Network Working Group H. Schulzrinne
Request for Comments: 3319 Columbia University
Category: Standards Track B. Volz
Ericsson
July 2003
Network Working Group H. Schulzrinne
Request for Comments: 3319 Columbia University
Category: Standards Track B. Volz
Ericsson
July 2003
Dynamic Host Configuration Protocol (DHCPv6) Options for Session Initiation Protocol (SIP) Servers
会话启动协议（SIP）服务器的动态主机配置协议（DHCPv6）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 (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 a Dynamic Host Configuration Protocol version 6 (DHCPv6) option that contains a list of domain names or IPv6 addresses that can be mapped to one or more Session Initiation Protocol (SIP) outbound proxy servers. This is one of the many methods that a SIP client can use to obtain the addresses of such a local SIP server.
本文档定义了动态主机配置协议版本6（DHCPv6）选项，该选项包含可映射到一个或多个会话启动协议（SIP）出站代理服务器的域名或IPv6地址列表。这是SIP客户端可以用来获取此类本地SIP服务器地址的许多方法之一。
This document uses the DHCP terminology defined in [1].
本文档使用[1]中定义的DHCP术语。
A SIP server is defined in RFC 3261 [2]. This server MUST be an outbound proxy server, as defined in [3]. In the context of this document, a SIP server refers to the host the outbound SIP proxy server is running on.
RFC 3261[2]中定义了SIP服务器。此服务器必须是[3]中定义的出站代理服务器。在本文档的上下文中，SIP服务器指出站SIP代理服务器运行的主机。
A SIP client is defined in RFC 3261 [2]. The client can be a user agent client or the client portion of a proxy server. In the context of this document, a SIP client refers to the host the SIP client is running on.
SIP客户端在RFC 3261[2]中定义。客户端可以是用户代理客户端或代理服务器的客户端部分。在本文档的上下文中，SIP客户端指的是SIP客户端运行的主机。
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 [4].
在本文件中，关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照BCP 14、RFC 2119[4]中的说明进行解释。
The Session Initiation Protocol (SIP) [2] is an application-layer control protocol that can establish, modify and terminate multimedia sessions or calls. A SIP system has a number of logical components: user agents, proxy servers, redirect servers and registrars. User agents MAY contain SIP clients, proxy servers always do.
会话发起协议（SIP）[2]是一种应用层控制协议，可以建立、修改和终止多媒体会话或呼叫。SIP系统有许多逻辑组件：用户代理、代理服务器、重定向服务器和注册器。用户代理可能包含SIP客户端，代理服务器通常包含SIP客户端。
This document specifies two DHCPv6 options [1] that allow SIP clients to locate a local SIP server that is to be used for all outbound SIP requests, a so-called outbound proxy server. (SIP clients MAY contact the address identified in the SIP URL directly, without involving a local SIP server. However in some circumstances, such as when firewalls are present, or local dialing plans, local emergency and other services need to be provided, SIP clients need to use a local server for outbound requests.) This is one of many possible solutions for locating the outbound SIP server; manual configuration is an example of another.
本文档指定了两个DHCPv6选项[1]，允许SIP客户端定位用于所有出站SIP请求的本地SIP服务器，即所谓的出站代理服务器。（SIP客户端可以直接联系SIP URL中标识的地址，而不涉及本地SIP服务器。但是，在某些情况下，如存在防火墙，或需要提供本地拨号计划、本地紧急情况和其他服务时，SIP客户端需要使用本地服务器进行出站请求。）这是定位出站SIP服务器的许多可能解决方案之一；手动配置是另一个示例。
This document defines two DHCPv6 options that describe a local outbound SIP proxy: one carries a list of domain names (Section 3.1), the other a list of 128-bit (binary) IPv6 addresses (Section 3.2).
本文档定义了两个描述本地出站SIP代理的DHCPv6选项：一个包含域名列表（第3.1节），另一个包含128位（二进制）IPv6地址列表（第3.2节）。
Since DHCPv6 does not suffer from a shortage of option codes, we avoid the encoding byte found in the IPv4 DHCP option for SIP servers [6]. This makes the option shorter, easier to parse, simplifies appropriate word alignment for the numeric addresses and allows the client to request either numeric or domain name options using the "option request option".
由于DHCPv6没有缺少选项代码，因此我们避免了SIP服务器的IPv4 DHCP选项中的编码字节[6]。这使得选项更短，更容易解析，简化了数字地址的适当单词对齐，并允许客户端使用“选项请求选项”请求数字或域名选项。
An implementation implementing this specification MUST support both options.
