Network Working Group M. Boucadair Internet-Draft France Telecom Intended status: Standards Track R. Penno Expires: November 11, 2010 Juniper Networks D. Wing Cisco May 10, 2010 DHCP and DHCPv6 Options for Port Control Protocol (PCP) draft-bpw-softwire-pcp-dhcp-01 Abstract This document specifies DHCP (IPv4 and IPv6) Options to convey the IP address or a FQDN of a PCP Server. A dedicated option to prevent overloading PCP Servers is also specified. 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 November 11, 2010. Copyright Notice Copyright (c) 2010 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 Boucadair, et al. Expires November 11, 2010 [Page 1] Internet-Draft PCP DHCP Options May 2010 (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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Consistent NAT and PCP Configuration . . . . . . . . . . . . . 3 3. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. PCP Server Address DHCPv6 Option . . . . . . . . . . . . . 4 3.2. PCP Server FQDN DHCPv6 Option . . . . . . . . . . . . . . 5 3.3. PCP Service Time Wait DHCPv6 Option . . . . . . . . . . . 6 3.4. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7 4. DHCP PCP Option . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. PCP Server Address Sub-Option . . . . . . . . . . . . . . 9 4.2. PCP Server FQDN Sub-Option . . . . . . . . . . . . . . . . 9 4.3. PCP Service Time Wait DHCP Sub-Option . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . . 12 8.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12 Boucadair, et al. Expires November 11, 2010 [Page 2] Internet-Draft PCP DHCP Options May 2010 1. Introduction [I-D.wing-softwire-port-control-protocol] recommends the use of DHCP as one of the mechanisms to discover a PCP Server. To that aim, this document defines DHCP [RFC2131] and DHCPv6 [RFC3315] Options which can be used to provision a PCP Server reachability information (IP address, FQDN) to a PCP Client. The use of DHCP or DHCPv6 depends on the PCP deployment scenarios. For flexibility reasons, this document defines both IP address and FQDN Options. It is up to Service Providers to decide which option is convenient for them according to their engineering policies. This document does not make any assumption on the IP address to be conveyed in a DHCP/DHCPv6 Option. In particular, this document does not prevent Service Providers to use the IANA-to-be-assigned IP address [I-D.wing-softwire-port-control-protocol] to be conveyed in DHCP/DHCPv6 Options. 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, this document suggests to include IPv4-mapped IPv6 addresses (see Section 3.1) as a reachability information of the PCP Server (or use the domain name option). As described in Section 3.1 of [I-D.wing-behave-dns64-config], dual-stack hosts can issue IPv4 datagrams successfully to that IP address. 2. Consistent NAT and PCP Configuration The PCP Server discovered through DHCP MUST be able to install mappings on the NAT that will be crossed by packets issued by the host or any terminal belonging to the same realm (e.g., DHCP client is embedded in a CP router). If DHCP is used to provision the reachability information of a PCP Server, Service Providers SHOULD configure appropriately their DHCP servers to meet this requirement. In case this prerequisite is not met, customers would experience service troubles and their service(s) won't be delivered appropriately. Note that this constraint is implicitly met in scenarios where only one single PCP-controlled device is deployed in the network. 3. DHCPv6 Options Two DHCPv6 Options defined in the following sub-sections are used to convey the PCP Server reachability information. The first option Boucadair, et al. Expires November 11, 2010 [Page 3] Internet-Draft PCP DHCP Options May 2010 (i.e., OPTION_PCP_SERVER_A) can be used to include an IPv6 address or an IPv4-mapped IPv6 address. The second option (i.e., OPTION_PCP_SERVER_D) conveys a domain name to be used to retrieve the IP address of the PCP Server. For example, in the context of a DS-Lite architecture [I-D.ietf-softwire-dual-stack-lite] DHCPv6 can be used to include the IPv4-mapped IPv6 address [RFC2373] of a PCP Server (a PCP Client can use an IPv4-mapped IPv6 address to send IPv4 PCP messages), and in the case of NAT64 [I-D.ietf-behave-v6v4-xlate-stateful] to provision the IPv6 address of the PCP Server. A third option (OPTION_PCP_SERVICE_T) is defined to convey a timer used to prevent overload events. 