RFC 5009
Private Header (P-Header) Extension to the Session Initiation Protocol (SIP) for Authorization of Early Media
RFC 5009: Private Header (P-Header) Extension to SIP for Authorization of Early Media ✨
Okay bestie, RFC 5009 is the Private Header (P-Header) Extension to the Session Initiation Protocol (SIP) for Authorization of Early Media 🎀 It was written by R. Ejzak at Alcatel-Lucent. It's Informational (category) and it's dated September 2007 📅 The title block doesn't list anything it obsoletes or updates, so it's standing on its own 💅
Status of This Memo ✨
This memo is here to provide information for the Internet community 📚 It does not specify an Internet standard of any kind. Distribution of this memo is unlimited 🌸
Abstract 🦋
This document describes a private SIP header field, called a P-header, that the European Telecommunications Standards Institute (ETSI) Telecommunications and Internet-converged Services and Protocols for Advanced Networks (TISPAN) uses to authorize early media flows in Third Generation Partnership Project (3GPP) IP Multimedia Subsystems (IMS) 🧚 It's super useful in any SIP network that's hooked up to other SIP networks and needs to control how media flows during the early dialog state 💜
Table of Contents 📖
1. Introduction ....................................................2
2. Applicability Statement .........................................3
3. Conventions and Acronyms ........................................3
4. Background on Early Media Authorization .........................4
4.1. Backward Early Media .......................................5
4.2. Forward Early Media ........................................5
5. Applicability of RFC 3959 and RFC 3960 ..........................6
6. Overview of Operation ...........................................6
7. Limitations of the P-Early-Media Header Field ...................8
8. The P-Early-Media Header Field ..................................8
8.1. Procedures at the User Agent Client .......................10
8.2. Procedures at the User Agent Server .......................10
8.3. Procedures at the Proxy ...................................11
9. Formal Syntax ..................................................11
10. Security Considerations .......................................11
11. IANA Considerations ...........................................12
11.1. Registration of the "P-Early-Media" SIP Header Field .....12
12. Acknowledgements ..............................................12
13. References ....................................................12
13.1. Normative References .....................................12
13.2. Informative References ...................................131. Introduction ✨
So this doc defines how to use the P-Early-Media header field inside SIP [1] messages 💖 The point is to authorize cutting through backward and/or forward early media, but only when the early media policies of the networks involved say it's allowed 🙌 This header is meant for a SIP network like a 3GPP IMS [13][14], and that kind of network has three main vibes: its early media policy bans end users from swapping early media with each other 🙅♀️, it's connected to other SIP networks whose policies are unknown, untrusted, or just different 🌍, and it can "gate" (enable/disable) early media going to and from user equipment 🔥
Inside a totally isolated SIP network, you can gate all the early media for every endpoint so the network enforces its own policy between its endpoints 🎀 But once a SIP network is interconnected with other SIP networks, only the boundary node facing the outside world can decide which early media policy applies to a session between endpoints on opposite sides of that boundary 👀 The P-Early-Media header field is the way that boundary node tells the other nodes inside the network what policy it picked 💅
2. Applicability Statement 🌸
This extension only applies inside a "Trust Domain" as defined in RFC 3325 [6] 🔐 Nodes in a Trust Domain are explicitly trusted by their users and end-systems to authorize early media requests, but only when the early media policy inside that Trust Domain allows it ✨
This document does NOT offer a general early media authorization model that works for inter-domain use or for the Internet at large 🚨 Early media requests aren't cryptographically certified, so they can be forged, replayed, and falsified in any architecture that doesn't meet the requirements of the Trust Domain 💀
An early media request also doesn't tell you who specifically is making or changing the request 😭 So you have to assume the Trust Domain is the one making it 🫶 That means the information only means something when it's securely received from a node you know is a member of the Trust Domain 🔒
Even though this extension can be used with parallel forking, it doesn't fix the known problems with early media and parallel forking described in RFC 3960 [4], unless you can assume symmetric RTP is in use 🙈
Okay but despite all that, there are specialized deployments that meet these assumptions and can live with the limitations, so this mechanism is worth publishing 🦋 An example would be a closed network that copies a traditional circuit switched telephone network 📞✨
3. Conventions and Acronyms 📚
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [2] 💜
Here's the acronym cheat sheet this doc uses 🧚
3GPP - the Third Generation Partnership Project
ABNF - Augmented Backus-Naur Form [5]
DTMF - Dual Tone Multi-Frequency
ETSI - European Telecommunications Standards Institute
IMS - Internet Protocol Multimedia Subsystem [13][14]
MIME - Multipurpose Internet Mail Extensions
NAT - Network Address Translation
PSTN - Public Switched Telephone Network
SDP - Session Description Protocol [7]
SIP - Session Initiation Protocol [1]
