| PCP Working Group | M. Boucadair |
| Internet-Draft | France Telecom |
| Intended status: Standards Track | R. Penno |
| Expires: September 27, 2013 | D. Wing |
| Cisco | |
| March 26, 2013 |
DHCP Options for the Port Control Protocol (PCP)
draft-ietf-pcp-dhcp-07
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.
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].
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 27, 2013.
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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.
This document makes use of the following terms:
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.
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
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.
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:
[RFC3396] MUST be used if the PCP Server Name option exceeds the maximum DHCPv4 option size of 255 octets.
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.
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.
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.
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.
The security considerations in [RFC2131], [RFC3315] and [I-D.ietf-pcp-base] are to be considered.
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 |
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 |
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.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, 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. |
| [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. |
| [RFC3396] | Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002. |
| [I-D.ietf-pcp-base] | Wing, D., Cheshire, S., Boucadair, M., Penno, R. and P. Selkirk, "Port Control Protocol (PCP)", Internet-Draft draft-ietf-pcp-base-29, November 2012. |
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:
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 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: