NETLMM WG A. Muhanna
Internet-Draft M. Khalil
Intended status: Standards Track Nortel
Expires: December 26, 2008 S. Gundavelli
K. Leung
Cisco Systems
June 24, 2008
GRE Key Option for Proxy Mobile IPv6
draft-muhanna-netlmm-grekey-option-03.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 26, 2008.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
The Proxy Mobile IPv6 base specification defined in [1] allows the
mobile node's IPv4 and IPv6 traffic between the local mobility anchor
and the mobile access gateway to be tunneled using IPv6, IPv4 or
IPv4-UDP encapsulation headers. These encapsulation modes do not
offer semantics for the tunnel end-points to expose a service
Muhanna, et al. Expires December 26, 2008 [Page 1]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
identifier that can be used to identify traffic for a certain
classification, such as for supporting mobile nodes that are using
overlapping private IPv4 addressing. The extensions defined in this
document allow the mobile access gateway and the local mobility
anchor to negotiate GRE encapsulation mode and along with the GRE
symmetric key or asymmetric keys for marking the flows, so that
differential processing can be applied by the tunnel peers over those
flows.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 3
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
4. Local Mobility Anchor Considerations . . . . . . . . . . . . . 5
4.1. GRE Tunneling and Encapsulation Procedures . . . . . . . . 5
4.2. Operational Summary . . . . . . . . . . . . . . . . . . . 6
5. Mobile Access Gateway Considerations . . . . . . . . . . . . . 6
5.1. Extensions to the Conceptual Data Structure . . . . . . . 7
5.2. Operational Summary . . . . . . . . . . . . . . . . . . . 7
6. Message Formats . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. GRE Key Identifier Option . . . . . . . . . . . . . . . . 8
6.2. Status Codes . . . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Intellectual Property and Copyright Statements . . . . . . . . . . 13
Muhanna, et al. Expires December 26, 2008 [Page 2]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
1. Introduction
The base Proxy Mobile IPv6 specification allows the use of IPv6, IPv4
or IPv4-UDP encapsulation modes for the tunneled traffic between the
local mobility anchor and the mobile access gateway. There are
scenarios where these encapsulation modes are not sufficient and
there is a need for an encapsulation mode with richer semantics. The
Generic Routing Encapsulation [2] and coupled with the Key and
Sequence Number extension [3], has the required semantics for use in
Proxy Mobile IPv6.
This document defines extensions to the base Proxy Mobile IPv6
specification, for allowing the mobile access gateway and the local
mobility anchor to negotiate GRE encapsulation mode and for
exchanging the GRE asymmetric key(s) that can be used for marking the
downlink and uplink traffics.
2. Conventions used in this document
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [4].
All the general mobility related terminology and abbreviations are to
be interpreted as defined in Mobile IPv6 specification [5] and Proxy
Mobile IPv6 specification [1].
Downlink Traffic
The traffic in the tunnel between the local mobility anchor and
the mobile access gateway, heading towards the mobile access
gateway and tunneled at the local mobility anchor. This traffic
is also referenced as forward direction traffic.
Uplink Traffic
The traffic in the tunnel between the mobile access gateway and
the local mobility anchor, heading towards the local mobility
anchor and tunneled at the mobile access gateway. This traffic is
also referenced as reverse direction traffic.
3. Protocol Overview
Using the extension defined in this specification, the mobile access
Muhanna, et al. Expires December 26, 2008 [Page 3]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
gateway and the local mobility anchor can negotiate GRE encapsulation
mode along with the GRE keys for marking the downlink and uplink
traffics.
Once the GRE keys have been negotiated between the mobile access
gateway and the local mobility anchor, the mobile access gateway will
use the uplink GRE key that is assigned by the local mobility anchor
in the GRE encapsulation header of the uplink payload packet.
Similarly, the local mobility anchor will use the downlink GRE key as
negotiated with the mobile access gateway in the GRE encapsulation
header of the downlink payload packet.
The following illustration explains the use of GRE encapsulation mode
and the use of GRE keys for supporting the scenario where overlapping
IPv4 private address allocation is in use.
