SIPPING S. Olson Internet-Draft O. Levin Expires: August 16, 2004 Microsoft Corporation February 16, 2004 Extended-REFER framework and other REFER extensions draft-olson-sipping-refer-extensions-01 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 16, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document proposes to generalize and extend REFER method for facilitating various advanced functionalities within SIP systems. The new extensions are explicitly signaled by inclusion of new option tags in the Require header of REFER. Olson & Levin Expires August 16, 2004 [Page 1] Internet-Draft Extended REFER Framework February 2004 Table of Contents 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1 The Extended REFER Framework . . . . . . . . . . . . . . . . 6 4.2 Additional REFER Extensions and Behaviors . . . . . . . . . 7 5. Preventing Forking of REFER Requests . . . . . . . . . . . . 8 6. Replacing Refer-To URI Syntax with a MIME Body . . . . . . . 9 7. Using Arbitrary Event Packages with REFER . . . . . . . . . 11 8. Suppressing the REFER Implicit Subscription . . . . . . . . 17 9. Applying REFER to SIP Response Codes . . . . . . . . . . . . 19 10. Adding callid and tag Parameters to Refer-To Header . . . . 27 11. Using of isfocus Feature Parameter with REFER . . . . . . . 28 12. REFER with a Referred-By Header with aib . . . . . . . . . . 29 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . 30 13.1 extended-refer Option Tag Registration . . . . . . . . . . . 30 13.2 norefersub Option Tag Registration . . . . . . . . . . . . . 30 13.3 refer-response Option Tag Registration . . . . . . . . . . . 30 14. Security Considerations . . . . . . . . . . . . . . . . . . 31 15. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 32 References . . . . . . . . . . . . . . . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 34 Intellectual Property and Copyright Statements . . . . . . . 35 Olson & Levin Expires August 16, 2004 [Page 2] Internet-Draft Extended REFER Framework February 2004 1. 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 RFC 2119 [1]. To simplify discussions of the REFER method and its extensions, three new terms are being used throughout the document: o REFER-Issuer: the UA issuing the REFER request o REFER-Recipient: the UA receiving the REFER request o REFER-Target: the UA designated in the Refer-To URI Olson & Levin Expires August 16, 2004 [Page 3] Internet-Draft Extended REFER Framework February 2004 2. Introduction The REFER [3] extension to SIP [2] defines a basis for remote call control that is useful for implementing features such as call transfer. In fact, originally the REFER was created by the SIP WG as a generic request to ask another UA to perform an operation on your behalf, which is much more powerful than just the phone-like transfer feature.) REFER has a few limitations with respect to implementing more advanced features in conjunction with the dialog info event package [7]. These limitations derive in part from the limited information available in the message/sipfrag [4] content of the associated NOTIFY. Another limiting factor is the requirement to compress the semantics of the referred request in the Refer-To URI by encoding the desired headers as parameters of that URI. Finally, there are situations where the party issuing the REFER request does not need the NOTIFY associated with the REFER, perhaps because that agent is already subscribed to the appropriate package outside of the REFER request. This represents additional unnecessary traffic and state in the REFER-Issuer and REFER-Recipient. This document proposes to generalize and extend REFER method for facilitating various advanced functionalities within SIP systems. The new extensions are explicitly signaled by inclusion of new option tags in the Require header of REFER. Olson & Levin Expires August 16, 2004 [Page 4] Internet-Draft Extended REFER Framework February 2004 3. Requirements Forking prevention: Prevent forking of a REFER request and allow targeting of that REFER request to a specific device or class of device. Watching period: Allow the REFER-Issuer to watch the progress of the operation triggered by REFER for the whole duration of the requested operation. For example: Beyond the end of the INVITE transaction and for the duration of the