draft-ietf-rohc-hcoipsec-11.txt   draft-ietf-rohc-hcoipsec-12.txt 
Network Working Group E. Ertekin Network Working Group E. Ertekin
Internet-Draft R. Jasani Internet-Draft R. Jasani
Intended status: Informational C. Christou Intended status: Informational C. Christou
Expires: February 13, 2010 Booz Allen Hamilton Expires: June 7, 2010 Booz Allen Hamilton
C. Bormann C. Bormann
Universitaet Bremen TZI Universitaet Bremen TZI
August 12, 2009 December 4, 2009
Integration of Robust Header Compression (ROHC) over IPsec Security Integration of Robust Header Compression (ROHC) over IPsec Security
Associations Associations
draft-ietf-rohc-hcoipsec-11 draft-ietf-rohc-hcoipsec-12
Abstract
IP Security (IPsec) provides various security services for IP
traffic. However, the benefits of IPsec come at the cost of
increased overhead. This document outlines a framework for
integrating Robust Header Compression (ROHC) over IPsec (ROHCoIPsec).
By compressing the inner headers of IP packets, ROHCoIPsec proposes
to reduce the amount of overhead associated with the transmission of
traffic over IPsec Security Associations (SAs).
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material provisions of BCP 78 and BCP 79.
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
copyright in some of this material may not have granted the IETF
Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
document may not be modified outside the IETF Standards Process, and
derivative works of it may not be created outside the IETF Standards
Process, except to format it for publication as an RFC or to
translate it into languages other than English.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 13, 2010. This Internet-Draft will expire on June 7, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents
publication of this document (http://trustee.ietf.org/license-info). (http://trustee.ietf.org/license-info) in effect on the date of
Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
and restrictions with respect to this document. carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Abstract include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
IP Security (IPsec) provides various security services for IP This document may contain material from IETF Documents or IETF
traffic. However, the benefits of IPsec come at the cost of Contributions published or made publicly available before November
increased overhead. This document outlines a framework for 10, 2008. The person(s) controlling the copyright in some of this
integrating Robust Header Compression (ROHC) over IPsec (ROHCoIPsec). material may not have granted the IETF Trust the right to allow
By compressing the inner headers of IP packets, ROHCoIPsec proposes modifications of such material outside the IETF Standards Process.
to reduce the amount of overhead associated with the transmission of Without obtaining an adequate license from the person(s) controlling
traffic over IPsec Security Associations (SAs). the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3
2. Audience . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Audience . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
4. Problem Statement: IPsec Packet Overhead . . . . . . . . . 5 4. Problem Statement: IPsec Packet Overhead . . . . . . . . . 4
5. Overview of the ROHCoIPsec Framework . . . . . . . . . . . 6 5. Overview of the ROHCoIPsec Framework . . . . . . . . . . . 5
5.1. ROHCoIPsec Assumptions . . . . . . . . . . . . . . . . . . 6 5.1. ROHCoIPsec Assumptions . . . . . . . . . . . . . . . . . . 5
5.2. Summary of the ROHCoIPsec Framework . . . . . . . . . . . 6 5.2. Summary of the ROHCoIPsec Framework . . . . . . . . . . . 5
6. Details of the ROHCoIPsec Framework . . . . . . . . . . . 7 6. Details of the ROHCoIPsec Framework . . . . . . . . . . . 6
6.1. ROHC and IPsec Integration . . . . . . . . . . . . . . . . 8 6.1. ROHC and IPsec Integration . . . . . . . . . . . . . . . . 7
6.1.1. Header Compression Protocol Considerations . . . . . . . . 10 6.1.1. Header Compression Protocol Considerations . . . . . . . . 9
6.1.2. Initialization and Negotiation of the ROHC Channel . . . . 10 6.1.2. Initialization and Negotiation of the ROHC Channel . . . . 9
6.1.3. Encapsulation and Identification of Header Compressed 6.1.3. Encapsulation and Identification of Header Compressed
Packets . . . . . . . . . . . . . . . . . . . . . . . . . 11 Packets . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1.4. Path MTU Considerations . . . . . . . . . . . . . . . . . 11 6.1.4. Motivation for the ROHC ICV . . . . . . . . . . . . . . . 10
6.2. ROHCoIPsec Framework Summary . . . . . . . . . . . . . . . 12 6.1.5. Path MTU Considerations . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . 12 6.2. ROHCoIPsec Framework Summary . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . 12 8. IANA Considerations . . . . . . . . . . . . . . . . . . . 12
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 12 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 12
10. Informative References . . . . . . . . . . . . . . . . . . 13 10. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
This document outlines a framework for integrating ROHC [ROHC] over This document outlines a framework for integrating ROHC [ROHC] over
IPsec [IPSEC] (ROHCoIPsec). The goal of ROHCoIPsec is to reduce the IPsec [IPSEC] (ROHCoIPsec). The goal of ROHCoIPsec is to reduce the
protocol overhead associated with packets traversing between IPsec SA protocol overhead associated with packets traversing between IPsec SA
endpoints. This can be achieved by compressing the transport layer endpoints. This can be achieved by compressing the transport layer
header (e.g., UDP, TCP, etc.) and inner IP header of packets at the header (e.g., UDP, TCP, etc.) and inner IP header of packets at the
ingress of the IPsec tunnel, and decompressing these headers at the ingress of the IPsec tunnel, and decompressing these headers at the
egress. egress.
