Network Working Group                                        C. Smith
Request for Comments: 2937                     Sun Microsystems, Inc.
Category: Standards Track                              September 2000
        
Network Working Group                                        C. Smith
Request for Comments: 2937                     Sun Microsystems, Inc.
Category: Standards Track                              September 2000

The Name Service Search Option for DHCP

DHCP的名称服务搜索选项

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 (2000). All Rights Reserved.

版权所有（C）互联网协会（2000年）。版权所有。

Abstract

摘要

This document defines a new Dynamic Host Configuration Protocol (DHCP) option which is passed from the DHCP Server to the DHCP Client to specify the order in which name services should be consulted when resolving hostnames and other information.

本文档定义了一个新的动态主机配置协议（DHCP）选项，该选项从DHCP服务器传递到DHCP客户端，以指定解析主机名和其他信息时应参考名称服务的顺序。

Introduction

介绍

The Dynamic Host Configuration Protocol (DHCP)[1] provides a framework for passing configuration information to hosts on a TCP/IP network. RFC 2132 [2] allows DHCP servers to specify configuration information for various kinds of name services to be passed to DHCP clients. Many clients use multiple name services and have crafted their own conventions that allow an individual host to express the order among the various name services with which lookups are done. However, no search order can be specified via DHCP. The purpose of this document is to allow DHCP servers to specify the search order to be used by DHCP clients. To avoid the need for inventing and maintaining a separate name space for this option, we rely on the existence of previously-defined DHCP options that specify the IP address(es) of servers which provide name services whose order we wish to express.

动态主机配置协议（DHCP）[1]提供了一个框架，用于将配置信息传递给TCP/IP网络上的主机。RFC 2132[2]允许DHCP服务器为要传递给DHCP客户端的各种名称服务指定配置信息。许多客户机使用多个名称服务，并制定了自己的约定，允许单个主机在各种名称服务中表示查找顺序。但是，无法通过DHCP指定搜索顺序。本文档的目的是允许DHCP服务器指定DHCP客户端使用的搜索顺序。为了避免为该选项创建和维护单独的名称空间，我们依赖于先前定义的DHCP选项的存在，这些选项指定了提供名称服务的服务器的IP地址，我们希望表示这些名称服务的顺序。

Definitions

定义

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]. This document also uses the following terms:

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。本文件还使用以下术语：

"DHCP client"

“DHCP客户端”

DHCP client or "client" is an Internet host using DHCP to obtain configuration parameters such as a network address.

DHCP客户端或“客户端”是使用DHCP获取配置参数（如网络地址）的Internet主机。

"DHCP server"

“DHCP服务器”

A DHCP server or "server" is an Internet host that returns configuration parameters to DHCP clients.

DHCP服务器或“服务器”是向DHCP客户端返回配置参数的Internet主机。

Name Service Search Option Format

名称服务搜索选项格式

The code for this option is 117, and its minimum length is 2 bytes. A DHCP server SHOULD return, in its preferred order, the 16-bit, network byte order (big-endian [4]) integer option code for the name services (the earlier in the list, the more preferred the name service).

此选项的代码为117，最小长度为2字节。DHCP服务器应以其首选顺序返回名称服务的16位网络字节顺序（big-endian[4]）整数选项代码（列表中越早，名称服务越首选）。 

       Code            Length      Name Service Search Order in Sequence
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     117       |     Len       |             ns1               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ns2               |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        
       Code            Length      Name Service Search Order in Sequence
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |     117       |     Len       |             ns1               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  |             ns2               |             ...               |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

In the above diagram, ns1 and ns2 are 16-bit integers corresponding to two DHCP options which specify the IP addresses of two different types of name server. The current list of name services and their DHCP option codes, taken from RFC 2132, includes

在上图中，ns1和ns2是对应于两个DHCP选项的16位整数，这两个选项指定两种不同类型名称服务器的IP地址。名称服务及其DHCP选项代码的当前列表取自RFC 2132，包括

Name Service Value

名称服务值

Domain Name Server Option 6 Network Information Servers Option 41 NetBIOS over TCP/IP Name Server Option 44 Network Information Service+ Servers Option 65

域名服务器选项6网络信息服务器选项41 TCP/IP上的NetBIOS名称服务器选项44网络信息服务+服务器选项65

A name service option code of 0 is used to indicate that the client should refer to local naming information (e.g., an /etc/hosts file on a UNIX machine).

