RFC 5362
The Session Initiation Protocol (SIP) Pending Additions Event Package
The Session Initiation Protocol (SIP) Pending Additions Event Package 🎀
Okay bestie, this is RFC 5362 💖 It's a Standards Track doc, so it's the real deal, and it was written by G. Camarillo at Ericsson back in October 2008. It came out of the Network Working Group. The title block doesn't list anything it obsoletes or updates, so it isn't rewriting anyone else's homework 💅
Status of This Memo 📜
This document is an Internet standards track protocol for the Internet community, and it asks for discussion and suggestions for improvements. Check the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol 🦋 Distribution of this memo is unlimited ✨
Abstract 💌
This document defines the SIP Pending Additions event package 🧚 It's used by SIP relays to tell user agents about the consent-related status of the entries that are about to be added to a resource list 🫶
Table of Contents 🗂️
1. Introduction ....................................................3
2. Terminology .....................................................3
3. Overview of Operation ...........................................3
4. XML Schema Definition ...........................................3
5. Pending Additions Event Package Definition ......................5
5.1. Event Package Name .........................................5
5.1.1. Event Package Parameters ............................5
5.1.2. SUBSCRIBE Bodies ....................................5
5.1.3. Subscription Duration ...............................5
5.1.4. NOTIFY Bodies .......................................5
5.1.5. Notifier Processing of SUBSCRIBE Requests ...........6
5.1.6. Notifier Generation of NOTIFY Requests ..............6
5.1.7. Subscriber Processing of NOTIFY Requests ............6
5.1.8. Handling of Forked Requests .........................7
5.1.9. Rate of Notifications ...............................7
5.1.10. State Agents .......................................7
5.1.11. Example ............................................7
6. Partial Notifications ...........................................8
6.1. Generation of Partial Notifications ........................8
6.2. Processing of Partial Notifications ........................9
6.3. XML Schema for Partial Notifications .......................9
6.4. Examples ..................................................11
7. IANA Considerations ............................................11
7.1. SIP Event Package Registration ............................11
7.2. URN Sub-Namespace Registration: consent-status ............12
7.3. XML Schema Registration: consent-status ...................12
7.4. XML Schema Registration: resource-lists ...................13
7.5. MIME Type Registration:
application/resource-lists-diff+xml .......................13
8. Security Considerations ........................................14
9. Acknowledgments ................................................14
10. Normative References ..........................................141. Introduction ✨
Okay so the framework for consent-based communications in SIP [RFC5360] points out that users who manipulate the translation logic at a relay (like adding a new recipient) need to know the consent-related status of the recipients of that translation 👑 Basically, the user doing the manipulating needs to know which recipients have given the relay permission to send them SIP requests 🙈
This document is the spot where it all clicks 💖 It defines a SIP event package that lets user agents subscribe to the consent-related state of the resources being added to a resource list that defines a translation 🌸
2. Terminology 📖
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 [RFC2119] 🎀
Relay: Any SIP server, be it a proxy, B2BUA (Back-to-Back User Agent), or some hybrid, that receives a request, translates its Request-URI into one or more next-hop URIs (i.e., recipient URIs), and delivers the request to those URIs ✨
3. Overview of Operation 🦋
A user agent subscribes to a relay using the Pending Additions event package. NOTIFY requests in this event package can carry an XML document in the application/resource-lists+xml format [RFC4826], or in the application/resource-lists-diff+xml format, which is based on XML patch operations [RFC5261] 💅
So a document in the application/resource-lists+xml format gives the user agent the whole list of resources being added to a resource list, plus the consent-related status of each of those resources 🌈 A document in the application/resource-lists-diff+xml format gives the user agent the changes the list of resources being added has experimented with since the last notification sent to the user agent 🍓
4. XML Schema Definition 🧚
This section defines the <consent-status> element, which gives consent-related information about a resource to be added to a relay's translation logic 💜
A consent-status document is an XML document that MUST be well-formed and SHOULD be valid. Consent-status documents MUST be based on XML 1.0 and MUST be encoded using UTF-8. This specification uses XML namespaces for identifying consent-status documents. The namespace URI for elements defined for this purpose is a URN, using the namespace identifier 'ietf'. This URN is:
urn:ietf:params:xml:ns:consent-status<?xml version="1.0" encoding="UTF-8"?>
<xs:schema targetNamespace="urn:ietf:params:xml:ns:consent-status"
elementFormDefault="qualified"
attributeFormDefault="unqualified"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:tns="urn:ietf:params:xml:ns:consent-status">
<xs:element name="consent-status">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="pending"/>
<xs:enumeration value="waiting"/>
<xs:enumeration value="error"/>
<xs:enumeration value="denied"/>
