PCP Working Group M. Boucadair Internet-Draft France Telecom Intended status: Standards Track R. Penno Expires: September 28, 2013 D. Wing Cisco March 27, 2013 DHCP Options for the Port Control Protocol (PCP) draft-ietf-pcp-dhcp-07 Abstract This document specifies DHCP (IPv4 and IPv6) options to configure hosts with Port Control Protocol (PCP) Server names. The use of DHCPv4 or DHCPv6 depends on the PCP deployment scenario. Requirements Language 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 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on September 28, 2013. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. 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 Boucadair, et al. Expires September 28, 2013 [Page 1] Internet-Draft PCP DHCP Options March 2013 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. DHCPv6 PCP Server Option . . . . . . . . . . . . . . . . . . 3 3.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Client Behavior . . . . . . . . . . . . . . . . . . . . . 4 4. DHCPv4 PCP Option . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. Client Behavior . . . . . . . . . . . . . . . . . . . . . 5 5. Use of PCP Server Names . . . . . . . . . . . . . . . . . . . 5 6. Dual-Stack Hosts . . . . . . . . . . . . . . . . . . . . . . 5 7. Guidance to Administrators . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 9.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 6 9.2. DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 7 11.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Rationale . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction This document defines DHCPv4 [RFC2131] and DHCPv6 [RFC3315] options which can be used to provision PCP Server [I-D.ietf-pcp-base] names. Motivations for not expressing the PCP option as a 32 or 128-bit binary address are discussed in Appendix A. In order to make use of these options, this document assumes appropriate name resolution means (e.g., Section 6.1.1 of [RFC1123]) are available on the host client. The use of DHCPv4 or DHCPv6 depends on the PCP deployment scenarios. 2. Terminology This document makes use of the following terms: Boucadair, et al. Expires September 28, 2013 [Page 2] Internet-Draft PCP DHCP Options March 2013 o PCP Server denotes a functional element which receives and processes PCP requests from a PCP Client. A PCP Server can be co- located with or be separated from the function (e.g., NAT, Firewall) it controls. Refer to [I-D.ietf-pcp-base]. o PCP Client denotes a PCP software instance responsible for issuing PCP requests to a PCP Server. Refer to [I-D.ietf-pcp-base]. o DHCP refers to both DHCPv4 [RFC2131] and DHCPv6 [RFC3315]. o DHCP client (or client) denotes a node that initiates requests to obtain configuration parameters from one or more DHCP servers. o DHCP server (or server) refers to a node that responds to requests from DHCP clients. o Name is a domain name (as per Section 8 of [RFC3315]) that contains one or more labels. In particular, a PCP name may be structured as DNS qualified name or be composed of strings such as can be passed to getaddrinfo (Section 6.1 of [RFC3493]), including address literals, etc. 3. DHCPv6 PCP Server Option This DHCPv6 option conveys a name to be used to retrieve the IP addresses of PCP Server(s). Appropriate name resolution queries should be issued to resolve the conveyed name. 3.1. Format The format of the DHCPv6 PCP Server option is shown in Figure 1. 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_PCP_SERVER | Option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : PCP Server Domain Name(s) : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: PCP Server Name DHCPv6 Option The fields of the option shown in Figure 1 are as follows: o Option-code: OPTION_PCP_SERVER (TBA, see Section 9.1) o Option-length: Length of the 'PCP Server Domain Name' field in octets. o PCP Server Domain Name(s): The domain name (s) of the PCP Server to be used by the PCP Client. The OPTION_PCP_SERVER option can include multiple PCP Server Domain Names; each name is treated as a separate PCP Server. The domain name is encoded as specified in Section 8 of [RFC3315]. Boucadair, et al. Expires September 28, 2013 [Page 3] Internet-Draft PCP DHCP Options March 2013 3.2. Client Behavior To discover a PCP Server [I-D.ietf-pcp-base], the DHCPv6 client MUST include an Option Request Option (ORO) requesting the DHCPv6 PCP Server Name option as described in Section 22.7 of [RFC3315] (i.e., include OPTION_PCP_SERVER on its OPTION_ORO). If the DHCPv6 client receives an OPTION_PCP_SERVER option from the DHCPv6 server, it extracts the name(s) conveyed in the OPTION_PCP_SERVER option and proceeds to validate it. The DHCPv6 client MUST verify the name(s) is properly encoded as detailed in Section 8 of [RFC3315]. Once each name conveyed in the OPTION_PCP_SERVER option is validated, the DHCPv6 client MUST follow the procedure specified in Section 5. 