Network Working Group E. Ertekin
Internet-Draft C. Christou
Expires: April 17, 2009 R. Jasani
J. Pezeshki
Booz Allen Hamilton
October 14, 2008
IKEv2 Extensions to Support Robust Header Compression over IPsec
(ROHCoIPsec)
draft-ietf-rohc-ikev2-extensions-hcoipsec-07
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Abstract
In order to integrate ROHC with IPsec [ROHCOIPSEC], a mechanism is
needed to negotiate ROHC configuration parameters between end-points.
Internet Key Exchange (IKE) is a mechanism which can be leveraged to
handle these negotiations. This document specifies extensions to
IKEv2 [IKEV2] that will allow ROHC and its associated configuration
parameters to be negotiated for IPsec security associations (SAs).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. ROHC Channel Negotiation . . . . . . . . . . . . . . . . . . . 3
2.1. Negotiation of ROHC Channel Parameters . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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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.
The operation of ROHCoIPsec [ROHCOIPSEC] requires configuration
parameters to be negotiated between 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 [ROHCPPP]). Since key exchange protocols (e.g.
IKEv2) can be used to negotiate parameters between IPsec peers, this
document defines extensions to IKEv2 to negotiate ROHC parameters for
ROHCoIPsec.
2. ROHC Channel Negotiation
The initialization of a ROHC session requires the negotiation of a
set of configuration parameters (e.g. MAX_CID, PROFILES, etc.). The
following subsections define extensions to IKEv2 which enables an
initiator to propose a set of ROHC parameters; the responder selects
the appropriate parameters from this list, and responds with the
accepted parameters for the ROHC channel.
2.1. Negotiation of ROHC Channel Parameters
ROHC configuration parameters will be negotiated 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 negotiate these parameters.
The Notify payload sent by the initiator contains the configuration
parameters for the ROHC implementation. 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 the accepted ROHC channel parameters.
The accepted parameters are an intersection between the parameters
proposed by the initiator and the parameters supported by the
responder (e.g. if the initiator proposes a MAX_CID value of 15, but
the responder only supports a MAX_CID value of 13, the responder will
respond with a value of 13, which is supported by both parties).
Note that only one Notify payload is used to convey ROHC parameters
per exchange. If multiple Notify payloads relaying ROHC parameters
are received by the responder, all but the first such Notify payload
must be dropped. If the initiator does not receive a Notify Payload
with the responder's accepted ROHC channel parameters, ROHC must not
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be enabled on the Child SA.
A new Notify Message Type value, denoted ROHC_SUPPORTED, will
indicate that the Notify payload is conveying ROHC channel
parameters. The Notify Payload (as defined in [IKEV2]) is
illustrated in Figure 1 below:
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.
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)
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This field must be set to ROHC_SUPPORTED.
ROHC configuration parameters will be communicated via a new Notify
message type, denoted ROHC_SUPPORTED. The ROHC configuration
parameters will be listed within the Notification Data field of the
Notify payload in the following format (default values for the
configuration parameters are consistent with [ROHCPPP]):
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! MAX_CID | RESERVED |PROFILES_LENGTH!
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! !
~ PROFILES... ~
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! !
~ INTEGRITY ALGORITHMS... ~
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. Notification Data field for the ROHC_SUPPORTED Notify
message type.
MAX_CID (2 octets)
The MAX_CID field indicates the maximum value of a context
identifier. This value must be at least 0 and at most 16383 (The
value 0 implies having one context).
Suggested value: 15
PROFILES_LENGTH (1 octet)
The total number of profiles contained within the PROFILES field
(note that each ROHC profile is 2-octets in length).
PROFILES (variable)
The set of profiles to be enabled for the ROHC process. Profiles
are further detailed in [ROHC]. In addition, several common
profiles are defined in [ROHCPROF]. These 16-bit profile
identifiers are to be sent in network byte order.
INTEGRITY ALGORITHMS
The set of Integrity Algorithms that may be use to ensure the
integrity of the decompressed packets (i.e. ensure that the packet
headers are properly decompressed). Each Integrity Algorithm is
represented by a 2-octet value that corresponds to the value
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listed in [IKEV2-PARA] "For Transform Type 3 (Integrity
Algorithm)" section.
It is noted that:
1. The length of this field is inferred from the Notify Payload's
"Payload Length" field.
2. 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).
3. A ROHCoIPsec implementation may choose to negotiate a value of
"0" in this field (i.e., NONE, as defined in the Integrity
Algorithm Transform ID registry).
The negotiated set of ROHC parameters are associated with the
inbound/outbound pair of SAs established by each IKEv2
CREATE_CHILD_SA exchange.
The following ROHC channel parameters are not negotiated:
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 negotiated.
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 negotiated 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.
5. Acknowledgments
The authors would like to thank Mr. Sean O'Keeffe, Mr. James Kohler,
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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. Tero
Kivinen for providing his technical expertise for this document. In
addition, the authors would like to thank the following for their
numerous reviews and comments to this document:
o Dr. Stephen Kent
o Dr. Carsten Bormann
o Mr. Lars-Erik Jonnson
o Mr. Pasi Eronen
o Dr. Joseph Touch
o Mr. Yoav Nir
Finally, the authors would also like to thank Mr. Tom Conkle, Ms.
Michele Casey, and Mr. Etzel Brower.
6. References
6.1. Normative References
[ROHCOIPSEC]
Ertekin, E., Christou, C., and R. Jasani, "Integration of
Robust Header Compression over IPsec Security
Associations", work in progress , October 2008.
[ROHC] 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.
[IPSEC] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
[ROHCPPP] Bormann, C., "Robust Header Compression (ROHC) over PPP",
RFC 3241, April 2002.
6.2. Informative References
[ROHCPROF]
Pelletier, G. and K. Sandlund, "RObust Header Compression
Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP
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Lite", www.iana.org/assignments/ROHC-pro-ids , May 2007.
[IKEV2-PARA]
IANA, "IKEv2 Parameters,
http://www.iana.org/assignments/ikev2-parameters",
January 2008.
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
Jonah Pezeshki
Booz Allen Hamilton
13200 Woodland Park Dr.
Herndon, VA 20171
US
Email: pezeshki_jonah@bah.com
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