remotely established dialog. Richness of the retrieved information: Expose rich information about the requested operation. For example: Expose the dialog information, caller preferences, and user defined headers of the dialog established at the REFER-Recipient as a result of the REFER. Operation efficiency: Reduce the number of messages exchanged to perform a REFER operation. For example, suppress the implicit subscription when the information is known by other means. Operation abstraction: Reduce the amount of detailed knowledge about the remote party that is required from the REFER-Issuer in order to perform a REFER. For example, for remote-cc applications as described in [11]. Olson & Levin Expires August 16, 2004 [Page 5] Internet-Draft Extended REFER Framework February 2004 4. Overview 4.1 The Extended REFER Framework The extended REFER behavior is signaled by inclusion of "extended-refer" option tag in the Require header of REFER. If the REFER-Recipient does not understand or does not support the "extended-refer" functionality defined in this specification, it MUST return a 420 (Unsupported Extension) response to the REFER request (as per baseline SIP behavior [2]). The REFER-Issuer SHOULD re-issue the REFER request using URI escaping and only the Refer-To: URI to convey the same information if possible. Support for this extension can be queried in advance using a standard OPTIONS request. This extension defines the following normative functionality for extended REFER method which differs from the basic REFER specification: o Refer-To header contains cid which points to the information placed in the REFER body in MIME form. o The actual format and the meaning of this information are specified by the value of the Content-Type header of REFER. o Additional application documents MAY introduce more complicate behavior logic and MAY require to use multipart MIME body in order to implement this logic. In these cases, the Content-Type header can not provide enough information to specify this logic. In these cases, the application template logic MUST be signaled by additional means such as by inclusion of a new dedicated "disposition type" in the Content-Disposition header of REFER. It is expected that new disposition types will be defined and registered with IANA per application for being used with extended REFER. o The REFER-Issuer MAY specify the request for subscription to any event package by including its MIME type in an Accept header. REFER-Recipient SHOULD maintain the subscription till the operation, requested in REFER, is completed. o REFER-Issuer MAY suppress the implicit refer subscription (by using the norefersub extension) and subscribe to any event package(s) of its interest independently from issuing the REFER. Olson & Levin Expires August 16, 2004 [Page 6] Internet-Draft Extended REFER Framework February 2004 4.2 Additional REFER Extensions and Behaviors Additional REFER extensions and behaviors are defined by this document. Although they are orthogonal to the extended-refer framework, many times they will be used together in advanced SIP applications: o "norefersub" feature tag suppresses implicit REFER subscription. In this case no dialog is established upon issuing REFER and REFER-Issuer MUST ensure that no forking will be applied to REFER in the network. o "refer-response" feature tag allows for injecting responses into remote dialogs. o "isfocus" feature parameter being used with REFER allows for conveying conferencing information to remote parties. For examples of the extended REFER framework usage and additional REFER extensions, please, refer to "SIP Remote CC" [11] and "Multiple REFER" [10]. The following sections discuss the need and specify the mechanism for each of the extended REFER features. Olson & Levin Expires August 16, 2004 [Page 7] Internet-Draft Extended REFER Framework February 2004 5. Preventing Forking of REFER Requests The REFER specification allows for the possibility of forking a REFER request which is sent outside of an existing dialog. In many situation, especially in conjunction with the extended-refer mechanism, forking a REFER may result in absolutely incorrect behavior. This is especially true when the REFER is intended to target a specific device, perhaps with specific capabilities. The REFER-Issuer can ensure that