1、 I n t e r n a t i o n a l T e l e c o m m u n i c a t i o n U n i o n ITU-T H.248.77 TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2017) SERIES H: AUDIOVISUAL AND MULTIMEDIA SYSTEMS Infrastructure of audiovisual services Communication procedures Gateway control protocol: Secure real-time tran
2、sport protocol (SRTP) package and procedures Recommendation ITU-T H.248.77 ITU-T H-SERIES RECOMMENDATIONS AUDIOVISUAL AND MULTIMEDIA SYSTEMS CHARACTERISTICS OF VISUAL TELEPHONE SYSTEMS H.100H.199 INFRASTRUCTURE OF AUDIOVISUAL SERVICES General H.200H.219 Transmission multiplexing and synchronization
3、H.220H.229 Systems aspects H.230H.239 Communication procedures H.240H.259 Coding of moving video H.260H.279 Related systems aspects H.280H.299 Systems and terminal equipment for audiovisual services H.300H.349 Directory services architecture for audiovisual and multimedia services H.350H.359 Quality
4、 of service architecture for audiovisual and multimedia services H.360H.369 Telepresence H.420H.429 Supplementary services for multimedia H.450H.499 MOBILITY AND COLLABORATION PROCEDURES Overview of Mobility and Collaboration, definitions, protocols and procedures H.500H.509 Mobility for H-Series mu
5、ltimedia systems and services H.510H.519 Mobile multimedia collaboration applications and services H.520H.529 Security for mobile multimedia systems and services H.530H.539 Security for mobile multimedia collaboration applications and services H.540H.549 VEHICULAR GATEWAYS AND INTELLIGENT TRANSPORTA
6、TION SYSTEMS (ITS) Architecture for vehicular gateways H.550H.559 Vehicular gateway interfaces H.560H.569 BROADBAND, TRIPLE-PLAY AND ADVANCED MULTIMEDIA SERVICES Broadband multimedia services over VDSL H.610H.619 Advanced multimedia services and applications H.620H.629 Ubiquitous sensor network appl
7、ications and Internet of Things H.640H.649 IPTV MULTIMEDIA SERVICES AND APPLICATIONS FOR IPTV General aspects H.700H.719 IPTV terminal devices H.720H.729 IPTV middleware H.730H.739 IPTV application event handling H.740H.749 IPTV metadata H.750H.759 IPTV multimedia application frameworks H.760H.769 I
8、PTV service discovery up to consumption H.770H.779 Digital Signage H.780H.789 E-HEALTH MULTIMEDIA SERVICES AND APPLICATIONS Personal health systems H.810H.819 Interoperability compliance testing of personal health systems (HRN, PAN, LAN, TAN and WAN) H.820H.859 Multimedia e-health data exchange serv
9、ices H.860H.869 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T H.248.77 (12/2017) i Recommendation ITU-T H.248.77 Gateway control protocol: Secure real-time transport protocol (SRTP) package and procedures Summary Recommendation ITU-T H.248.77 defines a new ITU-T
10、H.248 package, the secure real-time transport protocol (SRTP) package. In addition, this Recommendation covers a set of procedures related to SRTP key management. The combination of package and procedures allows a media gateway controller (MGC) to control the use of SRTP by a media gateway (MG). Thi
11、s revision contains an updated package that allows for the usage of datagram transport layer security (DTLS)-SRTP key management scheme that exchanges the peers certificates via the signalling path and then establishes a DTLS connection on the bearer path. History Edition Recommendation Approval Stu
12、dy Group Unique ID* 1.0 ITU-T H.248.77 2010-09-13 16 11.1002/1000/10987 2.0 ITU-T H.248.77 2017-12-14 16 11.1002/1000/13432 Keywords Key management, SRTP. _ * To access the Recommendation, type the URL http:/handle.itu.int/ in the address field of your web browser, followed by the Recommendations un
13、ique ID. For example, http:/handle.itu.int/11.1002/1000/ 11830-en. ii Rec. ITU-T H.248.77 (12/2017) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecom
14、munication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Ass
15、embly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology wh
16、ich fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with
17、this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory la
18、nguage such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTSITU draws attention to the possibility that the practice or implementation of this
