RFC 6364
Session Description Protocol Elements for the Forward Error Correction (FEC) Framework
RFC 6364 📚✨ Part 1 of 3
Okay bestie, RFC 6364 is literally about how to pack FEC setup details into SDP so the sender and receiver can finally be on the same page 🫶 Here's the title block, all the important bits:
- RFC number: 6364
- Title: Session Description Protocol Elements for the Forward Error Correction (FEC) Framework
- Author: A. Begen, from Cisco 💅
- Category: Standards Track
- Date: October 2011
- ISSN: 2070-1721
- Obsoletes / Updates: the title block doesn't list either one 🌸
Abstract
Okay so this doc is all about using the Session Description Protocol (SDP) to describe the parameters that the sender(s) and receiver(s) need so they can share the FEC Framework Configuration Information 🎀 It's giving "here's the setup, everyone get on the same page." It also has examples that show how to group multiple source and repair flows together, for apps that run several instances of the FEC Framework at the same time 🔥
Status of This Memo
This is an Internet Standards Track document 💖
It's a product of the Internet Engineering Task Force (IETF), so it represents the consensus of the IETF community. It went through public review and got approved for publication by the Internet Engineering Steering Group (IESG). If you want more on Internet Standards, check out Section 2 of RFC 5741 🌈
For the latest status, errata, and how to send feedback, go to http://www.rfc-editor.org/info/rfc6364 🧚
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. 🔒
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as they stand on the publication date. Please read these carefully, because they spell out your rights and restrictions for this doc 🙈 Code Components pulled out of this document have to include Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as the Simplified BSD License describes.
This document may include material from IETF Documents or IETF Contributions that were published or made publicly available before November 10, 2008. The people who control the copyright in some of that material may not have given the IETF Trust permission to allow modifications outside the IETF Standards Process. Unless you get an adequate license from those copyright holders, this document can't be modified outside the IETF Standards Process, and derivative works can't be created outside it either. The one exception is formatting it for publication as an RFC or translating it into languages other than English 💅
Table of Contents
1. Introduction ....................................................3
2. Requirements Notation ...........................................3
3. Forward Error Correction (FEC) and FEC Framework ................3
3.1. Forward Error Correction (FEC) .............................3
3.2. FEC Framework ..............................................4
3.3. FEC Framework Configuration Information ....................4
4. SDP Elements ....................................................5
4.1. Transport Protocol Identifiers .............................6
4.2. Media Stream Grouping ......................................6
4.3. Source IP Addresses ........................................6
4.4. Source Flows ...............................................6
4.5. Repair Flows ...............................................7
4.6. Repair Window ..............................................8
4.7. Bandwidth Specification ....................................9
5. Scenarios and Examples .........................................10
5.1. Declarative Considerations ................................10
5.2. Offer/Answer Model Considerations .........................10
6. SDP Examples ...................................................11
6.1. One Source Flow, One Repair Flow, and One FEC Scheme ......11
6.2. Two Source Flows, One Repair Flow, and One FEC Scheme .....12
6.3. Two Source Flows, Two Repair Flows, and Two FEC Schemes ...13
6.4. One Source Flow, Two Repair Flows, and Two FEC Schemes ....14
7. Security Considerations ........................................15
8. IANA Considerations ............................................15
8.1. Registration of Transport Protocols .......................15
8.2. Registration of SDP Attributes ............................16
9. Acknowledgments ................................................16
10. References ....................................................17
10.1. Normative References .....................................17
10.2. Informative References ...................................171. Introduction ✨
