Network Working Group G. Camarillo
Request for Comments: 3524 A. Monrad
Category: Standards Track Ericsson
April 2003
Network Working Group G. Camarillo
Request for Comments: 3524 A. Monrad
Category: Standards Track Ericsson
April 2003
Mapping of Media Streams to Resource Reservation Flows
媒体流到资源预留流的映射
Status of this Memo
本备忘录的状况
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 (2003). All Rights Reserved.
版权所有（C）互联网协会（2003年）。版权所有。
Abstract
摘要
This document defines an extension to the Session Description Protocol (SDP) grouping framework. It allows requesting a group of media streams to be mapped into a single resource reservation flow. The SDP syntax needed is defined, as well as a new "semantics" attribute called Single Reservation Flow (SRF).
本文档定义了会话描述协议（SDP）分组框架的扩展。它允许请求将一组媒体流映射到单个资源保留流中。定义了所需的SDP语法，以及一个称为单保留流（SRF）的新“语义”属性。
Table of Contents
目录
1. Introduction ........................................ 2
1.1 Terminology .................................... 2
2. SRF Semantics ....................................... 2
3. Applicability Statement ............................. 3
4. Examples ............................................ 3
5. IANA Considerations ................................. 4
6. Security Considerations ............................. 4
7. Acknowledgements .................................... 4
8. Normative References ................................ 5
9. Informative References .............................. 5
10. Authors' Addresses .................................. 5
11. Full Copyright Statement ............................ 6
1. Introduction ........................................ 2
1.1 Terminology .................................... 2
2. SRF Semantics ....................................... 2
3. Applicability Statement ............................. 3
4. Examples ............................................ 3
5. IANA Considerations ................................. 4
6. Security Considerations ............................. 4
7. Acknowledgements .................................... 4
8. Normative References ................................ 5
9. Informative References .............................. 5
10. Authors' Addresses .................................. 5
11. Full Copyright Statement ............................ 6
Resource reservation protocols assign network resources to particular flows of IP packets. When a router receives an IP packet, it applies a filter in order to map the packet to the flow it belongs. The router provides the IP packet with the Quality of Service (QoS) corresponding to its flow. Routers typically use the source and the destination IP addresses and port numbers to filter packets.
资源预留协议将网络资源分配给特定的IP数据包流。当路由器接收到一个IP数据包时，它会应用一个过滤器，以便将该数据包映射到它所属的流。路由器为IP数据包提供与其流相对应的服务质量（QoS）。路由器通常使用源和目标IP地址和端口号来过滤数据包。
Multimedia sessions typically contain multiple media streams (e.g. an audio stream and a video stream). In order to provide QoS for a multimedia session it is necessary to map all the media streams to resource reservation flows. This mapping can be performed in different ways. Two possible ways are to map all the media streams to a single resource reservation flow or to map every single media stream to a different resource reservation flow. Some applications require that the former type of mapping is performed while other applications require the latter. It is even possible that a mixture of both mappings is required for a particular media session. For instance, a multimedia session with three media streams might require that two of them are mapped into a single reservation flow while the third media stream uses a second reservation flow.
多媒体会话通常包含多个媒体流（例如音频流和视频流）。为了为多媒体会话提供QoS，有必要将所有媒体流映射到资源预留流。此映射可以以不同的方式执行。两种可能的方法是将所有媒体流映射到单个资源保留流，或者将每个媒体流映射到不同的资源保留流。某些应用程序要求执行前一种类型的映射，而其他应用程序则要求执行后一种类型的映射。对于特定的媒体会话，甚至可能需要两种映射的混合。例如，具有三个媒体流的多媒体会话可能需要将其中两个映射到单个保留流，而第三个媒体流使用第二个保留流。
This document defines the SDP [1] syntax needed to express how media streams need to be mapped into reservation flows. For this purpose, we use the SDP grouping framework [2] and define a new "semantics" attribute called Single Reservation Flow (SRF).
本文档定义了SDP[1]语法，用于表示媒体流需要如何映射到保留流。为此，我们使用SDP分组框架[2]，并定义一个新的“语义”属性，称为单保留流（SRF）。
In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [3] and indicate requirement levels for compliant SIP implementations.
在本文件中，关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照BCP 14、RFC 2119[3]中的描述进行解释，并表示符合SIP实施的要求级别。
We define a new "semantics" attribute within the SDP grouping framework [2]: Single Reservation Flow (SRF).
我们在SDP分组框架[2]中定义了一个新的“语义”属性：单保留流（SRF）。
Media lines grouped using SRF semantics SHOULD be mapped into the same resource reservation flow. Media lines that do not belong to a particular SRF group SHOULD NOT be mapped into the reservation flow used for that SRF group.
使用SRF语义分组的媒体行应映射到相同的资源保留流中。不属于特定SRF组的媒体行不应映射到用于该SRF组的保留流中。
Note that an SRF group MAY consist of a single media line. In that case, following the definition above, that media line will be mapped into one reservation flow. That reservation flow will carry traffic from that media line, and from no other media lines.
请注意，SRF组可能由单个媒体线路组成。在这种情况下，按照上面的定义，该媒体行将映射到一个预订流中。该预订流将承载来自该媒体线路的流量，而不会承载来自其他媒体线路的流量。
The way resource reservation works in some scenarios makes it unnecessary to use the mechanism described in this document. Some resource reservation protocols allow the entity generating the SDP session description to allocate resources in both directions (i.e., sendrecv) for the session. In this case, the generator of the session description can chose any particular mapping of media flows and reservation flows.
