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 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 August 21, 2006. 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]. Xia Expires February 21, 2007 [Page 1] Internet-Draft Consideration About CoA Location Privacy August 2006 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 Xia Expires April 24, 2006 [Page 2] Internet-Draft Consideration About CoA Location Privacy August 2006 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. Xia Expires April 24, 2006 [Page 3] Internet-Draft Consideration About CoA Location Privacy August 2006 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 Xia Expires April 24, 2006 [Page 4] Internet-Draft Consideration About CoA Location Privacy August 2006 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. Xia Expires April 24, 2006 [Page 5] Internet-Draft Consideration About CoA Location Privacy August 2006 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 Intellectual Property Statement 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. 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