实现此规范的实现必须支持这两个选项。
The option length is followed by a sequence of labels, encoded according to Section 3.1 of RFC 1035 [5], quoted below:
选项长度后面是一系列标签，按照RFC 1035[5]第3.1节进行编码，如下所述：
"Domain names in messages are expressed in terms of a sequence of labels. Each label is represented as a one octet length field followed by that number of octets. Since every domain name ends
“邮件中的域名是用一系列标签表示的。每个标签都表示为一个八位字节长度的字段，后跟该八位字节数。因为每个域名都以
with the null label of the root, a domain name is terminated by a length byte of zero. The high order two bits of every length octet must be zero, and the remaining six bits of the length field limit the label to 63 octets or less. To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
使用根的空标签，域名以长度为零的字节终止。每个长度八位字节的高阶两位必须为零，长度字段的其余六位将标签限制为63个八位字节或更少。为了简化实现，域名的总长度（即标签八位字节和标签长度八位字节）限制为255个八位字节或更少。”
RFC 1035 encoding was chosen to accommodate future internationalized domain name mechanisms.
选择RFC1035编码是为了适应未来的国际化域名机制。
The option MAY contain multiple domain names, but these SHOULD refer to different NAPTR records, rather than different A records. The client MUST try the records in the order listed, applying the mechanism described in Section 4.1 of RFC 3263 [3] for each. The client only resolves the subsequent domain names if attempts to contact the first one failed or yielded no common transport protocols between client and server or denote a domain administratively prohibited by client policy. Domain names MUST be listed in order of preference.
该选项可能包含多个域名，但这些域名应指向不同的NAPTR记录，而不是不同的A记录。客户必须按照列出的顺序尝试记录，并对每个记录应用RFC 3263[3]第4.1节中描述的机制。如果尝试联系第一个域名失败，或者在客户端和服务器之间未产生公共传输协议，或者表示客户端策略在管理上禁止的域，则客户端仅解析后续域名。域名必须按优先顺序列出。
Use of multiple domain names is not meant to replace NAPTR or SRV records, but rather to allow a single DHCP server to indicate outbound proxy servers operated by multiple providers.
使用多个域名并不意味着替换NAPTR或SRV记录，而是允许单个DHCP服务器指示由多个提供商操作的出站代理服务器。
The DHCPv6 option has the format shown in Fig. 1.
DHCPv6选项的格式如图1所示。
option-code: OPTION_SIP_SERVER_D (21)
选项代码：选项SIP服务器D（21）
option-length: Length of the 'SIP Server Domain Name List' field in octets; variable.
选项长度：“SIP服务器域名列表”字段的长度（以八位字节为单位）；变量
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIP_SERVER_D | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIP Server Domain Name List |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIP_SERVER_D | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIP Server Domain Name List |
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: DHCPv6 option for SIP Server Domain Name List
图1:SIP服务器域名列表的DHCPv6选项
SIP Server Domain Name List: The domain names of the SIP outbound proxy servers for the client to use. The domain names are encoded as specified in Section 8 ("Representation and use of domain names") of the DHCPv6 specification [1].
SIP服务器域名列表：客户端要使用的SIP出站代理服务器的域名。域名按照DHCPv6规范[1]第8节（“域名的表示和使用”）的规定进行编码。
This option specifies a list of IPv6 addresses indicating SIP outbound proxy servers available to the client. Servers MUST be listed in order of preference.
此选项指定IPv6地址列表，指示客户端可用的SIP出站代理服务器。服务器必须按优先顺序列出。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIP_SERVER_A | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SIP server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SIP server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_SIP_SERVER_A | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SIP server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SIP server (IP address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_SIP_SERVER_A (22)
选项代码：选项SIP服务器A（22）
option-length: Length of the 'options' field in octets; must be a multiple of 16.
选项长度：“选项”字段的长度（以八位字节为单位）；必须是16的倍数。
SIP server: IPv6 address of a SIP server for the client to use. The servers are listed in the order of preference for use by the client.
SIP服务器：客户端要使用的SIP服务器的IPv6地址。服务器按客户机使用的首选顺序列出。
A client may request either or both of the SIP Servers Domain Name List and SIP Servers IPv6 Address List options in an Options Request Option (ORO) as described in [1],
客户端可以在选项请求选项（ORO）中请求SIP服务器域名列表和SIP服务器IPv6地址列表选项中的一个或两个，如[1]中所述，
If a client receives both the SIP Servers Domain Name List and SIP Servers IPv6 Address List options, it SHOULD use the SIP Servers Domain Name List option. Only if no server in the SIP Servers Domain Name List can be resolved or reached, the client MAY use the SIP Servers IPv6 Address List option.
如果客户端同时收到SIP服务器域名列表和SIP服务器IPv6地址列表选项，则应使用SIP服务器域名列表选项。仅当无法解析或访问SIP服务器域名列表中的任何服务器时，客户端才可以使用SIP服务器IPv6地址列表选项。
A server MAY send a client one or both of the SIP Servers Domain Name List and SIP Servers IPv6 Address List options.
