Network Working Group P. Jones
Request for Comments: 4102 Cisco Systems, Inc.
Category: Standards Track June 2005
Network Working Group P. Jones
Request for Comments: 4102 Cisco Systems, Inc.
Category: Standards Track June 2005
Registration of the text/red MIME Sub-Type
文本/红色MIME子类型的注册
Status of This Memo
关于下段备忘
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2005).
版权所有（C）互联网协会（2005年）。
Abstract
摘要
This document defines the text/red MIME sub-type. "Red" is short for redundant. The actual RTP packetization for this MIME type is specified in RFC 2198.
此文档定义text/red MIME子类型。“Red”是redundant的缩写。RFC 2198中指定了此MIME类型的实际RTP打包。
Text is an important component of any multimedia communication system. Like audio, the transport of text can benefit from the use of redundancy in order to improve reliability and end-user experience.
文本是任何多媒体通信系统的重要组成部分。与音频一样，为了提高可靠性和最终用户体验，文本传输也可以受益于冗余的使用。
RFC 2198 [1] defines an RTP [2] payload format for redundant audio data. The format defined in that document is quite suitable for providing redundancy for text, as well as audio.
RFC 2198[1]为冗余音频数据定义RTP[2]有效负载格式。该文档中定义的格式非常适合为文本和音频提供冗余。
RFC 4103 [8] specifies one usage of RFC 2198 and the text/red MIME type for the transport of redundant text data.
RFC 4103[8]指定RFC 2198和文本/红色MIME类型的一种用法，用于传输冗余文本数据。
This memo provides the MIME sub-type registration information for text/red. While this document focuses on the use of this MIME sub-type in SDP [5], the application of this MIME sub-type is not restricted to SDP.
此备忘录提供text/red的MIME子类型注册信息。虽然本文档重点介绍在SDP[5]中使用此MIME子类型，但此MIME子类型的应用并不限于SDP。
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 RFC 2119 [3].
本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照RFC 2119[3]中所述进行解释。
One new MIME sub-type has been registered by the IANA, as described below:
IANA已注册了一个新的MIME子类型，如下所述：
MIME media type name: text
MIME媒体类型名称：text
MIME subtype name: RED
MIME子类型名称：红色
Required parameters: rate: the RTP clock rate of the payload carried within the RTP packet. Typically, this rate is 1000, but other rates MAY be specified. This parameter MUST be set equal to the clock rate of the text payload format carried as the primary encoding.
所需参数：速率：RTP数据包中承载的有效负载的RTP时钟速率。通常，该速率为1000，但可能指定其他速率。此参数必须设置为等于作为主要编码的文本有效负载格式的时钟频率。
pt: a comma-separated ordered list of RTP payload types enumerating the primary, secondary, etc., in accordance with RFC 2198. Because comma is a special character, the list MUST be a quoted-string (enclosed in double quotes). For static payload types, each list element is simply the type number. For dynamic payload types, each list element is a mapping of the dynamic payload type number to an embedded MIME content-type specification for the payload format corresponding to the dynamic payload type. The format of the mapping is:
pt：根据RFC 2198，以逗号分隔的RTP有效负载类型有序列表，列举主要、次要等。因为逗号是特殊字符，所以列表必须是带引号的字符串（用双引号括起来）。对于静态有效负载类型，每个列表元素只是类型编号。对于动态有效负载类型，每个列表元素都是动态有效负载类型编号到对应于动态有效负载类型的有效负载格式的嵌入式MIME内容类型规范的映射。映射的格式为：
dynamic-payload-type "=" content-type
动态有效负载类型“=”内容类型
If the content-type string includes a comma, then the content-type string MUST be a quoted-string. If the content-type string does not include a comma, it MAY still be quoted. Because it is part of the list, which must itself be a quoted-string, the quotation marks MUST be quoted with backslash quoting as specified in RFC 2045 [4]. If the content-type string itself contains a quoted-string, then the requirement for backslash quoting is recursively applied.