4. DHCPv4 PCP Option 4.1. Format The PCP Server Name DHCPv4 option can be used to configure a name to be used by the PCP Client to contact a PCP Server. The format of this option is illustrated in Figure 2. Code Length PCP Server Domain Name +-----+-----+-----+-----+-----+-----+-----+-- | TBA | n | s1 | s2 | s3 | s4 | s5 | ... +-----+-----+-----+-----+-----+-----+-----+-- Figure 2: PCP Server Name DHCPv4 Option The description of the fields is as follows: o Code: OPTION_PCP_SERVER (TBA, see Section 9.2); o Length: Includes the length of the "PCP Server Domain Name" field in octets; The maximum length is 255 octets. o PCP Server Domain Name(s): The domain name(s) of the PCP Server to be used by the PCP Client when issuing PCP messages. The OPTION_PCP_SERVER option can include multiple PCP Server Domain Names; each name is treated as a separate PCP Server. The encoding of the domain name is described in Section 8 of [RFC3315]. The OPTION_PCP_SERVER DHCPv4 option is a concatenation-requiring option. As such, the mechanism specified in [RFC3396] MUST be used if the PCP Server Name option exceeds the maximum DHCPv4 option size of 255 octets. Boucadair, et al. Expires September 28, 2013 [Page 4] Internet-Draft PCP DHCP Options March 2013 4.2. Client Behavior DHCPv4 client expresses the intent to get OPTION_PCP_SERVER by specifying it in Parameter Request List Option [RFC2132]. If the DHCPv4 client receives an OPTION_PCP_SERVER option from the DHCPv4 server, it extracts the name(s) conveyed in the option and proceeds to validate it. The DHCPv4 client MUST verify the name(s) is properly encoded as detailed in Section 8 of [RFC3315]. Once each name conveyed in the OPTION_PCP_SERVER option is validated, the DHCPv4 client MUST follow the procedure specified in Section 5. 5. Use of PCP Server Names If the OPTION_PCP_SERVER option conveys IP address literals, the trailing dot MUST be removed. Each configured PCP Server Name is passed to the name resolution library (e.g., Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the corresponding IP address(es) (IPv4 or IPv6). It is out of scope of this document to specify how the PCP Client selects the PCP Server(s) to contact. Multiple PCP Server Names may be configured to a PCP Client in some deployment contexts such as multi-homing. It is out of scope of this document to enumerate all deployment scenarios which require multiple Names to be configured. A host may have multiple network interfaces (e.g, 3G, WiFi, etc.); each configured differently. Each PCP Server learned MUST be associated with the interface via which it was learned. 6. Dual-Stack Hosts In some deployment contexts, the PCP Server may be reachable with an IPv4 address but DHCPv6 is used to provision the PCP Client. In such scenarios, a plain IPv4 address or an IPv4-mapped IPv6 address can be configured to reach the PCP Server. A Dual-Stack host may receive OPTION_PCP_SERVER via both DHCPv4 and DHCPv6. The content of these OPTION_PCP_SERVER options may refer to the same or distinct PCP Servers. This is deployment-specific and as such it is out of scope of this document. 7. Guidance to Administrators Boucadair, et al. Expires September 28, 2013 [Page 5] Internet-Draft PCP DHCP Options March 2013 If IPv4 address literals are to be returned in the OPTION_PCP_SERVER option, administrators should not configure ambiguous strings such as "10.0.258", "0xA000001", and "012.0x102"; the strict form is recommended instead. Refer to Section 3.1.1 and Section 3.1.2 of [I-D.iab-identifier-comparison] for a more generic discussion on IP address literals. 8. Security Considerations The security considerations in [RFC2131], [RFC3315] and [I-D.ietf-pcp-base] are to be considered. 9. IANA Considerations 9.1. DHCPv6 Option IANA is requested to assign the following new DHCPv6 Option Code in the registry maintained in http://www.iana.org/assignments/ dhcpv6-parameters: Option Name Value ----------------- ----- OPTION_PCP_SERVER TBA 9.2. DHCPv4 Option IANA is requested to assign the following new DHCPv4 Option Code in the registry maintained in http://www.iana.org/assignments/bootp- dhcp-parameters/: Option Name Value ----------------- ----- OPTION_PCP_SERVER TBA 10. Acknowledgements Many thanks to B. Volz, C. Jacquenet, R. Maglione, D. Thaler, T. Mrugalski, T. Reddy, S. Cheshire and M. Wasserman for their review and comments. Special thanks to T. Lemon for the review and his continuous effort to enhance this specification. 