The Forward Error Correction (FEC) Framework, described in [RFC6363], is a general framework for FEC-based error recovery in packet flows that carry media content. Continuous signaling between the sender(s) and receiver(s) isn't required for a Content Delivery Protocol (CDP) that uses the FEC Framework 💜 But a set of parameters about the FEC Framework still has to be shared up front, so a signaling protocol (like the one described in [FECFRAME-CFG-SIGNAL]) is required to carry them. The parameters also need to be encoded properly so the signaling protocol can carry them 🦋
One way to encode them is the Session Description Protocol (SDP) [RFC4566]. SDP is a simple text-based format for announcements and invitations that describe multimedia sessions. Those announcements and invitations include enough info for the sender(s) and receiver(s) to join the session 🌸 SDP also gives you a framework for capability negotiation, which can be used to negotiate all of the parameters for each session, or just a subset of them 🍓
This document introduces the SDP elements used by CDPs that use the FEC Framework and choose SDP [RFC4566] for their multimedia sessions. Iconic 👑
2. Requirements Notation 📝
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
3. Forward Error Correction (FEC) and FEC Framework 🧸
This section gives a quick overview of FEC and the FEC Framework, so you're not lost later 💖
3.1. Forward Error Correction (FEC) 🛡️
Any app that needs reliable transmission over an unreliable packet network has to deal with packet losses. FEC is a strong approach for reliable transmission, especially in multicast and broadcast apps where feedback from the receiver(s) is either not available or pretty limited 🔥
Here's the nutshell version: FEC groups source packets into blocks and applies protection to generate a desired number of repair packets. Those repair packets can be sent on demand, or independently of any receiver feedback 💅 Which one you pick depends on the FEC scheme or the Content Delivery Protocol the app uses, the packet loss characteristics of the underlying network, the transport scheme (e.g., unicast, multicast, and broadcast), and the app itself. On the receiver side, lost packets can be recovered by erasure decoding, as long as enough source and repair packets have arrived ✨
3.2. FEC Framework 🌈
The FEC Framework [RFC6363] is a general framework for using FEC codes in multimedia apps that stream audio, video, or other kinds of multimedia content. It defines the common components and aspects of Content Delivery Protocols (CDPs), and it also defines the requirements for the FEC schemes that need to be used within a CDP 🎀 However, the details of the FEC schemes aren't specified in the FEC Framework. For example, the FEC Framework defines what configuration information has to be known at the sender and receiver(s) at a minimum, but it doesn't say how the FEC repair packets get generated and used to recover missing source packets, and it doesn't dictate how the configuration information is communicated between the sender and receiver(s). Those things are specified by the individual FEC schemes or CDPs instead 🙈
3.3. FEC Framework Configuration Information 🦋
The FEC Framework [RFC6363] defines a minimum set of information that has to be communicated between the sender and receiver(s) for a FEC scheme to work properly. This info is called the "FEC Framework Configuration Information" 💜 It includes unique identifiers for the source and repair flows that carry the source and repair packets, respectively. It also specifies how the sender applies protection to the source flow(s), and how the repair flow(s) can be used to recover lost data 🫶
Multiple instances of the FEC Framework can exist at the same time at the sender and the receiver(s), for different source flows, for the same source flow, or for various combinations of source flows. Each instance of the FEC Framework provides the following FEC Framework Configuration Information:
- Identification of the repair flows.
- For each source flow protected by the repair flow(s):
- A. Definition of the source flow.
- B. An integer identifier for this flow definition (i.e., tuple). This identifier MUST be unique among all source flows that are protected by the same FEC repair flow. Integer identifiers can be allocated starting from zero and increasing by one for each flow. However, any random (but still unique) allocation is also possible. A source flow identifier need not be carried in source packets, since source packets are directly associated with a flow by virtue of their packet headers. 🧚
- The FEC Encoding ID, identifying the FEC scheme.
- The length of the Explicit Source FEC Payload ID (in octets).
- Zero or more FEC-Scheme-Specific Information (FSSI) elements, each consisting of a name and a value where the valid element names and value ranges are defined by the FEC scheme.