如果内容类型字符串包含逗号，则内容类型字符串必须是带引号的字符串。如果内容类型字符串不包含逗号，则仍可将其引用。由于它是列表的一部分，而列表本身必须是带引号的字符串，因此必须按照RFC 2045[4]中的规定使用反斜杠引号引引号。如果内容类型字符串本身包含带引号的字符串，则递归应用反斜杠引号的要求。
Optional parameters: ptime, maxptime (these attributes are originally defined in RFC 2327 [5] and RFC 3267 [6], respectively)
可选参数：ptime、maxptime（这些属性最初分别在RFC 2327[5]和RFC 3267[6]中定义）
Restrictions on Usage: This type is defined only for transfer via RTP. It shall not be defined for a storage format.
使用限制：此类型仅为通过RTP传输而定义。它不应定义为存储格式。
Encoding considerations: See restrictions on Usage above; this section is included per the requirements in RFC 3555 [7].
编码注意事项：参见上面的使用限制；本节包含在RFC 3555[7]中的要求中。
Security considerations: Refer to section 5 of RFC 4102.
安全注意事项：参考RFC 4102第5节。
Interoperability considerations: none
互操作性注意事项：无
Published specification: RFC 2198
已发布规范：RFC 2198
Applications which use this media type: Text streaming and conferencing tools.
使用此媒体类型的应用程序：文本流和会议工具。
Additional information: none
其他信息：无
Person & email address to contact for further information: Paul E. Jones E-mail: paulej@packetizer.com
联系人和电子邮件地址以获取更多信息：Paul E.Jones电子邮件：paulej@packetizer.com
Intended usage: COMMON
预期用途：普通
Author: Paul E. Jones paulej@packetizer.com
作者：保罗·E·琼斯paulej@packetizer.com
Change Controller: AVT Working Group delegated from the IESG
变更控制员：由IESG授权的AVT工作组
The information carried in the MIME media type specification has a specific mapping to fields in the Session Description Protocol (SDP) [5], which is commonly used to describe RTP sessions. When SDP is used to specify sessions employing the RFC 2198 in a text session, the mapping is as follows:
MIME媒体类型规范中包含的信息与会话描述协议（SDP）[5]中的字段具有特定映射，该协议通常用于描述RTP会话。当SDP用于指定在文本会话中使用RFC 2198的会话时，映射如下所示：
- The MIME type ("text") goes in SDP "m=" as the media name.
- MIME类型（“文本”）以SDP“m=”作为媒体名称。
- The value of the parameter "rate" goes in SDP "a=rtpmap".
- 参数“rate”的值进入SDP“a=rtpmap”。
- The MIME subtype (RED) goes in SDP "a=rtpmap" as the encoding name.
- MIME子类型（红色）以SDP“a=rtpmap”作为编码名称。
- The parameters "ptime" and "maxptime" go in the SDP "a=ptime" and "a=maxptime" attributes, respectively.
- 参数“ptime”和“maxptime”分别位于SDP“a=ptime”和“a=maxptime”属性中。
- The pt parameter is mapped to an a=fmtp attribute by eliminating the parameter name (pt) and changing the commas to slashes. For example, 'pt="101,102"' maps to 'a=fmtp:99 101/102', where = '99' is the payload type of the redundancy frames. Note that the single quote marks (') used in this example are not present in the actual message encoding, but are present here only for readability. The level of redundancy is shown by the number of elements in the payload type list.
- 通过删除参数名（pt）并将逗号更改为斜杠，pt参数映射到a=fmtp属性。例如，“pt=“101102”映射到“a=fmtp:99 101/102”，其中='99'是冗余帧的有效负载类型。请注意，本例中使用的单引号（'）不存在于实际的消息编码中，但此处仅用于可读性。冗余级别由有效负载类型列表中的元素数量显示。
Any dynamic payload type in the list MUST be represented by its payload type number and not by its content-type. The mapping of payload types to the content-type is done using the normal SDP procedures with "a=rtpmap".
