Network Working Group E. Ertekin
Internet-Draft C. Christou
Expires: February 13, 2010 R. Jasani
Booz Allen Hamilton
T. Kivinen
Safenet, Inc.
C. Bormann
Universitaet Bremen TZI
August 12, 2009
IKEv2 Extensions to Support Robust Header Compression over IPsec
(ROHCoIPsec)
draft-ietf-rohc-ikev2-extensions-hcoipsec-09
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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).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. ROHC Channel Initialization for ROHCoIPsec . . . . . . . . . . 4
2.1. ROHC Channel Parameters that are Signaled . . . . . . . . 4
2.1.1. ROHC_SUPPORTED Notify Message . . . . . . . . . . . . 5
2.1.2. ROHC Attribute Types . . . . . . . . . . . . . . . . . 6
2.2. ROHC Channel Parameters that are Implicitly Set . . . . . 9
3. Security Considerations . . . . . . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Normative References . . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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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.
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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
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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 five ROHC Attribute Types: MAX_CID,
ROHC_PROFILE, ROHC_INTEG, ROHC_ICV_LEN, and MRRU. The value
allocated for 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
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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.
ROHC Profile (ROHC_PROFILE, AF = 1)
The ROHC_PROFILE attribute is a mandatory attribute. Each
ROHC_PROFILE attribute has a fixed length of 4 octets, and its
attribute value is a two-octet long profile identifier. There may
be one or more ROHC_PROFILE attribute(s) included in the
ROHC_SUPPORTED Notify Message. If multiple ROHC_PROFILE
attributes are sent, the order is arbitrary. 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 (0x0002) and ROHCv2 UDP (0x0102), both profiles must
not be signaled. This restriction is needed, as packets
compressed by ROHC express only the 8 least significant bits of
the profile identifier; since the 8 least significant bits for
corresponding profiles in ROHCv1 and ROHCv2 are identical, the
decompressor is not capable of determining the ROHC version that
was used to compress the packet.
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).
Authentication algorithms that must be supported are specified in
Section 3.2 of [CRYPTO-ALG]. More explicitly, the implementation
conformance requirements for authentication algorithms are as
follows:
Requirement Algorithm
----------- ----------------
Must AUTH_HMAC_SHA1_96
Should+ AUTH_AES_XCBC_MAC_96
May AUTH_HMAC_MD5_96
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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). When a ROHC-enabled CHILD_SA is
rekeyed, the key associated with this integrity algorithm is
rekeyed as well.
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)
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.
Maximum reconstructed reception unit (MRRU, AF = 1)
The MRRU attribute is an optional attribute. There may be zero or
one MRRU attribute contained within the ROHC_SUPPORTED Notify
message. If present, the attribute value is two octets in length.
The attribute specifies the size of the largest reconstructed unit
in octets that the ROHCoIPsec decompressor is expected to
reassemble from ROHC segments. This size includes the CRC, and
the ROHC ICV. If MRRU is 0 or if no MRRU attribute is sent, no
segment headers are allowed on the ROHCoIPsec channel.
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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 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.
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 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 Maximum Reconstructed Reception Unit (MRRU) [rfcThis]
6-65536 Unassigned
Following the policies outlined in [IANA-CONSIDERATIONS], the IANA
policy for assigning new values for the ROHC Attribute Types registry
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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 Mr. Magnus Westerlund
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.
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.,
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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 , August 2009.
[ROHC-PPP]
Bormann, C., "Robust Header Compression (ROHC) over PPP",
RFC 3241, April 2002.
[CRYPTO-ALG]
Manral, V., "Cryptographic Algorithm Implementation
Requirements for Encapsulating Security Payload (ESP) and
Authentication Header (AH)", RFC 4835, April 2007.
[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.
Authors' Addresses
Emre Ertekin
Booz Allen Hamilton
13200 Woodland Park Dr.
Herndon, VA 20171
US
Email: ertekin_emre@bah.com
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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: ro@breakcheck.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
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