服务器可以向客户端发送一个或两个SIP服务器域名列表和SIP服务器IPv6地址列表选项。
If a client requests both options and the server is configured for both, the server MAY send a client only one of these options and SHOULD send the SIP Servers Domain Name List.
如果客户机同时请求这两个选项，并且服务器已为这两个选项配置，则服务器可能只向客户机发送其中一个选项，并应发送SIP服务器域名列表。
A server configured with the SIP Servers IPv6 Address List option MUST send a client the SIP Servers IPv6 Address List option if that client requested the SIP Servers IPv6 Address List option and not the SIP Servers Domain Name List option in an ORO (see [1]).
配置了SIP Servers IPv6地址列表选项的服务器必须向客户端发送SIP Servers IPv6地址列表选项，前提是该客户端在ORO中请求的是SIP Servers IPv6地址列表选项，而不是SIP Servers域名列表选项（请参见[1]）。
The following table summarizes the server's response:
下表总结了服务器的响应：
Client sends in ORO Domain Name List IPv6 Address List
__________________________________________________________________
Neither option SHOULD MAY
SIP Servers Domain Name List SHOULD MAY
SIP Servers IPv6 Address List MAY MUST
Both options SHOULD MAY
Client sends in ORO Domain Name List IPv6 Address List
__________________________________________________________________
Neither option SHOULD MAY
SIP Servers Domain Name List SHOULD MAY
SIP Servers IPv6 Address List MAY MUST
Both options SHOULD MAY
The security considerations in RFC 3315 [1], RFC 3261 [2] and RFC 3263 [3] apply. If an adversary manages to modify the response from a DHCP server or insert its own response, a SIP user agent could be led to contact a rogue SIP server, possibly one that then intercepts call requests or denies service. A modified DHCP answer could also omit host names that translated to TLS-based SIP servers, thus facilitating intercept.
RFC 3315[1]、RFC 3261[2]和RFC 3263[3]中的安全注意事项适用。如果对手设法修改来自DHCP服务器的响应或插入自己的响应，则SIP用户代理可能会被引导与恶意SIP服务器联系，该服务器可能会拦截呼叫请求或拒绝服务。修改后的DHCP应答还可以省略转换为基于TLS的SIP服务器的主机名，从而便于拦截。
The IANA has assigned a DHCPv6 option number of 21 for the "SIP Servers Domain Name List" and the DHCPv6 option number of 22 for the "SIP Servers IPv6 Address List" defined in this document.
IANA已为“SIP服务器域名列表”分配了DHCPv6选项编号21，为本文档中定义的“SIP服务器IPv6地址列表”分配了DHCPv6选项编号22。
Erik Nordmark and Alex Zinin provided helpful comments.
Erik Nordmark和Alex Zinin提供了有益的评论。
[1] Droms, R., Editor, Bounds, J., Volz, B., Lemon, T., Perkins, C. and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
[1] Droms，R.，编辑，Bounds，J.，Volz，B.，Lemon，T.，Perkins，C.和M.Carney，“IPv6的动态主机配置协议（DHCPv6）”，RFC3315，2003年7月。
[2] 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.
[2] 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。
[3] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP): Locating SIP Servers", RFC 3263, June 2002.
[3] Rosenberg，J.和H.Schulzrinne，“会话启动协议（SIP）：定位SIP服务器”，RFC3263，2002年6月。
[4] Bradner, S., "Key words for use in RFCs to indicate requirement levels", BCP 14, RFC 2119, March 1997.
[4] Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[5] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987.
[5] Mockapetris，P.，“域名-实现和规范”，STD 13，RFC 10351987年11月。
[6] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCP-for-IPv4) Option for Session Initiation Protocol (SIP) Servers," RFC 3361, August 2002.
[6] Schulzrinne，H.，“会话启动协议（SIP）服务器的动态主机配置协议（DHCP-for-IPv4）选项”，RFC 3361，2002年8月。
Henning Schulzrinne Department of Computer Science Columbia University 1214 Amsterdam Avenue, MC 0401 New York, NY 10027 USA
美国纽约州纽约市阿姆斯特丹大道1214号哥伦比亚大学计算机科学系，邮编：10027
EMail: schulzrinne@cs.columbia.edu
EMail: schulzrinne@cs.columbia.edu
Bernie Volz 116 Hawkins Pond Road Center Harbor, NH 03226-3103 USA
伯尼沃尔兹美国新罕布什尔州霍金斯池塘路中心港116号，邮编03226-3103
EMail: volz@metrocast.net
EMail: volz@metrocast.net
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Acknowledgement
确认
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