Internet Engineering Task Force (IETF)                    H. Schulzrinne
Request for Comments: 7826                           Columbia University
Obsoletes: 2326                                                   A. Rao
Category: Standards Track                                          Cisco
ISSN: 2070-1721                                              R. Lanphier

                                                           M. Westerlund
                                                                Ericsson
                                                     M. Stiemerling, Ed.
                                University of Applied Sciences Darmstadt
                                                           December 2016


                Real-Time Streaming Protocol Version 2.0

Abstract

   This memorandum defines the Real-Time Streaming Protocol (RTSP)
   version 2.0, which obsoletes RTSP version 1.0 defined in RFC 2326.

   RTSP is an application-layer protocol for the setup and control of
   the delivery of data with real-time properties.  RTSP provides an
   extensible framework to enable controlled, on-demand delivery of
   real-time data, such as audio and video.  Sources of data can include
   both live data feeds and stored clips.  This protocol is intended to
   control multiple data delivery sessions; provide a means for choosing
   delivery channels such as UDP, multicast UDP, and TCP; and provide a
   means for choosing delivery mechanisms based upon RTP (RFC 3550).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7826.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Contributions published or made publicly available before November
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   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ...................................................10
   2. Protocol Overview ..............................................11
      2.1. Presentation Description ..................................12
      2.2. Session Establishment .....................................12
      2.3. Media Delivery Control ....................................14
      2.4. Session Parameter Manipulations ...........................15
      2.5. Media Delivery ............................................16
           2.5.1. Media Delivery Manipulations .......................16
      2.6. Session Maintenance and Termination .......................19
      2.7. Extending RTSP ............................................20
   3. Document Conventions ...........................................21
      3.1. Notational Conventions ....................................21
      3.2. Terminology ...............................................21
   4. Protocol Parameters ............................................25
      4.1. RTSP Version ..............................................25
      4.2. RTSP IRI and URI ..........................................25
      4.3. Session Identifiers .......................................28

      4.4. Media-Time Formats ........................................28
           4.4.1. SMPTE-Relative Timestamps ..........................28
           4.4.2. Normal Play Time ...................................29
           4.4.3. Absolute Time ......................................30
      4.5. Feature Tags ..............................................31
      4.6. Message Body Tags .........................................32
      4.7. Media Properties ..........................................32
           4.7.1. Random Access and Seeking ..........................33
           4.7.2. Retention ..........................................34
           4.7.3. Content Modifications ..............................34
           4.7.4. Supported Scale Factors ............................34
           4.7.5. Mapping to the Attributes ..........................35
   5. RTSP Message ...................................................35
      5.1. Message Types .............................................36
      5.2. Message Headers ...........................................36
      5.3. Message Body ..............................................37
      5.4. Message Length ............................................37
   6. General-Header Fields ..........................................37
   7. Request ........................................................39
      7.1. Request Line ..............................................40
      7.2. Request-Header Fields .....................................42
   8. Response .......................................................43
      8.1. Status-Line ...............................................43
           8.1.1. Status Code and Reason Phrase ......................43
      8.2. Response Headers ..........................................47
   9. Message Body ...................................................47
      9.1. Message Body Header Fields ................................48
      9.2. Message Body ..............................................49
      9.3. Message Body Format Negotiation ...........................49
   10. Connections ...................................................50
      10.1. Reliability and Acknowledgements .........................50
      10.2. Using Connections ........................................51
      10.3. Closing Connections ......................................54
      10.4. Timing Out Connections and RTSP Messages .................56
      10.5. Showing Liveness .........................................57
      10.6. Use of IPv6 ..............................................58
      10.7. Overload Control .........................................58
   11. Capability Handling ...........................................60
      11.1. Feature Tag: play.basic ..................................62
   12. Pipelining Support ............................................62
   13. Method Definitions ............................................63
      13.1. OPTIONS ..................................................65
      13.2. DESCRIBE .................................................66
      13.3. SETUP ....................................................68
           13.3.1. Changing Transport Parameters .....................71
      13.4. PLAY .....................................................72
           13.4.1. General Usage .....................................72
           13.4.2. Aggregated Sessions ...............................77