For ROHCoIPsec, this document assumes that ROHC will be used to For ROHCoIPsec, this document assumes that ROHC will be used to
compress the inner headers of IP packets traversing an IPsec tunnel. compress the inner headers of IP packets traversing an IPsec tunnel.
However, since current specifications for ROHC detail its operation However, since current specifications for ROHC detail its operation
on a hop-by-hop basis, it requires extensions to enable its operation on a hop-by-hop basis, it requires extensions to enable its operation
over IPsec SAs. These extensions need to account for increased over IPsec SAs. This document outlines a framework for extending the
packet reordering and packet loss that may occur in the unprotected usage of ROHC to operate at IPsec SA endpoints.
domain. This document outlines a framework for extending the usage
of ROHC to operate at IPsec SA endpoints.
ROHCoIPsec targets the application of ROHC to tunnel mode SAs. ROHCoIPsec targets the application of ROHC to tunnel mode SAs.
Transport mode SAs only encrypt/authenticate the payload of an IP Transport mode SAs only encrypt/authenticate the payload of an IP
packet, leaving the IP header untouched. Intermediate routers packet, leaving the IP header untouched. Intermediate routers
subsequently use this IP header to route the packet to a decryption subsequently use this IP header to route the packet to a decryption
device. Therefore, if ROHC is to operate over IPsec transport-mode device. Therefore, if ROHC is to operate over IPsec transport-mode
SAs, (de)compression functionality can only be applied to the SAs, (de)compression functionality can only be applied to the
transport layer headers, and not to the IP header. Because current transport layer headers, and not to the IP header. Because current
ROHC specifications do not include support for the compression of ROHC specifications do not include support for the compression of
transport layer headers alone, the ROHCoIPsec framework outlined by transport layer headers alone, the ROHCoIPsec framework outlined by
skipping to change at page 4, line 45 skipping to change at page 4, line 43
2. Audience 2. Audience
The authors target members of both the ROHC and IPsec communities who The authors target members of both the ROHC and IPsec communities who
may consider extending the ROHC and IPsec protocols to meet the may consider extending the ROHC and IPsec protocols to meet the
requirements put forth in this document. In addition, this document requirements put forth in this document. In addition, this document
is directed towards vendors developing IPsec devices that will be is directed towards vendors developing IPsec devices that will be
deployed in bandwidth-constrained IP networks. deployed in bandwidth-constrained IP networks.
3. Terminology 3. Terminology
Terminology specific to ROHCoIPsec is introduced in this section.
ROHC Process ROHC Process
Generic reference to a ROHC instance (as defined in [ROHC-TERM]),
or any supporting ROHC components.
Compressed Traffic Generic reference to a ROHC instance (as defined in RFC 3759
[ROHC-TERM]), or any supporting ROHC components.
Compressed Traffic
Traffic that is processed through the ROHC compressor and Traffic that is processed through the ROHC compressor and
decompressor instances. Packet headers are compressed and decompressor instances. Packet headers are compressed and
decompressed using a specific header compression profile. decompressed using a specific header compression profile.
Uncompressed Traffic Uncompressed Traffic
Traffic that is not processed by the ROHC compressor instance. Traffic that is not processed by the ROHC compressor instance.
Instead, this type of traffic bypasses the ROHC process. Instead, this type of traffic bypasses the ROHC process.
IPsec Process IPsec Process
Generic reference to the Internet Protocol Security (IPsec) Generic reference to the Internet Protocol Security (IPsec)
process. process.
Next Header Next Header
Refers to the Protocol (IPv4) or Next Header (IPv6, Extension) Refers to the Protocol (IPv4) or Next Header (IPv6, Extension)
field. field.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [BRA97].
4. Problem Statement: IPsec Packet Overhead 4. Problem Statement: IPsec Packet Overhead
IPsec mechanisms provide various security services for IP networks. IPsec mechanisms provide various security services for IP networks.
However, the benefits of IPsec come at the cost of increased per- However, the benefits of IPsec come at the cost of increased per-
packet overhead. For example, traffic flow confidentiality packet overhead. For example, traffic flow confidentiality
(generally leveraged at security gateways) requires the tunneling of (generally leveraged at security gateways) requires the tunneling of
IP packets between IPsec implementations. Although these IPsec IP packets between IPsec implementations. Although these IPsec
tunnels will effectively mask the source-destination patterns that an tunnels will effectively mask the source-destination patterns that an
intruder can ascertain, tunneling comes at the cost of increased per- intruder can ascertain, tunneling comes at the cost of increased
packet overhead. Specifically, an ESP tunnel mode SA applied to an packet overhead. Specifically, an ESP tunnel mode SA applied to an
IPv6 flow results in at least 50 bytes of additional overhead per IPv6 flow results in at least 50 bytes of additional overhead per
packet. This additional overhead may be undesirable for many packet. This additional overhead may be undesirable for many
bandwidth-constrained wireless and/or satellite communications bandwidth-constrained wireless and/or satellite communications
networks, as these types of infrastructure are not overprovisioned. networks, as these types of infrastructure are not overprovisioned.
