Mobile IP Multihoming for Low Power Mobiles October 2005 MONAMI6 Working Group Internet Draft Shiao-Li Tsao National Chiao Tung University Expires: April 2006 October 2005 Benefits of multiple care-of addresses and home addresses for low power multimode mobiles 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 April, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract It is expected that future mobile devices will equip multiple wireless interfaces in order to access the Internet ubiquitously. For such a multimode mobile node (MMN) that might have multiple home addresses to associate with its interfaces, the MMN has to keep its interfaces awake to listen the packets to these home addresses (HoAs). Therefore, the MMN consumes a considerable energy to maintain the reachablilities of these HoAs/interfaces. The draft presents the benefits to use multiple care-of addresses and/or home addresses to save the idle-mode power consumption of an MMN, and also discusses the impacts and the requirements of the existing IETF protocols to support the proposed low power operations. Shiao-Li Tsao Expires - April 2006 [Page 1] Mobile IP Multihoming for Low Power Mobiles October 2005 Table of Contents 1. Introduction ....................................................2 2. Terminology......................................................3 3. Scenarios........................................................3 3.1 An MMN with multiple HoAs and multiple CoAs.................3 3.2 An MMN with one HoA and multiple CoAs.......................5 4. Impact Analysis..................................................6 4.1 An MMN with multiple HoAs and multiple CoAs.................6 4.2 An MMN with one HoA and multiple CoAs.......................6 5. Summary and Future Work..........................................6 Security Considerations.............................................6 References..........................................................7 Author's Addresses..................................................7 1. Introduction To support the access of Internet services from everywhere and at any time, future mobile devices are expected to be multimode [2][4]. A mobile node (MN) that equips multiple and heterogeneous wireless interfaces might activate one or some of its interfaces simultaneously to communicate with peer nodes. The benefits of multihomed mobiles that are summarized in [2] include permanent and ubiquitous access, redundancy, load sharing, load balancing, bi- casting, preferences, and increased bandwidth. However, to activate multiple interfaces simultaneously spends considerable energy of a battery operated device, and the power consumption posts a serious problem for a multimode mobile node (MMN). One possible solution is to set interfaces to sleep if there is no packet to send through the links, but the idle interfaces still consume a significant portion of the total power consumption of a mobile. For example, the power consumption of a single-mode cellular phone during idle is about 10mW, but the power consumption of a cellular/WLAN dual-mode phone that even both cellular and WLAN interfaces are set to sleep requires 50mW to 100mW. The problem becomes more serious for a mobile with multiple wireless interfaces, e.g. a 3G/WiMAX/WLAN/Bluetooth handset. Another alternative to reduce the power consumption of an MMN is to turn off some of its interfaces. However, the MMN might have home addresses (HoAs) to associate with these turned-off interfaces, the packets to these HoAs are lost. For example, a 3G/WLAN dual-mode handset might have two HoAs, one for 3G interface and the other for WLAN interface. To disable WLAN interface of the 3G/WLAN dual-mode handset to save power, the packets to the HoA of the WLAN can not be received. Shiao-Li Tsao Expires - April 2006 [Page 2] Mobile IP Multihoming for Low Power Mobiles October 2005 Here, we consider to utilize multiple care-of addresses (CoAs) and/or HoAs for an MMN that could be always reachable by HoAs and can also achieve energy-efficient operations during idle. We first present two scenarios that an MMN could improve the energy-efficiencies of the idle-mode operations by applying multiple CoAs and/or HoAs. Then, we analyze the impacts and requirements of the existing IETF protocols to support the proposed designs. 2. Terminology This draft is based on the terminology defined in [1]. For these terms which are used in this draft but not defined in the existing IETF documents are listed below. Multimode Mobile Node (MMN) A mobile node equips with more than one wireless interface. Each interface has zero, one or multiple home addresses (HoAs) and/or zero, one or multiple care-of addresses (CoAs). 3. Scenarios Two situations are considered in this draft. First, an MMN activates multiple interfaces, and each interface associates with an HoA and a CoA. The MMN decides to turn off some of its wireless interfaces in order to save the power, but does not want to lose packets to these HoAs/interfaces that are turned off. The second situation is that an MMN activates multiple interfaces, each interface associates with a CoA, but all interfaces share the same HoA. The MMN decides to turn off some of its wireless interfaces in order to save the power, while the MMN receives the packets to the HoA via a particular wireless interface, it turns on its preferred interface to communicate with peer nodes. 3.1 An MMN with multiple HoAs and multiple CoAs In this situation, an MMN has an HoA for each wireless interface (IF). The MMN acquires a CoA in the visiting network and registers the CoA to the home agent (HA) of the HoA for a particular interface. The MMN might associate multiple HoAs which are multi-prefixed for one interface, but here, we assume the each interface has one HoA in its home network (HNW), and one CoA in the visiting network (VNW). Figure 1 shows an example. Step 1 to Step 6 of Figure 1 demonstrate the message exchanging between the MMN and HAs. In order to save the power, the MMN decides to turn off interface two (IF#2) and interface three (IF#3), but it still wants to receive packets to home addresses of IF#2 and IF#3, i.e. HoA#2 and HoA#3. Then, the MMN uses the HoA#1 as the CoA to register HA#2 and HA#3, i.e. Step 7 and Step 9. Once Shiao-Li Tsao Expires - April 2006 [Page 3] Mobile IP Multihoming for Low Power Mobiles October 2005 the CoA registration is complete, the MMN can turn off the IF#2 and IF#3 to conserve the energy. In Step 11, the packets sent to HoA#3 of IF#3 are received by the HA#3, the packets are forwarded to the CoA of IF#3, i.e. the HoA#1. The HA#1 receives the packets, and forwards the packets to CoA#1 so that the MMN can receive the packets via the IF#1. Since the MMN can detect the packets which are sent to MMN's HoA#3, the packets can be seen as paging packets to wake up the MMN's IF#3. The MMN can either use the CoA#1/IF#1 to update the binding on the correspondent node (CN) if the MMN prefers to use the IF#1 to communicate with the CN. Otherwise, the MMN can turn on the IF#3, acquires the CoA#3, and updates the binding on CN and HA#3. To use multiple care-of addresses and home addresses for MMNs can reduce the power consumption of MMNs in the idle mode and all home addresses of the MMNs are always reachable even some interfaces are turned off. MMN Visiting Networks Home Networks IF#1 IF#2 IF#3 VNW#1 VNW#2 VNW#3 HNW#1 HNW#2 HNW#3 | | | | | | | | | |1. acquire CoA#1 | | | | | | |<---------------->| | | | | | |2. register CoA#1 to HA#1 | | | | |<-------------------------------------->| | | | | | | | | | | | | |3. acquire CoA#2 | | | | | | |<------------------>| | | | | | |4. register CoA#2 to HA#2 | | | | | |<---------------------------------------->| | | | | | | | | | | | | |5. acquire CoA#3 | | | | | | |<-------------------->| | | | | | |6. register CoA#3 to HA#3 | | | | | |<------------------------------------------>| | | | | | | | | | | |7. use HoA#1 as CoA to register HA#2 | | | |<---------------------------------------->| | | |8. turn off IF#2 | | | | | | X | | | | | | | | | | | | | | | | |9. use HoA#1 as CoA to register HA#3 | | |<------------------------------------------>| | |10. turn off IF#3 | | | | | X | | | | | | | | | | | | | | 11. incoming packets to HA#3, forwarded to HoA#1 | | | | | |<----------|<-- | 12. packets forwarded to CoA#1, then to the MMN via IF#1 |<-----------------|<--------------------| | | | 13. wake up IF#3, acquire CoA#3, BU CN, and HA#3 | | X | | | | | | Shiao-Li Tsao Expires - April 2006 [Page 4] Mobile IP Multihoming for Low Power Mobiles October 2005 | |<-------------------------------------------... | | | | | | | | Figure 1. An MMN with multiple HoAs and multiple CoAs 3.2 An MMN with one HoA and multiple CoAs The second situation is that an MMN has multiple interfaces, each interface associates with a CoA, but all interfaces share the same HoA. Figure 2 shows an example. Step 1 to Step 6 demonstrate to bind multiple CoAs to a given HoA. The binding update should have the information to tell the HA the priorities or the preferences of the interfaces from which an MMN prefers to receive the packets. Then, the MMN can turn off some of its wireless interfaces, i.e. Step 7 of Figure 2, to save the power. While incoming packets are received by the HA, it forwards the packets to MMN's CoAs based on the preferences of priorities. Once the MMN receives the packets, the