rfc2833.txt

RFC规范的翻译稿

    |                           timestamp                           |
    |                             48000                             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           synchronization source (SSRC) identifier            |
    |                            0x5234a8                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |F|   block PT  |     timestamp offset      |   block length    |
    |1|     98      |            16383          |         4         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |F|   block PT  |     timestamp offset      |   block length    |
    |1|     97      |            16383          |         8         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |F|   Block PT  |
    |0|     97      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  event=ring   |0|0| volume=0  |     duration=28383            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | modulation=0    |0| volume=63 |     duration=16383            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 0|     frequency=0       |0 0 0 0|    frequency=0        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | modulation=0    |0| volume=5  |     duration=12000            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0 0 0|     frequency=440     |0 0 0 0|    frequency=480      |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
图4：一个组合了话音和事件的RTP数据包
      可选参数：“events”参数列出了实现支持的事件。表中的多个事件元素由逗号分隔。
每个元素是单个整数或由连字符分开的两个整数。参数间不允许空白。整数指出了实现支持
的事件号。所有的实现都必须支持事件0～15，所以如果执行只支持这些事件的话，参数表
就可以省略。
      “rate”参数描述了采样速率，以赫兹为单位。数值可写为浮点或整数形式。若忽略
不写，则为默认值8000 Hz。
      编码考虑：这种类型只定义为通过RTP[1]传送。
      安全考虑：见本文中的“安全考虑“部分（第7节）。
      互操作性考虑：无
     已发行规范：本文
      使用该媒体的应用：电话事件音频子类型支持在Internet上传输电话系统事件。
      附加信息：
          1．幻数：N/A
          2．文件扩展名：N/A
          3．Macintosh 的文件类型代码：N/A
6．2 audio/tone
      MIME媒体类型名：audio
      MIME子类型名：tone
      必需参数：无
      可选参数：“rate”描述了取样品的速率，以赫兹为单位。数值可写为浮点或整数形式。
若忽略不写，则为默认值8000 Hz。
      编码考虑：只定义为通过RTP [1]传输。
      安全考虑：见本文中的“安全考虑“部分（第7节）。
互操作性考虑：无
       已发行规范：本文
      使用该媒体的应用：电话音音频子类型支持纯合成话音的传输，例如那些常用于当前
电话系统中表示呼叫进程的电话音。
      附加信息：
           1．幻数：N/A
           2．文件扩展名：N/A
           3．Macintosh 的文件类型代码：N/A
7．安全考虑
    使用本规范定义的负载格式的RTP数据包在安全考虑上要依照RTP规范(RFC 1889 
[1])，及任何合适的RTP框架（如RFC 1890 [19]）。这意味着媒体数据流的机密性要通过加
密来实现。因为负载格式的数据压缩应用于端到端场合，所以加密可在压缩之后进行，这样
两种操作间就不会有冲突。
    这种负载类型不会引起接收端包处理过程中在计算复杂性方面明显的不一致性，从而避
免了潜在的拒绝服务。
    在早期网络采用带内信令且缺乏相应的信号音滤波器，3.14小节中介绍的话音可以用于
收费欺诈。
    附加安全考虑在RFC 2198 [6]中描述。
8. IANA考虑
    本文定义了两种新的RTP负载格式，电话事件和电话音，以及相关的MIME类型，即
audio/event和audio/tone。
    在audio/event类型中，附加的事件必须由IANA注册。注册要得到当前IETF视听传输
工作组主席的正式批准，或者如果AVT组已经关闭，也可由传输领域主管任命的一个专家
正式批准。新事件的含义必须以RFC文档或者由其它标准化团体（如ITU-T）的等价标准
化文档形式发行。
鸣谢
    对Megaco工作组的建议表示万分感激。具体建议和意见由Fred Burg,，Steve Casner， 
Fatih Erdin， Bill Foster， Mike Fox，Gunnar Hellstrom，Terry Lyons，Steve Magnell,，Vern 
Paxson and Colin Perkins提供。
作者地址
   Henning Schulzrinne
   Dept. of Computer Science
   Columbia University
   1214 Amsterdam Avenue
   New York, NY 10027
   USA
   EMail:  [e-mail]
   Scott Petrack
   MetaTel
   45 Rumford Avenue
   Waltham, MA 02453
   USA
   EMail:  [e-mail]
参考书目
   [1]  Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
        "RTP:  A Transport Protocol for Real-Time Applications", RFC
        1889, January 1996.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.
   [3]  International Telecommunication Union, "Procedures for starting
        sessions of data transmission over the public switched telephone
        network," Recommendation V.8, Telecommunication Standardization
        Sector of ITU, Geneva, Switzerland, Feb. 1998.
   [4]  R. Kocen and T. Hatala, "Voice over frame relay implementation
        agreement", Implementation Agreement FRF.11, Frame Relay Forum,
        Foster City, California, Jan. 1997.
  [5]  International Telecommunication Union, "Multifrequency push-
        button signal reception," Recommendation Q.24, Telecommunication
        Standardization Sector of ITU, Geneva, Switzerland, 1988.
   [6]  Perkins, C., Kouvelas, I., Hodson, O., Hardman, V., Handley, M.,
        Bolot, J., Vega-Garcia, A. and S. Fosse-Parisis, "RTP Payload
        for Redundant Audio Data", RFC 2198, September 1997.
   [7]  Handley M. and V. Jacobson, "SDP: Session Description Protocol",
        RFC 2327, April 1998.
   [8]  International Telecommunication Union, "Automatic answering
        equipment and general procedures for automatic calling equipment
        on the general switched telephone network including procedures
        for disabling of echo control devices for both manually and
        automatically established calls," Recommendation V.25,
        Telecommunication Standardization Sector of ITU, Geneva,
        Switzerland, Oct. 1996.
   [9]  International Telecommunication Union, "Procedures for document
        facsimile transmission in the general switched telephone
        network," Recommendation T.30, Telecommunication Standardization
        Sector of ITU, Geneva, Switzerland, July 1996.
   [10] International Telecommunication Union, "Echo cancellers,"
        Recommendation G.165, Telecommunication Standardization Sector
        of ITU, Geneva, Switzerland, Mar. 1993.
   [11] International Telecommunication Union, "A modem operating at
        data signaling rates of up to 33 600 bit/s for use on the
        general switched telephone network and on leased point-to-point
        2-wire telephone-type circuits," Recommendation V.34,
        Telecommunication Standardization Sector of ITU, Geneva,
        Switzerland, Feb. 1998.
   [12] International Telecommunication Union, "Procedures for the
        identification and selection of common modes of operation
        between data circuit-terminating equipments (DCEs) and between
        data terminal equipments (DTEs) over the public switched
        telephone network and on leased point-to-point telephone-type
        circuits," Recommendation V.8bis, Telecommunication
        Standardization Sector of ITU, Geneva, Switzerland, Sept. 1998.