REFER doesnÆt get forked by specifying the REFER-Recipient as GRUU according to mechanism defined in [12]. No extension is required. Olson & Levin Expires August 16, 2004 [Page 8] Internet-Draft Extended REFER Framework February 2004 6. Replacing Refer-To URI Syntax with a MIME Body In the original REFER specification, much of the semantics of the REFER request is encapsulated in the Refer-To URI. This URI will commonly encode the method, From, To, Call-ID, Accept-Disposition, Accept-Contact [9], and other headers all in a properly escaped URI. Such a URI can become long, difficult to debug, and prone to URI escaping errors in SIP implementations. The situation becomes more complex if the method is itself a REFER complete with a Refer-To which must contain URI-escaped characters. This double escaping obfuscates things even more and increases the chances of improperly escaping/unescaping of the Refer-To URI. This specification makes use of the currently unused REFER body to encapsulate all the information about the requested operation (and that is placed and potentially escaped in the refer-To URI according to the original specification). The possible information includes the method, headers, and body of the request which is desired to be created by the REFER-Recipient. One obvious candidate for this is the message/sipfrag MIME type. This MIME type can express all of these: the method, Request-URI, headers, and body. Use of additional REFER MIME bodies MAY be defined in separate application specifications. According to this specification, a cid URI [6] is placed in the Refer-To header to reference the MIME content in the body of the REFER. In the example below, the body of the extended REFER is of type message/sipfrag. According to the basic REFER specification: REFER sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP issuer.tradewind.com;branch=z9hG4bK-a-1 From: ;tag=1a To: Call-ID: 1@issuer.tradewind.com CSeq: 234234 REFER Max-Forwards: 70 Refer-To: Accept: application/dialog-info+xml;q=0.5, message/sipfrag;q=0.1 Contact: sip:a@issuer.tradewind.com Olson & Levin Expires August 16, 2004 [Page 9] Internet-Draft Extended REFER Framework February 2004 Content-Length: 0 According to this extended REFER specification: REFER sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP issuer.tradewind.com;branch=z9hG4bK-a-1 From: ;tag=1a To: Call-ID: 1@issuer.tradewind.com Supported: gruu CSeq: 234234 REFER Max-Forwards: 70 Refer-To: cid:1239103912039@issuer.tradewind.com Accept: application/dialog-info+xml;q=0.5, message/sipfrag;q=0.1 Require: extended-refer Contact: sip:a@issuer.tradewind.com Content-Type: message/sipfrag Content-Id: <1239103912039@issuer.tradewind.com> Content-Length: ... SIP/2.0 200 OK Call-ID: 1@target.tradewind.com From: b@tradewind.com;tag=2b To: c@tradewind.com;tag=1c If the REFER-Recipient does not understand or doesnÆt support the extended-refer option tag, it MUST return a 420 (Unsupported Extension) response to the REFER request (as per baseline SIP behavior [2]). The REFER-Issuer SHOULD re-issue the REFER request using URI escaping and only the Refer-To: URI to convey the same information if possible. Olson & Levin Expires August 16, 2004 [Page 10] Internet-Draft Extended REFER Framework February 2004 7. Using Arbitrary Event Packages with REFER The REFER specification [3] mandates the use of the message/sipfrag [4] MIME type for NOTIFYs of the refer event package. These NOTIFYs are sent as part of the implicit subscription created by the REFER. The purpose of the NOTIFY is to communicate the state of the transaction between the REFER-Recipient and the REFER-Target that is created as a result of the REFER Where the purpose of sending the REFER is actually to ask to perform an operation, for example through an INVITE, the derivative state of interest is actually the progress and the result of this operation. While in some cases this may be inferred from the contents of the message/sipfrag body this information is neither general (abstract) nor sufficient. To address this shortcoming, this specification extends REFER to allow the use of any event package format. (Furthermore, subscription to the event package(s) MAY be decoupled from issuing the REFER. This is done by suppressing the implicit subscription as defined later in this