Network Working Group E. Ertekin Internet-Draft C. Christou Expires: August 6, 2009 R. Jasani Booz Allen Hamilton T. Kivinen Safenet, Inc. C. Bormann Universitaet Bremen TZI February 2, 2009 IKEv2 Extensions to Support Robust Header Compression over IPsec (ROHCoIPsec) draft-ietf-rohc-ikev2-extensions-hcoipsec-08 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 6, 2009. Copyright Notice Copyright (c) 2009 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 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Ertekin, et al. Expires August 6, 2009 [Page 1] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 to this document. Abstract In order to integrate ROHC with IPsec [ROHCOIPSEC], a mechanism is needed to signal ROHC channel parameters between end-points. Internet Key Exchange (IKE) is a mechanism which can be leveraged to exchange these parameters. This document specifies extensions to IKEv2 [IKEV2] that will allow ROHC and its associated channel parameters to be signaled for IPsec security associations (SAs). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. ROHC Channel Initialization for ROHCoIPsec . . . . . . . . . . 3 2.1. ROHC Channel Parameters that are Signaled . . . . . . . . . 3 2.1.1. ROHC_SUPPORTED Notify Message . . . . . . . . . . . . . 4 2.1.2. ROHC Attribute Types . . . . . . . . . . . . . . . . . 5 2.2. ROHC Channel Parameters that are Implicitly Set . . . . . . 7 3. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Ertekin, et al. Expires August 6, 2009 [Page 2] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 1. Introduction Increased packet header overhead due to IPsec [IPSEC] can result in the inefficient utilization of bandwidth. Coupling ROHC [ROHC] with IPsec offers an efficient way to transfer protected IP traffic. ROHCoIPsec [ROHCOIPSEC] requires configuration parameters to be initialized at the compressor and decompressor. Current specifications for hop-by-hop ROHC negotiate these parameters through a link-layer protocol such as Point-to-Point Protocol (PPP) (i.e. ROHC over PPP [ROHC-PPP]). Since key exchange protocols (e.g. IKEv2) can be used to dynamically establish parameters between IPsec peers, this document defines extensions to IKEv2 to signal ROHC parameters for ROHCoIPsec. 2. ROHC Channel Initialization for ROHCoIPsec The following subsections define extensions to IKEv2 which enables an initiator and a responder to signal parameters required to establish a ROHC channel for a ROHCoIPsec session. 2.1. ROHC Channel Parameters that are Signaled ROHC channel parameters will be signaled at either the establishment or rekeying of a Child SA. Specifically, a new Notify message type is used during the IKE_AUTH and CREATE_CHILD_SA exchanges to convey these parameters. The Notify payload sent by the initiator contains the channel parameters for the ROHC implementation. Specifically, these parameters indicate the capabilities of the ROHC decompressor at the initiator. Upon receipt of the initiator's request, the responder will either ignore the payload (if it doesn't support ROHC or the proposed parameters) or respond with a Notify payload that contains its own ROHC channel parameters. Note that only one Notify payload is used to convey ROHC parameters. If multiple Notify payloads containing ROHC parameters are received, all but the first such Notify payload must be dropped. If the initiator does not receive a Notify Payload with the responder's ROHC channel parameters, ROHC must not be enabled on the Child SA. A new Notify Message Type value, denoted ROHC_SUPPORTED, indicates that the Notify payload is conveying ROHC channel parameters. The value for the ROHC_SUPPORTED message is specified in Section 4. The Notify Payload (defined in [IKEV2]) is illustrated in Figure 1. Ertekin, et al. Expires August 6, 2009 [Page 3] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload !C! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Protocol ID ! SPI Size ! Notify Message Type ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! ! ~ Security Parameter Index (SPI) ~ ! ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! ! ~ Notification Data ~ ! ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1. Notify Payload format. The fields of the Notify Payload are set as follows: Next Payload (1 octet) Identifier for the payload type of the next payload in the message. Further details can be found in [IKEV2]. Critical (1 bit) Since all IKEv2 implementations must support the Notify Payload, this value is zero. Payload Length (2 octets) As defined in [IKEV2], this field indicates the length of the current payload, including the generic payload header. Protocol ID (1 octet) Since this Notification message is used during the creation of a Child SA, this field must be set to zero. SPI Size (1 octet) This value must be set to zero, since no SPI is applicable (ROHC parameters are set at SA creation, thus the SPI has not been defined). Notify Message Type (2 octets) This field must be set to ROHC_SUPPORTED. 