<xs:enumeration value="granted"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
</xs:schema>The <consent-status> element can take on the following values 🌟
- Pending: the relay has received a request to add a resource to its translation logic and will ask for permission to do so 🔥
- Waiting: the relay has requested permission to add the resource to its translation logic but has not gotten any answer from the resource yet ⏳
- Error: the relay has requested permission to add the resource to its translation logic and has received an error response (e.g., a SIP error response to the MESSAGE request sent to request permission). That is, the permission document requesting permission could not be delivered to the resource 💀
- Denied: the resource has denied the relay permission to add the resource to the relay's translation logic 🙅♀️
- Granted: the resource has granted the relay permission to add the resource to the relay's translation logic 🎉
Section 5.1.11 has an example of an "application/resource-lists+xml" document that carries consent-related state information using <consent-status> elements 🫶
5. Pending Additions Event Package Definition 🎁
This section gives the details for defining a SIP [RFC3261] event notification package, as specified by [RFC3265] 🍭 Support for this section (i.e., Section 5) is REQUIRED for implementations of this specification. Support for partial notifications is optional, but if a subscriber signals support for partial notifications, Section 6 MUST be implemented 🌸
5.1. Event Package Name 🏷️
The name of this event package is consent-pending-additions. This package name is carried in the Event and Allow-Events header, as defined in [RFC3265] 💌
5.1.1. Event Package Parameters 🎈
This package does not define any event package parameters 🙃
5.1.2. SUBSCRIBE Bodies 📦
A SUBSCRIBE for Pending Additions events MAY contain a body. This body would serve the purpose of filtering the subscription. Filter documents are not specified in this document and, at the time of writing, they are expected to be the subject of future standardization activity 🔮
A SUBSCRIBE for the Pending Additions event package MAY be sent without a body. This implies that the default session policy filtering policy has been requested. The default policy is that notifications are generated every time there is any change in the state of a resource in the list 🔔
5.1.3. Subscription Duration ⏰
The default expiration time for a subscription is one hour (3600 seconds) 🕐
5.1.4. NOTIFY Bodies 💅
In this event package, the body of the notifications contains a resource list document. This document describes the resources being added as recipients to a translation operation 🧾 All subscribers and notifiers MUST support the application/resource-lists+xml data format [RFC4826] and its extension to carry consent-related state information, which is specified in Section 4. The SUBSCRIBE request MAY contain an Accept header field. If no such header field is present, it has a default value of application/resource-lists+xml. If the header field is present, it MUST include application/resource-lists+xml, and MAY include any other types capable of representing consent-related state 🩷
Also, all subscribers and notifiers SHOULD support the application/resource-lists-diff+xml format 💜 Section 6 talks about how the Pending Additions event package is used with this format ✨
5.1.5. Notifier Processing of SUBSCRIBE Requests 🔐
The state of the resources to be added to a relay's translation logic can reveal sensitive information. Therefore, all subscriptions SHOULD be authenticated and then authorized before approval. Authorization policy is at the discretion of the administrator 🕵️♀️
5.1.6. Notifier Generation of NOTIFY Requests 🔔
A notifier for the Pending Additions event package SHOULD include the <consent-status> element, which is defined in Section 4. The <consent-status> element MUST be positioned as an instance of the <any> element within the <entry> element 🧩
Notifications SHOULD be generated for the Pending Additions package whenever there is a change in the consent-related state of a resource. When a resource moves to the error, denied, or granted states, and once a NOTIFY request is sent, the resource is removed from further notifications 👋
5.1.7. Subscriber Processing of NOTIFY Requests 📬
As stated in Section 3, a document in the application/resource-lists+xml format gives the subscriber the whole list of resources being added to a resource list, along with the consent-related status of those resources. On receiving a NOTIFY request with such a document, the subscriber SHOULD update its local information about the resources being added to the resource list with the information in the document. NOTIFY requests contain full state 🫧 The subscriber doesn't need to do any type of information aggregation, which is honestly so relieving 😭 Section 6 talks about how the Pending Additions event package works with partial notifications 🦋
5.1.8. Handling of Forked Requests 🍴
okay so the state of a resource list usually lives on a server and gets stored in a repository 🗄️. that means there's normally ONE place it's sitting, so a subscription for this info is totally handled by a single element that can reach that repo. there's no real reason for a pending additions subscription to fork, ngl 💅. so a subscriber MUST NOT create multiple dialogs from a single subscription request 🚫. the way to make sure only one dialog gets made is described in Section 4.4.9 of [RFC3265] 🔒
5.1.9. Rate of Notifications 🐢
congestion control is a whole thing 🚦, so the notifications can't get out of hand. it is RECOMMENDED that the server does not generate notifications for a single subscriber at a rate faster than once every 5 seconds ⏱️ bestie, that's the vibe!