ROHC applied on a per-hop basis over bandwidth-constrained links will ROHC applied on a per-hop basis over bandwidth-constrained links will
also suffer from reduced performance when encryption is used on the also suffer from reduced performance when encryption is used on the
tunneled header, since encrypted headers cannot be compressed. tunneled header, since encrypted headers cannot be compressed.
Consequently, the additional overhead incurred by an IPsec tunnel may Consequently, the additional overhead incurred by an IPsec tunnel may
result in the inefficient utilization of bandwidth. result in the inefficient utilization of bandwidth.
skipping to change at page 6, line 17 skipping to change at page 6, line 17
5. Overview of the ROHCoIPsec Framework 5. Overview of the ROHCoIPsec Framework
5.1. ROHCoIPsec Assumptions 5.1. ROHCoIPsec Assumptions
The goal of ROHCoIPsec is to provide efficient transport of IP The goal of ROHCoIPsec is to provide efficient transport of IP
packets between IPsec devices without compromising the security packets between IPsec devices without compromising the security
services offered by IPsec. The ROHCoIPsec framework has been services offered by IPsec. The ROHCoIPsec framework has been
developed based on the following assumptions: developed based on the following assumptions:
o ROHC will be leveraged to reduce the amount of overhead associated o ROHC will be leveraged to reduce the amount of overhead associated
with packets traversing an IPsec SA with unicast IP packets traversing an IPsec SA
o ROHC will be instantiated at the IPsec SA endpoints, and will be o ROHC will be instantiated at the IPsec SA endpoints, and will be
applied on a per-SA basis applied on a per-SA basis
o Once the decompression operation completes, decompressed packet o Once the decompression operation completes, decompressed packet
headers will be identical to the original packet headers before headers will be identical to the original packet headers before
compression compression
5.2. Summary of the ROHCoIPsec Framework 5.2. Summary of the ROHCoIPsec Framework
ROHC reduces packet overhead in a network by exploiting intra- and ROHC reduces packet overhead in a network by exploiting intra- and
inter-packet redundancies of network and transport-layer header inter-packet redundancies of network and transport-layer header
skipping to change at page 6, line 39 skipping to change at page 6, line 39
Current ROHC protocol specifications compress packet headers on a Current ROHC protocol specifications compress packet headers on a
hop-by-hop basis. However, IPsec SAs are instantiated between two hop-by-hop basis. However, IPsec SAs are instantiated between two
IPsec endpoints. Therefore, various extensions to both ROHC and IPsec endpoints. Therefore, various extensions to both ROHC and
IPsec need to be defined to ensure the successful operation of the IPsec need to be defined to ensure the successful operation of the
ROHC protocol at IPsec SA endpoints. ROHC protocol at IPsec SA endpoints.
The specification of ROHC over IPsec SAs is straightforward, since SA The specification of ROHC over IPsec SAs is straightforward, since SA
endpoints provide source/destination pairs where (de)compression endpoints provide source/destination pairs where (de)compression
operations can take place. Compression of the inner IP and upper operations can take place. Compression of the inner IP and upper
layer protocol headers in such a manner offers a reduction of per- layer protocol headers in such a manner offers a reduction of packet
packet protocol overhead between the two SA endpoints. Since ROHC overhead between the two SA endpoints. Since ROHC will now operate
will now operate between IPsec endpoints (over multiple intermediate between IPsec endpoints (over multiple intermediate nodes which are
nodes which are transparent to an IPsec SA), it is imperative to transparent to an IPsec SA), it is imperative to ensure that its
ensure that its performance will not be severely impacted due to performance will not be severely impacted due to increased packet
increased packet reordering and/or packet loss between the compressor reordering and/or packet loss between the compressor and
and decompressor. decompressor.
In addition, ROHC can no longer rely on the underlying link layer for In addition, ROHC can no longer rely on the underlying link layer for
ROHC channel parameter configuration and packet identification. The ROHC channel parameter configuration and packet identification. The
ROHCoIPsec framework proposes that ROHC channel parameter ROHCoIPsec framework proposes that ROHC channel parameter
configuration is accomplished by an SA management protocol (e.g., configuration is accomplished by an SA management protocol (e.g.,
IKEv2 [IKEV2]), while identification of compressed header packets is IKEv2 [IKEV2]), while identification of compressed header packets is
achieved through the Next Header field of the security protocol achieved through the Next Header field of the security protocol
(e.g., AH [AH], ESP [ESP]) header. (e.g., AH [AH], ESP [ESP]) header.
Using the ROHCoIPsec framework proposed below, outbound and inbound Using the ROHCoIPsec framework proposed below, outbound and inbound
IP traffic processing at an IPsec device needs to be modified. For IP traffic processing at an IPsec device needs to be modified. For
an outbound packet, a ROHCoIPsec implementation will compress an outbound packet, a ROHCoIPsec implementation will compress
appropriate packet headers, and subsequently encrypt and/or appropriate packet headers, and subsequently encrypt and/or
integrity-protect the packet. For tunnel mode SAs, compression may integrity-protect the packet. For tunnel mode SAs, compression may
be applied to the transport layer and the inner IP headers. For be applied to the transport layer and the inner IP headers. For
inbound packets, an IPsec device must first decrypt and/or integrity- inbound packets, an IPsec device must first decrypt and/or integrity-
check the packet. Then decompression of the inner packet headers is check the packet. Then decompression of the inner packet headers is
performed. After decompression, the packet is checked against the performed. After decompression, the packet is checked against the
access controls imposed on all inbound traffic associated with the SA access controls imposed on all inbound traffic associated with the SA
(as specified in [IPSEC]). (as specified in RFC 4301 [IPSEC]).
