IPSECME WG A. Dodd-Noble Internet-Draft S. Gundavelli Intended status: Informational Cisco Expires: October 25, 2015 J. Korhonen F. Baboescu Broadcom Corporation B. Weis Cisco April 23, 2015 3GPP IMS Option for IKEv2 draft-gundavelli-ipsecme-3gpp-ims-options-05.txt Abstract This document defines two new configuration attributes for Internet Key Exchange Protocol version 2 (IKEv2). These attributes can be used for carrying the IPv4 address and IPv6 address of the Proxy-Call Session Control Function (P-CSCF). When an IPsec gateway delivers these attributes to an IPsec client, the IPsec client can obtain the IPv4 and/or IPv6 address of the P-CSCF server located in the 3GPP network. 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 October 25, 2015. Copyright Notice Copyright (c) 2015 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 Dodd-Noble, et al. Expires October 25, 2015 [Page 1] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 (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. Conventions and Terminology . . . . . . . . . . . . . . . . . . 4 2.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 3. P_CSCF_IP4_ADDRESS Configuration Attribute . . . . . . . . . . 5 4. P_CSCF_IP6_ADDRESS Configuration Attribute . . . . . . . . . . 5 5. Example Scenario . . . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Dodd-Noble, et al. Expires October 25, 2015 [Page 2] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 1. Introduction The Third Generation Partnership Project (3GPP) S2b reference point [TS23402], specified by the 3GPP system architecture defines a mechanism for allowing a mobile node (MN) attached in an untrusted non-3GPP IP Access Network to securely connect to a 3GPP network and access IP services. In this scenario, the mobile node establishes an IPsec ESP tunnel [RFC4303] to the security gateway called evolved packet data gateway (ePDG) and which in turn establishes a Proxy Mobile IPv6 (PMIPv6) [RFC5213] or GPRS Tunneling Protocol (GTP) [TS23402] tunnel to the packet data gateway (PGW) [TS23402] where the mobile node's session is anchored. The below figure shows the interworking option for non-3GPP access over an untrusted-access network. The mobile access gateway (MAG) and the local mobility anchor (LMA) functions are defined in [RFC5213]. The ePDG and PGW functions are defined in [TS23402]. IPsec ESP tunnel is between the MN and the ePDG and PMIP or GTP tunnel between the ePDG and the PGW. +------------+ | ePDG | | +--------+ | +------+ _----_ | | IPsec | | _----_ +-----+ | MN | _( )_ | | Module | | _( )_ | LMA | | |<====( Internet )=====| +--------+ |===( Operator )===|(PGW)| +------+ (_ _) | : | (_Network_) +-----+ '----' | +--------+ | '----' IPsec Tunnel | | PMIPv6 | | PMIPv6/GTP Tunnel | | MAG | | | +--------+ | +------------+ |<------------ IKEv2/IPsec ------> | <------ PMIPv6/GTP ----->| Figure 1: Exchange of IPv4 Traffic Offload Selectors A mobile node in this scenario may potentially need to access the IP Multimedia Subsystem (IMS) services in the 3GPP network [TS23228] and [TS24229]. Currently, there are no attributes in IKEv2 [RFC7296] that can be used for carrying these information elements. In the absence of these attributes the mobile node needs to be statically configured with this information and this is proving to be an operational challenge. Any other approaches such as using DNS, or DHCP for discovering these functions would result in obtaining Dodd-Noble, et al. Expires October 25, 2015 [Page 3] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 configuration in the access network and not in the home network. Given that the above referenced 3GPP interface is primarily for allowing the mobile node to connect to the 3GPP network through an untrusted-access network, the access network may not have any relation with the home network provider and may be unable to deliver the mobile node's home network configuration. This specification therefore defines two new IKEv2 attributes [RFC7296] that allows an IPsec gateway to provide the IPv4 and/or IPv6 address of the P-CSCF server. These attributes can be exchanged by IKEv2 peers as part of the configuration payload exchange. The attributes follow the configuration attribute format defined in Section 3.15.1 of [RFC7296]. Furthermore, providing the P-CSCF server address(es) in IKEv2 as standard attribute(s) enables clients to directly access IMS services behind a VPN gateway without going through the 3GPP specific interfaces. 