名称服务选项代码0用于指示客户端应引用本地命名信息（例如UNIX计算机上的/etc/hosts文件）。

A DHCP server wishing to express that a client should first search DNS, then NIS+, would send

如果DHCP服务器希望表示客户端首先搜索DNS，然后搜索NIS+，则会发送 

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     117       |      4        |              6                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              65               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     117       |      4        |              6                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |              65               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

DHCP Client Behavior

DHCP客户端行为

The DHCP client will use this option to create a search list for name resolution. The client may receive name services in this option that it does not support or has not been configured to access. Likewise, a client may receive an option that lists name services for which no corresponding DHCP option was supplied. Clients will interpret this option in a system-specific manner whose specification is outside the scope of this document.

DHCP客户端将使用此选项创建名称解析的搜索列表。客户端可能会在此选项中接收其不支持或未配置为访问的名称服务。同样，客户机可能会收到一个选项，其中列出了没有提供相应DHCP选项的名称服务。客户将以特定于系统的方式解释此选项，其规范不在本文件范围内。

Security Considerations

安全考虑

DHCP currently provides no authentication or security mechanisms. Potential exposures to attack are discussed in section 7 of the DHCP protocol specification [1].

DHCP目前不提供身份验证或安全机制。DHCP协议规范[1]第7节讨论了潜在的攻击风险。

IANA Considerations

IANA考虑

IANA has assigned a value of 117 for the DHCP option code described in this document.

IANA已为本文档中描述的DHCP选项代码分配了117的值。

References

工具书类

[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.

[1] Droms，R.，“动态主机配置协议”，RFC 2131，1997年3月。

[2] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997.

[2] Alexander，S.和R.Droms，“DHCP选项和BOOTP供应商扩展”，RFC 21321997年3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] Cohen, D., "On Holy Wars and a Plea for Peace", Computer, IEEE, October 1981.

[4] Cohen，D.，“关于圣战与和平的呼吁”，计算机，IEEE，1981年10月。

Author's Address

作者地址

Carl Smith Sun Microsystems, Inc. 901 San Antonio Road Palo Alto, CA 94043

卡尔·史密斯太阳微系统公司，加利福尼亚州帕洛阿尔托市圣安东尼奥路901号，邮编94043 

   EMail:  cs@Eng.Sun.COM
        
   EMail:  cs@Eng.Sun.COM

Full Copyright Statement

完整版权声明

Copyright (C) The Internet Society (2000). All Rights Reserved.

版权所有（C）互联网协会（2000年）。版权所有。

This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.

本文件及其译本可复制并提供给他人，对其进行评论或解释或协助其实施的衍生作品可全部或部分编制、复制、出版和分发，不受任何限制，前提是上述版权声明和本段包含在所有此类副本和衍生作品中。但是，不得以任何方式修改本文件本身，例如删除版权通知或对互联网协会或其他互联网组织的引用，除非出于制定互联网标准的需要，在这种情况下，必须遵循互联网标准过程中定义的版权程序，或根据需要将其翻译成英语以外的其他语言。

The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.

上述授予的有限许可是永久性的，互联网协会或其继承人或受让人不会撤销。

This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

本文件和其中包含的信息是按“原样”提供的，互联网协会和互联网工程任务组否认所有明示或暗示的保证，包括但不限于任何保证，即使用本文中的信息不会侵犯任何权利，或对适销性或特定用途适用性的任何默示保证。

Acknowledgement

确认

Funding for the RFC Editor function is currently provided by the Internet Society.

RFC编辑功能的资金目前由互联网协会提供。