Note: Compression of inner headers is independent from compression Note: Compression of inner headers is independent from compression
of the security protocol (e.g., ESP) and outer IP headers. ROHC of the security protocol (e.g., ESP) and outer IP headers. ROHC
profiles have been defined to allow for the compression of the profiles have been defined to allow for the compression of the
security protocol and the outer IP header on a hop-by-hop basis. security protocol and the outer IP header on a hop-by-hop basis.
The applicability of ROHCoIPsec and hop-by-hop ROHC on an IPv4 The applicability of ROHCoIPsec and hop-by-hop ROHC on an IPv4
ESP-processed packet [ESP] is shown below in Figure 1. ESP-processed packet [ESP] is shown below in Figure 1.
----------------------------------------------------------- -----------------------------------------------------------
IPv4 | new IP hdr | | orig IP hdr | | | ESP | ESP| IPv4 | new IP hdr | | orig IP hdr | | | ESP | ESP|
|(any options)| ESP | (any options) |TCP|Data|Trailer| ICV| |(any options)| ESP | (any options) |TCP|Data|Trailer| ICV|
----------------------------------------------------------- -----------------------------------------------------------
|<-------(1)------->|<------(2)-------->| |<-------(1)------->|<------(2)-------->|
(1) Compressed by ROHC ESP/IP profile (1) Compressed hop-by-hop by the ROHC [ROHC] ESP/IP profile
(2) Compressed by ROHCoIPsec TCP/IP profile (2) Compressed end-to-end by the ROHCoIPsec [IPSEC-ROHC]
TCP/IP profile
Figure 1. Applicability of hop-by-hop ROHC and ROHCoIPsec on an Figure 1. Applicability of hop-by-hop ROHC and ROHCoIPsec on an
IPv4 ESP-processed packet. IPv4 ESP-processed packet.
If IPsec NULL encryption is applied to packets, ROHC may still be If IPsec NULL encryption is applied to packets, ROHC may still be
applied to the inner headers at the IPsec SA endpoints. However, applied to the inner headers at the IPsec SA endpoints. However,
this poses challenges for intermediary devices (within the this poses challenges for intermediary devices (within the
unprotected domain) inspecting ESP-NULL encrypted packets, since unprotected domain) inspecting ESP-NULL encrypted packets, since
these intermediary devices will require additional functionality to these intermediary devices will require additional functionality to
determine the content of the ROHC packets. determine the content of the ROHC packets.
skipping to change at page 8, line 20 skipping to change at page 8, line 20
| ROHC Module | | ROHC Module |
| | | |
| | | |
+-----+ | +-----+ +---------+ | +-----+ | +-----+ +---------+ |
| | | | | | ROHC | | | | | | | | ROHC | |
--| A |---------| B |-----| Process |------> Path 1 --| A |---------| B |-----| Process |------> Path 1
| | | | | | | | (ROHC-enabled SA) | | | | | | | | (ROHC-enabled SA)
+-----+ | +-----+ +---------+ | +-----+ | +-----+ +---------+ |
| | | | | | | |
| | |-------------------------> Path 2 | | |-------------------------> Path 2
| | | (ROHC-enabled SA) | | | (ROHC-enabled SA,
| +-------------------------------+ | +-------------------------------+ but no compression)
| |
| |
| |
| |
+-----------------------------------------> Path 3 +-----------------------------------------> Path 3
(ROHC-disabled SA) (ROHC-disabled SA)
Figure 2. Integration of ROHC with IPsec. Figure 2. Integration of ROHC with IPsec.
The process illustrated in Figure 2 augments the IPsec processing The process illustrated in Figure 2 augments the IPsec processing
model for outbound IP traffic (protected-to-unprotected). Initial model for outbound IP traffic (protected-to-unprotected). Initial
IPsec processing is consistent with [IPSEC] (Steps 1-2, Section 5.1). IPsec processing is consistent with RFC 4301 [IPSEC] (Steps 1-2,
Section 5.1).
Block A: The ROHC data item (part of the SA state information) Block A: The ROHC data item (part of the SA state information)
retrieved from the "relevant SAD entry" ([IPSEC], Section 5.1, retrieved from the "relevant SAD entry" ([IPSEC], Section 5.1,
Step3a) determines if the traffic traversing the SA is handed to the Step3a) determines if the traffic traversing the SA is handed to the
ROHC module. Packets selected to a ROHC-disabled SA must follow ROHC module. Packets selected to a ROHC-disabled SA MUST follow
normal IPsec processing and must not be sent to the ROHC module normal IPsec processing and MUST NOT be sent to the ROHC module
(Figure 1, Path 3). Conversely, packets selected to a ROHC-enabled (Figure 2, Path 3). Conversely, packets selected to a ROHC-enabled
SA must be sent to the ROHC module. SA MUST be sent to the ROHC module.