2.1.1. ROHC_SUPPORTED Notify Message The ROHC_SUPPORTED Notify message is used to signal channel parameters between ROHCoIPsec compressor and decompressor. The Ertekin, et al. Expires August 6, 2009 [Page 4] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 message contains a list of "ROHC Attributes" which contain the parameters required for the ROHCoIPsec session. The format for signaling ROHC Attributes takes a similar format to the Transform Attributes described in Section 3.3.5 of [IKEV2]. The ROHC Attribute is shown in Figure 2. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ !A! ROHC Attribute Type ! AF=0 ROHC Attribute Length ! !F! ! AF=1 ROHC Attribute Value ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! AF=0 ROHC Attribute Value ! ! AF=1 Not Transmitted ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2. Format of the ROHC Attribute. o ROHC Attribute Type (2 octets) - Unique identifier for each type of ROHC attribute (see Section 2.1.2). The most significant bit in the field is the Attribute Format (AF) bit. If the AF bit is a zero (0), then the ROHC Attribute is expressed in a Type/Length/ Value (TLV) format. If the AF bit is a one (1), then the ROHC Attribute is expressed in a Type/Value (TV) format. o ROHC Attribute Length (2 octets) - Length (in octets) of the Attribute Value. When the AF bit is a one (1), the ROHC Attribute Value is 2 octets and the ROHC Attribute Length field is not present. o ROHC Attribute Value (variable length) - Value of the ROHC Attribute associated with the ROHC Attribute Type. If the AF bit is a zero (0), this field's length is defined by the ROHC Attribute Length field. If the AF bit is a one (1), the length of the ROHC Attribute Value is 2 octets. 2.1.2. ROHC Attribute Types This section describes four ROHC Attribute Types: MAX_CID, ROHC_PROFILES, ROHC_INTEG, and ROHC_ICV_LEN. The value which defines each ROHC Attribute Type is specified in Section 4. Maximum Context Identifier (MAX_CID, AF = 1) The MAX_CID attribute is a mandatory attribute. Exactly one MAX_CID attribute must be sent. The MAX_CID field indicates the maximum value of a context Identifier supported by the ROHCoIPsec decompressor. This attribute value is two octets in length. The Ertekin, et al. Expires August 6, 2009 [Page 5] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 range of values for MAX_CID must be at least 0 and at most 16383 (the value 0 implies having one context). The recipient of the MAX_CID Attribute must only use up to MAX_CID context identifiers for compression. Suggested value: 15 ROHC Profile (ROHC_PROFILE, AF = 1) The ROHC_PROFILE attribute is a mandatory attribute. At least one ROHC_PROFILE attribute(s) must be sent. A ROHC_PROFILE attribute contains a two-octet profile supported by the ROHCoIPsec decompressor. The recipient of a ROHC_PROFILE attribute(s) must only use the profile(s) proposed for compression. Several common profiles are defined in [ROHCV1] and [ROHCV2]. Note, however, that two versions of the same profile must not be signaled. For example, if a ROHCoIPsec decompressor supports both ROHCv1 UDP and ROHCv2 UDP profiles, both profiles must not be signaled. Integrity Algorithm for Verification of Decompressed Headers (ROHC_INTEG, AF = 1) The ROHC_INTEG attribute is a mandatory attribute. There must be at least one ROHC_INTEG attribute contained within the ROHC_SUPPORTED Notify message. The attribute contains an integrity algorithm that is used to ensure the integrity of the decompressed packets (i.e. ensure that the packet headers are properly decompressed). The integrity algorithm is represented by a two octet value that corresponds to the value listed in [IKEV2- PARA] "For Transform Type 3 (Integrity Algorithm)" section. Upon receipt of the ROHC_INTEG attribute(s), the responder must select exactly one of proposed algorithms and send the selected algorithm back to the initiator. The selected integrity algorithm must be used in both directions. It is noted that: 1. The key for this Integrity Algorithm is computed using the same method as is used to compute IPsec's Integrity Algorithm key ([IKEV2], Section 2.17). 2. A ROHCoIPsec initiator may signal a value of zero (0x0000) in a ROHC_INTEG attribute. This corresponds to "NONE" in the Integrity Algorithm Transform ID registry. The ROHCoIPsec responder may select this value by responding to the initiator with a ROHC_INTEG attribute of zero (0x0000). In this scenario, no integrity algorithm is applied in either direction. Integrity Algorithm Length (ROHC_ICV_LEN, AF = 1) Ertekin, et al. Expires August 6, 2009 [Page 6] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 The ROHC_ICV_LEN attribute is an optional attribute. There may be zero or one ROHC_ICV_LEN attribute contained within the ROHC_SUPPORTED Notify message. The attribute specifies the number of ICV octets the sender expects to receive on incoming ROHC packets. The ICV of the negotiated ROHC_INTEG algorithms are truncated to ROHC_ICV_LEN bytes by taking the first ROHC_ICV_LEN bytes of the output. Both the initiator and responder announce their preference for their own ICV length. The recipient of the ROHC_ICV_LEN attribute must truncate the ICV to the length contained in the message. If ROHC_ICV_LEN length is zero, then no ICV is calculated or sent. If no ROHC_ICV_LEN attribute is sent at all or the ROHC_ICV_LEN is larger than the length of the ICV of selected algorithm, then the full ICV length as specified by the ROHC_INTEG algorithm is sent. If an unknown ROHC Attribute Type Value is received, it is silently ignored. 2.2. ROHC Channel Parameters that are Implicitly Set The following ROHC channel parameters are not signaled: o LARGE_CIDS: This value is implicitly determined by the value of MAX_CID (e.g. if MAX_CID is <= 15, LARGE_CIDS is assumed to be 0). o MRRU: IPsec implementations will always implement path MTU discovery; therefore, ROHC packets will never need to use ROHC segmentation over an IPsec SA. As a result, this value will always be zero, and does not need to be signaled. o FEEDBACK_FOR: When a pair of SAs are created (one in each direction), the ROHC channel parameter FEEDBACK_FOR is set implicitly to the other SA of the pair (i.e. the SA pointing in the reverse direction). 3. Security Considerations The ROHC channel parameters signaled via IKEv2 do not add any new vulnerabilities beyond those associated with the normal operation of IKEv2. 4. IANA Considerations This document defines a new Notify Message (Status Type). Therefore, IANA is requested to allocate one value from the IKEv2 Notify Message registry to indicate ROHC_SUPPORTED. Note that, since this Notify Message is a Status Type, values ranging from 0 to 16383 must not be allocated for ROHC_SUPPORTED. Ertekin, et al. Expires August 6, 2009 [Page 7] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 In addition, IANA is requested to allocate a "ROHC Attribute Types" registry in the IKEv2 Parameters Registry [IKEV2-PARA]. Within the "ROHC Attribute Types" registry, this document allocates the following values: Registry Value ROHC Attribute Type Reference ------------------------------------------------------------------ 0 RESERVED [rfcThis] 1 Maximum value of context identifier (MAX_CID) [rfcThis] 2 ROHC Profile (ROHC_PROFILE) [rfcThis] 3 ROHC Integrity Algorithm (ROHC_INTEG) [rfcThis] 4 ROHC ICV Length in bytes (ROHC_ICV_LEN) [rfcThis] 5-65536 Unassigned Following the policies outlined in [IANA-CONSIDERATIONS], the IANA policy for assigning new values for the ROHC Attribute Types registry shall be Specification Required: values and their meanings must be documented in a permanent and readily available public specification, in sufficient detail so that interoperability between independent implementations is possible. 5. Acknowledgments The authors would like to thank Mr. Sean O'Keeffe, Mr. James Kohler, and Ms. Linda Noone of the Department of Defense, as well as Mr. Rich Espy of OPnet for their contributions and support in the development of this document. The authors would also like to thank Mr. Yoav Nir, and Mr. Robert A Stangarone Jr.: both served as committed document reviewers for this specification. In addition, the authors would like to thank the following for their numerous reviews and comments to this document: o Dr. Stephen Kent o Mr. Lars-Erik Jonsson o Mr. Pasi Eronen o Dr. Jonah Pezeshki o Mr. Carl Knutsson o Dr. Joseph Touch Finally, the authors would also like to thank Mr. Tom Conkle, Ms. Michele Casey, and Mr. Etzel Brower. Ertekin, et al. Expires August 6, 2009 [Page 8] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 6. References 6.1. Normative References [IPSEC] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [ROHC] Jonsson, L-E., Pelletier, G., and K. Sandlund, "The RObust Header Compression (ROHC) Framework", RFC 4995, July 2007. [IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [ROHCV1] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H., Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K., Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header Compression (ROHC): Framework and four profiles: RTP, UDP, ESP, and uncompressed", RFC 3095, July 2001. [ROHCV2] Pelletier, G. and K. Sandlund, "RObust Header Compression Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP Lite", RFC 5225, April 2008. 6.2. Informative References [ROHCOIPSEC] Ertekin, E., Jasani, R., Christou, C., and C. Bormann, "Integration of Header Compression over IPsec Security Associations", work in progress , February 2009. [ROHC-PPP] Bormann, C., "Robust Header Compression (ROHC) over PPP", RFC 3241, April 2002. [IKEV2-PARA] IANA, "IKEv2 Parameters, http://www.iana.org/assignments/ikev2-parameters", January 2008. [IANA-CONSIDERATIONS] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, October 1998. Ertekin, et al. Expires August 6, 2009 [Page 9] Internet-Draft IKEv2 Extensions to Support ROHCoIPsec February 2009 Authors' Addresses Emre Ertekin Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: ertekin_emre@bah.com Chris Christou Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: christou_chris@bah.com Rohan Jasani Booz Allen Hamilton 13200 Woodland Park Dr. Herndon, VA 20171 US Email: jasani_rohan@bah.com Tero Kivinen Safenet, Inc. Fredrikinkatu 47 HELSINKI FI Email: kivinen@safenet-inc.com Carsten Bormann Universitaet Bremen TZI Postfach 330440 Bremen D-28334 Germany Email: cabo@tzi.org Ertekin, et al. Expires August 6, 2009 [Page 10]