           13.4.3. Updating Current PLAY Requests ....................78
           13.4.4. Playing On-Demand Media ...........................81
           13.4.5. Playing Dynamic On-Demand Media ...................81
           13.4.6. Playing Live Media ................................81
           13.4.7. Playing Live with Recording .......................82
           13.4.8. Playing Live with Time-Shift ......................83
      13.5. PLAY_NOTIFY ..............................................83
           13.5.1. End-of-Stream .....................................84
           13.5.2. Media-Properties-Update ...........................86
           13.5.3. Scale-Change ......................................87
      13.6. PAUSE ....................................................89
      13.7. TEARDOWN .................................................92
           13.7.1. Client to Server ..................................92
           13.7.2. Server to Client ..................................93
      13.8. GET_PARAMETER ............................................94
      13.9. SET_PARAMETER ............................................96
      13.10. REDIRECT ................................................98
   14. Embedded (Interleaved) Binary Data ...........................101
   15. Proxies ......................................................103
      15.1. Proxies and Protocol Extensions .........................104
      15.2. Multiplexing and Demultiplexing of Messages .............105
   16. Caching ......................................................106
      16.1. Validation Model ........................................107
           16.1.1. Last-Modified Dates ..............................108
           16.1.2. Message Body Tag Cache Validators ................108
           16.1.3. Weak and Strong Validators .......................108
           16.1.4. Rules for When to Use Message Body Tags
                   and Last-Modified Dates ..........................110
           16.1.5. Non-validating Conditionals ......................112
      16.2. Invalidation after Updates or Deletions .................112
   17. Status Code Definitions ......................................113
      17.1. Informational 1xx .......................................113
           17.1.1. 100 Continue .....................................113
      17.2. Success 2xx .............................................113
           17.2.1. 200 OK ...........................................113
      17.3. Redirection 3xx .........................................113
           17.3.1. 300 ..............................................114
           17.3.2. 301 Moved Permanently ............................114
           17.3.3. 302 Found ........................................114
           17.3.4. 303 See Other ....................................115
           17.3.5. 304 Not Modified .................................115
           17.3.6. 305 Use Proxy ....................................115
      17.4. Client Error 4xx ........................................116
           17.4.1. 400 Bad Request ..................................116
           17.4.2. 401 Unauthorized .................................116
           17.4.3. 402 Payment Required .............................116
           17.4.4. 403 Forbidden ....................................116
           17.4.5. 404 Not Found ....................................116

           17.4.6. 405 Method Not Allowed ...........................117
           17.4.7. 406 Not Acceptable ...............................117
           17.4.8. 407 Proxy Authentication Required ................117
           17.4.9. 408 Request Timeout ..............................117
           17.4.10. 410 Gone ........................................118
           17.4.11. 412 Precondition Failed .........................118
           17.4.12. 413 Request Message Body Too Large ..............118
           17.4.13. 414 Request-URI Too Long ........................118
           17.4.14. 415 Unsupported Media Type ......................119
           17.4.15. 451 Parameter Not Understood ....................119
           17.4.16. 452 Illegal Conference Identifier ...............119
           17.4.17. 453 Not Enough Bandwidth ........................119
           17.4.18. 454 Session Not Found ...........................119
           17.4.19. 455 Method Not Valid in This State ..............119
           17.4.20. 456 Header Field Not Valid for Resource .........119
           17.4.21. 457 Invalid Range ...............................120
           17.4.22. 458 Parameter Is Read-Only ......................120
           17.4.23. 459 Aggregate Operation Not Allowed .............120
           17.4.24. 460 Only Aggregate Operation Allowed ............120
           17.4.25. 461 Unsupported Transport .......................120
           17.4.26. 462 Destination Unreachable .....................120
           17.4.27. 463 Destination Prohibited ......................120
           17.4.28. 464 Data Transport Not Ready Yet ................121
           17.4.29. 465 Notification Reason Unknown .................121
           17.4.30. 466 Key Management Error ........................121
           17.4.31. 470 Connection Authorization Required ...........121
           17.4.32. 471 Connection Credentials Not Accepted .........121
           17.4.33. 472 Failure to Establish Secure Connection ......121
      17.5. Server Error 5xx ........................................122
           17.5.1. 500 Internal Server Error ........................122
           17.5.2. 501 Not Implemented ..............................122
           17.5.3. 502 Bad Gateway ..................................122
           17.5.4. 503 Service Unavailable ..........................122
           17.5.5. 504 Gateway Timeout ..............................123
           17.5.6. 505 RTSP Version Not Supported ...................123
           17.5.7. 551 Option Not Supported .........................123
           17.5.8. 553 Proxy Unavailable ............................123
   18. Header Field Definitions .....................................124
      18.1. Accept ..................................................134
      18.2. Accept-Credentials ......................................135
      18.3. Accept-Encoding .........................................135
      18.4. Accept-Language .........................................136
      18.5. Accept-Ranges ...........................................137
      18.6. Allow ...................................................138
      18.7. Authentication-Info .....................................138
      18.8. Authorization ...........................................138
      18.9. Bandwidth ...............................................139
      18.10. Blocksize ..............................................140