Block B: This step determines if the packet can be compressed. If it
is determined that the packet will be compressed, an Integrity
Algorithm may be used to compute an Integrity Check Value (ICV) for
the uncompressed packet ([IPSEC-ROHC], Section 3.2 [IKE-ROHC],
Section 2.1). The Next Header field of the security protocol header
(e.g., ESP, AH) is populated with a "ROHC" protocol number
[PROTOCOL], inner packet headers are compressed, and the computed
ICV, if present, is appended to the packet (Figure 1, Path 1).
However, if it is determined that the packet will not be compressed Block B: This step determines if the packet can be compressed. If
(e.g., due to one the reasons described in Section 6.1.3), the Next the packet is compressed, an Integrity Algorithm MAY be used to
Header field is populated with the appropriate value indicating the compute an Integrity Check Value (ICV) for the uncompressed packet
next level protocol (Figure 1, Path 2), and no ROHC processing is ([IPSEC-ROHC], Section 4.2; [IKE-ROHC], Section 3.1). The Next
applied to the packet. Header field of the security protocol header (e.g., ESP, AH) MUST be
populated with a "ROHC" protocol number [PROTOCOL], inner packet
headers MUST be compressed, and the computed ICV MAY be appended to
the packet (Figure 2, Path 1). However, if it is determined that the
packet will not be compressed (e.g., due to one the reasons described
in Section 6.1.3), the Next Header field MUST be populated with the
appropriate value indicating the next level protocol (Figure 2, Path
2), and ROHC processing MUST NOT be applied to the packet.
After the ROHC process completes, IPsec processing resumes, as After the ROHC process completes, IPsec processing resumes, as
described in Section 5.1, Step3a, of [IPSEC]. described in Section 5.1, Step3a, of RFC 4301 [IPSEC].
The process illustrated in Figure 2 also augments the IPsec The process illustrated in Figure 2 also augments the IPsec
processing model for inbound IP traffic (unprotected-to-protected). processing model for inbound IP traffic (unprotected-to-protected).
For inbound packets, IPsec processing is performed ([IPSEC], Section For inbound packets, IPsec processing is performed ([IPSEC], Section
5.2, Steps 1-3) followed by AH or ESP processing ([IPSEC], Section 5.2, Steps 1-3) followed by AH or ESP processing ([IPSEC], Section
5.2, Step 4). 5.2, Step 4).
Block A: After AH or ESP processing, the ROHC data item retrieved Block A: After AH or ESP processing, the ROHC data item retrieved
from the SAD entry will indicate if traffic traversing the SA is from the SAD entry will indicate if traffic traversing the SA is
processed by the ROHC module ([IPSEC], Section 5.2, Step 3a). processed by the ROHC module ([IPSEC], Section 5.2, Step 3a).
Packets traversing an ROHC-disabled SA must follow normal IPsec Packets traversing a ROHC-disabled SA MUST follow normal IPsec
processing and must not be sent to the ROHC module. Conversely, processing and MUST NOT be sent to the ROHC module. Conversely,
packets traversing an ROHC-enabled SA must be sent to the ROHC packets traversing a ROHC-enabled SA MUST be sent to the ROHC module.
module.
Block B: The decision at Block B is determined by the value of the Block B: The decision at Block B is determined by the value of the
Next Header field of the security protocol header. If the Next Next Header field of the security protocol header. If the Next
Header field does not indicate a ROHC header, the decompressor must Header field does not indicate a ROHC header, the decompressor MUST
not attempt decompression (Figure 1, Path 2). If the Next Header NOT attempt decompression (Figure 2, Path 2). If the Next Header
field indicates a ROHC header, decompression is applied. After field indicates a ROHC header, decompression is applied. After
decompression, the signaled ROHCoIPsec Integrity Algorithm, if decompression, the signaled ROHCoIPsec Integrity Algorithm, MAY be
present, is used to compute an ICV value for the decompressed packet. used to compute an ICV value for the decompressed packet. This ICV,
This ICV, if present, is compared to the ICV that was calculated at if present, is compared to the ICV that was calculated at the
the compressor: if the ICVs match, the packet is forwarded by the compressor: if the ICVs match, the packet is forwarded by the ROHC
ROHC module (Figure 1, Path 1); otherwise, the packet is dropped. module (Figure 2, Path 1); otherwise, the packet MUST be dropped.
Once the ROHC module completes processing, IPsec processing resumes, Once the ROHC module completes processing, IPsec processing resumes,
as described in Section 5.2, Step 4 of [IPSEC]. as described in Section 5.2, Step 4 of RFC 4301 [IPSEC].
When there is a single SA between a compressor and decompressor, ROHC When there is a single SA between a compressor and decompressor, ROHC
operates in unidirectional mode, as described in Section 5 of [ROHC- MUST operate in unidirectional mode, as described in Section 5 of RFC
TERM]. When there is pair of SAs instantiated between ROHCoIPsec 3759 [ROHC-TERM]. When there is a pair of SAs instantiated between
implementations, ROHC may operate in bidirectional mode, where an SA ROHCoIPsec implementations, ROHC MAY operate in bidirectional mode,
pair represents a bidirectional ROHC channel (as described in Section where an SA pair represents a bidirectional ROHC channel (as
6.1 and 6.2 of [ROHC-TERM]). described in Section 6.1 and 6.2 of RFC 3759[ROHC-TERM]).
