Internet Engineering Task Force (IETF)                      G. Salgueiro
Request for Comments: 6466                                 Cisco Systems
Category: Standards Track                                  December 2011
ISSN: 2070-1721
        
Internet Engineering Task Force (IETF)                      G. Salgueiro
Request for Comments: 6466                                 Cisco Systems
Category: Standards Track                                  December 2011
ISSN: 2070-1721

IANA Registration of the 'image' Media Type for the Session Description Protocol (SDP)

IANA会话描述协议（SDP）的“映像”媒体类型注册

Abstract

摘要

This document describes the usage of the 'image' media type and registers it with IANA as a top-level media type for the Session Description Protocol (SDP). This media type is primarily used by SDP to negotiate and establish T.38 media streams.

本文档描述了“图像”媒体类型的使用，并将其作为会话描述协议（SDP）的顶级媒体类型在IANA中注册。此媒体类型主要由SDP用于协商和建立T.38媒体流。

Status of This Memo

关于下段备忘

This is an Internet Standards Track document.

这是一份互联网标准跟踪文件。

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 5741.

本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。

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/rfc6466.

有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc6466.

Copyright Notice

版权公告

Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

版权所有（c）2011 IETF信托基金和确定为文件作者的人员。版权所有。

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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。

Table of Contents

目录 

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
        
   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
1. Overview
1. 概述

In an earlier version of the SDP specification [RFC2327] of packetized media types, such as those used with the Real-time Transport Protocol (RTP) [RFC3550], share the namespace with Multipurpose Internet Mail Extensions (MIME) media types registry [RFC4288] [RFC4289] (i.e., "MIME media types"). This is in contrast to the latest version of the SDP specification [RFC4566], which requested that an SDP-specific media type registry be created and maintained by IANA. The top-level SDP media content types registered by RFC 4566 [RFC4566] are 'audio', 'video', 'text', 'application', and 'message'. A glaring omission from this list is the 'image' media type.

在SDP规范[RFC2327]的早期版本中，已打包的媒体类型，例如与实时传输协议（RTP）[RFC3550]一起使用的媒体类型，与多用途Internet邮件扩展（MIME）媒体类型注册表[RFC4288][RFC4289]（即“MIME媒体类型”）共享名称空间。这与最新版本的SDP规范[RFC4566]不同，后者要求IANA创建和维护SDP特定的介质类型注册表。RFC 4566[RFC4566]注册的顶级SDP媒体内容类型为“音频”、“视频”、“文本”、“应用程序”和“消息”。此列表中一个明显的遗漏是“图像”媒体类型。

The 'image' media type is an existing top-level MIME media type and is widely used in SDP implementations for setting up T.38 Real-Time Facsimile [T38] media streams. This media type is extensively referenced by examples in ITU-T T.38 [T38] and IETF Standards Track documents like RFC 4145 [RFC4145]. The following example shows the media description of a T.38 media stream as commonly found in a Session Initiation Protocol (SIP) [RFC3261] INVITE; it contains an SDP offer for T.38 over both UDP Transport Layer (UDPTL) and TCP. For the sake of brevity, only the SDP body of the SIP INVITE request is displayed in this example.

“图像”媒体类型是现有的顶级MIME媒体类型，在SDP实现中广泛用于设置T.38实时传真[T38]媒体流。ITU-T T.38[T38]和IETF标准跟踪文件（如RFC 4145[RFC4145]）中的示例广泛引用了这种媒体类型。以下示例显示了会话发起协议（SIP）[rfc326]INVITE中常见的T.38媒体流的媒体描述；它包含通过UDP传输层（UDPTL）和TCP为T.38提供的SDP。为简洁起见，本例中仅显示SIP INVITE请求的SDP主体。 

       v=0
       o=alice 53655765 2353687637 IN IP4 pc33.example.com
       s=SDP image example
       c=IN IP4 192.0.2.2
       t=0 0
       m=image 49170 udptl t38
       a=T38FaxVersion:0
       a=T38MaxBitRate:14400
       a=T38FaxRateManagement:transferredTCF
       a=T38FaxMaxBuffer:262
       a=T38FaxMaxDatagram:90
       a=T38FaxUdpEC:t38UDPRedundancy
       a=sendrecv
       m=image 49172 tcp t38
       a=T38FaxRateManagement:localTCF
        
       v=0
       o=alice 53655765 2353687637 IN IP4 pc33.example.com
       s=SDP image example
       c=IN IP4 192.0.2.2
       t=0 0
       m=image 49170 udptl t38
       a=T38FaxVersion:0
       a=T38MaxBitRate:14400
       a=T38FaxRateManagement:transferredTCF
       a=T38FaxMaxBuffer:262
       a=T38FaxMaxDatagram:90
       a=T38FaxUdpEC:t38UDPRedundancy
       a=sendrecv
       m=image 49172 tcp t38
       a=T38FaxRateManagement:localTCF

The purpose of this document is to register with IANA the 'image' media type as a top-level SDP media type. This ensures seamless continuity with documentation that uses the 'image' MIME media type and the previously registered MIME media sub-types like 'image/t38' [RFC3362] that are used as SDP media descriptors for T.38 [T38].