3.1. PCP Server Address DHCPv6 Option This option specifies an IP address of the PCP Server to be used by the PCP Client to send PCP messages. 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_A | Option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | PCP Server (IP address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | PCP Server (IP address) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : .... : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: PCP Server IP Address DHCPv6 Option The description of the fields of the option shown in Figure 1 is described below: o Option-code: OPTION_PCP_SERVER_A (TBA, see Section 6) Boucadair, et al. Expires November 11, 2010 [Page 4] Internet-Draft PCP DHCP Options May 2010 o Option-length: MUST be a multiple of 16. o PCP Server: One or a list of IP address(es) of PCP Server(s) to be used by a PCP Client. In particular, IPv4-mapped IPv6 addresses can be included in this field when the PCP Server is reachable over IPv4 (e.g., in a DS-Lite architecture, the PCP Server can be reachable over IPv4 (i.e., PCP messages will be encapsulated in IPv6). An IPv4-mapped IPv6 address can be used to provision the PCP Client with the reachability information of the PCP Server). If several IP addresses are included in the option, these addresses MUST be listed in the order of preference. A PCP Client MUST use a reachable address with higher preference order. In case several addresses are to be conveyed in a DHCPv6 option, it is RECOMMENDED to use OPTION_PCP_SERVER_D DHCPv6 option. 3.2. PCP Server FQDN DHCPv6 Option This option includes a FQDN of the PCP Server to be used by the PCP Client. In order to exploit this option, this document assumes that a DNS server is configured on the host client by DHCP or other means. 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_D | Option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : PCP Server Domain Name : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: PCP Server FQDN DHCPv6 Option The fields of the option shown in Figure 2 are: o Option-code: OPTION_PCP_SERVER_D (TBA, see Section 6) o Option-length: Length of the 'PCP Server Domain Name' field in octets. This length is variable. o PCP Server Domain Name: The domain name of the PCP Server to be used by the PCP Client. The domain name is encoded as specified in [RFC3315]. Boucadair, et al. Expires November 11, 2010 [Page 5] Internet-Draft PCP DHCP Options May 2010 3.3. PCP Service Time Wait DHCPv6 Option [NOTE: This section will be removed if the avalanche restart concern is handled by a generic initiative such as HomeGate. See for example [RFC3435] how this issue is covered for MGCP.] In order to avoid overload phenomena (e.g., power outage event in a big city), the following option (Figure 3) is used to ask a PCP Client to wait N seconds before sending its first PCP message. If no overload control mechanism is supported, avalanche restart phenomena would lead to a huge amount of requests to the PCP Server which would impact the serviceability of the PCP-controlled device and would even induce a service outage for a large number of customers serviced by the same CGN device. Distributing all PCP requests in a random or a pre-defined manner will avoid experiencing load bursts. This option SHOULD be used only with a non-null TimeWait value. The format of the OPTION_PCP_SERVICE_T option is shown in Figure 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_PCP_SERVICE_T | Option-length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Method | TimeWait | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ This option can be generalized to all services (e.g., SIP, PCP, NTP, etc.) by including a field which specifies the associated service. Figure 3: PCP Service TimeWait DHCPv6 Option The description of the fields of this option is as follows: o Option-code: OPTION_PCP_SERVICE_T (TBA, see Section 6) o Option-length: 4. o Method: This field specifies