--- 1/draft-ietf-mmusic-sdp-cs-03.txt 2010-08-23 07:12:34.000000000 +0200 +++ 2/draft-ietf-mmusic-sdp-cs-04.txt 2010-08-23 07:12:34.000000000 +0200 @@ -1,66 +1,60 @@ MMUSIC WG M. Garcia-Martin Internet-Draft Ericsson Intended status: Standards Track S. Veikkolainen -Expires: August 21, 2010 Nokia - February 17, 2010 +Expires: February 23, 2011 Nokia + August 22, 2010 Session Description Protocol (SDP) Extension For Setting Up Audio and Video Media Streams Over Circuit-Switched Bearers In The Public Switched Telephone Network (PSTN) - draft-ietf-mmusic-sdp-cs-03 + draft-ietf-mmusic-sdp-cs-04 Abstract This memo describes use cases, requirements, and protocol extensions for using the Session Description Protocol (SDP) Offer/Answer model for establishing audio and video media streams over circuit-switched bearers in the Public Switched Telephone Network (PSTN). Status of this Memo - This Internet-Draft is submitted to IETF in full conformance with the + This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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. + Task Force (IETF). Note that other groups may also distribute + working documents as Internet-Drafts. The list of current Internet- + Drafts is at http://datatracker.ietf.org/drafts/current/. 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 21, 2010. + This Internet-Draft will expire on February 23, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as - described in the BSD License. + described in the Simplified BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format @@ -74,47 +68,45 @@ 3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 6 4.1. Example Call Flow . . . . . . . . . . . . . . . . . . . . 6 5. Protocol Description . . . . . . . . . . . . . . . . . . . . . 8 5.1. Level of Compliance . . . . . . . . . . . . . . . . . . . 8 5.2. Extensions to SDP . . . . . . . . . . . . . . . . . . . . 8 5.2.1. Connection Data . . . . . . . . . . . . . . . . . . . 8 5.2.2. Media Descriptions . . . . . . . . . . . . . . . . . . 9 5.2.3. Correlating the PSTN Circuit-Switched Bearer with SDP . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5.2.3.1. The "correlation" attribute . . . . . . . . . . . 11 + 5.2.3.1. The "cs-correlation" attribute . . . . . . . . . . 11 5.2.3.2. Caller-ID Correlation Mechanism . . . . . . . . . 11 5.2.3.3. User-User Information Element Correlation Mechanism . . . . . . . . . . . . . . . . . . . . 12 5.2.3.4. DTMF Correlation Mechanism . . . . . . . . . . . . 13 5.2.3.5. Negotiating the used correlation mechanisms . . . 15 5.3. Considerations for Usage of Existing SDP . . . . . . . . . 17 5.3.1. Originator of the Session . . . . . . . . . . . . . . 17 5.3.2. Contact information . . . . . . . . . . . . . . . . . 17 5.3.3. Determining the Direction of the Circuit-Switched Connection Setup . . . . . . . . . . . . . . . . . . . 17 5.4. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . 18 6. SDP Examples . . . . . . . . . . . . . . . . . . . . . . . . . 19 - 6.1. Basic SDP example: Single Circuit-Switched Audio Stream . 19 - 6.2. Advanced SDP example: Alternative and IP - Circuit-Switched Audio and Video Streams . . . . . . . . . 20 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 - 7.1. Registration of new correlation SDP attribute . . . . . . 22 - 7.2. Registration of a new "nettype" value . . . . . . . . . . 22 - 7.3. Registration of new "addrtype" values . . . . . . . . . . 22 - 7.4. Registration of a new "proto" value . . . . . . . . . . . 22 - 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 - 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 - 10.1. Normative References . . . . . . . . . . . . . . . . . . . 23 - 10.2. Informative References . . . . . . . . . . . . . . . . . . 24 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25 + 6.1. Basic SDP example: Single Circuit-Switched Audio Stream . 20 + 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 + 7.1. Registration of new correlation SDP attribute . . . . . . 21 + 7.2. Registration of a new "nettype" value . . . . . . . . . . 21 + 7.3. Registration of new "addrtype" values . . . . . . . . . . 21 + 7.4. Registration of a new "proto" value . . . . . . . . . . . 21 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22 + 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 + 10.1. Normative References . . . . . . . . . . . . . . . . . . . 22 + 10.2. Informative References . . . . . . . . . . . . . . . . . . 