FSSI holds the info that's specific to the FEC scheme the CDP uses. It carries info that can't be represented adequately any other way, and it's essential for proper FEC encoding and decoding 🔥 The reason the FSSI that only the sender needs gets separated out (into a Sender-Side FEC-Scheme-Specific Information (SS-FSSI) container) is to give the receiver or third-party entities a way to control the FEC operations at the sender 👑 Any FSSI other than the one solely required by the sender MUST be communicated via the FSSI container. 💀
The variable-length SS-FSSI and FSSI containers send the info in textual representation, and each one holds zero or more distinct elements. The fully specified FEC schemes provide the descriptions for those elements 🌸
4. SDP Elements 🎀
This section defines the SDP elements that MUST be used to describe the FEC Framework Configuration Information in multimedia sessions, by the CDPs that choose SDP [RFC4566] for their multimedia sessions. Example SDP descriptions are in Section 6 💖
4.1. Transport Protocol Identifiers 🎀
okay bestie, so this spec makes a brand new transport protocol identifier for the FEC schemes that take a UDP-formatted input stream and add an Explicit Source FEC Payload ID (see Section 5.3 of [RFC6363]) to make a source flow ✨. It's called FEC/UDP and it's giving main character energy 💖. If you want input streams formatted according to another <proto> (the ones listed in the table for the 'proto' field in the "Session Description Protocol (SDP) Parameters" registry 🧚), then the matching FEC/<proto> transport protocol identifier MUST be registered with IANA by following the instructions specified in [RFC4566].
ngl this next bit is so important 🫶 If a FEC scheme does not use the Explicit Source FEC Payload ID (see Section 4.1 of [RFC6363]), then the original transport protocol identifier MUST be used. That's how backward compatibility stays intact for receivers that don't support FEC at all 🌸.
This spec also defines a second transport protocol identifier, UDP/FEC, which is for the FEC repair packet format defined in Section 5.4 of [RFC6363] 🦋. For the full registration details, check out Section 8.1.
4.2. Media Stream Grouping 🍓
In the FEC Framework, the 'group' attribute is used together with the FEC grouping semantics from [RFC5888] and [RFC5956] (respectively) to link source and repair flows together. it's basically the friendship bracelet of SDP 💅
4.3. Source IP Addresses 🌈
The 'source-filter' attribute of SDP ("a=source-filter") as defined in [RFC4570] is what gets used to express the source addresses or fully qualified domain names in the FEC Framework 💜.
4.4. Source Flows ✨
Here's the tea 🍵 The FEC Framework allows that multiple source flows MAY be grouped and protected together by single or multiple FEC Framework instances. Because of that, as described in Section 3.3, individual source flows MUST be identified with unique identifiers. For that purpose, we introduce the attribute 'fec-source-flow' 👑.
The syntax for the new attribute in ABNF [RFC5234] looks like this:
fec-source-flow-line = "a=fec-source-flow:" SP source-id
[";" SP tag-length] CRLF
source-id = "id=" src-id
src-id = 1*DIGIT ; Represented as 32-bit non-negative
; integers, and leading zeros are ignored
tag-length = "tag-len=" tlen
tlen = %x31-39 *DIGITThe REQUIRED parameter 'id' is what identifies the source flow 🔥. Parameter 'id' MUST be an integer, no exceptions bestie 🙈.
The 'tag-len' parameter tells you how long the Explicit Source FEC Payload ID field is (in octets) 🧚. If an Explicit Source FEC Payload ID is used, the 'tag-len' parameter MUST exist and indicate its length. Otherwise, the 'tag-len' parameter MUST NOT exist 💀.
4.5. Repair Flows 💖
A repair flow MUST contain only repair packets formatted as described in [RFC6363] for a single FEC Framework instance. In other words, packets belonging to source flows or to other repair flows from a different FEC Framework instance cannot be sent within this flow 🙅♀️. We introduce the attribute 'fec-repair-flow' to describe the repair flows 🦋.