本文档的目的是向IANA注册“图像”媒体类型作为顶级SDP媒体类型。这确保了与使用“图像”MIME媒体类型和以前注册的MIME媒体子类型（如“图像/t38”[RFC3362]）的文档的无缝连续性，这些子类型用作T.38[t38]的SDP媒体描述符。

This document complies with the request of Section 8.2.1 of RFC 4566 [RFC4566] that indicates:

本文件符合RFC 4566[RFC4566]第8.2.1节的要求，其中指出：

The same rules should apply for media names as for top-level media content types, and where possible the same name should be registered for SDP as for MIME. For media other than existing top-level media content types, a Standards Track RFC MUST be produced for a new top-level content type to be registered, and the registration MUST provide good justification why no existing media name is appropriate.

媒体名称的规则应与顶级媒体内容类型的规则相同，并且在可能的情况下，SDP应注册与MIME相同的名称。对于现有顶级媒体内容类型以外的媒体，必须为要注册的新顶级内容类型生成标准曲目RFC，并且注册必须提供现有媒体名称不合适的充分理由。

2. Conventions Used in This Document
2. 本文件中使用的公约

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 [RFC2119].

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[RFC2119]中所述进行解释。

3. IANA Considerations
3. IANA考虑

IANA has registered an 'image' token in the media sub-registry of the Session Description Protocols (SDP) Parameters registry. This registration contains the required information elements outlined in the SDP registration procedure defined in Section 8.2.8 of RFC 4566 [RFC4566].

IANA已在会话描述协议（SDP）参数注册表的媒体子注册表中注册了“映像”令牌。该注册包含RFC 4566[RFC4566]第8.2.8节中定义的SDP注册程序中概述的所需信息元素。

(1) Contact Information:

(1) 联系方式：

Name: Gonzalo Salgueiro Email: gsalguei@cisco.com Telephone Number: (919) 392-3266

姓名：Gonzalo Salgueiro电子邮件：gsalguei@cisco.com电话号码：（919）392-3266

(2) Name being registered (as it will appear in SDP): image

(2) 正在注册的名称（将显示在SDP中）：图像

(3) Long-form name in English: image

(3) 英文长格式名称：image

(4) Type of name ('media', 'proto', 'fmt', 'bwtype', 'nettype', or 'addrtype'): media

(4) 名称类型（'media'、'proto'、'fmt'、'bwtype'、'nettype'或'addrtype'）：media

(5) Purpose of the registered name:

(5) 注册名称的目的：

The 'image' media type for the Session Description Protocol is used to describe a media stream whose content consists of one or more separate images that require appropriate hardware to display. The media subtype further describes the specific format of the image. Currently, the 'image' media type for SDP is used ubiquitously by the SIP control protocol to establish T.38 media streams.

会话描述协议的“图像”媒体类型用于描述其内容由一个或多个单独的图像组成的媒体流，这些图像需要适当的硬件来显示。媒体子类型进一步描述图像的特定格式。目前，SIP控制协议普遍使用SDP的“映像”媒体类型来建立T.38媒体流。

(6) Specification for the registered name: RFC 6466

(6) 注册名称规范：RFC 6466

4. Security Considerations
4. 安全考虑

The 'image' media type registered by this document in the SDP parameters registry maintained by IANA is primarily for use by the offer/answer model of the Session Description Protocol [RFC3264] for the negotiation and establishment of T.38 [T38] media streams using SIP [RFC3261]. This additional SDP media type does not introduce any security considerations beyond those detailed in Section 7 of RFC 4566 [RFC4566].

本文档在IANA维护的SDP参数注册表中注册的“图像”媒体类型主要用于会话描述协议[RFC3264]的提供/应答模型，用于使用SIP[RFC3261]协商和建立T.38[T38]媒体流。除了RFC 4566[RFC4566]第7节中详述的安全注意事项外，此附加SDP介质类型不会引入任何安全注意事项。

The security vulnerabilities in T.38 [T38] and its associated transport protocols (TCP [RFC0793], UDP [RFC0768], and RTP [RFC3550]) are well documented in each of their respective specifications. The ability to exchange images other than T.38 can expose the recipient to potentially malicious executable code.