Note that to further reduce the size of an IPsec-protected packet, Note that to further reduce the size of an IPsec-protected packet,
ROHCoIPsec and IPcomp [IPCOMP] can be implemented in a nested ROHCoIPsec and IPcomp [IPCOMP] can be implemented in a nested
fashion. This process is detailed in [IPSEC-ROHC], Section 3.2. fashion. This process is detailed in [IPSEC-ROHC], Section 4.4.
6.1.1. Header Compression Protocol Considerations 6.1.1. Header Compression Protocol Considerations
ROHCv2 [ROHCV2] profiles include various mechanisms that provide ROHCv2 [ROHCV2] profiles include various mechanisms that provide
increased robustness over reordering channels. These mechanisms must increased robustness over reordering channels. These mechanisms
be adopted for ROHC to operate efficiently over IPsec SAs. SHOULD be adopted for ROHC to operate efficiently over IPsec SAs.
A ROHC decompressor implemented within IPsec architecture may A ROHC decompressor implemented within IPsec architecture MAY
leverage additional mechanisms to improve performance over reordering leverage additional mechanisms to improve performance over reordering
channels (either due to random events, or to an attacker channels (either due to random events, or to an attacker
intentionally reordering packets). Specifically, IPsec's sequence intentionally reordering packets). Specifically, IPsec's sequence
number may be used by the decompressor to identify a packet as number MAY be used by the decompressor to identify a packet as
"sequentially late". This knowledge will increase the likelihood of "sequentially late". This knowledge will increase the likelihood of
successful decompression of a reordered packet. successful decompression of a reordered packet.
Additionally, ROHCoIPsec implementations should minimize the amount Additionally, ROHCoIPsec implementations SHOULD minimize the amount
of feedback sent from the decompressor to the compressor. If a ROHC of feedback sent from the decompressor to the compressor. If a ROHC
feedback channel is not used sparingly, the overall gains from feedback channel is not used sparingly, the overall gains from
ROHCoIPsec can be significantly reduced. More specifically, any ROHCoIPsec can be significantly reduced. More specifically, any
feedback sent from the decompressor to the compressor must be feedback sent from the decompressor to the compressor MUST be
processed by IPsec, and tunneled back to the compressor (as processed by IPsec, and tunneled back to the compressor (as
designated by the SA associated with FEEDBACK_FOR). As such, some designated by the SA associated with FEEDBACK_FOR). As such, some
implementation alternatives can be considered, including the implementation alternatives can be considered, including the
following: following:
o Eliminate feedback traffic altogether by operating only in ROHC o Eliminate feedback traffic altogether by operating only in ROHC
Unidirectional mode (U-mode) Unidirectional mode (U-mode)
o Piggyback ROHC feedback messages within the feedback element o Piggyback ROHC feedback messages within the feedback element
(i.e., on ROHC traffic that normally traverses the SA designated (i.e., on ROHC traffic that normally traverses the SA designated
by FEEDBACK_FOR). by FEEDBACK_FOR).
6.1.2. Initialization and Negotiation of the ROHC Channel 6.1.2. Initialization and Negotiation of the ROHC Channel
Hop-by-hop ROHC typically uses the underlying link layer (e.g., PPP) Hop-by-hop ROHC typically uses the underlying link layer (e.g., PPP)
to negotiate ROHC channel parameters. In the case of ROHCoIPsec, to negotiate ROHC channel parameters. In the case of ROHCoIPsec,
channel parameters can be set manually (i.e., administratively channel parameters can be set manually (i.e., administratively
configured for manual SAs), or negotiated by IKEv2. The extensions configured for manual SAs), or negotiated by IKEv2. The extensions
required for IKEv2 to support ROHC channel parameter negotiation are required for IKEv2 to support ROHC channel parameter negotiation are
detailed in [IKE-ROHC]. detailed in [IKE-ROHC].
If the ROHC protocol requires bidirectional communications, two SAs If the ROHC protocol requires bidirectional communications, two SAs
must be instantiated between the IPsec implementations. One of the MUST be instantiated between the IPsec implementations. One of the
two SAs is used for carrying ROHC-traffic from the compressor to the two SAs is used for carrying ROHC-traffic from the compressor to the
decompressor, while the other is used to communicate ROHC-feedback decompressor, while the other is used to communicate ROHC-feedback
from the decompressor to the compressor. Note that the requirement from the decompressor to the compressor. Note that the requirement
for two SAs aligns with the operation of IKE, which creates SAs in for two SAs aligns with the operation of IKE, which creates SAs in
pairs by default. However, IPsec implementations will dictate how pairs by default. However, IPsec implementations will dictate how
decompressor feedback received on one SA is associated with a decompressor feedback received on one SA is associated with a
compressor on the other SA. An IPsec implementation must relay the compressor on the other SA. An IPsec implementation MUST relay the
feedback received by the decompressor on an inbound SA to the feedback received by the decompressor on an inbound SA to the
compressor associated with the corresponding outbound SA. compressor associated with the corresponding outbound SA.
6.1.3. Encapsulation and Identification of Header Compressed Packets 6.1.3. Encapsulation and Identification of Header Compressed Packets
As indicated in Section 6.1, new state information (i.e., a new ROHC As indicated in Section 6.1, new state information (i.e., a new ROHC
data item) is defined for each SA. The ROHC data item is used by the data item) is defined for each SA. The ROHC data item MUST be used
IPsec process to determine whether it sends all traffic traversing a by the IPsec process to determine whether it sends all traffic
given SA to the ROHC module (ROHC-enabled) or bypasses the ROHC traversing a given SA to the ROHC module (ROHC-enabled) or bypasses
module and sends the traffic through regular IPsec processing (ROHC- the ROHC module and sends the traffic through regular IPsec
disabled). processing (ROHC- disabled).
