Network Working Group J. Pezeshki
Internet-Draft E. Ertekin
Expires: August 28, 2007 R. Jasani
C. Christou
Booz Allen Hamilton
February 24, 2007
IKEv2 Extensions to Support Header Compression over IPsec (HCoIPsec)
draft-ietf-rohc-ikev2-extensions-hcoipsec-01
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Copyright (C) The IETF Trust (2007).
Abstract
When using Header Compression (HC) schemes (e.g. ROHC [ROHC]) in
conjunction with IPsec [IPSEC] (i.e. [HCOIPSEC]) 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 extensions to Internet Key Exchange (IKEv2 [IKEV2]) that
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will allow ROHC and its associated configuration parameters to be
negotiated for IPsec security associations (SAs).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Header Compression Channel Negotiation . . . . . . . . . . . . 3
2.1. Negotiation of Header Compression Parameters . . . . . . . 3
2.1.1. Profiles Suboption . . . . . . . . . . . . . . . . . . 6
3. Security Considerations . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 10
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1. Introduction
Increased packet header overhead due to IPsec protection can result
in inefficient utilization of bandwidth. Coupling HC with IPsec
offers an efficient way to transfer protected IP traffic.
HC schemes require configuration parameters to be negotiated between
the compressor and decompressor, prior to operation. Current 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) exist,
which are commonly used to negotiate parameters between IPsec peers
before a SA can be established. This document proposes the use of
IPsec's parameter negotiation mechanism, IKE, to handle ROHC channel
configuration for HCoIPsec. Various extensions to IKEv2, designed to
provide this functionality, are detailed within this document.
2. Header Compression Channel Negotiation
The initialization of a ROHC session requires the negotiation of a
set of configuration parameters (e.g. maximum context identifier
length, etc.). As such, a mechanism must exist for a ROHC enabled
device to share a list of supported HC 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 Header Compression 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 HCoIPsec 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 negotiable parameters.
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A new Notify Message Type value, denoted ROHC_SUPPORTED, will be
added to indicate that the Notify payload is conveying ROHC channel
parameters. As defined in [IPSEC], the Notify payload is specified
as follows:
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 !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! !
~ Notification Data ~
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Notify Payload
To negotiate HCoIPsec, the values for the fields in the Notify
payload are defined as follows:
Next Payload (1 octet)
Identifier for the payload type of the next payload in the
message. 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.
Protocol ID (1 octet)
If this notification concerns an existing SA, this field indicates
the type of that SA (i.e. IKE_SA, AH [AH], or ESP [ESP]). 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)
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Length in octets of the SPI as defined by the IPsec protocol ID.
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)
Specifies the type of notification message. 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 in the
following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! HC PRMTR LNTH ! MAX_CID ! MRRU...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...MRRU ! MAX_HEADER ! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
! !
~ suboptions... ~
! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Notification Data field
HC PARAMETER LENGTH (1 octet)
>= 7 (i.e. the combined length of HC PARAMETER LENGTH, MAX_CID,
MRRU, and MAX_HEADER)
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).
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Suggested value: 0
Note: The MRRU value is used in conjunction with the segmentation
protocol defined in ROHC. Since a HCoIPsec compressor and
decompressor will generally be separated by multiple link-layer
"hops", segmentation will not be needed. In these cases the MRRU
value should be set to zero, indicating that no segmented ROHC
segmented-header packets 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.
suboptions
The suboptions field consists of one or more suboptions. Each
suboption consists of a type field, a length field and zero or
more parameter octets, as defined by the suboption type. The
value of the length field indicates the length of the suboption in
its entirety, including the lengths of the type and length fields.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Type ! Length ! Parameters...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Suboption
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).
2.1.1. Profiles Suboption
The set of profiles to be enabled on a Child SA is subject to
negotiation.
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Type ! Length ! Profiles...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Profiles suboption
Type
1
Length
2n+2
Value
n octet-pairs in ascending order, each octet-pair specifying a
ROHC profile supported. Values negotiated are assigned in the
ROHC profile identifiers registry [ROHCPROF].
3. Security Considerations
The negotiated HC schemes and 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 Type. Therefore, if the
proposal is accepted, IANA is requested to allocate on value from the
IKEv2 Notify Message Types 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:
Dr. Stephen Kent
Dr. Carsten Bormann
Mr. Lars-Erik Jonnson
Finally, the authors would also like to thank Mr. Tom Conkle, Ms.
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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.,
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.
[HCOIPSEC]
Ertekin, E., Christou, C., and R. Jasani, "Integration of
Header Compression over IPsec Security Associations", work
in progress , February 2007.
[IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005.
[ROHCPROF]
"RObust Header Compression (ROHC) Profile Identifiers",
www.iana.org/assignments/ROHC-pro-ids , October 2005.
6.2. Informative References
[ROHCPPP] Bormann, C., "Robust Header Compression (ROHC) over PPP",
RFC 3241, April 2002.
[AH] Kent, S., "IP Authentication Header", RFC 4302,
December 2005.
[ESP] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005.
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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
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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