TISPAN - Telecommunications and Internet-converged Services and
Protocols for Advanced Networks
UA - User Agent [1]
UAC - User Agent Client [1]
UAS - User Agent Server [1]4. Background on Early Media Authorization 🎀
PSTN networks usually send call progress info as backward early media from the terminating switch back to the calling party 📞 They also sometimes use forward early media from the calling party toward the terminating switch for stuff like digit collection for secondary dialing 🔢 PSTN networks typically allow backward and/or forward early media because it's only there to move the call along to the answer state and doesn't involve exchanging data between endpoints 💖
In a SIP network, backward early media flows from the User Agent Server (UAS) to the User Agent Client (UAC) 🔄 Forward early media flows from the UAC to the UAS 🔜 By default, SIP networks allow both kinds, which can carry user data once the media path is set up 👀 Early media is usually a good thing with a PSTN gateway as the UAS, but not with SIP user equipment as the UAS 🙅♀️
To stop user data from sneaking through early media while still letting early media work through PSTN gateways, a SIP network can have a policy that blocks backward early media from SIP user equipment and blocks forward media toward SIP user equipment, since either one could carry user data 🛡️ A SIP network with both PSTN gateways and SIP end devices can keep that policy by gating "off" any early media from a SIP end device acting as UAS, gating "on" early media from a SIP end device acting as UAC, and gating "on" early media at each PSTN gateway 🎀
Here's the tea though 🍵 A SIP network that's interconnected with another SIP network might have no way to make sure the other network is running a compatible early media policy, so user data can end up flowing through early media in some situations 😬 For example, say network "A" allows all early media with user equipment as UAC, and an interconnected network "B" allows all early media with user equipment as UAS 💀 Then any session between user equipment as UAC in "A" and user equipment as UAS in "B" will allow two-way user data exchange as early media 🙈 Other combos of early media policies can cause similar not-great results too 😭
So the whole purpose of this extension is to let a SIP network connected to other SIP networks with different early media policies correctly identify and enable authorized early media according to its own policies 👑
4.1. Backward Early Media 📞
In the PSTN, backward early media usually carries call progress info like ringing feedback ("ringback") or announcements about special handling, such as forwarding 🔔 It can also ask for more info, like a credit card number to be entered as forward early media using Dual Tone Multi-Frequency (DTMF) tones or speech 💳 This kind of backward early media gives info to the calling party strictly to move the call along, and there's no data exchanged between end users 🙌 The usual PSTN charging policy assumes no data gets exchanged until the call has been answered 💅
A terminating SIP User Agent (UA) that's outside the SIP network, on the other hand, can put any user data it wants into a backward early media stream 😳 So if the network uses the usual early media policy, the network equipment gating the backward early media flow for the originating UA has to tell apart authorized early media from a terminating SIP endpoint and unauthorized early media from some other SIP device outside the network 🕵️♀️ Since the network assumes a transitive trust relationship between its SIP servers, this can be handled by including some info in a backward SIP message that says authorized backward early media is present 🧚
But here's the catch 🙈 That indication has to come from a trusted source, so each server on the path back to the originating UA needs to be able to verify its trust relationship with the previous server, and it has to remove the indication when it can't do that 🛑 A server on the boundary to an untrusted SIP network can make sure no indication of authorized backward early media gets passed from an external UAS to a UAC inside the network 🚧 That's why a private header field that proxies can modify is the way to go over a Multipurpose Internet Mail Extensions (MIME) attachment, which can't be modified like that 🦋✨
4.2. Forward Early Media 🦋
okay so forward early media is way less common than backward early media in the PSTN 💅 It's typically used to collect secondary dialed digits, to collect credit card numbers, or to collect other DTMF or speech responses so the call can get directed further. Forward early media in the PSTN is always aimed at a network server to progress a call, and there's zero exchange of data between end users 🙈
A terminating SIP UA outside of the SIP network, on the other hand, may receive any user data in a forward early media stream 😭 So if the network runs the usual early media policy, the network equipment gating the forward early media flow for the originating UA has to tell apart a terminating endpoint that is authorized to receive forward early media, and another SIP device outside the network that is not authorized to receive forward early media containing user data. This authorization can be done the same way as for backward early media, by including some info in a backward SIP message that identifies that the terminating side is authorized to receive forward early media ✨
5. Applicability of RFC 3959 and RFC 3960 🎀
The private header extension defined in this document is applicable to the gateway model defined in RFC 3960 [4], since the PSTN gateway is the primary requestor of early media in an IMS. For the same reason, neither the application server model of RFC 3960, nor the early-session disposition type defined in RFC 3959 [3] is applicable.