5.1.10. State Agents 🙅
state agents have no role in handling this package. nothing to see here 💁
5.1.11. Example 📝
here's an example of an application/resource-lists+xml document carrying consent-related state info using <consent-status> elements 🧚
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:cs="urn:ietf:params:xml:ns:consent-status">
<list>
<entry uri="sip:bill@example.com">
<display-name>Bill Doe</display-name>
<cs:consent-status>pending</cs:consent-status>
</entry>
<entry uri="sip:joe@example.com">
<display-name>Joe Smith</display-name>
<cs:consent-status>pending</cs:consent-status>
</entry>
<entry uri="sip:nancy@example.com">
<display-name>Nancy Gross</display-name>
<cs:consent-status>granted</cs:consent-status>
</entry>
</list>
</resource-lists>6. Partial Notifications 🧩
okay this part is so important 😭 the lists of resources in this event package can have MANY resources in them. when the application/resource-lists+xml format is used and a resource's consent-related status changes, the server sends a notification with the whole list. but sending a huge notification to report a tiny change is not it for bandwidth-constrained environments 💀. so partial notifications are the more efficient way to report status changes ✨
subscribers flag that they support partial notifications by including the application/resource-lists-diff+xml format in the Accept header field of the SUBSCRIBE requests they generate 🫶. if a client subscribing to the Pending Additions event package generates an Accept header field that includes the MIME type application/resource-lists-diff+xml, the server gets to choose whether it returns documents in this format (instead of the application/resource-lists+xml format) 🎀
6.1. Generation of Partial Notifications 💫
once a subscription is accepted and installed, the server MUST deliver full state in its first notification 🥹 to report full state, the server uses the regular format for resource lists. so the server MUST set the Content-Type header field to the value application/resource-lists+xml 👑
to deliver a partial notification, the server MUST set the Content-Type header field to the value application/resource-lists-diff+xml. when the server generates a partial notification, the server SHOULD only include the information that has changed since the previous notification. it's up to the server's local policy to decide what counts as a change to the previous state 🧠
the server MUST construct partial notifications following this logic: all information that has been added to the document goes inside <add> elements, all information that has been removed goes inside <remove> elements, and all information that has been changed goes under <replace> elements 🍓
the server MUST NOT send a new NOTIFY request with a partial notification until it has received a final response from the subscriber for the previous one, or until the previous NOTIFY request has timed out ✋
when the server receives a SUBSCRIBE request (refresh or termination) within the associated subscription, it SHOULD send a NOTIFY request containing the full document using the application/resource-lists+xml content type 🔁
and if the server has used a content type other than application/resource-lists+xml in notifications within the existing subscription, and it changes to deliver partial notifications, the server MUST deliver full state using the application/resource-lists+xml content type before generating its first partial notification 🌈
6.2. Processing of Partial Notifications 🔍
when a subscriber receives the first notification containing full state in an application/resource-lists+xml MIME body, the subscriber MUST store the received full document as its local copy 📥
when the subscriber gets a later notification, the subscriber MUST modify its locally stored information using this logic:
- If the notification carries an
application/resource-lists+xmldocument, the subscriber MUST replace its local copy of the document with the document received in the notification. - If the notification carries an
application/resource-lists-diff+xmldocument, the subscriber MUST apply the changes indicated in the receivedapplication/resource-lists-diff+xmldocument to its local copy of the full document.