2. Conventions and Terminology 2.1. Conventions 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]. 2.2. Terminology All the IKEv2 related terms used in this document are to be interpreted as defined in [RFC7296] and [RFC5739]. All the mobility related terms are to interpreted as defined in [RFC5213] and [RFC5844]. Additionally, this document uses the following terms: Proxy-Call Session Control Function (P-CSCF) The P-CSCF is the entry point to the 3GPP IMS (IP Multimedia Subsystem) and serves as the SIP outbound proxy for the mobile node. The mobile node performs SIP registration to 3GPP IMS and initiates SIP sessions via a P-CSCF. Evolved Packet Data Gateway (ePDG) Its is a security gateway defined by the 3GPP system architecture. The protocol interfaces it supports include IKEv2 [RFC7296]. Dodd-Noble, et al. Expires October 25, 2015 [Page 4] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 3. P_CSCF_IP4_ADDRESS Configuration Attribute The P_CSCF_IP4_ADDRESS configuration attribute is formatted as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R| Attribute Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: IPv4 Address of P-CSCF Reserved (1 bit) Refer to IKEv2 specification Attribute Type (15 bits) Length (2 octets) Length of the IPv4 address field that follows. Possible values are (0) and (4). A value of (4) indicates the size of the 4-octet IPv4 address that follows. A value of (0) indicates that its a empty attribute with zero-length IPv4 address field, primarily used as a request indicator. IPv4 Address (4 octets) An IPv4 address of the P-CSCF server. The P_CSCF_IP4_ADDRESS configuration attribute provides an IPv4 address of a P-CSCF server within the network. If an instance of an empty P_CSCF_IP4_ADDRESS attribute with zero-length IPv4 Address field is included by mobile node, the responder MAY respond with zero, one or more P_CSCF_IP4_ADDRESS attributes. If several P_CSCF_IP4_ADDRESS attributes are provided in one IKEv2 message, there is no implied order among the P_CSCF_IP4_ADDRESS attributes. However, a system architecture using this specification may be able to enforce some order at both the peers. 4. P_CSCF_IP6_ADDRESS Configuration Attribute The P_CSCF_IP6_ADDRESS configuration attribute is formatted as follows: Dodd-Noble, et al. Expires October 25, 2015 [Page 5] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |R| Attribute Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | | IPv6 Address | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: IPv6 Address of P-CSCF Reserved (1 bit) Refer to IKEv2 specification Attribute Type (15 bits) Length (2 octets) Length of the IPv6 address field that follows. Possible values are (0) and (16). A value is (16) indicates the size of the 16- octet IPv6 address that follows. A value of (0) indicates that its a empty attribute with zero-length IPv6 address field, primarily used as a request indicator. IPv6 Address (16 octets) An IPv6 address of the P-CSCF server. The P_CSCF_IP6_ADDRESS configuration attribute provides an IPv6 address of a P-CSCF server within the network. If an instance of an empty P_CSCF_IP6_ADDRESS attribute with zero-length IPv6 Address field is included by mobile node, the responder MAY respond with zero, one or more P_CSCF_IP6_ADDRESS attributes. If several P_CSCF_IP6_ADDRESS attributes are provided in one IKEv2 message, there is no implied order among the P_CSCF_IP6_ADDRESS attributes. However, a system architecture using this specification may be able to enforce some order at both the peers. 