parity code. The second (enhancement) layer is based on the Raptor parity code. The second (enhancement) layer is based on the Raptor
code. By offering a layered approach, the DVB AL-FEC offers a good code. By offering a layered approach, the DVB AL-FEC offers a good
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to be in compliant with the AL-FEC protocol as specified in to be in compliant with the AL-FEC protocol as specified in
[DVB-A086r7]. [DVB-A086r7].
o SSRC o SSRC
In the DVB AL-FEC protocol, the SSRC fields of the FEC packets In the DVB AL-FEC protocol, the SSRC fields of the FEC packets
MUST be set to 0. MUST be set to 0.
This requirement conflicts with RTP [RFC3550]. Unless signaled This requirement conflicts with RTP [RFC3550]. Unless signaled
otherwise, RTP uses random SSRC values with collision detection. otherwise, RTP uses random SSRC values with collision detection.
An explicit SSRC signaling mechanism is currently defined in An explicit SSRC signaling mechanism is currently defined in
[I-D.ietf-mmusic-sdp-source-attributes]. It is RECOMMENDED that [RFC5576]. It is RECOMMENDED that the DVB AL-FEC protocol uses
the DVB AL-FEC protocol uses this mechanism for explicit SSRC this mechanism for explicit SSRC signaling.
signaling.
o CSRC o CSRC
The DVB AL-FEC protocol does not support the protection of the The DVB AL-FEC protocol does not support the protection of the
CSRC entries in the source packets. Thus, the source stream MUST CSRC entries in the source packets. Thus, the source stream MUST
NOT have any CSRC entries in its packets and the CC fields of the NOT have any CSRC entries in its packets and the CC fields of the
source RTP packets MUST be zero. source RTP packets MUST be zero.
Note that if there are no RTP mixers used in a system running the Note that if there are no RTP mixers used in a system running the
DVB AL-FEC protocol, the CC field of the source RTP packets will DVB AL-FEC protocol, the CC field of the source RTP packets will
be 0 and this is no longer an issue. Thus, if defined, the new be 0 and this is no longer an issue. Thus, if defined, the new
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in [I-D.ietf-fecframe-interleaved-fec-scheme]. Instead, it may use in [I-D.ietf-fecframe-interleaved-fec-scheme]. Instead, it may use
the payload format that has been registered by DVB IPI for the payload format that has been registered by DVB IPI for
[ETSI-TS-102-034v1.3.1]. [ETSI-TS-102-034v1.3.1].
v=0 v=0
o=ali 1122334455 1122334466 IN IP4 fec.example.com o=ali 1122334455 1122334466 IN IP4 fec.example.com
s=DVB AL-FEC Example s=DVB AL-FEC Example
t=0 0 t=0 0
a=group:FEC S1 R1 R2 a=group:FEC S1 R1 R2
m=video 30000 RTP/AVP 100 m=video 30000 RTP/AVP 100
c=IN IP4 224.1.1.1/127 c=IN IP4 233.252.0.1/127
a=rtpmap:100 MP2T/90000 a=rtpmap:100 MP2T/90000
a=mid:S1 a=mid:S1
m=application 30000 RTP/AVP 96 m=application 30000 RTP/AVP 96
c=IN IP4 224.1.2.1/127 c=IN IP4 233.252.0.2/127
a=rtpmap:96 vnd.dvb.iptv.alfec-base/90000 a=rtpmap:96 vnd.dvb.iptv.alfec-base/90000
a=mid:R1 a=mid:R1
m=application 30000 RTP/AVP 111 m=application 30000 RTP/AVP 111
c=IN IP4 224.1.2.2/127 c=IN IP4 233.252.0.3/127
a=rtpmap:111 vnd.dvb.iptv.alfec-enhancement/90000 a=rtpmap:111 vnd.dvb.iptv.alfec-enhancement/90000
a=mid:R2 a=mid:R2
Note that in the example above, the payload type has been chosen as Note that in the example above, the payload type has been chosen as
96 for the base-layer FEC stream and there is no "a=fmtp:" line to 96 for the base-layer FEC stream and there is no "a=fmtp:" line to
specify the format parameters. Due to the lack of the format specify the format parameters. Due to the lack of the format
parameters, it is not possible to learn the FEC parameters from the parameters, it is not possible to learn the FEC parameters from the
SDP description. This severely limits the ability of using multiple SDP description. This severely limits the ability of using multiple
FEC streams that are generated with different settings. FEC streams that are generated with different settings.
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ETSI TS 102 034 V1.3.1, "Transport of MPEG 2 TS Based DVB ETSI TS 102 034 V1.3.1, "Transport of MPEG 2 TS Based DVB
Services over IP Based Networks", October 2007. Services over IP Based Networks", October 2007.
[DVB-A086r7] [DVB-A086r7]
DVB Document A086 Rev. 7 (Draft ETSI TS 102 034 V1.4.1), DVB Document A086 Rev. 7 (Draft ETSI TS 102 034 V1.4.1),
"Transport of MPEG 2 TS Based DVB Services over IP Based "Transport of MPEG 2 TS Based DVB Services over IP Based
Networks", September 2008. Networks", September 2008.
[I-D.ietf-fecframe-interleaved-fec-scheme] [I-D.ietf-fecframe-interleaved-fec-scheme]
Begen, A., "RTP Payload Format for 1-D Interleaved Parity Begen, A., "RTP Payload Format for 1-D Interleaved Parity
FEC", draft-ietf-fecframe-interleaved-fec-scheme-01 (work FEC", draft-ietf-fecframe-interleaved-fec-scheme-05 (work
in progress), October 2008. in progress), May 2009.
[I-D.ietf-fecframe-raptor] [I-D.ietf-fecframe-raptor]
Watson, M., "Raptor FEC Schemes for FECFRAME", Watson, M., "Raptor FEC Schemes for FECFRAME",
draft-ietf-fecframe-raptor-00 (work in progress), draft-ietf-fecframe-raptor-01 (work in progress),
October 2008. July 2009.
[I-D.watson-fecframe-rtp-raptor] [I-D.watson-fecframe-rtp-raptor]
Watson, M., "RTP Payload Format for Raptor FEC", Watson, M., "RTP Payload Format for Raptor FEC",
draft-watson-fecframe-rtp-raptor-00 (work in progress), draft-watson-fecframe-rtp-raptor-00 (work in progress),
October 2008. October 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, July 2003.
[I-D.ietf-mmusic-sdp-source-attributes] [RFC5576] Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Lennox, J., Ott, J., and T. Schierl, "Source-Specific
Media Attributes in the Session Description Protocol Media Attributes in the Session Description Protocol
(SDP)", draft-ietf-mmusic-sdp-source-attributes-02 (work (SDP)", RFC 5576, June 2009.
in progress), October 2008.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC4756] Li, A., "Forward Error Correction Grouping Semantics in [RFC4756] Li, A., "Forward Error Correction Grouping Semantics in
Session Description Protocol", RFC 4756, November 2006. Session Description Protocol", RFC 4756, November 2006.
8.2. Informative References 8.2. Informative References
[DVB-A115] [DVB-A115]
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Ali Begen Ali Begen
Cisco Systems Cisco Systems
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: abegen@cisco.com Email: abegen@cisco.com
Thomas Stockhammer Thomas Stockhammer
Digital Fountain Nomor Research
39141 Civic Center Drive Brecherspitzstrasse 8
Suite 300 Munich, 81541
Fremont, CA 94538 Germany
USA
Email: stockhammer@digitalfountain.com Email: stockhammer@nomor.de
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