19、 Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date
20、of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the T
21、SB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2018 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T H.248.77 (12/2017) iii Table of Contents Page 1 Scope . 1 1.1 Connection model . 1 2 Refer
22、ences . 2 3 Definitions 3 3.1 Terms defined elsewhere 3 3.2 Terms defined in this Recommendation . 3 4 Abbreviations and acronyms 3 5 Conventions 4 6 Secure RTP package . 4 6.1 Properties 4 6.2 Events . 6 6.3 Signals 7 6.4 Statistics 7 6.5 Error codes 9 6.6 Procedures 9 7 Key management using SDP se
23、curity descriptions 11 7.1 Overspecification of SRTP parameters and multiple keys . 12 7.2 Wildcarding of SRTP parameters . 12 7.3 Interoperability with offer/answer-based implementations 13 7.4 SDES and SRTP cryptographic contexts . 13 7.5 Mapping of master keys for sent packets and received packet
24、s statistics 14 8 Key management using DTLS-SRTP . 14 8.1 Key management indication . 15 8.2 Bearer plane connection for “DTLS-SRTP“ 15 8.3 Multi key management operation . 17 9 Security considerations . 17 9.1 Relation to key management scheme “SDES“ . 17 9.2 Relation to key management scheme “DTLS
25、-SRTP“ 17 Appendix I Example call flows for key management scheme “SDES“ 18 I.1 Initial session setup using SDP security descriptions . 18 I.2 MG1s key is about to expire 21 I.3 Auditing SRTP capabilities 21 I.4 Auditing of SRTP statistics 22 Appendix II Sample use-cases of SRTP bearer encryption 24
26、 II.1 Use-case #1: ITU-T H.248 MG for peering IP and circuit-switched networks . 24 II.2 Use-case #2: ITU-T H.248 MG for peering IP networks . 24 II.3 Use-case #3: Transparent SRTP forwarding 25 Bibliography. 27 Rec. ITU-T H.248.77 (12/2017) 1 Recommendation ITU-T H.248.77 Gateway control protocol:
27、Secure real-time transport protocol (SRTP) package and procedures 1 Scope The secure real-time transport protocol (SRTP) is a real-time transport protocol (RTP) profile that provides confidentiality, message authentication and replay protection to RTP and RTP control protocol (RTCP) sessions. The se
28、cure RTP package allows a media gateway controller (MGC) to control the use of SRTP by a media gateway (MG). This package is defined in detail in clause 6. By itself, the secure RTP package is incomplete, as it does not provide procedures for key management. Instead, it is designed to rely on existi
29、ng key-management schemes (see also b-IETF RFC 7202). b-IETF RFC 5479 provides an example selection of key-management protocol options for SRTP in “SIP networks“. Clause 7 provides procedures for the use of one such key-management scheme: session description protocol (SDP) security descriptions. Cla
30、use 8 provides procedures for the use of one such key-management scheme: datagram transport layer security (DTLS)-SRTP. Several reasons exist why this Recommendation is required, in addition to the existing (usually SDP-based) SRTP key-management schemes. The most significant of which are listed bel
31、ow: Most existing SDP key-management schemes rely on the SDP offer/answer model (see b-IETF RFC 3264). However, the offer/answer model is not used in ITU-T H.248 as it does not fit the nature of the connection between an ITU-T H.248 MGC and a MG. Existing SDP key-management schemes do not contain pr
32、ocedures relating to parameter overspecification and wildcarding, which are unique to ITU-T H.248. The limited lifetime of SRTP master keys calls for mechanisms for handling master key expiry. The existing mechanisms cannot be used in ITU-T H.248. The SRTP package allows explicit control over the ke
33、y-management scheme employed, allowing easy interoperability with, and migration to future schemes. The SRTP package allows an MGC to audit the SRTP capabilities of an MG through the use of the packages descriptor and the properties of the new package. The SRTP package allows an MGC to collect stati
34、stics regarding the number of security violations encountered by the MG, and the volume of SRTP traffic it processed. The scope of the (09/2010) edition of this Recommendation is limited to use-cases in which a MG applies SRTP procedures, as described in section 3.3 of IETF RFC 3711, to the SRTP pac
