Internet Engineering Task Force (IETF) D. Thaler
Request for Comments: 6034 Microsoft
Category: Standards Track October 2010
ISSN: 2070-1721
Internet Engineering Task Force (IETF) D. Thaler
Request for Comments: 6034 Microsoft
Category: Standards Track October 2010
ISSN: 2070-1721
Unicast-Prefix-Based IPv4 Multicast Addresses
基于单播前缀的IPv4多播地址
Abstract
摘要
This specification defines an extension to the multicast addressing architecture of the IP Version 4 protocol. The extension presented in this document allows for unicast-prefix-based assignment of multicast addresses. By delegating multicast addresses at the same time as unicast prefixes, network operators will be able to identify their multicast addresses without needing to run an inter-domain allocation protocol.
本规范定义了对IP版本4协议的多播寻址体系结构的扩展。本文档中提供的扩展允许基于单播前缀的多播地址分配。通过将多播地址与单播前缀同时委派，网络运营商将能够识别其多播地址，而无需运行域间分配协议。
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/rfc6034.
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/rfc6034.
Copyright Notice
版权公告
Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2010 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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Address Space . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 5
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Address Space . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 5
RFC 3180 [RFC3180] defines an allocation mechanism (called "GLOP") in 233/8 whereby an Autonomous System (AS) number is embedded in the middle 16 bits of an IPv4 multicast address, resulting in 256 multicast addresses per AS. Advantages of this mechanism include the ability to get multicast address space without an inter-domain multicast address allocation protocol, and the ease of determining the AS that was assigned the address for debugging and auditing purposes.
RFC 3180 [RFC3180]定义了233/8中的分配机制（称为“GLOP”），由此自治系统（AS）号被嵌入IPv4多播地址的中间16位，从而导致每个AS的256个组播地址。这种机制的优点包括能够在不使用域间多播地址分配协议的情况下获得多播地址空间，并且易于确定为调试和审核目的分配了地址的AS。
Some disadvantages of GLOP include:
GLOP的一些缺点包括：
o RFC 4893 [RFC4893] expands the size of an AS number to 4 bytes, and GLOP cannot work with 4-byte AS numbers.
o RFC 4893[RFC4893]将AS编号的大小扩展为4字节，而GLOP无法使用4字节AS编号。
o When an AS covers multiple sites or organizations, administration of the multicast address space within an AS must be handled by other mechanisms, such as manual administrative effort or the Multicast Address Dynamic Client Allocation Protocol (MADCAP) [RFC2730].
o 当AS覆盖多个站点或组织时，AS内多播地址空间的管理必须由其他机制处理，例如手动管理工作或多播地址动态客户端分配协议（MADCAP）[RFC2730]。
o During debugging, identifying the AS does not immediately identify the correct organization when an AS covers multiple organizations.
o 在调试期间，当AS覆盖多个组织时，识别AS不会立即识别正确的组织。
o Only 256 addresses are automatically available per AS, and obtaining any more requires administrative effort.
o 每个AS只有256个地址自动可用，获取更多地址需要管理工作。
More recently, a mechanism [RFC3306] has been developed for IPv6 that provides a multicast range to every IPv6 subnet, which is at a much finer granularity than an AS. As a result, the first three disadvantages above are avoided (and the last disadvantage does not apply to IPv6 due to the extended size of the address space).
最近，为IPv6开发了一种机制[RFC3306]，该机制为每个IPv6子网提供多播范围，其粒度比AS细得多。因此，避免了上述前三个缺点（由于地址空间的扩展，最后一个缺点不适用于IPv6）。
Another advantage of providing multicast space to a subnet, rather than just to an entire AS, is that multicast address assignments within the range need only be coordinated within the subnet.
为子网（而不仅仅是整个AS）提供多播空间的另一个优点是，范围内的多播地址分配只需要在子网内协调。
This document specifies a mechanism similar to [RFC3306], whereby a range of global IPv4 multicast address space is provided to each organization that has unicast address space. A resulting advantage over GLOP is that the mechanisms in IPv4 and IPv6 become more similar.
