Network Working Group Y-G. Hong Internet-Draft J-C. Lee Expires: April 17, 2006 J-S. Park H-J. Kim ETRI October 16, 2005 Virtual network interface for multiple interfaces in a Mobile node using Mobile IPv6 draft-hong-virtualif-mn-mipv6-00 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 17, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The use of Mobile IPv6 in a mobile node and NEMO Basic Support in a mobile router with multiple network interfaces may have some problems. This document discusses how to solve the problems of multiple interfaces in a mobile node and proposes a virtual network interface model which describes the use of Mobile IPv6 to support Hong, et al. Expires April 17, 2006 [Page 1] Internet-Draft Virtual network interface model for a MN October 2005 multiple network interfaces in a mobile node. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction of a Virtual network interface model . . . . . . 4 3. Motivations of using of a virtual network interface model . . 5 3.1. Mobile IPv6-specific Issues . . . . . . . . . . . . . . . 5 3.2. General network Issues . . . . . . . . . . . . . . . . . . 5 4. Mechanism to use a virtual network interface in a mobile node . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1. Architecture of a virtual network interface model in a mobile node . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Operations of Mobile IPv6 in a mobile node with a virtual network interface model . . . . . . . . . . . . . 8 5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Normative References . . . . . . . . . . . . . . . . . . . 10 6.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . . . 12 Hong, et al. Expires April 17, 2006 [Page 2] Internet-Draft Virtual network interface model for a MN October 2005 1. Introduction In traditional TCP/IP network environments, a communication entity usually has a wire connection with a single network interface and it is fixed. As an introduction of wireless technologies and heterogeneous access technologies, a communication entity is able to move around between different networks and have multiple network interfaces [3]. Because traditional network applications and TCP/IP stack are developed for a communication entity which has a single network interface, the adoption of multiple network interfaces into a general communication entity makes some problems. Mobile IPv6[1] and NEMO Basic Support[2] are also developed for a mobile node which has a single network interface and a mobile router which has a single egress network interface and we cannot directly use Mobile IPv6 for a mobile node with multiple network interfaces [4,5]. In order to solve the problems mentioned above, we propose a virtual network interface model for a mobile node with multiple network interfaces. We currently use a virtual network interface model to provide the duplication of network connections with multiple network interface cards on an important network node. With a virtual network interface model, the mobile node with multiple network interfaces can operate as it has a single network interface irrespective to the number of network interfaces. We have implemented a mobile node and a mobile router with one WLAN interface and one CDMA interface using this virtual network interface model and checked that this approach can be a good solution to handle multiple network interfaces in a mobile node or a mobile router. Hong, et al. Expires April 17, 2006 [Page 3] Internet-Draft Virtual network interface model for a MN October 2005 2. Introduction of a Virtual network interface model In some Operating Systems such as Linux (or Unix), most network interfaces, such as eth0, wlan0, and ppp0, are associated to a physical device that is in charge of transmitting and receiving data packets. However, there are exceptions to this rule, and some logical network interfaces do not feature any physical packet transmission [7]. The virtual network interface model is not a real physical device and it is a logical network interface. It has connections with physical devices within a network entity and the path between the virtual network interface and real physical devices is determined dynamically according to some policy. The virtual network interface is registered to network layer and is regarded as a general network interface. Then real physical interfaces are connected to the virtual network interface. The network layer does not know the existence of these physical interfaces. The virtual network interface model can be used for the duplication of network connections (the duplication of network interface cards) for fault tolerance or load sharing. If an important server has multiple physical network interface cards, it can survive even though one network interface card is down. It can keep a communication session with other live network interface cards. In this case, the presence of multiple network interface cards can be hidden to network layer and network layer regards the virtual network interface as a general network interface. The traditional network applications and network modules do not need to be modified to support multiple network interfaces. We can use this approach in a mobile