draft-ietf-fecframe-sdp-elements-07.txt   draft-ietf-fecframe-sdp-elements-08.txt 
FEC Framework A. Begen FEC Framework A. Begen
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track July 12, 2010 Intended status: Standards Track August 12, 2010
Expires: January 13, 2011 Expires: February 13, 2011
Session Description Protocol (SDP) Elements for FEC Framework Session Description Protocol (SDP) Elements for FEC Framework
draft-ietf-fecframe-sdp-elements-07 draft-ietf-fecframe-sdp-elements-08
Abstract Abstract
This document specifies the use of Session Description Protocol (SDP) This document specifies the use of Session Description Protocol (SDP)
to describe the parameters required to signal the Forward Error to describe the parameters required to signal the Forward Error
Correction (FEC) Framework Configuration Information between the Correction (FEC) Framework Configuration Information between the
sender(s) and receiver(s). This document also provides examples that sender(s) and receiver(s). This document also provides examples that
show the semantics for grouping multiple source and repair flows show the semantics for grouping multiple source and repair flows
together for the applications that simultaneously use multiple together for the applications that simultaneously use multiple
instances of the FEC Framework. instances of the FEC Framework.
skipping to change at page 1, line 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 13, 2011. This Internet-Draft will expire on February 13, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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3. Forward Error Correction (FEC) and FEC Framework . . . . . . . 4 3. Forward Error Correction (FEC) and FEC Framework . . . . . . . 4
3.1. Forward Error Correction (FEC) . . . . . . . . . . . . . . 4 3.1. Forward Error Correction (FEC) . . . . . . . . . . . . . . 4
3.2. FEC Framework . . . . . . . . . . . . . . . . . . . . . . 5 3.2. FEC Framework . . . . . . . . . . . . . . . . . . . . . . 5
3.3. FEC Framework Configuration Information . . . . . . . . . 5 3.3. FEC Framework Configuration Information . . . . . . . . . 5
4. SDP Elements . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. SDP Elements . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Transport Protocol Identifiers . . . . . . . . . . . . . . 6 4.1. Transport Protocol Identifiers . . . . . . . . . . . . . . 6
4.2. Media Stream Grouping . . . . . . . . . . . . . . . . . . 7 4.2. Media Stream Grouping . . . . . . . . . . . . . . . . . . 7
4.3. Source IP Addresses . . . . . . . . . . . . . . . . . . . 7 4.3. Source IP Addresses . . . . . . . . . . . . . . . . . . . 7
4.4. Source Flows . . . . . . . . . . . . . . . . . . . . . . . 7 4.4. Source Flows . . . . . . . . . . . . . . . . . . . . . . . 7
4.5. Repair Flows . . . . . . . . . . . . . . . . . . . . . . . 8 4.5. Repair Flows . . . . . . . . . . . . . . . . . . . . . . . 8
4.6. Repair Window . . . . . . . . . . . . . . . . . . . . . . 9 4.6. Repair Window . . . . . . . . . . . . . . . . . . . . . . 10
4.7. Bandwidth Specification . . . . . . . . . . . . . . . . . 10 4.7. Bandwidth Specification . . . . . . . . . . . . . . . . . 11
5. Scenarios and Examples . . . . . . . . . . . . . . . . . . . . 11 5. Scenarios and Examples . . . . . . . . . . . . . . . . . . . . 12
5.1. Declarative Considerations . . . . . . . . . . . . . . . . 11 5.1. Declarative Considerations . . . . . . . . . . . . . . . . 12
5.2. Offer/Answer Model Considerations . . . . . . . . . . . . 11 5.2. Offer/Answer Model Considerations . . . . . . . . . . . . 12
6. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . . 12 6. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. One Source Flow, One Repair Flow and One FEC Scheme . . . 12 6.1. One Source Flow, One Repair Flow and One FEC Scheme . . . 13
6.2. Two Source Flows, One Repair Flow and One FEC Scheme . . . 13 6.2. Two Source Flows, One Repair Flow and One FEC Scheme . . . 13
6.3. Two Source Flows, Two Repair Flows and Two FEC Schemes . . 14 6.3. Two Source Flows, Two Repair Flows and Two FEC Schemes . . 14
6.4. One Source Flow, Two Repair Flows and Two FEC Schemes . . 15 6.4. One Source Flow, Two Repair Flows and Two FEC Schemes . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8.1. Registration of Transport Protocols . . . . . . . . . . . 16 8.1. Registration of Transport Protocols . . . . . . . . . . . 16