+------------+
| Operator-A |
| |
| 10.x.0.0/16|
+------------+
/
+------+ +------+ /
| | ========================== | | /
MN-1---| | / \ | | / Key-1
| M | / ---Flows with GRE Key-1 ---- \ | L | / Traffic
MN-2---| A |--| |--| M |-
| G | \ ---Flows with GRE Key-2 ---- / | A | \ Key-2
MN-3---| | \ / | | \Traffic
| | ========================== | | \
MN-4---| | Proxy Mobile IPv6 Tunnel | | \
+------+ +------+ \
\
Operator-C: Access Network +------------+
| Operator-B |
| |
| 10.x.0.0/16|
+------------+
Figure 1: Overlapping IPv4 Private Address Space
Figure 1 illustrates a local mobility anchor providing mobility
service to mobile nodes that are from different operators and are
Muhanna, et al. Expires December 26, 2008 [Page 4]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
assigned IPv4 addresses from overlapping private address space. In
this scenario, the mobile access gateway and the local mobility
anchor must be able distinguish the flows belonging to a given
operator from the flows belonging to some other operator.
The mobile nodes, MN-1 and MN-2 are visiting from Operator-A, and
mobile nodes, MN-3 and MN-4 are visiting from Operator-B. The mobile
access gateway and the local mobility anchor agree upon downlink and
uplink keys for identifying the flows belonging to each mobile node.
The local mobility anchor and the mobile access gateway will be able
to distinguish these flows based on the key present in the GRE header
of the tunneled packet, and can route them accordingly.
4. Local Mobility Anchor Considerations
4.1. GRE Tunneling and Encapsulation Procedures
As per the base Proxy Mobile IPv6 specification, the tunnel transport
between the mobile access gateway and the local mobility anchor can
be IPv6, IPv4 or IPv4-UDP. When GRE tunneling is negotiated as per
this specification, the semantics related to the tunnel transport is
not impacted, but an additional GRE header is added above the payload
packet as indicated below.
+---------------------------+
| Delivery Header |
| |
| IPv4, IPv4-UDP or IPv6 |
+---------------------------+
| |
| GRE Header with |
| Key, Sequence Number Ext |
+---------------------------+ +---------------------------+
| | | |
| Payload Packet | ====> | Payload Packet |
| (IPv4 or IPv6) | | |
+---------------------------+ +---------------------------+
Figure 2: GRE Encapsulation
Muhanna, et al. Expires December 26, 2008 [Page 5]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
4.2. Operational Summary
o Upon receiving a Proxy Binding Update message with the GRE Key
Identifier Option, the local mobility anchor, if it does not
support GRE encapsulation mode, MUST send the Proxy Binding
Acknowledgement message to the mobile access gateway with the
status code TBA1, (GRE Encapsulation not supported).
o If the received Proxy Binding Update message does not contain the
GRE Key Identifier Option, and if the local mobility anchor
determines that GRE encapsulation is required, e.g., overlapping
IPv4 private addressing is in use, the local mobility anchor MUST
reject the request, and MUST send the Proxy Binding
Acknowledgement message to the mobile access gateway with the
status code TBA2, indicating that GRE encapsulation is required.
o Upon receiving a Proxy Binding Update message with the GRE Key
Identifier Option, the local mobility anchor MUST include the GRE
Key Identifier option as per this document when responding with a
successful Proxy Binding Acknowledgement message to the mobile
access gateway.
o If the GRE tunneling is negotiated between the local mobility
anchor and the mobile access gateway, every packet that is
destined to the mobile node through the local mobility anchor MUST
be encapsulated with a GRE header using the negotiated downlink
GRE key and the chosen transport header such as IPv4, IPv4-UDP or
IPv6, just as per the base Proxy Mobile IPv6 specification.
o On receiving a packet from the tunnel with the GRE encapsulation
header, the local mobility anchor MUST use the GRE Key present in
the GRE extension header to lookup the mobile node's home gateway
address for forwarding the packet after removing the encapsulation
headers.
5. Mobile Access Gateway Considerations
For requesting the GRE Tunneling support, the mobile access gateway
MUST include the GRE Key Identifier Option in the Proxy Binding
Update message sent to the local mobility anchor. Additionally, the
mobile access gateway MUST include the downlink key in the GRE key
Identifier Option. In the successful Proxy Binding Update, the LMA
must send two GRE keys in the GRE Key Identifier option, with the
first key being the downlink key which was sent by the mobile access
gateway and the second is the uplink key. In this case, the GRE Key
Identifier option length MUST be set to 10.