T.38[T38]及其相关传输协议（TCP[RFC0793]、UDP[RFC0768]和RTP[RFC3550]）中的安全漏洞在各自的规范中均有详细记录。交换T.38以外的图像的能力会使收件人暴露于潜在的恶意可执行代码中。

5. Acknowledgements
5. 致谢

Thanks go to the chairs of the IETF Multiparty Multimedia Session Control (MMUSIC) working group (Miguel A. Garcia and Flemming Andreasen) for their guidance, encouragement, and the creation of the

感谢IETF多方多媒体会话控制（MMUSIC）工作组主席（Miguel A.Garcia和Flemming Andreasen）的指导、鼓励和创建

media type registry. Special thanks to Miguel A. Garcia for his thorough and insightful review of the many draft revisions of this document.

媒体类型注册表。特别感谢Miguel A.Garcia对本文件的许多修订草案进行了透彻和深入的审查。

This document has benefited from the discussion and review of the MMUSIC working group, especially the detailed and thoughtful comments and corrections of Keith Drage, Yasubumi Chimura, Kevin P. Fleming, Bert Greevenbosch, and Gonzalo Camarillo.

本文件得益于MMUSIC工作组的讨论和审查，特别是Keith Drage、Yasubumi Chimura、Kevin P.Fleming、Bert Greevenbosch和Gonzalo Camarillo的详细和深思熟虑的评论和更正。

The author would also like to acknowledge the considerable efforts of Kevin P. Fleming and the members of the Fax-over-IP (FoIP) TG in the SIP Forum that contributed to the new revision of the ITU-T T.38 Recommendation that prompted the need to register the 'image' media type for SDP.

作者还想感谢Kevin P.Fleming和IP传真（FoIP）TG成员在SIP论坛上做出的巨大努力，这些努力促成了ITU-T T.38建议的新修订，促使需要为SDP注册“图像”媒体类型。

6. References
6. 工具书类
6.1. Normative References
6.1. 规范性引用文件

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。

[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006.

[RFC4566]Handley，M.，Jacobson，V.，和C.Perkins，“SDP：会话描述协议”，RFC4566，2006年7月。

6.2. Informative References
6.2. 资料性引用

[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980.

[RFC0768]Postel，J.，“用户数据报协议”，STD 6，RFC 768，1980年8月。

[RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981.

[RFC0793]Postel，J.，“传输控制协议”，标准7，RFC 793，1981年9月。

[RFC2327] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998.

[RFC2327]Handley，M.和V.Jacobson，“SDP：会话描述协议”，RFC 2327，1998年4月。

[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002.

[RFC3261]Rosenberg，J.，Schulzrinne，H.，Camarillo，G.，Johnston，A.，Peterson，J.，Sparks，R.，Handley，M.，和E.Schooler，“SIP：会话启动协议”，RFC 3261，2002年6月。

[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with Session Description Protocol (SDP)", RFC 3264, June 2002.

[RFC3264]Rosenberg，J.和H.Schulzrinne，“具有会话描述协议（SDP）的提供/应答模型”，RFC 3264，2002年6月。

[RFC3362] Parsons, G., "Real-time Facsimile (T.38) - image/t38 MIME Sub-type Registration", RFC 3362, August 2002.

[RFC3362]Parsons，G.，“实时传真（T.38）-图像/t38 MIME子类型注册”，RFC 3362，2002年8月。

[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003.

[RFC3550]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。

[RFC4145] Yon, D. and G. Camarillo, "TCP-Based Media Transport in the Session Description Protocol (SDP)", RFC 4145, September 2005.

[RFC4145]Yon，D.和G.Camarillo，“会话描述协议（SDP）中基于TCP的媒体传输”，RFC 41452005年9月。

[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and Registration Procedures", BCP 13, RFC 4288, December 2005.

[RFC4288]Freed，N.和J.Klensin，“介质类型规范和注册程序”，BCP 13，RFC 4288，2005年12月。

[RFC4289] Freed, N. and J. Klensin, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 4289, December 2005.

[RFC4289]Freed，N.和J.Klensin，“多用途互联网邮件扩展（MIME）第四部分：注册程序”，BCP 13，RFC 4289，2005年12月。

[T38] International Telecommunication Union, "Procedures for real-time Group 3 facsimile communication over IP Networks", ITU-T Recommendation T.38 (Pre-Published), September 2010, <http://www.itu.int/rec/T-REC-T.38-201009-P/en>.

[T38]国际电信联盟，“IP网络实时第3组传真通信程序”，ITU-T建议T.38（预发布），2010年9月<http://www.itu.int/rec/T-REC-T.38-201009-P/en>.

Author's Address

作者地址

Gonzalo Salgueiro Cisco Systems 7200-12 Kit Creek Road Research Triangle Park, NC 27709 US

Gonzalo Salgueiro思科系统7200-12美国北卡罗来纳州Kit Creek Road研究三角公园，邮编27709 

   EMail: gsalguei@cisco.com
        
   EMail: gsalguei@cisco.com