本文件规定了一种类似于[RFC3306]的机制，即向具有单播地址空间的每个组织提供一系列全局IPv4多播地址空间。与GLOP相比，IPv4和IPv6中的机制更加相似，这是一个优势。
This document does not obsolete or update RFC 3180, as the mechanism described in RFC 3180 is still required for organizations with prefix allocations more specific than /24. Organizations using RFC 3180 allocations may continue to do so. In fact, it is conceivable that an organization might use both RFC 3180 allocations and the allocation method described in this document.
由于前缀分配比/24更具体的组织仍然需要RFC 3180中描述的机制，因此本文档不会过时或更新RFC 3180。使用RFC 3180分配的组织可以继续这样做。事实上，可以想象组织可能同时使用RFC 3180分配和本文档中描述的分配方法。
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 [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
A multicast address with the prefix 234/8 indicates that the address is a Unicast-Based Multicast (UBM) address. The remaining 24 bits are used as follows:
前缀为234/8的多播地址表示该地址是基于单播的多播（UBM）地址。剩余的24位按如下方式使用：
Bits: | 0 thru 7 | 8 thru N | N+1 thru 31 |
+-------+--------------------+-----------------------------+
Value: | 234 | Unicast Prefix | Group ID |
+-------+--------------------+-----------------------------+
Bits: | 0 thru 7 | 8 thru N | N+1 thru 31 |
+-------+--------------------+-----------------------------+
Value: | 234 | Unicast Prefix | Group ID |
+-------+--------------------+-----------------------------+
For organizations with a /24 or shorter prefix, the unicast prefix of the organization is appended to the common /8. Any remaining bits may be assigned by any mechanism the organization wishes.
对于前缀为/24或更短的组织，该组织的单播前缀将附加到公共/8。任何剩余位可由组织希望的任何机制分配。
For example, an organization that has a /16 prefix assigned might choose to assign multicast addresses manually from the /24 multicast prefix derived from the above method. Alternatively, the organization might choose to delegate the use of multicast addresses to individual subnets that have a /24 or shorter unicast prefix, or it might choose some other method.
例如，分配了/16前缀的组织可能会选择从上述方法派生的/24多播前缀手动分配多播地址。或者，组织可以选择将多播地址的使用委托给具有/24或更短单播前缀的单个子网，或者选择其他方法。
Organizations with a prefix length longer than 24 do not receive any multicast address space from this mechanism; in such cases, another mechanism must be used.
前缀长度大于24的组织不从该机制接收任何多播地址空间；在这种情况下，必须使用另一种机制。
Compared to GLOP, an AS will receive more address space via this mechanism if it has more than a /16 for unicast space. An AS will receive less address space than it does from GLOP if it has less than a /16.
与GLOP相比，如果AS的单播空间大于a/16，则AS将通过该机制接收更多的地址空间。如果AS少于a/16，则其从GLOP接收的地址空间将小于它从GLOP接收的地址空间。
The organization that is assigned a UBM address can be determined by taking the multicast address, shifting it left by 8 bits, and identifying who has been assigned the address space covering the resulting unicast address.
分配了UBM地址的组织可以通过获取多播地址，将其向左移动8位，并识别谁已被分配了覆盖结果单播地址的地址空间来确定。
The embedded unicast prefix MUST be a global unicast prefix (i.e., no loopback, multicast, link-local, or private-use IP address space). In addition, since global unicast addresses are not permanently assigned, UBM addresses MUST NOT be hard-coded in applications.
嵌入的单播前缀必须是全局单播前缀（即，无环回、多播、链路本地或专用IP地址空间）。此外，由于全局单播地址不是永久分配的，因此在应用程序中不能硬编码UBM地址。
The following are a few examples of the structure of unicast-prefix-based multicast addresses.
以下是基于单播前缀的多播地址结构的几个示例。
o Consider an organization that has been assigned the global unicast address space 192.0.2.0/24. This means that organization can use the global multicast address 234.192.0.2 without coordinating with any other entity. Someone who sees this multicast address and wants to find who is using it can mentally shift the address left by 8 bits to get 192.0.2.0, and can then look up who has been assigned unicast address space that includes that address.
o 考虑已经分配了全局单播地址空间192.0.2.0/24的组织。这意味着组织可以使用全局多播地址234.192.0.2，而无需与任何其他实体协调。看到这个多播地址并想知道谁在使用它的人可以将地址左移8位，得到192.0.2.0，然后可以查找谁被分配了包含该地址的单播地址空间。
o Consider an organization that has been assigned a larger address space, x.y.0.0/16. This organization can use the global multicast address space 234.x.y.0/24 without coordinating with any other entity, and can assign addresses within this space by any mechanism the organization wishes. Someone who sees a multicast address (say) 234.x.y.10 and wants to find who is using it can mentally shift the address left by 8 bits to get x.y.10.0, and can then look up who has been assigned unicast address space that includes that address.
o 考虑一个被分配了更大地址空间X.Y.0.0/16的组织。该组织可以使用全局多播地址空间234.x.y.0/24，而无需与任何其他实体协调，并且可以通过该组织希望的任何机制在该空间内分配地址。看到一个多播地址（比如）234.x.y.10并想知道是谁在使用它的人可以在心里将地址左移8位以得到x.y.10.0，然后可以查找谁被分配了包含该地址的单播地址空间。
The same well-known intra-domain security techniques can be applied as with GLOP. Furthermore, when dynamic allocation is used within a prefix, the approach described here may have the effect of reduced exposure to denial-of-service attacks, since the topological area within which nodes compete for addresses within the same prefix is reduced from an entire AS to only within an individual organization or an even smaller area.
与GLOP一样，可以应用相同的众所周知的域内安全技术。此外，当在前缀内使用动态分配时，这里描述的方法可能具有减少拒绝服务攻击的暴露的效果，因为节点在同一前缀内竞争地址的拓扑区域从整体减少到仅在单个组织或更小的区域内。
IANA has assigned a /8 in the global IPv4 multicast address space for this purpose.
IANA已为此在全局IPv4多播地址空间中分配了a/8。
This document was updated based on feedback from the MBoneD working group. In particular, Tim Chown, Toerless Eckert, Prashant Jhingran, Peter Koch, John Linn, Dave Meyer, Pekka Savola, Greg Shepherd, and Stig Venaas provided valuable suggestions on the text.
本文件根据MBoneD工作组的反馈进行了更新。特别是，Tim Chown、Toerless Eckert、Prashant Jhingran、Peter Koch、John Linn、Dave Meyer、Pekka Savola、Greg Shepherd和Stig Venaas就文本提供了宝贵的建议。
[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。
[RFC2730] Hanna, S., Patel, B., and M. Shah, "Multicast Address Dynamic Client Allocation Protocol (MADCAP)", RFC 2730, December 1999.
[RFC2730]Hanna，S.，Patel，B.，和M.Shah，“多播地址动态客户端分配协议（MADCAP）”，RFC2730，1999年12月。
[RFC3180] Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8", BCP 53, RFC 3180, September 2001.
[RFC3180]Meyer，D.和P.Lothberg，“233/8中的GLOP寻址”，BCP 53，RFC 31802001年9月。
[RFC3306] Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 Multicast Addresses", RFC 3306, August 2002.
[RFC3306]Haberman，B.和D.Thaler，“基于单播前缀的IPv6多播地址”，RFC3306，2002年8月。
[RFC4893] Vohra, Q. and E. Chen, "BGP Support for Four-octet AS Number Space", RFC 4893, May 2007.
[RFC4893]Vohra，Q.和E.Chen，“BGP支持四个八位组作为数字空间”，RFC 4893，2007年5月。
Author's Address
作者地址
Dave Thaler Microsoft Corporation One Microsoft Way Redmond, WA 98052 USA
Dave Thaler微软公司美国华盛顿州雷德蒙微软大道一号，邮编：98052
Phone: +1 425 703 8835
EMail: dthaler@microsoft.com
Phone: +1 425 703 8835
EMail: dthaler@microsoft.com