23 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 1. Introduction The Session Description Protocol (SDP) [RFC4566] is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. SDP is most commonly used for describing media streams that are transported over the Real-Time Transport Protocol (RTP) [RFC3550], using the profiles for audio and video media defined in RTP Profile for Audio and Video Conferences with Minimal Control @@ -170,24 +162,24 @@ codecs for each access type and get an agreement on the bearer together with the remote endpoint. There are additional use cases related to third party call control where the session setup time is improved when the circuit-switched bearer in the PSTN is described together with one or more codecs. The rest of the document is structured as follows: Section 2 provides the document conventions, Section 3 introduces the requirements, Section 4 presents an overview of the proposed solutions, and - Section 5 contains the protocol description. Section 6 provides a - few examples of descriptions of circuit-switched audio or video - streams in SDP. Section 7 and Section 8 contain the IANA and - Security considerations, respectively. + Section 5 contains the protocol description. Section 6 provides an + example of descriptions of circuit-switched audio or video streams in + SDP. Section 7 and Section 8 contain the IANA and Security + considerations, respectively. 2. Conventions Used in This Document 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 BCP 14, RFC 2119 [RFC2119] and indicate requirement levels for compliant implementations. 3. Requirements @@ -439,28 +431,29 @@ The second mechanism is based on the inclusion in SDP of a value that is also sent in the User-to-User Information Element that is part of the bearer setup signaling in the PSTN. The third mechanism is based on sending in SDP a string that represents Dual Tone MultiFrequency (DTMF) digits that will be later sent right after the circuit-switched bearer is established. Implementations MAY use any of these mechanisms and MAY use two or more mechanisms simultaneously. -5.2.3.1. The "correlation" attribute +5.2.3.1. The "cs-correlation" attribute In order to provide support for the correlation mechanisms, we define a new SDP attribute called "cs-correlation". This "cs-correlation" attribute can include any of the "callerid", "uuie", or "dtmf" parameters, which specify additional information required by the Caller-ID, User to User Information, or DTMF correlation mechanisms, - respectively. + respectively. The list of correlation mechanisms may be extended by + other specifications. The following sections provide more detailed information of these parameters. The "cs-correlation" attribute has the following format: "a=cs-correlation: "callerid:" | "uuie:" | "dtmf:" The values "callerid", "uuie" and "dtmf" refer to the correlation mechanisms defined in Section 5.2.3.2, Section 5.2.3.3, and @@ -524,21 +517,21 @@ A second correlation mechanism is based on indicating in SDP a string that represents the User-User Information Element that is part of the call setup signaling of the circuit-switched bearer. The User-User Information Element is specified in ITU-T Q.931 [ITU.Q931.1998] and 3GPP TS 24.008 [3GPP.24.008], among others. The User-User Information Element has a maximum size of 35 or 131 octets, depending on the actual message of the PSTN protocol where it is included. The mechanism works as follows: An endpoint creates a User-User - Information Element, according to the requirement of the call setup + Information Element, according to the requirements of the call setup signaling protocol. The same value is included in the SDP offer or SDP answer, in a "cs-correlation:uuie" attribute. When the SDP offer/answer exchange is completed, each endpoint has become aware of the value that will be used in the User-User Information Element of the call setup message of the PSTN protocol. The endpoint that initiates the call setup attempt includes this value in the User-User Information Element. The recipient of the call setup attempt can extract the User-User Information Element and correlate it with the value previously received in the SDP. If both values match, then the call setup attempt corresponds to that indicated in the SDP. @@ -570,21 +563,21 @@ hand, the generation of the User-User Information Element is controlled by the PSTN circuit-switched call protocol, which might not offer enough freedom for generating different values from one endpoint to another one, or from one call to another in the same endpoint. This might result in the same value of the User-User Information Element for all calls. 