The gateway model of RFC 3960 [4] allows for individual networks to create local policy with respect to the handling of early media, but it doesn't address the case where a network is interconnected with other networks with unknown, untrusted, or different early media policies. Without the kind of information in the P-Early-Media header field, it is not possible for the network to determine whether cut-through of early media could lead to the transfer of data between end-users during session establishment 😬
Thus, the private header extension in this document is a natural extension of the gateway model of RFC 3960 [4] that is applicable within a transitive trust domain 🫶
6. Overview of Operation 🌈
okay this is the main event 👑 This document defines a new P-Early-Media header field for the purpose of requesting and authorizing requests for backward and/or forward early media. A UAC that can recognize the P-Early-Media header field may include the header field in an INVITE request. The P-Early-Media header field in an INVITE request contains the "supported" parameter.
As members of the Trust Domain, each proxy receiving an INVITE request has to decide whether to insert or delete the P-Early-Media header field before forwarding. 🧚
A UAS receiving an INVITE request can use the presence of the P-Early-Media header field in the request to decide whether to request early media authorization in subsequent messages towards the UAC. After receiving an incoming INVITE request, the UAS requesting backward and/or forward early media will include the P-Early-Media header field in a message towards the UAC within the dialog. That header includes direction parameter(s) that identify, for each media line in the session, whether the early media request is for backward media, forward media, both, or neither. The UAS can change its request for early media by including a modified P-Early-Media header field in a subsequent message towards the UAC within the dialog 🔥
Each proxy in the network receiving the P-Early-Media header field in a message towards the UAC is responsible for making sure that the early media request comes from an authorized source. If a P-Early-Media header field arrives from either an untrusted source, a source not allowed to send backward early media, or a source not allowed to receive forward early media, then the proxy may remove the P-Early-Media header field or alter the direction parameter(s) of the P-Early-Media header field before forwarding the message, based on local policy. 💀
A proxy in the network that does not receive the P-Early-Media header field in a message towards the UAC may insert one based on local policy.
If the proxy also performs gating of early media, then it uses the parameter(s) of the P-Early-Media header field to decide whether to open or close the gates for backward and forward early media flow(s) between the UAs. The proxy performing gating of early media may also add a "gated" parameter to the P-Early-Media header field before forwarding the message, so that other gating proxies in the path can choose to leave open their gates 🦋
If the UAC is a trusted server within the network (e.g., a PSTN gateway), then the UAC may use the parameter(s) of the P-Early-Media header field in messages received from the UAS to decide whether to perform early media gating or cut-through. It can also use them to decide whether or not to render backward early media in preference to generating ringback based on the receipt of a 180 Ringing response 🎀
If the UAC is associated with user equipment, then the network will have assigned a proxy the task of performing early media gating. So the parameter(s) of the P-Early-Media header field received at such a UAC do not require that the UAC police the early media flow(s). They do, however, provide additional information that the UAC may use to render media ✨
The UAC and proxies in the network may also insert, delete, or modify the P-Early-Media header field in messages towards the UAS within the dialog according to local policy. The interpretation of the header field when used in this way is a matter of local policy and not defined herein. The use of direction parameter(s) in this header field could be used to inform the UAS of the final early media authorization status 💜
7. Limitations of the P-Early-Media Header Field 🙈
The P-Early-Media header field does not apply to any SDP with Content-Disposition: early-session [3].