      18.11. Cache-Control ..........................................140
      18.12. Connection .............................................143
      18.13. Connection-Credentials .................................143
      18.14. Content-Base ...........................................144
      18.15. Content-Encoding .......................................145
      18.16. Content-Language .......................................145
      18.17. Content-Length .........................................146
      18.18. Content-Location .......................................146
      18.19. Content-Type ...........................................148
      18.20. CSeq ...................................................148
      18.21. Date ...................................................150
      18.22. Expires ................................................151
      18.23. From ...................................................151
      18.24. If-Match ...............................................152
      18.25. If-Modified-Since ......................................152
      18.26. If-None-Match ..........................................153
      18.27. Last-Modified ..........................................154
      18.28. Location ...............................................154
      18.29. Media-Properties .......................................154
      18.30. Media-Range ............................................156
      18.31. MTag ...................................................157
      18.32. Notify-Reason ..........................................158
      18.33. Pipelined-Requests .....................................158
      18.34. Proxy-Authenticate .....................................159
      18.35. Proxy-Authentication-Info ..............................159
      18.36. Proxy-Authorization ....................................159
      18.37. Proxy-Require ..........................................160
      18.38. Proxy-Supported ........................................160
      18.39. Public .................................................161
      18.40. Range ..................................................162
      18.41. Referrer ...............................................164
      18.42. Request-Status .........................................164
      18.43. Require ................................................165
      18.44. Retry-After ............................................166
      18.45. RTP-Info ...............................................167
      18.46. Scale ..................................................169
      18.47. Seek-Style .............................................170
      18.48. Server .................................................171
      18.49. Session ................................................172
      18.50. Speed ..................................................173
      18.51. Supported ..............................................174
      18.52. Terminate-Reason .......................................175
      18.53. Timestamp ..............................................175
      18.54. Transport ..............................................176
      18.55. Unsupported ............................................183
      18.56. User-Agent .............................................184
      18.57. Via ....................................................184
      18.58. WWW-Authenticate .......................................185

   19. Security Framework ...........................................185
      19.1. RTSP and HTTP Authentication ............................185
           19.1.1. Digest Authentication ............................186
      19.2. RTSP over TLS ...........................................187
      19.3. Security and Proxies ....................................188
           19.3.1. Accept-Credentials ...............................189
           19.3.2. User-Approved TLS Procedure ......................190
   20. Syntax .......................................................192
      20.1. Base Syntax .............................................193
      20.2. RTSP Protocol Definition ................................195
           20.2.1. Generic Protocol Elements ........................195
           20.2.2. Message Syntax ...................................198
           20.2.3. Header Syntax ....................................201
      20.3. SDP Extension Syntax ....................................209
   21. Security Considerations ......................................209
      21.1. Signaling Protocol Threats ..............................210
      21.2. Media Stream Delivery Threats ...........................213
           21.2.1. Remote DoS Attack ................................215
           21.2.2. RTP Security Analysis ............................216
   22. IANA Considerations ..........................................217
      22.1. Feature Tags ............................................218
           22.1.1. Description ......................................218
           22.1.2. Registering New Feature Tags with IANA ...........218
           22.1.3. Registered Entries ...............................219
      22.2. RTSP Methods ............................................219
           22.2.1. Description ......................................219
           22.2.2. Registering New Methods with IANA ................219
           22.2.3. Registered Entries ...............................220
      22.3. RTSP Status Codes .......................................220
           22.3.1. Description ......................................220
           22.3.2. Registering New Status Codes with IANA ...........220
           22.3.3. Registered Entries ...............................221
      22.4. RTSP Headers ............................................221
           22.4.1. Description ......................................221
           22.4.2. Registering New Headers with IANA ................221
           22.4.3. Registered Entries ...............................222
      22.5. Accept-Credentials ......................................223
           22.5.1. Accept-Credentials Policies ......................223
           22.5.2. Accept-Credentials Hash Algorithms ...............224
      22.6. Cache-Control Cache Directive Extensions ................224
      22.7. Media Properties ........................................225
           22.7.1. Description ......................................225
           22.7.2. Registration Rules ...............................226
           22.7.3. Registered Values ................................226
      22.8. Notify-Reason Values ....................................226
           22.8.1. Description ......................................226
           22.8.2. Registration Rules ...............................226
           22.8.3. Registered Values ................................227