8.2. Registration of SDP Attributes . . . . . . . . . . . . . . 17 8.2. Registration of SDP Attributes . . . . . . . . . . . . . . 17
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . . 18 10.1. Normative References . . . . . . . . . . . . . . . . . . . 18
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[";" SP sender-side-scheme-specific] [";" SP sender-side-scheme-specific]
[";" SP scheme-specific] CRLF [";" SP scheme-specific] CRLF
fec-encoding-id = "encoding-id=" enc-id fec-encoding-id = "encoding-id=" enc-id
enc-id = 1*DIGIT ; FEC Encoding ID enc-id = 1*DIGIT ; FEC Encoding ID
flow-preference = "preference-lvl=" preference-level-of-the-flow flow-preference = "preference-lvl=" preference-level-of-the-flow
preference-level-of-the-flow = *DIGIT preference-level-of-the-flow = *DIGIT
sender-side-scheme-specific = "ss-fssi=" sender-info sender-side-scheme-specific = "ss-fssi=" sender-info
sender-info = *CHAR sender-info = [ element *( ',' element ) ]
element = name ':' value
name = token
token = 1*<any CHAR except CTLs or separators>
value = *<any CHAR except CTLs or separators>
separator = "(" | ")" | "<" | ">" | "@"
| "," | ";" | ":" | "\" | <">
| "/" | "[" | "]" | "?" | "="
| "{" | "}" | SP | HT
scheme-specific = "fssi=" scheme-info scheme-specific = "fssi=" scheme-info
scheme-info = *CHAR scheme-info = [ element *( ',' element ) ]
element = name ':' value
name = token
token = 1*<any CHAR except CTLs or separators>
value = *<any CHAR except CTLs or separators>
separator = "(" | ")" | "<" | ">" | "@"
| "," | ";" | ":" | "\" | <">
| "/" | "[" | "]" | "?" | "="
| "{" | "}" | SP | HT
The REQUIRED parameter 'encoding-id' is used to identify the FEC The REQUIRED parameter 'encoding-id' is used to identify the FEC
scheme used to generate this repair flow. These identifiers MUST be scheme used to generate this repair flow. These identifiers MUST be
registered with IANA by the FEC schemes that use the FEC Framework. registered with IANA by the FEC schemes that use the FEC Framework.
The OPTIONAL parameter 'preference-lvl' is used to indicate the The OPTIONAL parameter 'preference-lvl' is used to indicate the
preferred order of using the repair flows. The exact usage of the preferred order of using the repair flows. The exact usage of the
parameter 'preference-lvl' and the pertaining rules MAY be defined by parameter 'preference-lvl' and the pertaining rules MAY be defined by
the FEC scheme or the CDP. If no value is specified for the the FEC scheme or the CDP. If no value is specified for the
parameter 'preference-lvl', it means that the receiver(s) MAY receive parameter 'preference-lvl', it means that the receiver(s) MAY receive
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repair-window-line = "a=repair-window:" window-size repair-window-line = "a=repair-window:" window-size
[unit] CRLF [unit] CRLF
window-size = 1*DIGIT window-size = 1*DIGIT
unit = ms / us unit = ms / us
<unit> is the unit of time the repair window size is specified with. <unit> is the unit of time the repair window size is specified with.
Two units are defined here: 'ms', which stands for milliseconds and Two units are defined here: 'ms', which stands for milliseconds and
'us', which stands for microseconds. 'us', which stands for microseconds. The default unit is 'ms'.
The 'a=repair-window' attribute is a media-level attribute since each The 'a=repair-window' attribute is a media-level attribute since each
repair flow MAY have a different repair window size. repair flow MAY have a different repair window size.
Specifying the repair window size in an absolute time value does not Specifying the repair window size in an absolute time value does not
necessarily correspond to an integer number of packets or exactly necessarily correspond to an integer number of packets or exactly
match with the clock rate used in RTP (in case of RTP transport) match with the clock rate used in RTP (in case of RTP transport)
causing mismatches among subsequent repair windows. However, in causing mismatches among subsequent repair windows. However, in
practice, this mismatch does not break anything in the FEC decoding practice, this mismatch does not break anything in the FEC decoding
process. process.
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