Internet DRAFT - draft-xia-mip6-coa-privacy-consideration
draft-xia-mip6-coa-privacy-consideration
Mobile IPv6 Working Group Zhongqi Xia
Internet Draft Huawei Technologies Co., Ltd
Expires: 21 February 2007 August 21, 2006
Consideration about Location Privacy of CoA in MIP6
draft-xia-mip6-coa-privacy-consideration-01.txt
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Abstract
In this document, we discuss the problem about location privacy of
CoA in Mobile IPv6. And some possible policies and solutions are
discussed in order to protect location privacy of CoA in route
optimization mode.
Conventions used in this document
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 [1].
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Table of Contents
1. Introduction................................................2
2. Policies and solutions.......................................3
2.1. Consideration for Route Optimization Agent (ROA).........3
2.2. Security Consideration..................................4
2.2.1. Consideration for authenticating ROA/CN............4
2.2.2. Consideration for relations between ROA and CN......4
2.2.3. Other security consideration.......................5
3. Miscellaneous...............................................5
4. IANA consideration..........................................5
5. Acknowledgments.............................................5
6. References..................................................6
6.1. Normative References....................................6
6.2. Informative References..................................6
Author's Addresses.............................................6
Intellectual Property Statement.................................6
Disclaimer of Validity.........................................7
Copyright Statement............................................7
Acknowledgment.................................................7
1. Introduction
In communication systems, especially in IP environment, privacy is an
important issue and more and more attention is being paid to it.
Location privacy is a subset of the overall privacy issue [1]. For
traditional IP communication, there is no location privacy between
communication peers (devices or users) since the IP address in the IP
packet reveals the location of communication peers. Similarly, this
location privacy deficiency is applicable to Mobile IPv6 as well and
it is more serious for Mobile IPv6 users than for traditional IP
users.
When away from home network, mobile node uses a new IPv6 address
called Care of Address (CoA). The CoA is an indication representing
the new location of the mobile node. In the tunnel mode, CoA is
encapsulated in the outer layer IPv6 packet header. The eavesdroppers
on the path between new location and home network can intercept the
tunneled packets and get to know CoA of mobile node. But for
correspondence node, it does not receive the tunneled packets and
does not know the new CoA of mobile node. The correspondence node
always assumes that it communicates with mobile node in its home
network.
If mobile node wants to improve the communication efficiency and to
adopt route-optimization mode, it has to execute Return Routability
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Procedure (RRP) firstly. Then mobile user can registers its CoA with
its correspondent and finally the correspondent will know the mobile
user's current CoA and mapped location.
2. Policies and solutions
2.1. Consideration for Route Optimization Agent (ROA)
Because correspondent node (CN) has the binding cache between HoA and
CoA of mobile node (MN), it can determine the location information of
mobile node. So it is necessary to separate the binding cache from
the correspondent node. One solution is to place the binding cache on
another physical entity or device called Route Optimization Agent
(ROA) here. The following figure is the basic network model when ROA
is involved.
|-----------------|
|-----| | | |-----| |-----|
| MN |-------| NETWORK |-----| ROA |-----| CN |
|-----| | | |-----| |-----|
|-----------------|
Fig1 ROA network model
In Fig1, the correspondent node accesses Internet through the route
optimization agent. When MN starts the RRP and registers itself with
CN, ROA intercepts signaling messages from MN to CN and processes
them on behalf of correspondent node. The final processing results,
including the binding relation information between HoA and CoA of MN,
will be maintained on ROA. Therefore, it is not necessary for
correspondent node to have the capability to process the route
optimization procedure. This makes the implementation and
administration of the correspondent node more simple and safe.
After finishing the route optimization procedure, mobile node will
communicate with correspondent node directly, using its CoA as
packets' source address. Meanwhile, Home Address Option is used
within packets. When ROA intercepts traffic packets which are from MN
to CN, it will change the content of these packets, e.g. CoA will be
substituted with HoA of MN, and Home Address Option will be removed.
Likewise, when ROA intercepts traffic packets from CN to MN, MN's HoA
will be substituted with its CoA and the Destination Route Option
will be added to the traffic packets.
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2.2. Security Consideration
If the network model of ROA is used, many other security and
authentication related factors must be considered carefully.