The Next Header field of the IPsec security protocol (e.g., AH or The Next Header field of the IPsec security protocol (e.g., AH or
ESP) header is used to demultiplex header-compressed traffic from ESP) header MUST be used to demultiplex header-compressed traffic
uncompressed traffic traversing an ROHC-enabled SA. This from uncompressed traffic traversing an ROHC-enabled SA. This
functionality is needed in situations where packets traversing a functionality is needed in situations where packets traversing a
ROHC-enabled SA contain uncompressed headers. Such situations may ROHC-enabled SA contain uncompressed headers. Such situations may
occur when, for example, a compressor supports strictly n compressed occur when, for example, a compressor supports strictly n compressed
flows and cannot compress the n+1 flow that arrives. Another example flows and cannot compress the n+1 flow that arrives. Another example
is when traffic is selected to a ROHC-enabled SA, but cannot be is when traffic is selected to a ROHC-enabled SA, but cannot be
compressed by the ROHC process because the appropriate ROHC Profile compressed by the ROHC process because the appropriate ROHC Profile
has not been signaled for use. As a result, the decompressor must be has not been signaled for use. As a result, the decompressor MUST be
able to identify packets with uncompressed headers and not attempt to able to identify packets with uncompressed headers and MUST NOT
decompress them. The Next Header field is used to demultiplex these attempt to decompress them. The Next Header field is used to
header-compressed and uncompressed packets where the ROHC protocol demultiplex these header-compressed and uncompressed packets where
number will indicate that the packet contains compressed headers. To the ROHC protocol number will indicate that the packet contains
accomplish this, an official IANA allocation from the Protocol ID compressed headers. To accomplish this, an official IANA allocation
registry [PROTOCOL] is required. from the Protocol ID registry [PROTOCOL] is required.
The ROHC Data Item, IANA Protocol ID allocation, and other IPsec The ROHC Data Item, IANA Protocol ID allocation, and other IPsec
extensions to support ROHCoIPsec, are specified in [IPSEC-ROHC]. extensions to support ROHCoIPsec, are specified in [IPSEC-ROHC].
6.1.4. Path MTU Considerations 6.1.4. Motivation for the ROHC ICV
Although ROHC was designed to tolerate packet loss and reordering,
the algorithm does not guarantee that packets reconstructed at the
decompressor are identical to the original packet. As stated in
Section 5.2 of RFC 4224 [REORDR], the consequences of packet
reordering between ROHC peers may include undetected decompression
failures, where erroneous packets are constructed and forwarded to
upper layers.
When using IPsec integrity protection, a packet received at the
egress of an IPsec tunnel is identical to the packet that was
processed at the ingress (given that the key is not compromised,
etc.).
When ROHC is integrated into the IPsec processing framework, the ROHC
processed packet is protected by the AH/ESP ICV. However, bits in
the original IP header are not protected by this ICV. Therefore,
under certain circumstances, erroneous packets may be constructed and
forwarded into the protected domain.
To ensure the integrity of the original IP header within the
ROHCoIPsec-processing model, an additional integrity check MAY be
applied before the packet is compressed. This integrity check will
ensure that erroneous packets are not forwarded into the protected
domain. The specifics of this integrity check are documented in
Section 4.2 of [IPSEC-ROHC].
6.1.5. Path MTU Considerations
By encapsulating IP packets with AH/ESP and tunneling IP headers, By encapsulating IP packets with AH/ESP and tunneling IP headers,
IPsec increases the size of IP packets. This increase may result in IPsec increases the size of IP packets. This increase may result in
Path MTU issues in the unprotected domain. Several approaches to Path MTU issues in the unprotected domain. Several approaches to
resolving these path MTU issues are documented in Section 8 of resolving these path MTU issues are documented in Section 8 of RFC
[IPSEC]; approaches include fragmenting the packet before or after 4301[IPSEC]; approaches include fragmenting the packet before or
IPsec processing (if the packet's DF bit is clear), or possibly after IPsec processing (if the packet's DF bit is clear), or possibly
discarding packets (if the packet's DF bit is set). discarding packets (if the packet's DF bit is set).
The addition of ROHC within the IPsec processing model may result in The addition of ROHC within the IPsec processing model may result in
a similar path MTU challenges. For example, under certain a similar path MTU challenges. For example, under certain
circumstances, ROHC headers are larger than the original uncompressed circumstances, ROHC headers are larger than the original uncompressed
headers. In addition, if an integrity algorithm is used to validate headers. In addition, if an integrity algorithm is used to validate
packet headers post-decompression, this integrity algorithm will packet headers, the resulting ICV will increase the size of packets.
increase the size of packets. Both of these properties of ROHCoIPsec Both of these properties of ROHCoIPsec increase the size of packets,
increase the size of packets, and therefore may result in additional and therefore may result in additional challenges associated with
challenges associated with path MTU. path MTU.