Muhanna, et al. Expires December 26, 2008 [Page 6]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
5.1. Extensions to the Conceptual Data Structure
Every mobile access gateway maintains a Binding Update List entry for
each currently attached mobile node, as explained in Section 6.1 of
the base Proxy Mobile IPv6 specification [1]. The Binding Update
List entry is a conceptual data structure, described in Section 11.1
of the Mobile IPv6 base specification [5]. For supporting this
specification, the conceptual Binding Update List entry data
structure must be extended with the following two new additional
fields related to bi-directional GRE Key identifiers used for tagging
the mobile node's tunneled traffic.
o The Uplink GRE Key Identifier used in the GRE encapsulation header
of the tunneled packet from the mobile access gateway to the local
mobility anchor and that is originating from the mobile node.
This GRE Key identifier is obtained from the GRE Key Identifier
Option present in the received Proxy Binding Acknowledgement
message sent by the local mobility anchor as specified in this
document.
o The Downlink GRE Key Identifier used in the GRE encapsulation
header of the tunneled packet from the local mobility anchor to
the mobile access gateway and that is destined to the mobile node.
This GRE Key identifier is generated by the mobile access gateway
and communicated to the local mobility anchor in the GRE key
Identifier option in the proxy binding update message.
5.2. Operational Summary
o If IPv4 Home Address support is enabled for the mobile node and if
the IPv4 Home Address Option is included in the Proxy Binding
Update message that is sent by the mobile access gateway to the
mobile node's local mobility anchor, the GRE Key Identifier Option
SHOULD be included in the Proxy Binding Update message. The MAG
MUST include the downlink key in the GRE Key Identifier Option,
the local mobility anchor must use this key to identify the mobile
node's traffic encapsulated in a GRE header as specified in the
GRE specification [2] and using the GRE Key and Sequence Number
extension [3] with the assigned GRE key.
o After receiving a Proxy Binding Acknowledgment message with the
status code indicating the acceptance of the Proxy Binding Update
message and with the GRE Key Identifier Option, the mobile access
gateway MUST use GRE encapsulation and the assigned uplink GRE Key
for tunneling all the traffic originating from the mobile node.
Muhanna, et al. Expires December 26, 2008 [Page 7]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
o For a given mobile node, if the local mobility anchor rejects the
Proxy Binding Update by sending the Proxy Binding Acknowledgement
with the status code TBA1 (GRE Encapsulation not supported), the
mobile access gateway MUST NOT include the GRE Key Identifier
Option in the subsequent Proxy Binding Update messages that are
sent to that Local Mobility Anchor.
o If the mobile access gateway has sent a Proxy Binding Update
message without the GRE Key Identifier Option, but the received
Proxy Binding Acknowledgement has the Status Code TBA2, indicating
that the GRE encapsulation is required, the mobile access gateway
SHOULD resend the Proxy Binding Update message with the GRE Key
Identifier Option.
o If the mobile access gateway has sent a Proxy Binding Update
message with the GRE Key Identifier Option, but the received Proxy
Binding Acknowledgement has the Status Code success without the
GRE Key Identifier option, indicating that the GRE encapsulation
is not required for this mobile node, the mobile access gateway
must not use GRE encapsulation for this Mobile node.
o If the GRE tunneling is negotiated between the local mobility
anchor and the mobile access gateway, every packet originating
from the mobile node MUST be encapsulated with a GRE header using
the uplink GRE key and the chosen transport header such as IPv4,
IPv4-UDP or IPv6, just as per the base Proxy Mobile IPv6
specification.
o One receiving a packet from the tunnel with the GRE encapsulation
header, the mobile access gateway MUST use the GRE Key to lookup
the mobile node's layer-2 address and use it for forwarding the
packet after removing the encapsulation headers.
6. Message Formats
This section defines extensions to the Mobile IPv6 [5] protocol
messages for supporting this specification.
6.1. GRE Key Identifier Option
A new option, the GRE Key Identifier Option, is defined for use in
the Proxy Binding Update and Acknowledgment messages exchanged
between the mobile access gateway and the local mobility anchor.
This option can be used for exchanging the GRE key(s) to be applied
by the peer on all GRE encapsulated packets over either IPv4 or IPv6
transport.