document). The REFER-Issuer MAY specify the request for subscription to a specific package by including the MIME type in an Accept header. REFER-Recipient SHOULD maintain the subscription till the completion of the requested operation. For example, in case of method=INVITE, for the duration of the resultant (INVITE) dialog and RECOMMENDED that the subscription be maintained at least until the dialog is in "confirmed" state. In the INVITE example, two things that are generally lacking from the message/sipfrag content are the dialog identifier (Call-ID plus local and remote tags) and the state of the dialog. Not coincidentally, this is the same information available in the application/ dialog-info+xml MIME type [7] used for the dialog event package. Olson & Levin Expires August 16, 2004 [Page 11] Internet-Draft Extended REFER Framework February 2004 Figure 1: Example of using application/dialog-info+xml REFER-Issuer REFER-Recipient REFER-Target | | | | M1 REFER (INVITE) | | |--------------------------->| | | M2 202 Accepted | | |<---------------------------| | | M3 NOTIFY | | |<---------------------------| | | M4 200 OK | | |--------------------------->| | | | M5 INVITE | | |----------------------->| | M6 NOTIFY | | |<---------------------------| | | M7 200 OK | | |--------------------------->| | | | M8 180 Ringing | | |<-----------------------| | M9 NOTIFY | | |<---------------------------| | | M10 200 OK | | |--------------------------->| | | | M11 200 OK | | |<-----------------------| | M12 NOTIFY | | |<---------------------------| | | M13 200 OK | | |--------------------------->| M14 ACK | | |----------------------->| Message flow: M1: The REFER-Issuer creates a REFER, specifying support for extended-refer and expressing its interest in the application/ dialog-info+xml MIME type. Olson & Levin Expires August 16, 2004 [Page 12] Internet-Draft Extended REFER Framework February 2004 REFER sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP issuer.tradewind.com;branch=z9hG4bK-a-1 From: ;tag=1ab To: Call-ID: 1@issuer.tradewind.com Supported: gruu CSeq: 234234 REFER Max-Forwards: 70 Refer-To: cid:1239103912039@issuer.tradewind.com Accept: application/dialog-info+xml Require: extended-refer Contact: sip:a@issuer.tradewind.com Content-Type: message/sipfrag Content-Id: <1239103912039@issuer.tradewind.com> Content-Length: ... M5: The REFER-Recipient creates an appropriate INVITE based on the REFER and sends it to the REFER-Target. INVITE sip:c@tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-1 From: ;tag=1bc To: Call-ID: 1@recipient.tradewind.com CSeq: 1234567 INVITE Max-Forwards: 70 Contact: sip:b@recipient.tradewind.com Content-Length: ... M6: The REFER-Recipient sends a NOTIFY triggered by the INVITE being sent to the REFER-Target. The body of the NOTIFY contains the dialog identifier and current state ("trying"). Olson & Levin Expires August 16, 2004 [Page 13] Internet-Draft Extended REFER Framework February 2004 NOTIFY sip:a@issuer.tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-2 From: ;tag=1ab To: ;tag=1ba Call-ID: 1@issuer.tradewind.com CSeq: 1278784 NOTIFY Max-Forwards: 70 Event: refer;id=234234 Subscription-State: active;expires=3600 Contact: sip:b@recipient.tradewind.com Content-Type: application/dialog-info+xml Content-Length: ... trying M9: The REFER-Recipient sends a NOTIFY triggered by the 180 Ringing received from the REFER-Target. The body of the NOTIFY contains the dialog identifier and current state ("early"). Olson & Levin Expires August 16, 2004 [Page 14] Internet-Draft Extended REFER Framework February 2004 NOTIFY sip:a@issuer.tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-3 From: ;tag=1ab To: ;tag=1ba Call-ID: 1@issuer.tradewind.com CSeq: 1278785 NOTIFY Max-Forwards: 70 Event: refer;id=234234 Subscription-State: active;expires=3600 Contact: sip:b@recipient.tradewind.com Content-Type: application/dialog-info+xml Content-Length: ... early M12: The REFER-Recipient sends a NOTIFY triggered by the 200 OK received from the REFER-Target. The body of the NOTIFY contains the dialog identifier and current state ("confirmed"). Olson & Levin Expires August 16, 2004 [Page 15] Internet-Draft Extended REFER Framework February 2004 NOTIFY sip:a@issuer.tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-4 From: ;tag=1ab To: ;tag=1ba