Approaches to addressing these ROHCoIPsec path MTU issues are Approaches to addressing these path MTU issues are specified in
specified in Section 3.3 of [IPSEC-ROHC]. Section 4.3 of [IPSEC-ROHC].
6.2. ROHCoIPsec Framework Summary 6.2. ROHCoIPsec Framework Summary
To summarize, the following items are needed to achieve ROHCoIPsec: To summarize, the following items are needed to achieve ROHCoIPsec:
o IKEv2 Extensions to Support ROHCoIPsec o IKEv2 Extensions to Support ROHCoIPsec
o IPsec Extensions to Support ROHCoIPsec o IPsec Extensions to Support ROHCoIPsec
7. Security Considerations 7. Security Considerations
A malfunctioning ROHC compressor (i.e., the compressor located at the A malfunctioning ROHC compressor (i.e., the compressor located at the
ingress of the IPsec tunnel) has the ability to send packets to the ingress of the IPsec tunnel) has the ability to send packets to the
decompressor (i.e., the decompressor located at the egress of the decompressor (i.e., the decompressor located at the egress of the
IPsec tunnel) that do not match the original packets emitted from the IPsec tunnel) that do not match the original packets emitted from the
end-hosts. Such a scenario will result in a decreased efficiency end-hosts. Such a scenario will result in decreased efficiency
between compressor and decompressor. Furthermore, this may result in between compressor and decompressor. Furthermore, this may result in
Denial of Service, as the decompression of a significant number of Denial of Service, as the decompression of a significant number of
invalid packets may drain the resources of an IPsec device. invalid packets may drain the resources of an IPsec device.
8. IANA Considerations 8. IANA Considerations
None. None.
9. Acknowledgments 9. Acknowledgments
skipping to change at page 13, line 30 skipping to change at page 14, line 10
Header Compression (ROHC) Framework", RFC 4995, July 2007. Header Compression (ROHC) Framework", RFC 4995, July 2007.
[IPSEC] Kent, S. and K. Seo, "Security Architecture for the [IPSEC] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005. Internet Protocol", RFC 4301, December 2005.
[ROHC-TERM] [ROHC-TERM]
Jonsson, L-E., "Robust Header Compression (ROHC): Jonsson, L-E., "Robust Header Compression (ROHC):
Terminology and Channel Mapping Examples", RFC 3759, Terminology and Channel Mapping Examples", RFC 3759,
April 2004. April 2004.
[BRA97] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", [IKEV2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
RFC 4306, December 2005. RFC 4306, December 2005.
[ESP] Kent, S., "IP Encapsulating Security Payload (ESP)", [ESP] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, December 2005. RFC 4303, December 2005.
[AH] Kent, S., "IP Authentication Header", RFC 4302, [AH] Kent, S., "IP Authentication Header", RFC 4302,
December 2005. December 2005.
[IPCOMP] Shacham, A., Monsour, R., Pereira, and Thomas, "IP Payload [IPSEC-ROHC]
Compression Protocol (IPComp)", RFC 3173, September 2001. Ertekin, E., Christou, C., and C. Bormann, "IPsec
Extensions to Support ROHCoIPsec", work in progress ,
[ROHCV2] Pelletier, G. and K. Sandlund, "RObust Header Compression December 2009.
Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP
Lite", RFC 5225, April 2008.
[IKE-ROHC] [IKE-ROHC]
Ertekin, E., Christou, C., Jasani, R., Kivinen, T., and C. Ertekin, E., Christou, C., Jasani, R., Kivinen, T., and C.
Bormann, "IKEv2 Extensions to Support ROHCoIPsec", work in Bormann, "IKEv2 Extensions to Support ROHCoIPsec", work in
progress , August 2009. progress , December 2009.
[PROTOCOL] [PROTOCOL]
IANA, "Assigned Internet Protocol Numbers, IANA registry IANA, "Assigned Internet Protocol Numbers, IANA registry
at: http://www.iana.org/assignments/protocol-numbers". at: http://www.iana.org/assignments/protocol-numbers",
June 2009.
[IPSEC-ROHC] [IPCOMP] Shacham, A., Monsour, R., Pereira, and Thomas, "IP Payload
Ertekin, E., Christou, C., and C. Bormann, "IPsec Compression Protocol (IPComp)", RFC 3173, September 2001.
Extensions to Support ROHCoIPsec", work in progress ,
August 2009. [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.
[REORDR] Pelletier, G., Jonsson, L-E., and K. Sandlund, "Robust
Header Compression (ROHC): ROHC over Channels That Can
Reorder Packets", RFC 4224, January 2006.
Authors' Addresses Authors' Addresses
Emre Ertekin Emre Ertekin
Booz Allen Hamilton Booz Allen Hamilton
13200 Woodland Park Dr. 5220 Pacific Concourse Drive, Suite 200
Herndon, VA 20171 Los Angeles, CA 90045
US US
Email: ertekin_emre@bah.com Email: ertekin_emre@bah.com
Rohan Jasani Rohan Jasani
Booz Allen Hamilton Booz Allen Hamilton
13200 Woodland Park Dr. 13200 Woodland Park Dr.
Herndon, VA 20171 Herndon, VA 20171
US US
 End of changes. 53 change blocks. 
153 lines changed or deleted 195 lines changed or added

This html diff was produced by rfcdiff 1.37b. The latest version is available from http://tools.ietf.org/tools/rfcdiff/