列表中的任何动态有效负载类型必须由其有效负载类型编号表示，而不是由其内容类型表示。有效负载类型到内容类型的映射是使用带有“a=rtpmap”的正常SDP过程完成的。
An example of SDP is:
SDP的一个例子是：
m=text 11000 RTP/AVP 98 100
a=rtpmap:98 t140/1000
a=rtpmap:100 red/1000
a=fmtp:100 98/98
m=text 11000 RTP/AVP 98 100
a=rtpmap:98 t140/1000
a=rtpmap:100 red/1000
a=fmtp:100 98/98
For each redundancy payload type defined, the ordering of the primary and redundancy encoding(s) is fixed. If more than one combination of primary and redundancy encoding(s) is desired, multiple redundancy payload types needs to be defined.
对于定义的每个冗余有效负载类型，主编码和冗余编码的顺序是固定的。如果需要主编码和冗余编码的多个组合，则需要定义多个冗余有效负载类型。
The security considerations listed in RFC 2198 apply. Further, it should be understood that text data, perhaps even more so than audio data, is susceptible to unwanted modification that may lead to undesired results. To prevent modification of the primary, secondary, or header information, payload integrity protection over at least the complete RTP packet is RECOMMENDED, for example using SRTP [9].
RFC 2198中列出的安全注意事项适用。此外，应当理解，文本数据可能甚至比音频数据更容易受到可能导致不希望的结果的不希望的修改的影响。为了防止修改主要、次要或报头信息，建议至少对完整的RTP数据包进行有效负载完整性保护，例如使用SRTP[9]。
[1] 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.
[1] 帕金斯，C.，库维拉斯，I.，霍德森，O.，哈德曼，V.，汉德利，M.，博洛特，J.，维加·加西亚，A.，和S.福斯·帕里斯，“冗余音频数据的RTP有效载荷”，RFC 21981997年9月。
[2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003.
[2] Schulzrinne，H.，Casner，S.，Frederick，R.，和V.Jacobson，“RTP：实时应用的传输协议”，STD 64，RFC 35502003年7月。
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[3] Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
[4] Freed，N.和N.Borenstein，“多用途互联网邮件扩展（MIME）第一部分：互联网邮件正文格式”，RFC 20451996年11月。
[5] Handley, M., Jackson, V., "SDP: Session Description Protocol", RFC 2327, April 1998.
[5] Handley，M.，Jackson，V.，“SDP：会话描述协议”，RFC23271998年4月。
[6] Sjoberg, J., Westerlund, M., Lakaniemi, A., and Q. Xie, "Real-Time Transport Protocol (RTP) Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs", RFC 3267, June 2002.
[6] Sjoberg，J.，Westerlund，M.，Lakaniemi，A.，和Q.Xie，“自适应多速率（AMR）和自适应多速率宽带（AMR-WB）音频编解码器的实时传输协议（RTP）有效载荷格式和文件存储格式”，RFC 3267，2002年6月。
[7] Casner, S. and P. Hoschka, "MIME Type Registration of RTP Payload Formats", RFC 3555, July 2003.
[7] Casner，S.和P.Hoschka，“RTP有效载荷格式的MIME类型注册”，RFC 3555，2003年7月。
[8] Hellstrom, G. and P. Jones, "RTP Payload for Text Conversation", RFC 4103, June 2005.
[8] Hellstrom，G.和P.Jones，“文本对话的RTP有效载荷”，RFC 4103，2005年6月。
[9] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, "The Secure Real-time Transport Protocol (SRTP)", RFC 3711, March 2004.
[9] Baugher，M.，McGrew，D.，Naslund，M.，Carrara，E.，和K.Norrman，“安全实时传输协议（SRTP）”，RFC 37112004年3月。
Author's Address
作者地址
Paul E. Jones Cisco Systems, Inc. 7025 Kit Creek Rd. Research Triangle Park, NC 27709, USA
Paul E.Jones Cisco Systems，Inc.美国北卡罗来纳州三角研究公园Kit Creek路7025号，邮编27709
Phone: +1 919 392 6948
EMail: paulej@packetizer.com
Phone: +1 919 392 6948
EMail: paulej@packetizer.com
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