Muhanna, et al. Expires December 26, 2008 [Page 8]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
The alignment requirement for this option is 4n.
0 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: GRE Key Identifier Option
Type
<IANA>
Length
Eight-bit unsigned integer indicating the length in octets of the
option, excluding the type and length fields. This field is set
to a value of 6 or 10.
Reserved
These fields are unused. They MUST be initialized to zero by the
sender and MUST be ignored by the receiver.
GRE Key Identifier
four-byte field containing the Downlink GRE Key Identifier. or
eight-byte field containing the Downlink and Uplink GRE keys,
respectively.
6.2. Status Codes
Proxy Binding Acknowledgment Status Values
The following status code values are defined for using them in the
Binding Acknowledgment message when using Proxy Mobile IPv6 protocol.
The value allocation for this usage needs to be approved by the IANA
and must be updated in the IANA registry.
TBA1: GRE Encapsulation not required.
Muhanna, et al. Expires December 26, 2008 [Page 9]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
TBA2: GRE Encapsulation and GRE Key Identifier option required.
Status values less than 128 indicate that the Binding Update was
processed successfully by the receiving nodes. Values greater than
128 indicate that the Binding Update was rejected by the Home Agent.
7. IANA Considerations
This document defines a new Option, the GRE Key Option, described in
Section 3. This option is carried in the Mobility Header. The type
value for this option needs to be assigned from the same numbering
space as allocated for the other mobility options defined in the
Mobile IPv6 specification [5].
This document also defines two new Binding Acknowledgement status
codes TBA1 and TBA2 as described in Section 6.2. This document
requests that these two codes be allocated from the "Status Codes"
registry of the Mobility IPv6 Parameters located at
http://www.iana.org/assignments/mobility-parameters and that the
numeric value of these codes be greater than 128.
8. Security Considerations
The GRE Key Option, defined in this document, that can be carried in
Proxy Binding Update and Proxy Binding Acknowledgement messages,
reveals the group affiliation of a mobile node identified by its NAI
or an IP address. It may help an attacker in targeting flows
belonging to a specific group. This vulnerability can be prevented,
by enabling confidentiality protection on the Proxy Binding Update
and Acknowledgement messages where the presence of the NAI and GRE
Key Options establish a mobile node's relation to a specific group.
This vulnerability can also be avoided by enabling confidentiality
protection on all the tunneled data packets between the mobile access
gateway and the local mobility anchor, for hiding all the markings.
9. Acknowledgements
The authors would like to thank Allesio Casati, Barney Barownsky,
Mark Grayson and Parviz Yegani for their input on the need for this
option. The authors would like to thank Curtis Provost, Irfan Ali,
Julien Langanier, Jouni Korhonen, Suresh Krishnan, Kuntal Chowdhury,
and Vijay Devarapalli for their review and comments.
10. References
Muhanna, et al. Expires December 26, 2008 [Page 10]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
10.1. Normative References
[1] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and
B. Patil, "Proxy Mobile IPv6", draft-ietf-netlmm-proxymip6-18
(work in progress), May 2008.
[2] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina,
"Generic Routing Encapsulation (GRE)", RFC 2784, March 2000.
[3] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, September 2000.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[5] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004.
[6] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
Specification", RFC 2473, December 1998.
[7] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303,
December 2005.
[8] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy Mobile
IPv6", draft-ietf-netlmm-pmip6-ipv4-support-03 (work in
progress), May 2008.
10.2. Informative References
[9] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[10] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998.
[11] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[12] Kent, S. and K. Seo, "Security Architecture for the Internet
Protocol", RFC 4301, December 2005.
Muhanna, et al. Expires December 26, 2008 [Page 11]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
Authors' Addresses
Ahmad Muhanna
Nortel Networks
2221 Lakeside Blvd.
Richardson, TX 75082
USA
Email: amuhanna@nortel.com
Mohamed Khalil
Nortel Networks
2221 Lakeside Blvd.
Richardson, TX 75082
USA
Email: mkhalil@nortel.com
Sri Gundavelli
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
Kent Leung
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
USA
Email: kleung@cisco.com
Muhanna, et al. Expires December 26, 2008 [Page 12]
Internet-Draft GRE Key Option for Proxy Mobile IPv6 June 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Muhanna, et al. Expires December 26, 2008 [Page 13]