      22.9. Range Header Formats ....................................227
           22.9.1. Description ......................................227
           22.9.2. Registration Rules ...............................227
           22.9.3. Registered Values ................................228
      22.10. Terminate-Reason Header ................................228
           22.10.1. Redirect Reasons ................................228
           22.10.2. Terminate-Reason Header Parameters ..............229
      22.11. RTP-Info Header Parameters .............................229
           22.11.1. Description .....................................229
           22.11.2. Registration Rules ..............................229
           22.11.3. Registered Values ...............................230
      22.12. Seek-Style Policies ....................................230
           22.12.1. Description .....................................230
           22.12.2. Registration Rules ..............................230
           22.12.3. Registered Values ...............................230
      22.13. Transport Header Registries ............................231
           22.13.1. Transport Protocol Identifier ...................231
           22.13.2. Transport Modes .................................233
           22.13.3. Transport Parameters ............................233
      22.14. URI Schemes ............................................234
           22.14.1. The "rtsp" URI Scheme ...........................234
           22.14.2. The "rtsps" URI Scheme ..........................235
           22.14.3. The "rtspu" URI Scheme ..........................237
      22.15. SDP Attributes .........................................238
      22.16. Media Type Registration for text/parameters ............238
   23. References ...................................................240
      23.1. Normative References ....................................240
      23.2. Informative References ..................................245
   Appendix A. Examples .............................................248
      A.1. Media on Demand (Unicast) ................................248
      A.2. Media on Demand Using Pipelining .........................251
      A.3. Secured Media Session for On-Demand Content ..............254
      A.4. Media on Demand (Unicast) ................................257
      A.5. Single-Stream Container Files ............................260
      A.6. Live Media Presentation Using Multicast ..................263
      A.7. Capability Negotiation ...................................264
   Appendix B. RTSP Protocol State Machine ..........................265
      B.1. States ...................................................266
      B.2. State Variables ..........................................266
      B.3. Abbreviations ............................................266
      B.4. State Tables .............................................267
   Appendix C. Media-Transport Alternatives .........................272
      C.1. RTP ......................................................272
        C.1.1. AVP ..................................................272
        C.1.2. AVP/UDP ..............................................273
        C.1.3. AVPF/UDP .............................................274
        C.1.4. SAVP/UDP .............................................275
        C.1.5. SAVPF/UDP ............................................277

