--- 1/draft-ietf-mmusic-sdp-cs-14.txt 2012-12-18 16:39:23.007709271 +0100 +++ 2/draft-ietf-mmusic-sdp-cs-15.txt 2012-12-18 16:39:23.067708202 +0100 @@ -1,21 +1,21 @@ MMUSIC WG M. Garcia-Martin Internet-Draft Ericsson Intended status: Standards Track S. Veikkolainen -Expires: May 30, 2013 Nokia - November 26, 2012 +Expires: June 20, 2013 Nokia + December 17, 2012 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-14 + draft-ietf-mmusic-sdp-cs-15 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 @@ -25,21 +25,21 @@ Internet-Drafts are working documents of the Internet Engineering 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." - This Internet-Draft will expire on May 30, 2013. + This Internet-Draft will expire on June 20, 2013. Copyright Notice Copyright (c) 2012 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 @@ -342,37 +342,37 @@ syntax. Please note that these "E164" and "-" address types defined in this memo are exclusively defined to be used in conjunction with the "PSTN" network type in accordance with [RFC4566]. Usage of "E164" or "-" address types in conjunction with other network types may be defined elsewhere. This memo exclusively uses the international representation of E.164 numbers, i.e., those including a country code and, as described above - prepended with a '+' sign. The syntax (see Section 5.7) refers to - the representation of a 'global-number' construction already - specified in RFC 3966 [RFC3966]. This representation requires the - presence of the '+' sign. Additionally, this representation allows - for the presence of one or more 'visual-separator' constructions. - Implementations conforming to this specification and using the "E164" - address type together with the "PSTN" network type MUST only use - international E.164 representation prepended with a '+' sign. + prepended with a '+' sign. Implementations conforming to this + specification and using the "E164" address type together with the + "PSTN" network type MUST use the 'global-number-digits' construction + specified in RFC 3966 [RFC3966] for representing international E.164 + numbers. This representation requires the presence of the '+' sign, + and additionally allows for the presence of one or more 'visual- + separator' constructions for easier human readability (see + Section 5.7). Note that and/or MUST NOT be omitted when unknown since this would violate basic syntax of SDP [RFC4566]. In such cases, they MUST be set to a "-". The following are examples of the extension to the connection data line: - c=PSTN E164 +441134690123 + c=PSTN E164 +441134960123 c=PSTN - - When the is PSTN, the connection address is defined as follows: o an international E.164 number When the is "-", the connection address is defined as follows: @@ -516,21 +516,21 @@ The Caller-ID correlation mechanisms consists of an exchange of the calling party number as an international E.164 number in SDP, followed by the availability of the Calling Party Number information element in the call setup signaling of the circuit switched connection. If both pieces of information match, the circuit- switched bearer is correlated to the session described in SDP. Example of inclusion of an international E.164 number in the "cs- correlation" attribute is: - a=cs-correlation:callerid:+441134690123 + a=cs-correlation:callerid:+441134960123 The presence of the "callerid" subfield indicates that the endpoint supports use of the calling party number as a means of correlating a PSTN call with the session being negotiated. The "callerid" subfield MAY be accompanied by the international E.164 number of the party inserting the parameter. Note that there are no guarantees that this correlation mechanism works or is even available, due a number of problems: @@ -1199,22 +1199,22 @@ Figure 2 shows the formal syntax of the extensions defined in this memo. ; extension to the connection field originally specified ; in RFC 4566 connection-field = [%x63 "=" nettype SP addrtype SP connection-address CRLF] ;nettype and addrtype are defined in RFC 4566 - connection-address /= global-number / "-" - ; global-number specified in RFC 3966 + connection-address /= global-number-digits / "-" + ; global-number-digits specified in RFC 3966 ;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 / ext-mech caller-id-mech = "callerid" [":" caller-id-value] caller-id-value = "+" 1*15DIGIT @@ -1269,24 +1269,24 @@ of it in the "a=setup" attribute line. The SDP Offer also includes correlation identifiers that this endpoint will insert in the Calling Party Number and/or User-User Information Element of the PSTN call setup if eventually this endpoint initiates the PSTN call. v=0 o=jdoe 2890844526 2890842807 IN IP4 192.0.2.5 s= t=0 0 m=audio 9 PSTN - - c=PSTN E164 +441134690123 + c=PSTN E164 +441134960123 a=setup:actpass a=connection:new - a=cs-correlation:callerid:+441134690123 \ + a=cs-correlation:callerid:+441134960123 \ uuie:56A390F3D2B7310023 Figure 4: SDP offer (1) Bob generates a SDP Answer (Figure 5), describing a PSTN audio media on port 9 without information on the media sub-type on the "m=" line. The "c=" line contains Bob's international E.164 number. In the "a=setup" line Bob indicates that he is willing to become the active endpoint when establishing the PSTN call, and he also includes the "a=cs-correlation" attribute line containing the values he is going @@ -1352,30 +1352,30 @@ Figure 6 shows an example of negotiating audio and video media streams over circuit-switched bearers. v=0 o=jdoe 2890844526 2890842807 IN IP4 192.0.2.5 s= t=0 0 a=setup:actpass a=connection:new - c=PSTN E164 +441134690123 + c=PSTN E164 +441134960123 m=audio 9 PSTN - a=cs-correlation:dtmf:1234536 m=video 9 PSTN 34 a=rtpmap:34 H263/90000 - a=cs-correlation:callerid:+441134690123 + a=cs-correlation:callerid:+441134960123 Figure 7: SDP offer with circuit-switched audio and video (1) - Upon receiving the SDP offer descibed in Figure 7, Bob rejects the + Upon receiving the SDP offer described in Figure 7, Bob rejects the video stream as his device does not currently support video, but accepts the circuit-switched audio stream. As Alice indicated that she is able to become either the active, or passive party, Bob gets to select which role he would like to take. Since the Offer contained the international E.164 number of Alice, Bob decides that he becomes the active party in setting up the circuit-switched bearer. Bob includes a new value in the "dtmf" subfield of the "cs- correlation" attribute, which he is going to send as DTMF tones once the bearer setup is complete. For the video bearer, caller ID based correlation is used. The Answer is described in Figure 8 @@ -1395,22 +1395,22 @@ 7. Security Considerations This document provides an extension on top of RFC 4566 [RFC4566], and RFC 3264 [RFC3264]. As such, the security considerations of those documents apply. This memo provides mechanisms to agree on a correlation identifier or identifiers that are used to evaluate whether an incoming circuit- switched bearer is related to an ongoing session in the IP domain. - If an attacker replicates the correlation identifer and establishes a - call within the time window the receiving endpoint is expecting a + If an attacker replicates the correlation identifier and establishes + a call within the time window the receiving endpoint is expecting a call, the attacker may be able to hijack the circuit-switched bearer. These types of attacks are not specific to the mechanisms presented in this memo. For example, caller ID spoofing is a well known attack in the PSTN. Users are advised to use the same caution before revealing sensitive information as they would on any other phone call. Furthermore, users are advised that mechanisms that may be in use in the IP domain for securing the media, like Secure RTP (SRTP) [RFC3711], are not available in the CS domain. For the purposes of establishing a circuit-switched bearer, the @@ -1419,21 +1419,21 @@ not to reveal their phone numbers when calling using supplementary services like Calling Line Identification Restriction (CLIR) in GSM. Implementations should take the caller's preferences regarding calling line identification into account if possible, by restricting the inclusion of the phone number in SDP "c=" line if the caller has chosen to use CLIR. If this is not possible, implementations may present a prompt informing the user that their phone number may be transmitted to the other party. Similarly as with IP addresses, if there is a desire to protect the - SDP containing phone numbers carried in SIP, implementers are adviced + SDP containing phone numbers carried in SIP, implementers are advised to follow the security mechanisms defined in [RFC3261]. It is possible that an attacker creates a circuit-switched session whereby the attacked endpoint should dial a circuit-switched number, perhaps even a premium-rate telephone number. To mitigate the consequences of this attack, endpoints MUST authenticate and trust remote endpoints users who try to remain passive in the circuit- switched connection establishment. It is RECOMMENDED that endpoints have local policies precluding the active establishment of circuit switched connections to certain numbers (e.g., international, @@ -1568,22 +1568,22 @@ May 2008. [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. 10.2. Informative References [I-D.ietf-cuss-sip-uui] Johnston, A. and J. Rafferty, "A Mechanism for Transporting User to User Call Control Information in - SIP", draft-ietf-cuss-sip-uui-07 (work in progress), - July 2012. + SIP", draft-ietf-cuss-sip-uui-08 (work in progress), + December 2012. [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.