The syntax for the new attribute in ABNF is as follows (CHAR and CTL are defined in [RFC5234]):
fec-repair-flow-line = "a=fec-repair-flow:" SP fec-encoding-id
[";" SP flow-preference]
[";" SP sender-side-scheme-specific]
[";" SP scheme-specific] CRLF
fec-encoding-id = "encoding-id=" enc-id
enc-id = 1*DIGIT ; FEC Encoding ID
flow-preference = "preference-lvl=" preference-level-of-the-flow
preference-level-of-the-flow = 1*DIGIT
sender-side-scheme-specific = "ss-fssi=" sender-info
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 = "(" / ")" / "<" / ">" / "@"
/ "," / ";" / ":" / "\" / DQUOTE
/ "/" / "[" / "]" / "?" / "="
/ "{" / "}" / SP / HTAB
scheme-specific = "fssi=" scheme-info
scheme-info = element *( "," element )The REQUIRED parameter 'encoding-id' is what identifies the FEC scheme used to generate this repair flow 🌸. These identifiers (in the range of [0 - 255]) are registered by the FEC schemes that use the FEC Framework, and IANA maintains them 🧚.
The OPTIONAL parameter 'preference-lvl' shows the preferred order for using the repair flows 🍓. The exact usage of 'preference-lvl' and the rules around it MAY be defined by the FEC scheme or the CDP. If the parameter 'preference-lvl' doesn't exist, the receiver(s) MAY receive and use the repair flows in any order. But if a preference level is assigned to the repair flow(s), the receivers are encouraged to follow that order when receiving and using them 🫶.
The OPTIONAL parameters 'ss-fssi' and 'fssi' are containers for the FEC-Scheme-Specific Information (FSSI). That info is specific to the FEC scheme used by the CDP and is needed for proper FEC encoding and decoding ✨. FSSI that's only required by the sender (the Sender-Side FSSI) MUST be communicated in the container specified by the parameter 'ss-fssi'. Any other FSSI MUST be communicated in the container specified by the parameter 'fssi'. In both containers, FSSI is sent as a textual representation and MAY contain multiple distinct elements 🌈. If the FEC scheme doesn't need any specific information, the 'ss-fssi' and 'fssi' parameters MUST NOT exist 💅.
4.6. Repair Window ⭐
The repair window is the time that spans a FEC block, which is made up of the source block and the corresponding repair packets 🕰️.
On the sender side, the FEC encoder processes a block of source packets and generates a number of repair packets. Then both the source and repair packets get transmitted within a certain duration that's not larger than the value of the repair window 🚀. The value of the repair window affects the maximum number of source packets that can be included in a FEC block 👑.
On the receiver side, the FEC decoder should wait at least for the duration of the repair window after it gets the first packet in a FEC block, so all the repair packets have time to arrive 🎧. (The waiting time can be adjusted if there are missing packets at the beginning of the FEC block.) The FEC decoder can start decoding the packets it already has sooner, but it SHOULD NOT register a FEC decoding failure until it has waited at least for the duration of the repair window 🙈.
This document specifies a brand new attribute to describe the size of the repair window in milliseconds and microseconds 🍭.
The syntax for the attribute in ABNF is as follows:
repair-window-line = "a=repair-window:" window-size unit CRLF
window-size = %x31-39 *DIGIT ; Represented as
; 32-bit non-negative integers
unit = "ms" / "us"<unit> is the unit of time used for the repair window size. Two units are defined here: 'ms', which stands for milliseconds, and 'us', which stands for microseconds 🫧.
The 'a=repair-window' attribute is a media-level attribute, since each repair flow MAY have a different repair window size 🦋.
Here's the thing 🤓 Specifying the repair window size as an absolute time value doesn't necessarily correspond to an integer number of packets or exactly match the clock rate used in RTP (when RTP is the transport). That can cause mismatches among subsequent repair windows. However, in practice, this mismatch does not break anything in the FEC decoding process 💖.
4.7. Bandwidth Specification 💸
The bandwidth specification defined in [RFC4566] denotes the proposed bandwidth to be used by the session or media. Specifying bandwidth is OPTIONAL 🌸.
In the context of the FEC Framework, the bandwidth specification can express the bandwidth of the repair flows or the bandwidth of the session. If it's included in the SDP, it SHALL adhere to the following rules 📜.