Call-ID: 1@issuer.tradewind.com CSeq: 1278786 NOTIFY Max-Forwards: 70 Event: refer;id=234234 Subscription-State: active;expires=3600 Contact: sip:b@recipient.tradewind.com Content-Type: application/dialog-info+xml Content-Length: ... confirmed Olson & Levin Expires August 16, 2004 [Page 16] Internet-Draft Extended REFER Framework February 2004 8. Suppressing the REFER Implicit Subscription The REFER specification mandates that every REFER creates an implicit subscription between the REFER-Issuer and the REFER-Recipient. This subscription results in at least one NOTIFY being sent from the REFER-Recipient to the REFER-Issuer. The REFER-Recipient may choose to cancel the implicit subscription with this NOTIFY. The REFER-Issuer may choose to cancel this implicit subscription with an explicit SUBSCRIBE (Expires: 0) after receipt of the initial NOTIFY or by sending a 481 response to this initial NOTIFY request. The purpose of requiring the implicit subscription and initial NOTIFY is to allow for the situation where the REFER request gets forked and the REFER-Issuer needs a way to see the multiple dialogs that may be established as a result of the forked REFER. This is the same approach used to handle forking of SUBSCRIBE [5] requests. Where the REFER-Issuer explicitly specifies that forking not occur, the requirement that an implicit subscription be established is unnecessary. Another purpose of the NOTIFY is to inform the REFER-Issuer of the progress of the SIP transaction that results from the REFER at the REFER-Recipient. In the case where the REFER-Issuer is already aware of the progress of the requested operation, such as when the REFER-Issuer has an explicit subscription to the dialog event package at the REFER-Recipient, the implicit subscription and resultant NOTIFY traffic related to the REFER is superfluous and unnecessary network overhead. To avoid this unnecessary overhead, this document defines a new option tag, norefersub, which specifies that an implicit subscription for event package refer should not be created as a result of accepting this REFER request. Consequently, no dialog is created as the result of sending REFER with Require header containing the norefersub option tag. This MUST be used by the REFER-Issuer only when the REFER-Issuer can be certain that the REFER request will not be forked. The REFER-Recipient MUST signal support for this extension by inserting a Supported: norefersub header in the 2xx response to the REFER request. Example of extended REFER which suppresses the implicit subscription Olson & Levin Expires August 16, 2004 [Page 17] Internet-Draft Extended REFER Framework February 2004 REFER sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP issuer.tradewind.com;branch=z9hG4bK-a-1 From: ;tag=1a To: Call-ID: 1@issuer.tradewind.com Supported: gruu CSeq: 234234 REFER Max-Forwards: 70 Refer-To: Require: extended-refer; norefersub Accept-Contact: *;audio;require Contact: sip:a@issuer.tradewind.com Content-Type: message/sipfrag Content-Id: <1239103912039@issuer.tradewind.com> Content-Length: ... Olson & Levin Expires August 16, 2004 [Page 18] Internet-Draft Extended REFER Framework February 2004 9. Applying REFER to SIP Response Codes The original REFER is defined to trigger the sending of a request from the REFER-Recipient to the REFER-Target. The intention is most often to initiate a dialog from the REFER-Recipient to the REFER-Target. This is an excellent way to generate an action at the REFER-Recipient based on an event or action that takes places at the REFER-Issuer. The classic example is call transfer as a result of a user at the REFER-Issuer taking some action. With the use of the dialog event package, it is possible for one UA to monitor events at another UA related to a dialog, such as the receipt of an INVITE to establish a new dialog. What is lacking is a way for the watcher to indicate what should be the response to such an INVITE request. For example, the dialog watcher would like the recipient of the session initiation request to accept the initiation (send a 200 OK response to the INVITE request). One motivating scenario for this is a set of co-operating User Agents (devices) that belong to the same user. The user, while using one SIP device, wishes to answer a call that is being received on another of that user's