MMN further decides and turns on a proper interface to communicate with peer nodes. To use multiple care-of addresses for one home addresses for MMNs can also reduce the power consumption of an MMN in the idle mode. MMN Visiting Networks Home Networks IF#1 IF#2 IF#3 VNW#1 VNW#2 VNW#3 HNW#1 | | | | | | | |1. acquire CoA#1 | | | | |<---------------->| | | | |2. register CoA#1 to HA#1 (preferred paging CoA) |<-------------------------------------->| | | | | | | | | |3. acquire CoA#2 | | | | |<------------------>| | | | |4. register CoA#2 to HA#1 | | | |<---------------------------------->| | | | | | | | | | |5. acquire CoA#3 | | | | |<-------------------->| | | | |6. register CoA#3 to HA#1 | | | |<------------------------------>| | |7. turn off IF#2 and IF#3 | | | X X | | | | | | | | | | | | | | | 8. incoming packets to HA#1, forwarded to CoA#1 first | |<--------------------|<-- | 9. packets sent to the MMN via IF#1 | |<-----------------| | | | | 10. MMN decides to use IF#3 to communicate with the CN Shiao-Li Tsao Expires - April 2006 [Page 5] Mobile IP Multihoming for Low Power Mobiles October 2005 | 11. MMN wakes up IF#3, acquire CoA#3, BU the CN | X | | | | | |<--------------------------------... | | | | | | Figure 2. An MMN with one HoA and multiple CoAs 4. Impact Analysis To implement the above operations on MMNs, the impacts to the existing protocols are analyzed. 4.1 An MMN with multiple HoAs and multiple CoAs To implement the low power operation of an MMN with multiple HoAs and multiple CoAs described in Section 3.1, the requirements are similar to the Section 6.2.2 in [5] that presents the requirements to use one HoA as a CoA and its implementation based on the current mobile IPv6 [3]. However, an MMN should implement its own power management scheme to decide which and the number of interfaces to sleep and to wake up, and the time to wake up and to sleep. That is an implementation issue. 4.2 An MMN with one HoA and multiple CoAs To implement the operation of an MMN with one HoA and multiple CoAs described in Section 3.2, the requirements are described in the Section 6.2.1 in [5] that presents the requirements to bind multiple CoAs to a given HoA. Unfortunately, the MIPv6 specification does not support this function currently. Besides the requirements to bind multiple CoAs to a given HoA, the priorities or the preferences of the CoAs that packets should be forwarded to should be carried in the binding update or other MIP messages and extensions such as [6]. Moreover, an MMN should implement its own power management scheme to decide which and the number of interfaces to sleep and to wake up, and the time to wake up and to sleep. That is also an implementation issue. 5. Summary and Future Work The draft suggested to use multiple care-of addresses and/or home addresses for an MMN in order to save the power consumption of a mobile with multiple interfaces. Two usage scenarios are presented to demonstrate the benefits of the design. The impact analysis shows that the extension of the existing mobile IPv6 is required and needs to be further designed to support this feature. Security Considerations Security concerns should be further studied. Shiao-Li Tsao Expires - April 2006 [Page 6] Mobile IP Multihoming for Low Power Mobiles October 2005 References 1.J. Manner and M. Kojo, "Mobility Related Terminology," RFC 3753, June 2004. 2. T. Ernst, N. Montavont, R. Wakikawa, E. Paik, C. Ng, K. Kuladinithi, and T. Noel, "Goals and Benefits of Multihoming," Internet-Draft, draft-ernst-generic-goals-and-benefits-01, Feb. 2005. 3. D. Johnson, C. Perkins, and J. Arkko, "Mobility Support in IPv6," RFC 3775, June 2004. 4. C. Ng, E. Paik, T. Ernst, and M. Bagnuloet,"Analysis of Multihoming in Network Mobility Support," Internet-Draft, draft-ietf- nemo-multihoming-issues-03, July 2005. 5. N. Montavont, R. Wakikawa, T. Ernst, C. Ng, and K. Kuladinithi, " Analysis of Multihoming in Mobile IPv6," Internet-Draft, draft- montavont-mobileip-multihoming-pb-statement-04.txt, June 2005. 6. Ryuji Wakikawa, Keisuke Uehara, Thierry Ernst, and Kenichi Nagami, "Multiple Care-of Addresses Registration," Internet-Draft, draft- wakikawa-mobileip-multiplecoa-04.txt, June 2005. Author's Addresses Shiao-Li Tsao Department of Computer Science, National Chiao Tung University EC426, 1001 Ta Hsueh Road, Hsinchu, Taiwan 300, ROC Phone: +886-3-5712121 ext. 54717 Email: sltsao@cs.nctu.edu.tw Disclaimer of Validity 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 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. Copyright Statement Copyright (C) The Internet Society (2005). 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. Shiao-Li Tsao Expires - April 2006 [Page 7]