The session-level bandwidth for a FEC Framework instance, or the media-level bandwidth for the individual repair flows, MAY be specified. In this case, it is RECOMMENDED that the Transport Independent Application Specific (TIAS) bandwidth modifier [RFC3890] and the 'a=maxprate' attribute be used, unless the Application-Specific (AS) bandwidth modifier [RFC4566] is used. Using the AS bandwidth modifier is NOT RECOMMENDED, because TIAS lets you calculate the bitrate according to the IP version and transport protocol, whereas AS doesn't 🙅♀️. So, in TIAS-based bitrate calculations, the packet size SHALL include all headers and payload, excluding the IP and UDP headers. In AS-based bitrate calculations, the packet size SHALL include all headers and payload, plus the IP and UDP headers 🧮.
For the ABNF syntax of TIAS and AS, look at [RFC3890] and [RFC4566], respectively 📖.
5. Scenarios and Examples 🎬
This section talks about the considerations for Session Announcement and Offer/Answer Models 💫.
5.1. Declarative Considerations 📣
In multicast-based applications, the FEC Framework Configuration Information for all FEC protection options available at the sender MAY be advertised to the receivers as part of a session announcement 📡. This way, the sender can let receivers know every option available for FEC protection. Based on their needs, receivers can choose protection provided by one or more FEC Framework instances and subscribe to the respective multicast session(s) to receive the repair flow(s) 🌈. Unless the CDP explicitly requires it, receivers SHOULD NOT send an answer back to the sender specifying their choices, since that can easily overwhelm the sender, especially in large-scale multicast applications 😭.
5.2. Offer/Answer Model Considerations 🤝
In unicast-based applications, a sender and receiver MAY adopt the Offer/Answer Model [RFC3264] to set the FEC Framework Configuration Information. In this case, the sender offers the options available to that particular receiver, and the receiver answers back to the sender with its choice(s) 💌.
Receivers supporting the SDP Capability Negotiation Framework [RFC5939] MAY also use this framework to negotiate all, or a subset, of the FEC Framework parameters 🧩.
Backward compatibility in the Offer/Answer Model is handled as specified in [RFC5956] 🫶.
6. SDP Examples 🍰
This section provides SDP examples that can be used by the FEC Framework 💜.
[RFC5888] defines the media stream identification attribute ('mid') as a token in ABNF. In contrast, the identifiers for the source flows are integers and can be allocated starting from zero, increasing by one for each flow. To avoid any ambiguity, using the same values for identifying the media streams and the source flows is NOT RECOMMENDED, even when 'mid' values are integers 🙃.
In the examples below, random FEC Encoding IDs will be used for illustrative purposes. Artificial content for the SS-FSSI and FSSI will also be provided 🎀.
6.1. One Source Flow, One Repair Flow, and One FEC Scheme 🎀
okay bestie, this first example is the simplest one, so start here 💅 we've got ONE source video flow (mid:S1) and ONE FEC repair flow (mid:R1). we bundle them into one FEC group with the a=group:FEC-FR S1 R1 line. both flows go to the same port but on different multicast groups, and the repair window is set to 150 ms ✨
SOURCE FLOWS | INSTANCE #1
S1: Source Flow |--------| R1: Repair Flow
|
Figure 1: Scenario #1here's the SDP for it 🧚
v=0
o=ali 1122334455 1122334466 IN IP4 fec.example.com
s=FEC Framework Examples
t=0 0
a=group:FEC-FR S1 R1
m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127
a=rtpmap:100 MP2T/90000
a=fec-source-flow: id=0
a=mid:S1
m=application 30000 UDP/FEC
c=IN IP4 233.252.0.2/127
a=fec-repair-flow: encoding-id=0; ss-fssi=n:7,k:5
a=repair-window:150ms
a=mid:R16.2. Two Source Flows, One Repair Flow, and One FEC Scheme 🌸