   [13] International Telecommunication Union, "Application of tones and
        recorded announcements in telephone services," Recommendation
        E.182, Telecommunication Standardization Sector of ITU, Geneva,
        Switzerland, Mar. 1998.
   [14] Bellcore, "Functional criteria for digital loop carrier
        systems," Technical Requirement TR-NWT-000057, Telcordia
        (formerly Bellcore), Morristown, New Jersey, Jan. 1993.
   [15] J. G. van Bosse, Signaling in Telecommunications Networks
        Telecommunications and Signal Processing, New York, New York:
        Wiley, 1998.
   [16] International Telecommunication Union, "AAL type 2 service
        specific convergence sublayer for trunking," Recommendation
        I.366.2, Telecommunication Standardization Sector of ITU,
        Geneva, Switzerland, Feb. 1999.
   [17] International Telecommunication Union, "Various tones used in
        national networks," Recommendation Supplement 2 to
        Recommendation E.180, Telecommunication Standardization Sector
        of ITU, Geneva, Switzerland, Jan. 1994.
   [18] International Telecommunication Union, "Technical
        characteristics of tones for telephone service," Recommendation
        Supplement 2 to Recommendation E.180, Telecommunication
        Standardization Sector of ITU, Geneva, Switzerland, Jan. 1994.
   [19] Schulzrinne, H., "RTP Profile for Audio and Video Conferences
        with Minimal Control", RFC 1890, January 1996.
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致谢
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RFC 2833——RTP Payload for DTMF Digits,                          用于DTMF数字信号、电话音
Telephony Tones and Telephony Signals                     和电话信号的RTP负载格式


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