the method to apply on the TimeWait. Two methods MUST be supported by any OPTION_PCP_SERVICE_T implementation: 0: Basic. When this method is used, the PCP Client MUST wait until the expiry of TimeWait seconds before issuing a PCP message. Boucadair, et al. Expires November 11, 2010 [Page 6] Internet-Draft PCP DHCP Options May 2010 1: Random. When this method is indicated, a RAND() function MUST be used to generate a value between 0 and TimeWait. The PCP Client MUST wait until the expiry of the generated value before issuing a PCP message to a PCP Server. o TimeWait: This field specifies a number of seconds to be used when applying the function indicated in the Method field. 3.4. Requirements If OPTION_PCP_SERVER_D is used to configure the PCP Server, the client MUST issue a AAAA DNS query to resolve an IPv6 address, if the query has failed the PCP Client MUST issue an A DNS query. [[Note: In order to avoid the delay, a field can be added to the option to inform the client about the type of the DNS query to be issued]]]. OPTION_PCP_SERVER_D and OPTION_PCP_SERVER_A DHCPv6 option MUST be supported. OPTION_PCP_SERVICE_T DHPCv6 option MAY (SHOULD?) be supported. 4. DHCP PCP Option The PCP Server DHCP Option can be used to configure an IPv4 address or a DNS FQDN to be used by the PCP Client to contact a PCP Server. It can also be used to indicate a timer to constraint emitting PCP messages. The generic format of this option is illustrated in Figure 4. Boucadair, et al. Expires November 11, 2010 [Page 7] Internet-Draft PCP DHCP Options May 2010 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Code | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : Sub-option 1 : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : ... : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : Sub-option n : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: DHCP PCP Option o Code: OPTION_PCP_SERVER (TBA, see Section 6); o Length: Includes the length of included sub-options; o One or several sub-options can be included in a PCP DHCP option. The format of each sub-option follows the structure shown in Figure 5. Sub-option Code Len Data +-----+-----+-----...---+ | code| n | Data | +-----+-----+-----...---+ Figure 5: PCP Server sub-option Three sub-options are defined in this document: 1: PCP Server Address Sub-option (Section 4.1); 2: PCP Domain Name Sub-option (Section 4.2); 3: PCP Service Time Wait Sub-option (Section 4.3). Both PCP Server Address and PCP Domain Name Sub-options MUST be supported. PCP Service Time Wait Sub-option MAY (SHOULD?) be supported. Boucadair, et al. Expires November 11, 2010 [Page 8] Internet-Draft PCP DHCP Options May 2010 PCP Server Address Sub-option and PCP Domain Name Sub-option are exclusive. PCP Service Time Wait Sub-option MAY be jointly included in the same DHCP message carrying PCP Server Address Sub-option or PCP Domain Name Sub-option. When a PCP Domain Name Sub-option is used, the PCP client MUST issue A DNS queries to retrieve an IPv4 address. 4.1. PCP Server Address Sub-Option This sub-option specifies one or a list of IPv4 addresses of the PCP Server to be used by the PCP Client to send PCP messages. Sub-option Code Len PCP Server IP Address PCP Server IP Address +-----+-----+-----+-----+-----+-----+-----+-----+-- | 1 | n | a1 | a2 | a3 | a4 | a1 | a2 | ... +-----+-----+-----+-----+-----+-----+-----+-----+-- This format assumes that an IPv4 address is encoded as a1.a2.a3.a4. Figure 6: PCP Server IPv4 Address DHCP Sub-Option The fields of the sub-option shown in Figure 6 are: o Sub-option Code: 1. o Len: Must be a multiple of 4. o PCP Server IP Address: contains one or several IPv4 addresses of a PCP Server to be used by a PCP Client. If several addresses are included, they are included in the preference order. A client MUST use the reachable address with the highest preference order. Instead of including several addresses in the DHCP option, it is RECOMMENDED to use PCP Server FQDN Sub-option. 