Network Working Group J. Pezeshki
Internet-Draft E. Ertekin
Expires: February 28, 2008 R. Jasani
C. Christou
Booz Allen Hamilton
August 27, 2007
IKEv2 Extensions to Support Robust Header Compression over IPsec
(RoHCoIPsec)
draft-ietf-rohc-ikev2-extensions-hcoipsec-03
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Copyright (C) The IETF Trust (2007).
Abstract
When using Robust Header Compression (RoHC [ROHC]) in conjunction
with IPsec [IPSEC] (i.e. [ROHCOIPSEC]) a mechanism is needed to
negotiate RoHC configuration parameters between end-points prior to
operation. Internet Key Exchange (IKE) is a mechanism which can be
leveraged to handle these negotiations. This document specifies
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extensions to Internet Key Exchange (IKEv2 [IKEV2]) that will allow
RoHC and its associated configuration parameters to be negotiated for
IPsec security associations (SAs).
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 . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. Normative References . . . . . . . . . . . . . . . . . . . 6
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Introduction
Increased packet header overhead due to IPsec protection can result
in inefficient utilization of bandwidth. Coupling RoHC with IPsec
offers an efficient way to transfer protected IP traffic.
For proper RoHCoIPsec [ROHCOIPSEC] operation, RoHC requires
configuration parameters to be negotiated between the compressor and
decompressor, prior to operation. Current specifications of hop-by-
hop RoHC schemes negotiate these parameters through a link-layer
protocol such as Point-to-Point Protocol (PPP) (i.e. RoHC over PPP
[ROHCPPP]). Similarly, key exchange protocols (e.g. IKEv2) are
commonly used to negotiate parameters between IPsec peers before a SA
can be established. This document proposes the use of IKEv2 to
handle RoHC channel configuration for RoHCoIPsec, and details various
extensions to IKEv2 which are intended to provide this functionality.
2. RoHC Channel Negotiation
The initialization of a RoHC session requires the negotiation of a
set of configuration parameters (e.g. MAX_CID, etc.). As such, a
mechanism must exist for a RoHC enabled device to share a list of
supported RoHC parameters with its peer, and for the peer to select
the appropriate parameters from this list.
Similarly, negotiable parameters must also be shared between IPsec
peers before a SA can be established. To perform this negotiation, a
key exchange protocol, IKEv2, is commonly used. IKEv2 is an
extensible protocol that negotiates parameters via request/response
message pairs (i.e. exchanges).
A set of extensions to IKEv2 can be defined, which will allow for
RoHC parameters to be negotiated during the creation and rekeying of
Child SAs. This new Notify payload will contain values for the set
of RoHC parameters to be negotiated between the two RoHC peers.
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 Notify
payload will be used during the IKE_AUTH and CREATE_CHILD_SA
exchanges to negotiate the RoHCoIPsec session. The Notify payload
sent by the initiator will contain the configuration parameters for
the RoHC scheme. 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. These accepted
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parameters are a subset of 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.
A new Notify Message Type value, denoted ROHC_SUPPORTED, will be
added to indicate that the Notify payload is conveying RoHC channel
parameters. Additionally, the fields of the Notify payload (as
defined in [IKEV2]) are set as follows:
Next Payload (1 octet)
If the current payload is the last in the message, then this field
will be 0. The Next Payload value of the previous payload must be
41, indicating that this current payload is a Notify Payload.
Critical (1 bit)
This value is set to zero, indicating that the recipient must skip
this payload if it does not understand the payload type code in
the Next Payload field of the previous payload.
RESERVED (7 bits)
Must be sent as zero, and must be ignored on receipt.
Payload Length (2 octets)
Length in octets of the current payload, including the generic
payload header (the generic payload header is defined in [IKEV2],
section 3.2).
Protocol ID (1 octet)
Since the RoHC parameters are set at SA creation, and thus do not
relate to an existing 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.
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:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! MAX_CID ! MRRU !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! MAX_HEADER ! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
! !
~ PROFILES... ~
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Notification Data field
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
Note: The value of LARGE_CIDS will be implicitly determined by
this value (i.e. if MAX_CID is <= 15, LARGE_CIDS will be assumed
to be 0).
MRRU (2 octets)
The MRRU field indicates the maximum reconstructed reception unit
(see [ROHC], section 5.1.1).
Suggested value: 0
The MRRU value is used in conjunction with the segmentation
protocol defined in RoHC. Since RoHCoIPsec will generally be
implemented across multiple link-layer "hops", segmentation will
not normally be required. In these cases the MRRU value will be
set to zero, indicating that no segment headers are allowed on the
channel.
MAX_HEADER (2 octets)
The largest header size in octets that may be compressed.
Suggested value: 168 octets
Note: The MAX_HEADER parameter is not used for all RoHC profiles.
If none of the RoHC profiles require this field, this value is
ignored.
PROFILES
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The set of profiles to be enabled for the RoHC process. This
field may be set to one (or multiple) values listed in 'ROHC
profile identifiers' [ROHCPROF].
Note: 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 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.
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. 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
Finally, the authors would also like to thank Mr. Tom Conkle, Ms.
Michele Casey, and Mr. Etzel Brower.
6. References
6.1. Normative References
[ROHC] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K.,
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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.
[ROHCPROF]
IANA, ""RObust Header Compression (ROHC) Profile
Identifiers", IANA registry at:
http://www.iana.org/assignments/rohc-pro-ids", July 2007.
6.2. Informative References
[ROHCOIPSEC]
Ertekin, E., Christou, C., Jasani, R., and J. Pezeshki,
"Integration of Robust Header Compression (ROHC) over
IPsec Security Associations", work in progress ,
August 2007.
[ROHCPPP] Bormann, C., "Robust Header Compression (ROHC) over PPP",
RFC 3241, April 2002.
Authors' Addresses
Jonah Pezeshki
Booz Allen Hamilton
13200 Woodland Park Dr.
Herndon, VA 20171
US
Email: pezeshki_jonah@bah.com
Emre Ertekin
Booz Allen Hamilton
13200 Woodland Park Dr.
Herndon, VA 20171
US
Email: ertekin_emre@bah.com
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Rohan Jasani
Booz Allen Hamilton
13200 Woodland Park Dr.
Herndon, VA 20171
US
Email: jasani_rohan@bah.com
Chris Christou
Booz Allen Hamilton
13200 Woodland Park Dr.
Herndon, VA 20171
US
Email: christou_chris@bah.com
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