ooh this one is giving protection for TWO sources with just ONE repair flow 🦋 we have two source video flows (mid:S2 and mid:S3) and one FEC repair flow (mid:R2) covering both of them. the FEC group is made with a=group:FEC-FR S2 S3 R2. same deal as before, the source and repair flows share a port but sit on different multicast groups, and the repair window is 150500 us (yes, microseconds, not ms, so pay attention 🙈)
SOURCE FLOWS
S2: Source Flow | | INSTANCE #1
|---------| R2: Repair Flow
S3: Source Flow |
Figure 2: Scenario #2 v=0
o=ali 1122334455 1122334466 IN IP4 fec.example.com
s=FEC Framework Examples
t=0 0
a=group:FEC-FR S2 S3 R2
m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127
a=rtpmap:100 MP2T/90000
a=fec-source-flow: id=0
a=mid:S2
m=video 30000 RTP/AVP 101
c=IN IP4 233.252.0.2/127
a=rtpmap:101 MP2T/90000
a=fec-source-flow: id=1
a=mid:S3
m=application 30000 UDP/FEC
c=IN IP4 233.252.0.3/127
a=fec-repair-flow: encoding-id=0; ss-fssi=n:7,k:5
a=repair-window:150500us
a=mid:R26.3. Two Source Flows, Two Repair Flows, and Two FEC Schemes 💖
now we're doubling everything 👑 two source video flows (mid:S4 and mid:S5) and two FEC repair flows (mid:R3 and mid:R4). S4 is protected by R3, and S5 is protected by R4, so each source gets its own bodyguard. we make two FEC groups, a=group:FEC-FR S4 R3 and a=group:FEC-FR S5 R4. the repair windows are 200 ms for the first group and 400 ms for the second one. iconic structure, honestly ✨
SOURCE FLOWS | INSTANCE #1
S4: Source Flow |--------| R3: Repair Flow
S5: Source Flow |--------| INSTANCE #2
| R4: Repair Flow
Figure 3: Scenario #3 v=0
o=ali 1122334455 1122334466 IN IP4 fec.example.com
s=FEC Framework Examples
t=0 0
a=group:FEC-FR S4 R3
a=group:FEC-FR S5 R4
m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127
a=rtpmap:100 MP2T/90000
a=fec-source-flow: id=0
a=mid:S4
m=video 30000 RTP/AVP 101
c=IN IP4 233.252.0.2/127
a=rtpmap:101 MP2T/90000
a=fec-source-flow: id=1
a=mid:S5
m=application 30000 UDP/FEC
c=IN IP4 233.252.0.3/127
a=fec-repair-flow: encoding-id=0; ss-fssi=n:7,k:5
a=repair-window:200ms
a=mid:R3
m=application 30000 UDP/FEC
c=IN IP4 233.252.0.4/127
a=fec-repair-flow: encoding-id=0; ss-fssi=n:14,k:10
a=repair-window:400ms
a=mid:R46.4. One Source Flow, Two Repair Flows, and Two FEC Schemes 🧚
last one, and it's a fun twist 🌈 we have ONE source video flow (mid:S6) with TWO FEC repair flows (mid:R5 and mid:R6) that have different preference levels. S6 is covered by both repair flows, so we form two FEC groups, a=group:FEC-FR S6 R5 and a=group:FEC-FR S6 R6. same port, different multicast groups, and the repair window is 200 ms for both groups 💜
SOURCE FLOWS | INSTANCE #1
S6: Source Flow |--------| R5: Repair Flow
|
|--------| INSTANCE #2
| R6: Repair Flow
Figure 4: Scenario #4 v=0
o=ali 1122334455 1122334466 IN IP4 fec.example.com
s=FEC Framework Examples
t=0 0
a=group:FEC-FR S6 R5
a=group:FEC-FR S6 R6
m=video 30000 RTP/AVP 100
c=IN IP4 233.252.0.1/127
a=rtpmap:100 MP2T/90000
a=fec-source-flow: id=0
a=mid:S6
m=application 30000 UDP/FEC
c=IN IP4 233.252.0.3/127
a=fec-repair-flow: encoding-id=0; preference-lvl=0; ss-fssi=n:7,k:5
a=repair-window:200ms
a=mid:R5
m=application 30000 UDP/FEC
c=IN IP4 233.252.0.4/127
a=fec-repair-flow: encoding-id=1; preference-lvl=1; ss-fssi=t:3
a=repair-window:200ms
a=mid:R67. Security Considerations 🔥
okay this part is seriously important, so listen up 👀 there's a weak threat if someone changes the SDP so that it shows a wrong association and/or grouping of the source and repair flows. that kind of attack can break FEC protection and/or mess up other media streams, which is not it 💀 it is RECOMMENDED that the receiver runs an integrity check on the SDP so it only trusts SDP from trusted sources 🫶 the receiver MUST also follow the security considerations of SDP [RFC4566]. for other general SDP security stuff, check [RFC4566], and for the security considerations around using source address filters in SDP, check [RFC4570].