5. Example Scenario The mobile node MAY request the IP address of an P-CSCF server as shown below. Dodd-Noble, et al. Expires October 25, 2015 [Page 6] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 Client Gateway -------- --------- HDR(IKE_SA_INIT), SAi1, KEi, Ni --> <-- HDR(IKE_SA_INIT), SAr1, KEr, Nr, [CERTREQ] HDR(IKE_AUTH), SK { IDi, CERT, [CERTREQ], AUTH, [IDr], CP(CFG_REQUEST) = { INTERNAL_IP4_ADDRESS(), INTERNAL_IP4_DNS(), P_CSCF_IP4_ADDRESS() }, SAi2, TSi = (0, 0-65535, 0.0.0.0-255.255.255.255), TSr = (0, 0-65535, 0.0.0.0-255.255.255.255) } --> <-- HDR(IKE_AUTH), SK { IDr, CERT, AUTH, CP(CFG_REPLY) = { INTERNAL_IP4_ADDRESS(192.0.2.234), P_CSCF_IP4_ADDRESS(192.0.2.1), P_CSCF_IP4_ADDRESS(192.0.2.4), INTERNAL_IP4_DNS(198.51.100.33) }, SAr2, TSi = (0, 0-65535, 192.0.2.234-192.0.2.234), TSr = (0, 0-65535, 0.0.0.0-255.255.255.255) } Figure 4: P-CSCF Attribute Exchange 6. IANA Considerations This document requires the following two IANA actions. o Action-1: This specification defines a new IKEv2 attribute for carrying the IPv4 address of P-CSCF server. This attribute is defined in Section 3. The Type value for this Attribute needs to be assigned from the IKEv2 Configuration Payload Attribute Types namespace defined in [RFC7296]. o Action-2: This specification defines a new IKEv2 attribute for carrying the IPv6 address of P-CSCF server. This attribute is defined in Section 4. The Type value for this Attribute needs to be assigned from the IKEv2 Configuration Payload Attribute Types namespace defined in [RFC7296]. Dodd-Noble, et al. Expires October 25, 2015 [Page 7] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 7. Security Considerations This document is an extension to IKEv2 [RFC7296] and therefore it inherits all the security properties of IKEv2. The two new IKEv2 attributes defined in this specification are for carrying the IPv4 and IPv6 address of the P-CSCF server. These attributes can be exchanged by IKE peers as part of the configuration payload and the currently defined IKEv2 security framework provides the needed integrity and privacy protection for these attributes. Therefore this specification does not introduce any new security vulnerabilities. 8. Acknowledgements The Authors would like to specially thank Tero Kivinen for the detailed reviews. Authors would also like to thank Vojislav Vucetic, Heather Sze, Sebastian Speicher, Maulik Vaidya, Ivo Sedlacek, Pierrick Siete and Hui Deng for all the discussions related to this topic. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, October 2014. 9.2. Informative References [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. [RFC5739] Eronen, P., Laganier, J., and C. Madson, "IPv6 Configuration in Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5739, February 2010. [RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy Mobile IPv6", RFC 5844, May 2010. Dodd-Noble, et al. Expires October 25, 2015 [Page 8] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 [TS23228] 3GPP, "Service requirements for the Internet Protocol (IP) multimedia core network subsystem (IMS); Stage 1", 2014. [TS23402] 3GPP, "Architecture enhancements for non-3GPP accesses", 2014. [TS24229] 3GPP, "IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3", 2014. Authors' Addresses Aeneas Noble Cisco 30 International Pl TEWKSBURY, MASSACHUSETTS 95134 USA Email: noblea@cisco.com Sri Gundavelli Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: sgundave@cisco.com Jouni Korhonen Broadcom Corporation Porkkalankatu 24 Helsinki FIN-00180 Finland Email: jouni.nospam@gmail.com Florin Baboescu Broadcom Corporation 100 Mathilda Place Sunnyvale, CA 94086 USA Email: baboescu@broadcom.com> Dodd-Noble, et al. Expires October 25, 2015 [Page 9] Internet-Draft 3GPP IMS Option for IKEv2 April 2015 Brian Weis Cisco 170 West Tasman Drive San Jose, CA 95134 USA Email: bew@cisco.com Dodd-Noble, et al. Expires October 25, 2015 [Page 10]