5.2.3.4. DTMF Correlation Mechanism We introduce a third mechanism for correlating the circuit-switched - bearer with the session controlled with SDP. This is based in + bearer with the session controlled with SDP. This is based on agreeing on a sequence of digits that are negotiated in the SDP Offer/Answer exchange and sent as Dual Tone Multifrequency (DTMF)tones over the circuit-switched bearer once this bearer is established. If the DTMF digit sequence received through the circuit-switched bearer matches the digit string negotiated in the SDP, the circuit-switched bearer is correlated with the session described in the SDP. The mechanism is similar to many voice conferencing systems which require the user to enter a PIN code using DTMF tones in order to be accepted in a voice conference. @@ -831,33 +824,34 @@ connection-address /= e164-address / "-" e164-address = ["+"] 1*15DIGIT ; DIGIT is specified in RFC 5234 ;subrules for correlation attribute attribute /= cs-correlation-attr ; attribute defined in RFC 4566 cs-correlation-attr= "cs-correlation:" corr-mechanisms corr-mechanisms = corr-mech *(SP corr-mech) - corr-mech = caller-id-mech / uuie-mech / dtmf-mech + corr-mech = caller-id-mech / uuie-mech / dtmf-mech / ext-mech caller-id-mech = "callerid" [":" caller-id-value] caller-id-value = ["+"] 1*DIGIT uuie-mech = "uuie" [":" uuie-value] uuie-value = 1*32(ALPHA/DIGIT) dtmf-mech = "dtmf" [":" dtmf-value] dtmf-value = 1*32(DIGIT / %x41-44 / %x23 / %x2A ) ;0-9, A-D, '#' and '*' + ext-mech = token + ; token is specified in RFC4566 Figure 2: Syntax of the SDP extensions 6. SDP Examples - 6.1. Basic SDP example: Single Circuit-Switched Audio Stream Alice Bob | | | (1) SDP Offer (PSTN audio) | |--------------------------------->| | | | (2) SDP Answer (PSTN audio) | |<---------------------------------| | | @@ -884,93 +878,20 @@ s= t=0 0 m=audio 9 PSTN - c=PSTN E164 +15551234 a=setup:actpass a=connection:new a=cs-correlation:uuie:2890W284hAT452612908awudfjang908 Figure 4: SDP offer (1) -6.2. Advanced SDP example: Alternative and IP Circuit-Switched Audio - and Video Streams - - Alice Bob - | | - | (1) SDP Offer (IP and PSTN audio and video)| - |------------------------------------------->| - | | - | (2) SDP Answer (PSTN audio and video) | - |<-------------------------------------------| - | | - | PSTN call setup | - |<-------------------------------------------| - | | - |<======== media over PSTN bearer ==========>| - | | - - Figure 5: Alternative media - - Figure 5 shows an example of negotiating audio and video media - streams over IP or circuit-switched bearers. Using the mechanisms - described in SDP Capability Negotiation Framework - [I-D.ietf-mmusic-sdp-capability-negotiation] and extensions thereof - (SDP media capabilities Negotiation - [I-D.ietf-mmusic-sdp-media-capabilities] and SDP Miscellaneous - Capabilities [I-D.garcia-mmusic-sdp-misc-cap]) it is possible to - construct an SDP offer where audio and video media can be offered - alternatively over IP or circuit-switched bearer. - - v=0 - o=jdoe 2890844526 2890842807 IN IP4 192.0.2.5 - s= - t=0 0 - c=IN IP4 192.0.2.5 - a=sescap:1 1,3 - a=sescap:2 2,4 - a=creq:med-v0,ccap-v0 - a=acap:1 cs-correlation:uuie:2890W284hAT452612908awudfjang908 - a=acap:2 setup:actpass - a=acap:3 connection:new - a=tcap:1 PSTN - m=audio 49170 RTP/AVP 0 8 3 - a=mcap:1 - - a=ccap:1 PSTN E164 +15551234 9 - a=pcfg:1 - a=pcfg:2 m=1 t=1 c=1 a=1,2,3 - m=video 49174 RTP/AVP 34 - a=mcap:2 - - a=ccap:2 PSTN E164 +15551234 9 - a=pcfg:3 - a=pcfg:4 m=2 t=1 c=2 a=1,2,3 - - Figure 6: SDP offer with alternative media (1) - - Upon receiving the SDP offer descibed in Figure 6, Bob decided to - select the circuit-switched bearer and generates the answer described - in Figure 7 - - v=0 - o=- 2890973824 2890987289 IN IP4 192.0.2.7 - s= - t=0 0 - a=setup:active - a=connection:new - a=cs-correlation:uuie:2890W284hAT452612908awudfjang908 - m=audio 9 PSTN - - c= PSTN E164 +1551234 - m=video 9 PSTN - - c=PSTN E164 +1551234 - a=acfg:2 - - Figure 7: SDP answer with circuit-switched media (2) - 7. IANA Considerations This document instructs IANA to register a number of SDP tokens according to the following data. 7.1. Registration of new correlation SDP attribute Contact: Miguel Garcia Attribute name: cs-correlation @@ -1069,38 +990,20 @@ [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. 10.2. Informative References [3GPP.24.008] 3GPP, "Mobile radio interface Layer 3 specification; Core network protocols; Stage 3", 3GPP TS 24.008 3.20.0, December 2005. - [I-D.garcia-mmusic-sdp-misc-cap] - Garcia, M., Veikkolainen, S., and R. Gilman, - "Miscellaneous Capabilities Negotiation in the Session - Description Protocol (SDP)", - draft-garcia-mmusic-sdp-misc-cap-01 (work in progress), - July 2009. - - [I-D.ietf-mmusic-sdp-capability-negotiation] - Andreasen, F., "SDP Capability Negotiation", - draft-ietf-mmusic-sdp-capability-negotiation-10 (work in - progress), May 2009. - - [I-D.ietf-mmusic-sdp-media-capabilities] - Gilman, R., Even, R., and F. Andreasen, "SDP media - capabilities Negotiation", - draft-ietf-mmusic-sdp-media-capabilities-08 (work in - progress), July 2009. - [ITU.E164.1991] International Telecommunications Union, "The International Public Telecommunication Numbering Plan", ITU- T Recommendation E.164, 1991. [ITU.Q931.1998] "Digital Subscriber Signalling System No. 1 (DSS 1) - ISDN User - Network Interface Layer 3 Specification for Basic Call Control", ISO Standard 9594-1, May 1998.