35、kets it sends and receives. Use-cases in which the MG handles SRTP packets without using those procedures (e.g., transparent forwarding, storage in encrypted form, etc.) are intentionally left out of this Recommendation. This revision (12/2017) of the Recommendation extends the scope for further SRT
36、P key management schemes, such as DTLS-SRTP according to b-IETF RFC 5763 and IETF RFC 5764. 1.1 Connection model All protocol elements and procedures described in this Recommendation are limited to the extent of a single ITU-T H.248 termination. In addition, no assumptions are made regarding either
37、the lower layer protocols beneath the SRTP level or the upper layer protocols/codecs being carried by the SRTP. 2 Rec. ITU-T H.248.77 (12/2017) This allows the use of the Recommendations procedures in various connection models and use-cases (e.g., an SRTP-enabled announcement server, an SRTP to RTP
38、translator, etc.). Figure 1 details the generic connection-model where an SRTP-enabled termination is connected to a single other termination (either SRTP-enabled or not). The generalization to any number of terminations is trivial. H. 2 4 8 . 7 7 ( 1 0 ) _ F 0 1*I T U - T H . 2 4 8 c o n t e x tS R
39、 T P - e n a b l e dt e r m i n a t i o nO t h e rt e r m i n a t i o nR T P / R T C PL o w e r - l a y e rp r o t o c o l sS R T P s e s s i o nA n y t y p e o f b e a r e r / s e s s i o nL o w e r - l a y e r b e a r e rU p p e r - l a y e rc o d e c sS R T P / S R T C PFigure 1 Two-termination c
40、ontext with an SRTP termination 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other r
41、eferences are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The refere
42、nce to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T H.248.1 Recommendation ITU-T H.248.1 (2013), Gateway control protocol: Version 3. ITU-T H.248.8 Recommendation ITU-T H.248.8 (2013), Gateway control protocol: Error code an
43、d service change reason description. ITU-T H.248.47 Recommendation ITU-T H.248.47 (2008), Gateway control protocol: Statistic conditional reporting package. ITU-T H.248.49 Recommendation ITU-T H.248.49 (2007), Gateway control protocol: Session description protocol RFC and capabilities packages. ITU-
44、T H.248.90 Recommendation ITU-T H.248.90 (2014), Gateway control protocol: ITU-T H.248 packages for control of transport security using transport layer security (TLS). ITU-T H.248.93 Recommendation ITU-T H.248.93 (2014), Gateway control protocol: ITU-T H.248 support for control of transport security
45、 using the datagram transport layer security (DTLS) protocol. IETF RFC 3550 IETF RFC 3550 (2003), RTP: A Transport Protocol for Real-Time Applications. IETF RFC 3711 IETF RFC 3711 (2004), The Secure Real-time Transport Protocol (SRTP). IETF RFC 4568 IETF RFC 4568 (2006), Session Description Protocol
46、 (SDP) Security Descriptions for Media Streams. Rec. ITU-T H.248.77 (12/2017) 3 IETF RFC 4572 IETF RFC 4572 (2017), Connection-Oriented Media Transport over the Transport Layer Security (TLS) Protocol in the Session Description Protocol (SDP). IETF RFC 5246 IETF RFC 5246 (2008), The Transport Layer
47、Security (TLS) Protocol Version 1.2. IETF RFC 5764 IETF RFC 5764 (2010), Datagram Transport Layer Security (DTLS) Extension to Establish Keys for the Secure Real-time Transport Protocol (SRTP). IETF RFC 6347 IETF RFC 6347 (2012), Datagram Transport Layer Security Version 1.2. 3 Definitions 3.1 Terms
48、 defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 RTP session (section 2.2.2 of b-IETF RFC 7656 | b-ITU-T H.248.95): An association among a group of participants communicating with RTP. It is a group communications channel which can potentially carry a number o
49、f RTP Streams. Within an RTP Session, every Participant can find meta-data and control information (over RTCP) about all the RTP Streams in the RTP Session. The bandwidth of the RTCP control channel is shared between all Participants within an RTP Session. 3.1.2 SRTP cryptographic context IETF RFC 3711: The set of cryptographic state information that an SRTP sender or receiver must maintain per SRTP session participant. NOTE This term is often ab