资源保留在某些场景中的工作方式使得不必使用本文档中描述的机制。某些资源保留协议允许生成SDP会话描述的实体在会话的两个方向（即sendrecv）分配资源。在这种情况下，会话描述的生成器可以选择媒体流和保留流的任何特定映射。
The mechanism described in this document is useful when the remote party needs to be involved in the resource reservation.
当远程方需要参与资源保留时，本文档中描述的机制非常有用。
For this example, we have chosen to use SIP [4] to transport SDP sessions and RSVP [5] to establish reservation flows. However, other protocols or mechanisms could be used instead without affecting the SDP syntax.
对于本例，我们选择使用SIP[4]传输SDP会话，使用RSVP[5]建立预约流。但是，可以使用其他协议或机制，而不影响SDP语法。
A user agent receives a SIP INVITE with the SDP below:
用户代理通过以下SDP接收SIP邀请：
v=0
o=Laura 289083124 289083124 IN IP4 one.example.com
t=0 0
c=IN IP4 192.0.0.1
a=group:SRF 1 2
m=audio 30000 RTP/AVP 0
a=mid:1
m=video 30002 RTP/AVP 31
a=mid:2
v=0
o=Laura 289083124 289083124 IN IP4 one.example.com
t=0 0
c=IN IP4 192.0.0.1
a=group:SRF 1 2
m=audio 30000 RTP/AVP 0
a=mid:1
m=video 30002 RTP/AVP 31
a=mid:2
This user agent uses RSVP to perform resource reservation. Since both media streams are part of an SRF group, the user agent will establish a single RSVP session. An RSVP session is defined by the triple: (DestAddress, ProtocolId[, DstPort]). Table 1 shows the parameters used to establish the RSVP session.
此用户代理使用RSVP执行资源保留。由于两个媒体流都是SRF组的一部分，因此用户代理将建立单个RSVP会话。RSVP会话由三元组定义：（DestAddress，ProtocolId[，DstPort]）。表1显示了用于建立RSVP会话的参数。
If the same user agent received an SDP session description with the same media streams but without the group line, it would be free to map the two media streams into two different RSVP sessions.
如果同一用户代理接收到具有相同媒体流但没有组行的SDP会话描述，则可以将两个媒体流映射到两个不同的RSVP会话中。
Session Number DestAddress ProtocolId DstPort
________________________________________________
1 192.0.0.1 UDP any
Session Number DestAddress ProtocolId DstPort
________________________________________________
1 192.0.0.1 UDP any
Table 1: Parameters needed to establish the RSVP session
表1：建立RSVP会话所需的参数
IANA has registered the following new "semantics" attribute for the SDP grouping framework [2]. It has been registered in the SDP parameters registry (http://www.iana.org/assignments/sdp-parameters) under Semantics for the "group" SDP Attribute:
IANA已经为SDP分组框架注册了以下新的“语义”属性[2]。它已在SDP参数注册表中注册(http://www.iana.org/assignments/sdp-parameters)在“group”SDP属性的语义下：
Semantics Token Reference
------------------- ----- ---------
Single Reservation flow SRF [RFC3524]
Semantics Token Reference
------------------- ----- ---------
Single Reservation flow SRF [RFC3524]
An attacker adding group lines using the SRF semantics to an SDP session description could force a user agent to establish a larger or a smaller number of resource reservation flows than needed. This could consume extra resources in the end-point or degrade the quality of service for a particular session. It is thus STRONGLY RECOMMENDED that integrity protection be applied to the SDP session descriptions. For session descriptions carried in SIP, S/MIME is the natural choice to provide such end-to-end integrity protection, as described in RFC 3261 [4]. Other applications MAY use a different form of integrity protection.
攻击者将使用SRF语义的组行添加到SDP会话描述中，可能会迫使用户代理建立比所需数量更多或更少的资源保留流。这可能会消耗端点中的额外资源，或降低特定会话的服务质量。因此，强烈建议对SDP会话描述应用完整性保护。对于SIP中的会话描述，S/MIME是提供端到端完整性保护的自然选择，如RFC 3261[4]所述。其他应用程序可能使用不同形式的完整性保护。
Jonathan Rosenberg provided useful comments about the applicability of the mechanism described in this document.
Jonathan Rosenberg就本文件所述机制的适用性提供了有用的意见。
[1] Handley, M. and V. Jacobson, "SDP: Session Description Protocol", RFC 2327, April 1998.
[1] Handley，M.和V.Jacobson，“SDP：会话描述协议”，RFC 2327，1998年4月。
[2] Camarillo, G., Eriksson, G., Holler, J. and H. Schulzrinne, "Grouping of Media Lines in the Session Description Protocol (SDP)", December 2002.
[2] Camarillo，G.，Eriksson，G.，Holler，J.和H.Schulzrinne，“会话描述协议（SDP）中媒体线路的分组”，2002年12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] 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.
[4] 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。
[5] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin, "Resource ReSerVation protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997.
[5] Braden，R.，Zhang，L.，Berson，S.，Herzog，S.和S.Jamin，“资源预留协议（RSVP）——第1版功能规范”，RFC 22052997年9月。
Gonzalo Camarillo Ericsson Advanced Signalling Research Lab. FIN-02420 Jorvas Finland
Gonzalo Camarillo Ericsson高级信号研究实验室FIN-02420 Jorvas芬兰
EMail: Gonzalo.Camarillo@ericsson.com
EMail: Gonzalo.Camarillo@ericsson.com
Atle Monrad Ericsson N-4898 Grimstad Norway
挪威格里姆施塔德大西洋蒙拉德爱立信N-4898
EMail: atle.monrad@ericsson.com
EMail: atle.monrad@ericsson.com
Copyright (C) The Internet Society (2003). All Rights Reserved.
版权所有（C）互联网协会（2003年）。版权所有。
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Acknowledgement
确认
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