        C.1.6. RTCP Usage with RTSP .................................278
      C.2. RTP over TCP .............................................279
        C.2.1. Interleaved RTP over TCP .............................280
        C.2.2. RTP over Independent TCP .............................280
      C.3. Handling Media-Clock Time Jumps in the RTP Media Layer ...284
      C.4. Handling RTP Timestamps after PAUSE ......................287
      C.5. RTSP/RTP Integration  ....................................290
      C.6. Scaling with RTP .........................................290
      C.7. Maintaining NPT Synchronization with RTP Timestamps ......290
      C.8. Continuous Audio .........................................290
      C.9. Multiple Sources in an RTP Session .......................290
      C.10. Usage of SSRCs and the RTCP BYE Message during an RTSP
            Session .................................................290
      C.11. Future Additions ........................................291
   Appendix D. Use of SDP for RTSP Session Descriptions .............292
      D.1. Definitions  .............................................292
        D.1.1. Control URI ..........................................292
        D.1.2. Media Streams ........................................294
        D.1.3. Payload Type(s) ......................................294
        D.1.4. Format-Specific Parameters ...........................294
        D.1.5. Directionality of Media Stream .......................295
        D.1.6. Range of Presentation ................................295
        D.1.7. Time of Availability .................................296
        D.1.8. Connection Information ...............................297
        D.1.9. Message Body Tag .....................................297
      D.2. Aggregate Control Not Available ..........................298
      D.3. Aggregate Control Available ..............................298
      D.4. Grouping of Media Lines in SDP ...........................299
      D.5. RTSP External SDP Delivery ...............................300
   Appendix E. RTSP Use Cases .......................................300
      E.1. On-Demand Playback of Stored Content .....................300
      E.2. Unicast Distribution of Live Content .....................302
      E.3. On-Demand Playback Using Multicast .......................303
      E.4. Inviting an RTSP Server into a Conference ................303
      E.5. Live Content Using Multicast .............................304
   Appendix F. Text Format for Parameters ...........................305
   Appendix G. Requirements for Unreliable Transport of RTSP ........305
   Appendix H. Backwards-Compatibility Considerations ...............306
      H.1. Play Request in Play State ...............................307
      H.2. Using Persistent Connections .............................307
   Appendix I. Changes ..............................................307
      I.1. Brief Overview ...........................................308
      I.2. Detailed List of Changes .................................309
   Acknowledgements .................................................316
   Contributors  ....................................................317
   Authors' Addresses ...............................................318

1.  Introduction

   This memo defines version 2.0 of the Real-Time Streaming Protocol
   (RTSP 2.0).  RTSP 2.0 is an application-layer protocol for the setup
   and control over the delivery of data with real-time properties,
   typically streaming media.  Streaming media is, for instance, video
   on demand or audio live streaming.  Put simply, RTSP acts as a
   "network remote control" for multimedia servers.

   The protocol operates between RTSP 2.0 clients and servers, but it
   also supports the use of proxies placed between clients and servers.
   Clients can request information about streaming media from servers by
   asking for a description of the media or use media description
   provided externally.  The media delivery protocol is used to
   establish the media streams described by the media description.
   Clients can then request to play out the media, pause it, or stop it
   completely.  The requested media can consist of multiple audio and
   video streams that are delivered as time-synchronized streams from
   servers to clients.

   RTSP 2.0 is a replacement of RTSP 1.0 [RFC2326] and this document
   obsoletes that specification.  This protocol is based on RTSP 1.0 but
   is not backwards compatible other than in the basic version
   negotiation mechanism.  The changes between the two documents are
   listed in Appendix I.  There are many reasons why RTSP 2.0 can't be
   backwards compatible with RTSP 1.0; some of the main ones are as
   follows:

   o  Most headers that needed to be extensible did not define the
      allowed syntax, preventing safe deployment of extensions;

   o  the changed behavior of the PLAY method when received in Play
      state;

   o  the changed behavior of the extensibility model and its mechanism;
      and

   o  the change of syntax for some headers.

   There are so many small updates that changing versions became
   necessary to enable clarification and consistent behavior.  Anyone
   implementing RTSP for a new use case in which they have not installed
   RTSP 1.0 should only implement RTSP 2.0 to avoid having to deal with
   RTSP 1.0 inconsistencies.

   This document is structured as follows.  It begins with an overview
   of the protocol operations and its functions in an informal way.
   Then, a set of definitions of terms used and document conventions is

   introduced.  These are followed by the actual RTSP 2.0 core protocol
   specification.  The appendices describe and define some
   functionalities that are not part of the core RTSP specification, but
   which are still important to enable some usages.  Among them, the RTP
   usage is defined in Appendix C, the Session Description Protocol
   (SDP) usage with RTSP is defined in Appendix D, and the "text/
   parameters" file format Appendix F, are three normative specification
   appendices.  Other appendices include a number of informational parts
   discussing the changes, use cases, different considerations or
   motivations.