if a subscriber runs into a processing error while processing an application/resource-lists-diff+xml encoded document, the subscriber SHOULD renew its subscription 🔄 a subscriber can fall back to normal operations by not including the application/resource-lists-diff+xml format in a new SUBSCRIBE request 🦋
if the server changes the content type used in notifications within the existing subscription, the subscriber MUST discard all the previously received information and process the new content as specified for that content type 🗑️
6.3. XML Schema for Partial Notifications 🧾
this is the XML schema for the application/resource-lists-diff+xml data format. the urn:ietf:params:xml:schema:xml-patch-ops schema is defined in [RFC5261] 📐
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema
targetNamespace="urn:ietf:params:xml:ns:resource-lists"
xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified">
<!-- include patch-ops type definitions -->
<xs:include
schemaLocation="urn:ietf:params:xml:schema:patch-ops"/>
<!-- partial updates -->
<xs:element name="resource-lists-diff">
<xs:sequence minOccurs="0" maxOccurs="unbounded">
<xs:choice>
<xs:element name="add">
<xs:complexType mixed="true">
<xs:complexContent>
<xs:extension base="add">
<xs:anyAttribute processContents="lax"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="remove">
<xs:complexType>
<xs:complexContent>
<xs:extension base="remove">
<xs:anyAttribute processContents="lax"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:element name="replace">
<xs:complexType mixed="true">
<xs:complexContent>
<xs:extension base="replace">
<xs:anyAttribute processContents="lax"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
</xs:element>
<xs:any namespace="##other" processContents="lax"/>
</xs:choice>
</xs:sequence>
<xs:anyAttribute processContents="lax"/>
</xs:element>
</xs:schema>6.4. Examples 🎨
Section 5.1.11 has an example of an application/resource-lists+xml document, which carries full state. here's an application/resource-lists-diff+xml partial update document 💖
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists-diff xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:cs="urn:ietf:params:xml:ns:consent-status">
<replace
sel="*/list/entry[@uri='sip:bill@example.com']/cs:consent-status/text()"
>granted</replace>
</resource-lists-diff>and this is the resulting application/resource-lists+xml document after the partial update is applied ✨
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:cs="urn:ietf:params:xml:ns:consent-status">
<list>
<entry uri="sip:bill@example.com">
<display-name>Bill Doe</display-name>
<cs:consent-status>granted</cs:consent-status>
</entry>
<entry uri="sip:joe@example.com">
<display-name>Joe Smith</display-name>
<cs:consent-status>pending</cs:consent-status>
</entry>
<entry uri="sip:nancy@example.com">
<display-name>Nancy Gross</display-name>
<cs:consent-status>granted</cs:consent-status>
</entry>
</list>
</resource-lists>7. IANA Considerations 📋
there are five IANA considerations associated with this specification 🌸
7.1. SIP Event Package Registration 🎀
this specification registers a SIP event package per the procedures in [RFC3265] 💅
Package name: consent-pending-additions
Type: package
Contact: Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com>
Published Specification: RFC 5362.7.2. URN Sub-Namespace Registration: consent-status 🌈
this section registers a new XML namespace per the procedures in [RFC3688] 🧚
URI: The URI for this namespace is
urn:ietf:params:xml:ns:consent-status
Registrant Contact: IETF SIPPING working group <sipping@ietf.org>,
Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com>
XML:
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>Pending Additions Extension Namespace</title>
</head>
<body>
<h1>Namespace for Consent-related Status Information Extension</h1>
<h2>urn:ietf:params:xml:ns:consent-status</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/rfc5362.txt">RFC 5362
</a>.</p>
</body>
</html>7.3. XML Schema Registration: consent-status 🧾
this section registers an XML schema per the procedures in [RFC3688] 💫
URI: urn:ietf:params:xml:schema:consent-status
Registrant Contact: IETF SIPPING working group <sipping@ietf.org>,
Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com>the XML for this schema can be found in Section 4 🫶
7.4. XML Schema Registration: resource-lists ✨
okay so this section registers an XML schema 🗂️ following the procedures in [RFC3688], and it's basically an extension to the schema with the ID resource-list that's defined in [RFC4826]. the IANA added a new row to the XML schema registry with these values:
ID: resource-lists-diff
URI: urn:ietf:params:xml:schema:resource-lists-diff
Filename: resource-lists-diff
Reference [RFC5362]Registrant Contact: IETF SIPPING working group <sipping@ietf.org>, Gonzalo Camarillo <Gonzalo.Camarillo@ericsson.com> 💌
the XML for this schema is in Section 6.3, so go check it out 🫶
7.5. MIME Type Registration: application/resource-lists-diff+xml 🎀
this section registers the application/resource-lists-diff+xml MIME type. here's the whole template, verbatim:
MIME media type name: application
MIME subtype name: resource-lists-diff+xml
Mandatory parameters: none
Optional parameters: Same as charset parameter application/xml as
specified in [RFC3023].