When parallel forking occurs, there is no reliable way to correlate early media authorization in a dialog with the media from the corresponding endpoint, unless one can assume the use of symmetric RTP. That's because the SDP messages do not identify the RTP source address of any media stream 😭 When a UAC or proxy receives multiple early dialogs and cannot accurately identify the source of each media stream, it SHOULD use the most restrictive early media authorization it receives on any of the dialogs to decide the policy to apply towards all received media. When early media usage is desired for any reason and one cannot assume the use of symmetric RTP, it is advisable to disable parallel forking using callerprefs [9] 🌸
Although the implementation of media gating is outside the scope of this extension, note that media gating must be implemented carefully in the presence of NATs and protocols that aid in NAT traversal. Media gating may also introduce a potential for media clipping. That's similar to what can happen during parallel forking, or with any other feature that may disable early media, such as custom ringback 🫠
8. The P-Early-Media Header Field ✨
The P-Early-Media header field with the supported parameter MAY be included in an INVITE request to indicate that the UAC or a proxy on the path recognizes the header field. Okay bestie, this is the header that lets the network say "hey, I'm handling early media over here" 🎀
A network entity MAY request the authorization of early media or change a request for authorization of early media by including the P-Early-Media header field in any message allowed by Table 1 within the dialog towards the sender of the INVITE request. The header field includes one or more direction parameters, and each one has one of the values sendrecv, sendonly, recvonly, or inactive, following the same convention SDP uses for stream directionality [7][8] 🦋 Each parameter applies, in order, to the media lines in the corresponding SDP messages that set up the session media. Unrecognized parameters SHALL be silently discarded. Non-direction parameters are ignored for early media authorization, so they don't count here 💅 If there are more direction parameters than media lines, the excess SHALL be silently discarded. If there are fewer direction parameters than media lines, the value of the last direction parameter SHALL apply to all remaining media lines. And a message going to the UAC with a P-Early-Media header field that has no recognized direction parameters SHALL NOT be interpreted as an early media authorization request. Not me being picky, but this matters 🙈
The value sendrecv asks for authorization of early media on that media line in both directions, from the UAS to the UAC and from the UAC to the UAS (both backward and forward early media) 🌈 The value sendonly asks for early media from the UAS towards the UAC only (backward early media), and not the other way. The value recvonly asks for early media from the UAC towards the UAS only (forward early media), and not the other way. The value inactive means either "please don't authorize any early media on that media line" or "please revoke the authorization for early media that was already authorized" 🫶
The P-Early-Media header field in any message within a dialog towards the sender of the INVITE request MAY also include the non-direction parameter gated, which says a network entity on the path towards the UAS is already gating the early media according to the direction parameter(s). When gated is included, it SHALL come after all direction parameters in the parameter list. Order matters, babe 💖
When a message going toward the UAC arrives without the P-Early-Media header field, and no earlier early media authorization request has been received in the dialog, the default early media authorization depends on local policy and may depend on whether the header field was included in the INVITE request. After an early media authorization request has been received in a dialog, if a later message comes in without the P-Early-Media header field, the previous early media authorization stays exactly as it was ✨
The P-Early-Media header field in any message within a dialog towards the UAS MAY be ignored or interpreted according to local policy. Totally up to whoever's running things 💜
The P-Early-Media header field does not interact with SDP offer/answer procedures in any way. Early media authorization isn't influenced by the state of the SDP offer/answer procedures (including preconditions and directionality), and it doesn't influence them either. The header field may or may not be present in messages that contain SDP 🌸 The most recently received early media authorization applies to the corresponding media line in the session established for the dialog, until the 200 OK response to the INVITE request is received. At that point, all media lines in the session are implicitly authorized 👑 Early media flowing in a particular direction needs three things: early media in that direction is authorized, media in that direction is enabled by the SDP direction attribute for the stream, and any applicable preconditions [11] are met. Early media authorization does not override the SDP direction attribute or preconditions state, and the SDP direction attribute does not override early media authorization. Both have to agree, no cap 🧚
Table 1 is an extension of Tables 2 and 3 in RFC 3261 [1] for the P-Early-Media header field. The column "PRA" is for the PRACK method [12]. The column "UPD" is for the UPDATE method [10].