11. References Boucadair, et al. Expires September 28, 2013 [Page 6] Internet-Draft PCP DHCP Options March 2013 11.1. Normative References [I-D.ietf-pcp-base] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. Selkirk, "Port Control Protocol (PCP)", draft-ietf-pcp- base-29 (work in progress), November 2012. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002. 11.2. Informative References [I-D.iab-identifier-comparison] Thaler, D., "Issues in Identifier Comparison for Security Purposes", draft-iab-identifier-comparison-03 (work in progress), July 2012. [I-D.ietf-behave-lsn-requirements] Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A., and H. Ashida, "Common requirements for Carrier Grade NATs (CGNs)", draft-ietf-behave-lsn-requirements-10 (work in progress), December 2012. [I-D.ietf-dhc-option-guidelines] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and S. Krishnan, "Guidelines for Creating New DHCPv6 Options", draft-ietf-dhc-option-guidelines-10 (work in progress), February 2013. [RFC1123] Braden, R., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October 1989. Boucadair, et al. Expires September 28, 2013 [Page 7] Internet-Draft PCP DHCP Options March 2013 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. Stevens, "Basic Socket Interface Extensions for IPv6", RFC 3493, February 2003. [RFC6055] Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on Encodings for Internationalized Domain Names", RFC 6055, February 2011. [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", RFC 6146, April 2011. [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011. [RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite", RFC 6334, August 2011. Appendix A. Rationale Distinct IP-Address and Name DHCP options have been considered in early stages of this specification. This flexibility aims to let service providers make their own engineering choices and use the most convenient option according to their deployment context. Nevertheless, the DHC WG's position is this flexibility has some drawbacks such as inducing errors (See Section 7 of [I-D.ietf-dhc-option-guidelines]). Therefore, only the Name option is maintained within this document. This choice is motivated by operational considerations: In particular, some Service Providers are considering two levels of redirection: (1) The first level is national-wise and undertaken by DHCP: a regional-specific Name will be returned; (2) The second level is done during the resolution of the regional- specific Name to redirect the customer to a regional PCP server among a pool deployed regionally. Distinct operational teams are responsible for each of the above mentioned levels. A clear separation between the functional perimeter of each team is a sensitive task for the maintenance of the offered services. Regional teams will require to introduce new resources (e.g., new PCP-controlled devices such as Carrier Grade NATs (CGNs, [I-D.ietf-behave-lsn-requirements])) to meet an increase in customer base. Operations related to the introduction of these Boucadair, et al. Expires September 28, 2013 [Page 8] Internet-Draft PCP DHCP Options March 2013 new devices (e.g., addressing, redirection, etc.) are implemented locally. Having this regional separation provides flexibility to manage portions of network operated by dedicated teams. This two- level redirection can not be met by the IP Address option. In addition to the operational considerations: o The use of the Name for NAT64 [RFC6146] might be suitable for load-balancing purposes; o For the DS-Lite case [RFC6333], if the encapsulation mode is used to send PCP messages, an IP address may be used since the AFTR selection is already done via the AFTR_NAME DHCPv6 option [RFC6334]. Of course, this assumes that the PCP Server is co- located with the AFTR function. If these functions are not co- located, conveying the Name would be more convenient. Returning a Name requires the host to embed a name resolution service. Some may present this as an argument against defining a Name option. Nevertheless, this argument may be objected as implementing a name resolution library (e.g., embed a DNS resolver) is cheap and devices which don't embed DNS resolver are uncommon. Authors' Addresses Mohamed Boucadair France Telecom Rennes 35000 France Email: mohamed.boucadair@orange.com Reinaldo Penno Cisco USA Email: repenno@cisco.com Dan Wing Cisco Systems, Inc. 170 West Tasman Drive San Jose, California 95134 USA Email: dwing@cisco.com Boucadair, et al. Expires September 28, 2013 [Page 9]