the security considerations for the FEC Framework also apply, so go read [RFC6363] for the details 🔐
8. IANA Considerations 🌷
8.1. Registration of Transport Protocols
this spec updates the "Session Description Protocol (SDP) Parameters" registry from Section 8.2.2 of [RFC4566] 🦋 specifically, it adds these values to the table for the 'proto' field:
Type SDP Name Reference
------ ---------- -----------
proto FEC/UDP [RFC6364]
proto UDP/FEC [RFC6364]8.2. Registration of SDP Attributes
this document registers three brand new attribute names in SDP ✨ each one is an "att-field" that shows up at the media level, and none of them are subject to charset.
SDP Attribute ("att-field"):
Attribute name: fec-source-flow
Long form: Pointer to FEC Source Flow
Type of name: att-field
Type of attribute: Media level
Subject to charset: No
Purpose: Provide parameters for a FEC source flow
Reference: [RFC6364]
Values: See [RFC6364]
SDP Attribute ("att-field"):
Attribute name: fec-repair-flow
Long form: Pointer to FEC Repair Flow
Type of name: att-field
Type of attribute: Media level
Subject to charset: No
Purpose: Provide parameters for a FEC repair flow
Reference: [RFC6364]
Values: See [RFC6364]
SDP Attribute ("att-field"):
Attribute name: repair-window
Long form: Pointer to FEC Repair Window
Type of name: att-field
Type of attribute: Media level
Subject to charset: No
Purpose: Indicate the size of the repair window
Reference: [RFC6364]
Values: See [RFC6364]9. Acknowledgments 🫶
the author would like to thank the FEC Framework Design Team for their inputs, suggestions, and contributions. the whole squad showed up for this one 💜
10. References 📚
10.1. Normative References
[RFC6363] Watson, M., Begen, A., and V. Roca, "Forward Error
Correction (FEC) Framework", RFC 6363, October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
[RFC4570] Quinn, B. and R. Finlayson, "Session Description Protocol
(SDP) Source Filters", RFC 4570, July 2006.
[RFC5888] Camarillo, G. and H. Schulzrinne, "The Session Description
Protocol (SDP) Grouping Framework", RFC 5888, June 2010.
[RFC5956] Begen, A., "Forward Error Correction Grouping Semantics in
the Session Description Protocol", RFC 5956,
September 2010.
[RFC3890] Westerlund, M., "A Transport Independent Bandwidth
Modifier for the Session Description Protocol (SDP)",
RFC 3890, September 2004.
[RFC5234] Crocker, D., Ed., and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234,
January 2008.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
June 2002.10.2. Informative References
[FECFRAME-CFG-SIGNAL]
Asati, R., "Methods to convey FEC Framework Configuration
Information", Work in Progress, September 2011.
[RFC5939] Andreasen, F., "Session Description Protocol (SDP)
Capability Negotiation", RFC 5939, September 2010.Author's Address 🌈
Ali Begen
Cisco
181 Bay Street
Toronto, ON M5J 2T3
Canada
EMail: abegen@cisco.com📦 where this page comes from
- ietf: rfc6364 2011-10
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms