Internet Engineering Task Force (IETF) B. Trammell
Request for Comments: 7125 ETH Zurich
Category: Informational P. Aitken
ISSN: 2070-1721 Cisco Systems, Inc
February 2014
Internet Engineering Task Force (IETF) B. Trammell
Request for Comments: 7125 ETH Zurich
Category: Informational P. Aitken
ISSN: 2070-1721 Cisco Systems, Inc
February 2014
Revision of the tcpControlBits IP Flow Information Export (IPFIX) Information Element
tcpControlBits IP流信息导出（IPFIX）信息元素的修订版
Abstract
摘要
This document revises the tcpControlBits IP Flow Information Export (IPFIX) Information Element as originally defined in RFC 5102 to reflect changes to the TCP Flags header field since RFC 793.
本文档修改了最初在RFC 5102中定义的tcpControlBits IP流信息导出（IPFIX）信息元素，以反映自RFC 793以来对TCP标志标头字段的更改。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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。并非IESG批准的所有文件都适用于任何级别的互联网标准；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/rfc7125.
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/rfc7125.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 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。
Octets 12 and 13 (counting from zero) of the TCP header encode the data offset (header length) in 4 bits, as well as 12 bits of flags. The least significant 6 bits of these were defined in [RFC0793] as URG, ACK, PSH, RST, SYN, and FIN for TCP control. Subsequently, [RFC3168] defined the CWR and ECE flags for Explicit Congestion Notification (ECN) negotiation and signaling; [RFC3540] additionally defined the NS flag for the ECN Nonce Sum.
TCP报头的八位字节12和13（从零开始计数）以4位以及12位标志对数据偏移量（报头长度）进行编码。[RFC0793]将其中最低有效位定义为URG、ACK、PSH、RST、SYN和FIN，用于TCP控制。随后，[RFC3168]定义了用于显式拥塞通知（ECN）协商和信令的CWR和ECE标志；[RFC3540]另外定义了ECN Nonce Sum的NS标志。
As defined in the IANA IPFIX Information Element Registry [IANA-IPFIX], taken from [RFC5102], the tcpControlBits Information Element for IPFIX [RFC7011] only covers the original 6 bits from [RFC0793]. To allow IPFIX to be used to measure the use of ECN, and to bring the IPFIX Information Element definition in line with the current definition of the TCP Flags header field, it is necessary to revise this definition.
根据IANA IPFIX信息元素注册表[IANA-IPFIX]中的定义，取自[RFC5102]，IPFIX[RFC7011]的tcpControlBits信息元素仅涵盖[RFC0793]中的原始6位。为了允许IPFIX用于测量ECN的使用情况，并使IPFIX信息元素定义与TCP标志标头字段的当前定义一致，有必要修改此定义。
The revised definition of the Information Element in Section 3 was developed and approved through the IE-DOCTORS process [RFC7013] in August 2013. Section 5.1 of [RFC7013] states "This process should not in any way be construed as allowing the IE-DOCTORS to overrule IETF consensus. Specifically, Information Elements in the IANA Information Element registry that were added with IETF consensus require IETF consensus for revision or deprecation". Since the tcpControlBits Information Element was originally defined in [RFC5102], an IETF Proposed Standard, any revision of this Information Element definition requires IETF Consensus. The publication of this document fulfills that requirement.
2013年8月，通过IE-DOCTORS流程[RFC7013]制定并批准了第3节中信息元素的修订定义。[RFC7013]第5.1节规定，“此过程不应以任何方式解释为允许IE-DOCTORS否决IETF共识。具体而言，IANA信息元素注册表中添加IETF共识的信息元素需要IETF共识进行修订或否决”。由于tcpControlBits信息元素最初是在IETF提议的标准[RFC5102]中定义的，因此对该信息元素定义的任何修订都需要IETF的一致意见。本文件的发布满足该要求。
Section 3 defines the revised tcpControlBits Information Element as in Section 9.1 of [RFC7013].
第3节定义了[RFC7013]第9.1节中修订的tcpControlBits信息元素。
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "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”、“建议”、“不建议”、“可”和“可选”应按照[RFC2119]中的说明进行解释。
ElementId: 6
元素ID:6
Data Type: unsigned16
数据类型：unsigned16
Data Type Semantics: flags
数据类型语义：标志
Description: TCP control bits observed for the packets of this Flow. This information is encoded as a bit field; for each TCP control bit, there is a bit in this set. The bit is set to 1 if any observed packet of this Flow has the corresponding TCP control bit set to 1. The bit is cleared to 0 otherwise.
描述：观察到此流的数据包的TCP控制位。该信息被编码为位字段；对于每个TCP控制位，此集合中都有一个位。如果此流的任何观察数据包的相应TCP控制位设置为1，则该位设置为1。否则该位被清除为0。
The values of each bit are shown below, per the definition of the bits in the TCP header [RFC0793] [RFC3168] [RFC3540]:
根据TCP头[RFC0793][RFC3168][RFC3540]中位的定义，每个位的值如下所示：
MSb LSb
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| | | N | C | E | U | A | P | R | S | F |
| Zero | Future | S | W | C | R | C | S | S | Y | I |
| (Data Offset) | Use | | R | E | G | K | H | T | N | N |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
MSb LSb
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| | | N | C | E | U | A | P | R | S | F |
| Zero | Future | S | W | C | R | C | S | S | Y | I |
| (Data Offset) | Use | | R | E | G | K | H | T | N | N |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
bit flag
value name description
------+-----+-------------------------------------
0x8000 Zero (see tcpHeaderLength)
0x4000 Zero (see tcpHeaderLength)
0x2000 Zero (see tcpHeaderLength)
0x1000 Zero (see tcpHeaderLength)
0x0800 Future Use
0x0400 Future Use
0x0200 Future Use
0x0100 NS ECN Nonce Sum
0x0080 CWR Congestion Window Reduced
0x0040 ECE ECN Echo
0x0020 URG Urgent Pointer field significant
0x0010 ACK Acknowledgment field significant
0x0008 PSH Push Function
0x0004 RST Reset the connection
0x0002 SYN Synchronize sequence numbers
0x0001 FIN No more data from sender
bit flag
value name description
------+-----+-------------------------------------
0x8000 Zero (see tcpHeaderLength)
0x4000 Zero (see tcpHeaderLength)
0x2000 Zero (see tcpHeaderLength)
0x1000 Zero (see tcpHeaderLength)
0x0800 Future Use
0x0400 Future Use
0x0200 Future Use
0x0100 NS ECN Nonce Sum
0x0080 CWR Congestion Window Reduced
0x0040 ECE ECN Echo
0x0020 URG Urgent Pointer field significant
0x0010 ACK Acknowledgment field significant
0x0008 PSH Push Function
0x0004 RST Reset the connection
0x0002 SYN Synchronize sequence numbers
0x0001 FIN No more data from sender
As the most significant 4 bits of octets 12 and 13 (counting from zero) of the TCP header [RFC0793] are used to encode the TCP data offset (header length), the corresponding bits in this Information Element MUST be exported as zero and MUST be ignored by the collector. Use the tcpHeaderLength Information Element to encode this value.
由于TCP报头[RFC0793]的八位字节12和13（从零开始计数）的最高有效4位用于编码TCP数据偏移量（报头长度），因此此信息元素中的相应位必须导出为零，并且收集器必须忽略。使用tcpHeaderLength信息元素对该值进行编码。
Each of the 3 bits (0x800, 0x400, and 0x200), which are reserved for future use in [RFC0793], SHOULD be exported as observed in the TCP headers of the packets of this Flow.
[RFC0793]中保留供将来使用的3位（0x800、0x400和0x200）中的每一位都应按照此流数据包的TCP头中的观察结果导出。
If exported as a single octet with reduced-size encoding, this Information Element covers the low-order octet of this field (i.e, bits 0x80 to 0x01), omitting the ECN Nonce Sum and the three Future Use bits. A collector receiving this Information Element with reduced-size encoding must not assume anything about the content of these four bits.
如果导出为具有缩减编码的单个八位字节，则此信息元素覆盖此字段的低阶八位字节（即，位0x80到0x01），省略ECN Nonce Sum和三个未来使用位。以较小编码接收此信息元素的收集器不得假设这四位的内容。
Exporting Processes exporting this Information Element on behalf of a Metering Process that is not capable of observing any of the ECN Nonce Sum or Future Use bits SHOULD use reduced-size encoding, and only export the least significant 8 bits of this Information Element.
导出进程代表无法观察任何ECN Nonce Sum或Future Use位的计量进程导出此信息元素应使用缩减大小编码，并且仅导出此信息元素的最低有效8位。
Note that previous revisions of this Information Element's definition specified that the CWR and ECE bits must be exported as zero, even if observed. Collectors should therefore not assume that a value of zero for these bits in this Information Element indicates the bits were never set in the observed traffic, especially if these bits are zero in every Flow Record sent by a given exporter.
请注意，此信息元素定义的先前修订版规定，CWR和ECE位必须导出为零，即使遵守。因此，收集器不应假定此信息元素中这些位的值为零表示从未在观察到的流量中设置这些位，尤其是在给定导出器发送的每个流记录中这些位为零的情况下。
Units:
单位：
Range:
范围：
References: [RFC0793] [RFC3168] [RFC3540]
参考文献：[RFC0793][RFC3168][RFC3540]
Revision: 1
修订：1
IANA has updated the definition of the tcpControlBits Information Element in the IANA IPFIX Information Element Registry [IANA-IPFIX] to reflect the changes in Section 3 above, setting the revision to 1 as noted, and the revision date to the date of publication of this document.
IANA已更新了IANA IPFIX信息元素注册表[IANA-IPFIX]中tcpControlBits信息元素的定义，以反映上述第3节中的变更，将修订设置为1，如上所述，修订日期设置为本文件的出版日期。
This document changes the data type (and therefore the native size) of the tcpControlBits Information Element, from unsigned8 (1 octet) to unsigned16 (2 octets). As Exporting and Collecting Processes use the Information Element Length field in Templates, Options Templates, and specifications for reduced-size encoding where appropriate, as opposed to abstract data type sizes, for encoding and decoding Data Records, it is not expected that this will have any impact on buffer sizing during encoding and decoding. Otherwise, note that the security considerations for IPFIX [RFC7011] apply.
本文档将tcpControlBits信息元素的数据类型（以及本机大小）从unsigned8（1个八位字节）更改为unsigned16（2个八位字节）。由于导出和收集过程使用模板、选项模板和规范中的信息元素长度字段进行适当的压缩编码，而不是使用抽象数据类型大小对数据记录进行编码和解码，在编码和解码期间，这不会对缓冲区大小产生任何影响。否则，请注意IPFIX[RFC7011]的安全注意事项适用。
Thanks to Andrew Feren, Lothar Braun, Michael Scharf, and Simon Josefsson for comments on the revised definition. This work is partially supported by the European Commission under grant agreement FP7-ICT-318627 mPlane; this does not imply endorsement by the Commission.
感谢Andrew Feren、Lothar Braun、Michael Scharf和Simon Josefsson对修订定义的评论。根据FP7-ICT-318627 mPlane赠款协议，这项工作得到了欧盟委员会的部分支持；这并不意味着委员会的认可。
[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。
[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。
[RFC3168] Ramakrishnan, K., Floyd, S., and D. Black, "The Addition of Explicit Congestion Notification (ECN) to IP", RFC 3168, September 2001.
[RFC3168]Ramakrishnan，K.，Floyd，S.，和D.Black，“向IP添加显式拥塞通知（ECN）”，RFC 3168，2001年9月。
[RFC3540] Spring, N., Wetherall, D., and D. Ely, "Robust Explicit Congestion Notification (ECN) Signaling with Nonces", RFC 3540, June 2003.
[RFC3540]Spring，N.，Weterral，D.，和D.Ely，“带有nonce的鲁棒显式拥塞通知（ECN）信令”，RFC 35402003年6月。
[RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, September 2013.
[RFC7011]Claise，B.，Trammell，B.，和P.Aitken，“流量信息交换的IP流量信息导出（IPFIX）协议规范”，STD 77，RFC 7011，2013年9月。
[RFC7013] Trammell, B. and B. Claise, "Guidelines for Authors and Reviewers of IP Flow Information Export (IPFIX) Information Elements", BCP 184, RFC 7013, September 2013.
[RFC7013]Trammell，B.和B.Claise，“IP流信息导出（IPFIX）信息元素的作者和评审员指南”，BCP 184，RFC 7013，2013年9月。
[IANA-IPFIX] IANA, "IP Flow Information Export (IPFIX) Entities", <http://www.iana.org/assignments/ipfix>.
[IANA-IPFIX]IANA，“IP流信息导出（IPFIX）实体”<http://www.iana.org/assignments/ipfix>.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J. Meyer, "Information Model for IP Flow Information Export", RFC 5102, January 2008.
[RFC5102]Quitek，J.，Bryant，S.，Claise，B.，Aitken，P.，和J.Meyer，“IP流信息导出的信息模型”，RFC 5102，2008年1月。
Authors' Addresses
作者地址
Brian Trammell Swiss Federal Institute of Technology Zurich Gloriastrasse 35 8092 Zurich Switzerland
Brian Trammell瑞士联邦理工学院苏黎世Gloriastrasse 35 8092瑞士苏黎世
Phone: +41 44 632 70 13
EMail: trammell@tik.ee.ethz.ch
Phone: +41 44 632 70 13
EMail: trammell@tik.ee.ethz.ch
Paul Aitken Cisco Systems, Inc. 96 Commercial Quay Commercial Street, Edinburgh EH6 6LX United Kingdom
Paul Aitken Cisco Systems，Inc.英国爱丁堡商业码头商业街96号EH6 6LX
Phone: +44 131 561 3616
EMail: paitken@cisco.com
Phone: +44 131 561 3616
EMail: paitken@cisco.com