2.2.1. Consideration for authenticating ROA/CN
The mobile node has to authenticate ROA before it can start Care of
Test procedure and register its CoA with the correspondent node
(actually with ROA, but the mobile node is not aware of this; in the
following text, we will only refer to ROA and will not mention
correspondent node). If the authentication result is ok, mobile node
continues to register its CoA with ROA. Otherwise, route optimization
should be terminated immediately.
There are many kinds of authentication methods, such as user
ID/password, CA, and secret key etc. These methods should be
supported when mobile node authenticates ROA. Nonetheless, no
authentication should be supported so as to be incompatible with the
current mechanism of Mobile IPv6.
In fact it is difficult for mobile node to decide when and where to
authenticate ROA or correspondent node. Authentication has to be
carried out before mobile node's CoA is revealed to ROA i.e.
authentication should be finished before mobile node starts Care of
Test, because the test message tells ROA mobile node's CoA implicitly.
Therefore, there are three left possibilities to finish
authentication procedure. One is that in the tunnel mode
authentication goes with traffic packets; another is that
authentication goes with Home of Test packets; and the last is to
define new message type to finish the authentication procedure.
It is not reasonable that mobile node authenticates ROA alone. Mobile
node needs help from its home network, such as the participation of
Home Agent. Because the contract of keeping privacy is provided by
network operators, there are AAA databases in mobile node's home
network. Therefore, the network element (i.e. Home Agent) has the
ability to authenticate ROA. It's very important for home network to
assist mobile node with finishing authentication procedure. If mobile
node's home network has no ability to authenticate the ROA, mobile
node has to decide the authentication method and result alone.
2.2.2. Consideration for relations between ROA and CN
Because mobile node registers its CoA with ROA, it's very important
that ROA is secure enough to protect its privacy data from evil
node's attack and eavesdropping. Since ROA serves correspondent node
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as a route optimization agent for CN, the ROA should have the
capability to authenticate the CN and the CN should have the
capability to authorize the ROA in order to accomplish the route
optimization.
2.2.3. Other security consideration
Even though mobile node's CoA is shielded from the correspondent node
when ROA is used, the CoA is still in the clear on the path from
mobile node to ROA. However, this issue is not derived from the
introduction of Mobile IPv6 and route optimization but a legacy
problem raised from traditional IP communication. If Home Address
Option is encrypted [2], the impacts will be mitigated significantly.
3. Miscellaneous
If ROA network model is used, ROA might become the bottleneck of the
access network. The traffic burden will be very heavy for ROA because
all traffic packets must go through ROA and ROA must perform a great
deal of translation processing. For large scale access network,
efficiency and performance should be considered carefully when
deploying.
If Home Agent is used to assist mobile node for authentication, the
authentication burden will be very heavy for Home Agent when many
mobile nodes request Home Agent's help for authentication at the same
time. It is necessary to consider the deployment issues of home
network carefully.
When deployment, ROA should be the access router. If CN's access
network does not contain an ROA, no privacy for the MN will be in
effect. And if CN and MN are attached to the same link, the traffic
packets have to go through ROA. Otherwise, MN's privacy is revealed
to CN.
4. IANA consideration
There is no IANA consideration introduced by this draft.
5. Acknowledgments
Thanks Robert P Jaksa, Carl Williams, Hongfei Chen, Jian Zhang,
Xianfeng Dai, Wei Cao, Hui Liu and Lianshu Zheng for reviewing the
earlier version of this draft.
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6. References
6.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, Internet Mail Consortium and
Demon Internet Ltd., November 1997.
6.2. Informative References
[3] Rajeev Koodli; IP Address Location Privacy and Mobile IPv6:
Problem Statement; Internet Draft, Internet Engineering Task
Force, October 2005.
[4] Rajeev Koodli, Vijay Devarapalli, Hannu Flinck, Charlie Perkins;
Solutions for IP Address Location Privacy in the presence of IP
Mobility; Internet Draft, Internet Engineering Task Force, Feb
2005.
Author's Addresses
Zhongqi Xia
Huawei Technologies Co., Ltd.
Huawei Building, No. 3 Xinxi Road,
Shand-Di Information Industry Base,
Hai-Dian District,
Beijing P.R.China,100085
Phone: 86-10-82836050
Email: xiazhongqi@huawei.com
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