SIP devices. This gives the user a single UI focus for control while allowing multiple devices with differing capabilities. To enable such a scenario, this document defines an extension to the SIP(S) URI syntax as defined in SIP [2]. The extension is analogous to the "method" uri-parameter that currently exists to communicate a method for use in the Refer-To header. A new uri-parameter, "response", is proposed that is used in conjunction with the "method" uri-parameter and associated call-id, local tag, and remote tag to request that the REFER-Recipient send a response within the identified SIP transaction to the REFER-Target. TBD: Generalize the discussion of the "response" uri-parameter to be used with methods other than REFER. The REFER-Issuer MUST specify a "method" parameter in addition to the "response" parameter. The REFER-Issuer MUST also include the appropriate local-uri, local-tag, remote-uri, and remote-tag encoded as From and To headers in the Refer-To URI (or using a message/ sipfrag body when used in conjunction with the extended-refer mechanism). Note that in order to satisfy this requirement, the REFER-Issuer must have access to this information. In particular, it is assumed that the REFER-Issuer receives the local-uri and remote-uri in the NOTIFY for the dialog event package from the REFER-Recipient. These elements are optional in the XML schema. It is anticipated that User Agents that support these REFER extensions will also include these optional elements in the application/ dialog-info+xml payload (as privacy concerns allow). Olson & Levin Expires August 16, 2004 [Page 19] Internet-Draft Extended REFER Framework February 2004 To ensure the REFER-Recipient conformant with RFC3515 does not misinterpret this as a REFER to send a request of the specified method, the REFER-Issuer MUST also include a Require: refer-response header in the REFER request. REFER-Recipients which do not understand this extension will return a 420 response. The REFER-Target does not need to understand this extension for this to work. Support for this extension can be queried in advance using a standard OPTIONS request. The REFER-Issuer MUST request the use of the application/ dialog-info+xml MIME type in NOTIFYs associated with a REFER request which uses the "refer-response" extension. Note that, although it is RECOMMENDED to use the "refer-response" extension in conjunction to the "extended-refer" framework, the extensions are orthogonal to each other. The extended REFER framework does not include the "refer-response" behavior by default. The "refer-response" extension can be used both with the original REFER mechanism and with the extended REFER framework. uri-parameters = *( ";" uri-parameter) uri-parameter = transport-param / user-param / method-param / ttl-param / maddr-param / lr-param / response-param / other-param response-param = "response=" 1*3DIGIT An example call flow follows: Olson & Levin Expires August 16, 2004 [Page 20] Internet-Draft Extended REFER Framework February 2004 Figure 2: Example of using the "response" uri-parameter in the Refer-To header REFER-Issuer REFER-Recipient REFER-Target | | | | N1 SUBSCRIBE (dialog) | | |--------------------------->| | | N2 202 Accepted | | |<---------------------------| | | N3 NOTIFY | | |<---------------------------| | | N4 200 OK | | |--------------------------->| | | | N5 INVITE | | |<-----------------------| | N6 NOTIFY | | |<---------------------------| | | N7 200 OK | | |--------------------------->| | | | N8 180 Trying | | |----------------------->| | N9 NOTIFY | | |<---------------------------| | | N10 200 OK | | |--------------------------->| | | | | | N11 REFER (200) | | |--------------------------->| | | N12 200 OK | | |<---------------------------| N13 200 | | |----------------------->| | N14 NOTIFY | | |<---------------------------| | | N15 200 OK | | |--------------------------->| | Message flow: N1: The REFER-Issuer subscribes to the dialog event package at the REFER-Recipient. Olson & Levin Expires August 16, 2004 [Page 21] Internet-Draft Extended REFER Framework February 2004 SUBSCRIBE sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP issuer.tradewind.com;branch=z9hG4bK-a-1 From: ;tag=1ab To: Call-ID: 1@issuer.tradewind.com CSeq: 234234 SUBSCRIBE Max-Forwards: 70 Event: dialog Accept: application/dialog-info+xml Contact: sip:a@issuer.tradewind.com Content-Length: 0 N5: The REFER-Recipient receives an INVITE from the REFER-Target to start a new call. INVITE sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP target.tradewind.com;branch=z9hG4bK-c-1 From: ;tag=1cb To: Call-ID: 1@target.tradewind.com CSeq: 1234567 INVITE Max-Forwards: 70 Contact: sip:c@target.tradewind.com Content-Length: ... N6: The REFER-Recipient sends a NOTIFY triggered by the INVITE received from the REFER-Target. The body of the NOTIFY contains the dialog identifier and current state ("trying"). Olson & Levin Expires August 16, 2004 [Page 22] Internet-Draft Extended REFER Framework February 2004 NOTIFY sip:a@issuer.tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-2 From: ;tag=1ab To: ;tag=1ba Call-ID: 1@issuer.tradewind.com CSeq: 454545 NOTIFY Max-Forwards: 70 Event: dialog;id=234234 Subscription-State: active;expires=3600 Contact: sip:b@recipient.tradewind.com Content-Type: application/dialog-info+xml Content-Length: ... b@tradewind.com c@tradewind.com trying N8: The REFER-Recipient sends a 180 Ringing response to the REFER-Target. SIP/2.0 180 Ringing Via: SIP/2.0/TCP target.tradewind.com;branch=z9hG4bK-b-3 From: ;tag=1cb To: ;tag=1bc Call-ID: 1@target.tradewind.com CSeq: 1234567 INVITE Contact: sip:b@recipient.tradewind.com Content-Length: 0 N9: The REFER-Recipient sends a NOTIFY triggered by the 180 Ringing sent to the REFER-Target. The body of the NOTIFY contains the dialog identifier and current state ("early"). Olson & Levin Expires August 16, 2004 [Page 23] Internet-Draft Extended REFER Framework February 2004 NOTIFY sip:a@issuer.tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-4 From: ;tag=1ab To: ;tag=1ba Call-ID: 1@issuer.tradewind.com CSeq: 454546 NOTIFY Max-Forwards: 70 Event: dialog;id=234234 Subscription-State: active;expires=3600 Contact: sip:b@recipient.tradewind.com Content-Type: application/dialog-info+xml Content-Length: ... b@tradewind.com c@tradewind.com early N11: The REFER-Issuer creates a REFER, specifying that the REFER-Recipient should send a 200 OK to accept the session invitation. The From and To headers of the 200 OK are encoded in the Refer-To URI. The local and remote tags for this are determined from the information provided in the NOTIFY for the dialog package. This allows the REFER-Issuer to specify a particular dialog. Combined with the "method" parameter, this identifies a specific transaction within the dialog. Olson & Levin Expires August 16, 2004 [Page 24] Internet-Draft Extended REFER Framework February 2004 REFER sip:b@tradewind.com SIP/2.0 Via: SIP/2.0/TCP issuer.tradewind.com;branch=z9hG4bK-a-2 From: ;tag=1ab To: Call-ID: 2@issuer.tradewind.com CSeq: 818181 REFER Max-Forwards: 70 Accept: application/dialog-info+xml;q=0.5, message/sipfrag;q=0.1 Require: refer-response Refer-To: Contact: sip:a@issuer.tradewind.com Content-Length: 0 N13: The REFER-Recipient sends a 200 OK to the REFER-Target constructed using the information in the Refer-To header. SIP/2.0 200 OK Via: SIP/2.0/TCP target.tradewind.com;branch=z9hG4bK-c-1 From: ;tag=1cb To: ;tag=1bc Call-ID: 1@target.tradewind.com Supported: refer-response CSeq: 1234567 INVITE Contact: sip:b@recipient.tradewind.com Content-Length: 0 N14: The REFER-Recipient sends a NOTIFY triggered by the 200 OK sent to the REFER-Target. The body of the NOTIFY contains the dialog identifier and current state ("confirmed"). Olson & Levin Expires August 16, 2004 [Page 25] Internet-Draft Extended REFER Framework February 2004 NOTIFY sip:a@issuer.tradewind.com SIP/2.0 Via: SIP/2.0/TCP recipient.tradewind.com;branch=z9hG4bK-b-4 From: ;tag=1ab To: ;tag=1ba Call-ID: 1@issuer.tradewind.com CSeq: 454547 NOTIFY Max-Forwards: 70 Event: dialog;id=234234 Subscription-State: active;expires=3600 Contact: sip:b@recipient.tradewind.com Content-Type: application/dialog-info+xml Content-Length: ... b@tradewind.com c@tradewind.com confirmed Olson & Levin Expires August 16, 2004 [Page 26] Internet-Draft Extended REFER Framework February 2004 10. Adding callid and tag Parameters to Refer-To Header TBD: Motivation and examples. Olson & Levin Expires August 16, 2004 [Page 27] Internet-Draft Extended REFER Framework February 2004 11. Using of isfocus Feature Parameter with REFER This specification allows for using