Header field where proxy ACK BYE CAN INV OPT REG PRA UPD
________________________________________________________________
P-Early-Media R amr - - - o - - o o
P-Early-Media 18x amr - - - o - - - -
P-Early-Media 2xx amr - - - - - - o o
Table 1: P-Early-Media Header Field8.1. Procedures at the User Agent Client 🍓
A User Agent Client MAY include the P-Early-Media header field with the supported parameter in an INVITE request to indicate that it recognizes the header field.
A User Agent Client that receives a P-Early-Media header field MAY use the parameter(s) of the header field to gate or cut through early media, and to decide whether to render early media from the UAS to the UAC in preference to any locally generated ringback triggered by a 180 Ringing response. If a proxy is doing the early media gating for the User Agent Client, then the gateway model of RFC 3960 [4] for rendering early media applies. A User Agent Client without a proxy in the network doing early media gating that receives a P-Early-Media header field SHOULD gate or cut through early media according to the parameter(s) of the header field. Be a good client, please 🙌
8.2. Procedures at the User Agent Server 🎀
A User Agent Server that is requesting authorization to send or receive early media MAY insert a P-Early-Media header field with appropriate parameter(s) in any message allowed in Table 1 towards the UAC within the dialog. A User Agent Server MAY request changes in early media authorization by inserting a P-Early-Media header field with appropriate parameter(s) in any later message allowed in Table 1 towards the UAC within the dialog.
If the P-Early-Media header field is not present in the INVITE request, the User Agent Server MAY choose to suppress early media authorization requests and MAY choose to execute alternate early media procedures. Plot twist, it can just do its own thing 🦋
8.3. Procedures at the Proxy 🌈
When forwarding an INVITE request, a proxy MAY add, retain, or delete the P-Early-Media header field, depending on local policy and the trust relationship with the sender and/or receiver of the request.
When forwarding a message allowed in Table 1 towards the UAC, a proxy MAY add, modify, or delete a P-Early-Media header field, depending on local policy and the trust relationship with the sender and/or receiver of the message. In addition, if the proxy controls the gating of early media for the User Agent Client, it SHOULD use the contents of the P-Early-Media header field to gate the early media, according to the definitions of the header field parameters in clause 8. Proxies have a lot of power, so they should use it wisely 💅
9. Formal Syntax 💜
The syntax of the P-Early-Media header field is described below in ABNF, according to RFC 4234 [5], as an extension to the ABNF for SIP in RFC 3261 [1]. Note that not all combinations of em-param elements are semantically valid. Not every combo is a vibe 🙈
P-Early-Media = "P-Early-Media" HCOLON
[ em-param *(COMMA em-param) ]
em-param = "sendrecv" / "sendonly" / "recvonly"
/ "inactive" / "gated" / "supported" / token10. Security Considerations 🔥
The use of this extension is only applicable inside a "Trust Domain", as defined in RFC 3325 [6]. This document does NOT offer a general early media authorization model suitable for inter-domain use or use in the Internet at large. Do NOT take this outside the trust domain, seriously, it is not built for the wild internet 💀
There are no confidentiality concerns associated with the P-Early-Media header field. It is desirable to maintain the integrity of the direction parameters in the header field across each hop between servers, to avoid the potential for unauthorized use of early media. It is assumed that the P-Early-Media header field is used within the context of the 3GPP IMS trust domain or a similar trust domain, consisting of a collection of SIP servers maintaining pairwise security associations.