Encoding considerations: Same as encoding considerations of
application/xml as specified in [RFC3023].
Security considerations: See Section 10 of [RFC3023] and Section 7 of
[RFC4826].
Interoperability considerations: none
Published specification: RFC 5362
Applications that use this media type: This document type has been
defined to support partial notifications in subscriptions to
resource lists.
Additional Information:
Magic number: none
File extension: .rld
Macintosh file type code: "TEXT"
Personal and email address for further information: Gonzalo
Camarillo <Gonzalo.Camarillo@ericsson.com>
Intended usage: COMMON
Author/Change controller: The IETF8. Security Considerations 🔐
okay this part is SERIOUS bestie, so pay attention 🥺
"A Framework for Consent-Based Communications in the Session Initiation Protocol (SIP)" [RFC5360] talks about security issues that are related to this spec 📚
subscriptions to the Pending Additions event package can reveal sensitive information 😬 so it is RECOMMENDED that relays use strong means for authentication and information confidentiality. and it gets worse, because attackers may try to modify the contents of the notifications a relay sends to its subscribers 🫣 which is why it is RECOMMENDED that relays use a strong means for information integrity protection.
it is RECOMMENDED that relays authenticate subscribers using the normal SIP authentication mechanisms, like Digest, as defined in [RFC3261] 🔑
the mechanism used to convey information to subscribers SHOULD ensure the integrity and confidentially of the information. to get that, an end-to-end SIP encryption mechanism, like S/MIME as described in [RFC3261], SHOULD be used 🦋
and if strong end-to-end security (like the stuff above) is NOT available, then it is RECOMMENDED that hop-by-hop security based on TLS and SIPS URIs, as described in [RFC3261], is used 💜
9. Acknowledgments 🌸
Jonathan Rosenberg gave useful ideas on this document 🧠. Ben Campbell and Mary Barnes did a thorough review of it 👀. And Jari Urpalainen helped improve the partial notifications mechanism 🧚. thank you queens 👑
10. Normative References 📖
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3261] 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.
[RFC3265] Roach, A.B., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC4826] Rosenberg, J., "Extensible Markup Language (XML) Formats
for Representing Resource Lists", RFC 4826, May 2007.
[RFC5261] Urpalainen, J., "An Extensible Markup Language (XML) Patch
Operations Framework Utilizing XML Path Language (XPath)
Selectors", RFC 5261, September 2008.
[RFC5360] Rosenberg, J., Camarillo, G., and D. Willis, "A Framework
for Consent-Based Communications in the Session Initiation
Protocol (SIP)", RFC 5360, October 2008.Author's Address 📮
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
EMail: Gonzalo.Camarillo@ericsson.comFull Copyright Statement ©️
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an "AS IS" basis and 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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Copies of IPR disclosures made to the IETF Secretariat, any assurances of licenses to be made available, or the result of an attempt to get a general license or permission for implementers or users to use these proprietary rights can be found in the IETF online IPR repository at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology needed to implement this standard. Please send that info to the IETF at ietf-ipr@ietf.org 🦋
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