of isfocus feature parameter defined in [8] with REFER. TBD: Motivation and examples. Olson & Levin Expires August 16, 2004 [Page 28] Internet-Draft Extended REFER Framework February 2004 12. REFER with a Referred-By Header with aib REFER with a Referred-By header with an authenticated identity body (aib) with multipart MIME. TBD: Mechanism and examples. Olson & Levin Expires August 16, 2004 [Page 29] Internet-Draft Extended REFER Framework February 2004 13. IANA Considerations 13.1 extended-refer Option Tag Registration This document defines a new option tag, extended-refer, which specifies that the recipient of the REFER request is expected to understand and act upon the extended REFER framework as specified in this document. This option tag is only meaningful for the REFER request defined in RFC3515. 13.2 norefersub Option Tag Registration This document defines a new option tag, norefersub, which specifies that an implicit subscription for event package refer should not be created as a result of accepting this REFER request. This option tag is only meaningful for the REFER request defined in RFC3515. 13.3 refer-response Option Tag Registration This document defines a new option tag, refer-response, which specifies that the recipient of the REFER request is expected to issue a response for the SIP transaction requested within the REFER. This option tag is only meaningful for the REFER request defined in RFC3515. Olson & Levin Expires August 16, 2004 [Page 30] Internet-Draft Extended REFER Framework February 2004 14. Security Considerations Security considerations regarding inclusion of sensitive information inside the REFER body in MIME format will be addressed in the next version of this document. Olson & Levin Expires August 16, 2004 [Page 31] Internet-Draft Extended REFER Framework February 2004 15. Acknowledgements The authors would like to thank Rohan Mahy, Gonzallo Camarillo, and Fran‡ois Audet for their insightful comments and inputs. The authors would also like to thank Sriram Parameswar for his ideas being originally presented in draft-parameswar-sipping-norefersub-00 and incorporated in this document. Olson & Levin Expires August 16, 2004 [Page 32] Internet-Draft Extended REFER Framework February 2004 References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] 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. [3] Sparks, R., "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, April 2003. [4] Sparks, R., "Internet Media Type message/sipfrag", RFC 3420, November 2002. [5] Roach, A., "Session Initiation Protocol (SIP)-Specific Event Notification", RFC 3265, June 2002. [6] Levinson, E., "Content-ID and Message-ID Uniform Resource Locators", RFC 2392, August 1998. [7] Rosenberg, J. and H. Schulzrinne, "An INVITE Inititiated Dialog Event Package for the Session Initiation Protocol (SIP)", draft-ietf-sipping-dialog-package-03 (work in progress), October 2003. [8] Rosenberg, J., "Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)", draft-ietf-sip-callee-caps-03 (work in progress), January 2004. [9] Rosenberg, J., Schulzrinne, H. and P. Kyzivat, "Caller Preferences for the Session Initiation Protocol (SIP)", draft-ietf-sip-callerprefs-10 (work in progress), October 2003. [10] Camarillo, G., "Refering to Multiple Resources in the Session Initiation Protocol (SIP)", draft-camarillo-sipping-multiple-refer-00 (work in progress), February 2004. [11] Mahy, R., "Remote Call Control in SIP using the REFER method and the session-oriented dialog package", draft-mahy-sip-remote-cc-01 (work in progress), February 2004. [12] Rosenberg, J., "Obtaining and Using Globally Routable User Agent (UA) URIs (GRUU) in the Session Initiation Protocol (SIP)", draft-ietf-sip-gruu-00 (work in progress), January 2004. Olson & Levin Expires August 16, 2004 [Page 33] Internet-Draft Extended REFER Framework February 2004 Authors' Addresses Sean Olson Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA Phone: +1-425-707-2846 EMail: seanol@microsoft.com Orit Levin Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA Phone: +1-425-722-2225 EMail: oritl@microsoft.com Olson & Levin Expires August 16, 2004 [Page 34] Internet-Draft Extended REFER Framework February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. 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