Within the trust domain of a network, it is only necessary to police the use of the P-Early-Media header field at the boundary to user equipment served by the network and at the boundary to peer networks. It is assumed that boundary servers in the trust domain of a network will have local policy for the treatment of the P-Early-Media header field as it is sent to or received from any possible server external to the network. Since boundary servers are free to modify or remove any P-Early-Media header field in SIP messages forwarded across the boundary, the integrity of the P-Early-Media header field can be verified only to the extent that the connections to external servers are secured. The authenticity of the P-Early-Media header field can only be assured to the extent that the external servers are trusted to police the authenticity of the header field. Trust is everything, bestie 🫶
11. IANA Considerations 🌸
11.1. Registration of the "P-Early-Media" SIP Header Field 🧚
Name of Header field: P-Early-Media
Short form: none
Registrant: Richard Ejzak
ejzak@alcatel-lucent.com
Normative description: Section 8 of this document12. Acknowledgements 💖
The author would like to thank Miguel Garcia-Martin, Jan Holm, Sebastien Garcin, Akira Kurokawa, Erick Sasaki, James Calme, Greg Tevonian, Aki Niemi, Paul Kyzivat, Gonzalo Camarillo, Brett Tate, Jon Peterson, Alfred Hoenes, and David Black for their significant contributions made throughout the writing and reviewing of this document. Iconic cast, honestly ✨
13. References ⭐
13.1. Normative References 📚
okay so these are the docs this one totally leans on, bestie 🫶 I'm keeping every single title, number, and date so you can look them up.
[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. ✨
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 🎀
[3] Camarillo, G., "The Early Session Disposition Type for the Session Initiation Protocol (SIP)", RFC 3959, December 2004. 🦋
[4] Camarillo, G. and H. Schulzrinne, "Early Media and Ringing Tone Generation in the Session Initiation Protocol (SIP)", RFC 3960, December 2004. 🌸
[5] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 4234, October 2005. 💅
[6] Jennings, C., Peterson, J., and M. Watson, "Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks", RFC 3325, November 2002. 🔥
[7] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. 🌈
[8] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002. ⭐
[9] Rosenberg, J., Schulzrinne, H., and P. Kyzivat, "Caller Preferences for the Session Initiation Protocol (SIP)", RFC 3841, August 2004. 💜
[10] Rosenberg, J., "The Session Initiation Protocol (SIP) UPDATE Method", RFC 3311, October 2002. 🧚
[11] Camarillo, G., Marshall, W., and J. Rosenberg, "Integration of Resource Management and Session Initiation Protocol (SIP)", RFC 3312, October 2002. 🍓
[12] Rosenberg, J. and H. Schulzrinne, "Reliability of Provisional Responses in Session Initiation Protocol (SIP)", RFC 3262, June 2002. 👑
13.2. Informative References 🌸
these ones are the extra reading, not required to get the core ideas, but super helpful if you want the full picture 🧠
[13] 3GPP "TS 23.228: IP Multimedia Subsystem (IMS); Stage 2 (Release 7)", 3GPP 23.228, March 2007, ftp://ftp.3gpp.org/specs/archive/23_series/23.228/. 💖
[14] 3GPP "TS 24.229: IP Multimedia Call Control Protocol based on SIP and SDP; Stage 3 (Release 7)", 3GPP 24.229, March 2007, ftp://ftp.3gpp.org/specs/archive/24_series/24.229/. 🦋
ETSI documents can be downloaded from the ETSI Web server at http://www.etsi.org/. Any 3GPP document can be downloaded from the 3GPP Web server at http://www.3gpp.org/. See specifications. ✨
Authors Address 🎀
say hi to the author, Richard, who wrote this from Alcatel-Lucent 💅
Richard Ejzak
Alcatel-Lucent
1960 Lucent Lane
Naperville, IL 60566
USA
Phone: +1 630 979 7036
EMail: ejzak@alcatel-lucent.comFull Copyright Statement 🌈
Copyright (C) The IETF Trust (2007). 💜
This document is covered by the rights, licenses, and restrictions in BCP 78. Apart from what that says, the authors keep all of their rights. 🫶
This document and the info in it are provided on an "AS IS" basis. THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 😭
Intellectual Property 👑
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The IETF also invites anyone who's interested to flag any copyrights, patents, patent applications, or other proprietary rights that might cover technology needed to implement this standard. Send that info to the IETF at ietf-ipr@ietf.org. 💌 ✨
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