4.2. PCP Server FQDN Sub-Option This sub-option includes a FQDN of the PCP Server to be used by the PCP Client to send PCP messages. In order to exploit this option, this document assumes that a DNS server is configured on the host client by DHCP or other means. Boucadair, et al. Expires November 11, 2010 [Page 9] Internet-Draft PCP DHCP Options May 2010 Sub-option Code Len FQDN of PCP Server +-----+-----+-----+-----+-----+-----+-----+-- | 2 | n | s1 | s2 | s3 | s4 | s5 | ... +-----+-----+-----+-----+-----+-----+-----+-- Figure 7: PCP Server FQDN DHCP Sub-option The fields of the sub-option shown in Figure 7 are: o Sub-option Code: 2. o Len: Length of the "PCP Server Domain Name" field in octets. This length is variable. o PCP Server Domain Name: The domain name of the PCP Server to be used by the PCP Client. The encoding of the domain name is described [RFC2131]. 4.3. PCP Service Time Wait DHCP Sub-Option [NOTE: This section will be removed if the avalanche restart concern is handled by a generic initiative such as HomeGate] This sub-option is used to indicate to a host, the time to wait before issuing a PCP message. The purpose of this option is to prevent overload phenomena. This sub-option SHOULD be used only with a non-null TimeWait value. The format of the PCP Service Time Wait DHCP Sub-option is shown in Figure 8. Sub-option Code Len Method TimeWait +-----+-----+-----+-----+-----+ | 3 | 3 | M | TimeWait | +-----+-----+-----+-----+-----+ Figure 8: PCP Service TimeWait DHCP Sub-option The fields of this sub-option are: o Sub-option Code: 3. o Len: 3. Boucadair, et al. Expires November 11, 2010 [Page 10] Internet-Draft PCP DHCP Options May 2010 o Method: This field specifies the method to apply on the TimeWait. Two methods MUST be supported: 0: Basic. When this method is indicated, the PCP Client MUST wait until the expiry of TimeWait seconds before issuing a PCP message. 1: Random. When this method is indicated, a RAND() function MUST be used to generate a value between 0 and TimeWait. The PCP Client MUST wait until the expiry of the generated value before issuing a PCP message to a PCP Server. o TimeWait: This field specifies a number of seconds to be used when applying the function indicated in the Method field. 5. Security Considerations The security considerations in [RFC2131], [RFC3315] and [I-D.wing-softwire-port-control-protocol] are to be considered. 6. IANA Considerations This document request three DHCPv6 Option codes and one DHCP Option code. DHCPv6 Option codes: 1. OPTION_PCP_SERVER_A 2. OPTION_PCP_SERVER_D 3. OPTION_PCP_SERVICE_T DHCP Option code: 1. OPTION_PCP_SERVER 7. Acknowledgements Many thanks to B. Volz and C. Jacquenet for their review and comments. 8. References Boucadair, et al. Expires November 11, 2010 [Page 11] Internet-Draft PCP DHCP Options May 2010 8.1. Normative References [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. [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. 8.2. Informative References [I-D.ietf-behave-v6v4-xlate-stateful] Bagnulo, M., Matthews, P., and I. Beijnum, "Stateful NAT64: Network Address and Protocol Translation from IPv6 Clients to IPv4 Servers", draft-ietf-behave-v6v4-xlate-stateful-11 (work in progress), March 2010. [I-D.ietf-softwire-dual-stack-lite] Durand, A., Droms, R., Haberman, B., Woodyatt, J., Lee, Y., and R. Bush, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion", draft-ietf-softwire-dual-stack-lite-04 (work in progress), March 2010. [I-D.wing-behave-dns64-config] Wing, D., "DNS64 Resolvers and Dual-Stack Hosts", draft-wing-behave-dns64-config-02 (work in progress), February 2010. [I-D.wing-softwire-port-control-protocol] Wing, D., Penno, R., and M. Boucadair, "Port Control Protocol (PCP)", draft-wing-softwire-port-control-protocol-01 (work in progress), March 2010. [RFC2373] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [RFC3435] Andreasen, F. and B. Foster, "Media Gateway Control Protocol (MGCP) Version 1.0", RFC 3435, January 2003. Boucadair, et al. Expires November 11, 2010 [Page 12] Internet-Draft PCP DHCP Options May 2010 Authors' Addresses Mohamed Boucadair France Telecom Rennes, 35000 France Email: mohamed.boucadair@orange-ftgroup.com Reinaldo Penno Juniper Networks 1194 N Mathilda Avenue Sunnyvale, California 94089 USA Email: rpenno@juniper.net Dan Wing Cisco Systems, Inc. 170 West Tasman Drive San Jose, California 95134 USA Email: dwing@cisco.com Boucadair, et al. Expires November 11, 2010 [Page 13]