node which is using Mobile IPv6 and has multiple network interfaces. Although the purpose of the above case is not the same, using a virtual network interface model in a multiple interface mobile node can be sufficiently one of the solutions to solve the problems of the multiple interfaces in a mobile node using Mobile IPv6. Hong, et al. Expires April 17, 2006 [Page 4] Internet-Draft Virtual network interface model for a MN October 2005 3. Motivations of using of a virtual network interface model In this section, we describe the motivations of the use of a virtual network interface model. To describe the motivations, we present some problems of multiple network interfaces in a mobile node which are using Mobile IPv6. The document [4] lists the issues of Mobile IPv6 that prevent the use of multiple interfaces in a mobile node. Another document [5] also presents the problematic of having multiple interfaces. The document [6] describes the problems for a mobile node which has multiple interfaces when it uses Mobile IPv6 as an aspect of a node. 3.1. Mobile IPv6-specific Issues Because a mobile node in Mobile IPv6 knows its movement by comparing the prefix information which is included in Router Advertisement messages, the receiving of Router Advertisement message is an important job to initiate other Mobile IPv6 operations. To determine network movement, a mobile node carefully observes received Router Advertisement message through one specific network interface which is configured when Mobile IPv6 module starts. If a mobile node has multiple network interfaces, after it moves to another networks and not the specific network interface but another network interface is used to receive Router Advertisement messages, a mobile node must have the capability to observe the two network interfaces simultaneously. But Mobile IPv6 and currently implemented Mobile IPv6 code (HUT MIPL)[8] do not support this feature. Question) To support this feature, which module (layer) should have this capability to observe all Router Advertisement messages through multiple network interfaces? 3.2. General network Issues Traditional network applications and TCP/IP stacks do not consider about the change of network addresses and the change of network interfaces. The change of network address can be solved by the use of Mobile IPv6. But the change of network interfaces is not fully studied. The problem of multiple network interfaces in a mobile node is the relation between a destination address and a network interface. When a network application sends packets to another node, firstly looks up the routing table and finds a appropriate network interface according to the destination address. When a mobile node moves to another network, even though it gets a new Care of Address through another network interface, the destination address is not changed. The destination address is continually mapped to the previous network Hong, et al. Expires April 17, 2006 [Page 5] Internet-Draft Virtual network interface model for a MN October 2005 interface. If this situation happens, the communication sessions will be terminated. When a network interface is newly selected to send/receive packets, a mobile node should update the relation between a destination address and a network interface. Question) To update the information for the relation between a destination address and a network interface, which module (layer) should do that job? (In Linux, making a network interface up and down (e.g. ifconfig eth0 down, ifconfig eth1 up) automatically updates the relation between a destination address and a network interface. But, we think that this approach is not reasonable.) Hong, et al. Expires April 17, 2006 [Page 6] Internet-Draft Virtual network interface model for a MN October 2005 4. Mechanism to use a virtual network interface in a mobile node To answer the questions in the previous section, we think that there are many answers. To choose the best answer, there are also many considerations (The considerations are out of the scope of this document). To answer the questions, we propose a virtual network interface model. In this section, we describe a mechanism to use a virtual network interface in a mobile node which uses Mobile IPv6. The virtual network interface model can be used for a mobile router which has multiple egress interfaces in NEMO Basic Support. 4.1. Architecture of a virtual network interface model in a mobile node In the following figure, network interfaces I1, I2 are real network interfaces. The network interface VI is a virtual network interface. The virtual network interface is connected to the real network interfaces and it is shown to the network layer. In this model, the IP layer including Mobile IPv6 module use the virtual network interface VI instead of real network interfaces I1, I2. To handle the virtual network interface, a mobile node needs a specific module (IFS: Interface Switching Module) to manage the virtual network interface and selects the path between the virtual network interface and real network interfaces. +-------------------------------+ | Applications | |-------------------------------| | TCP/UDP/SCTP | |-------------------------------| | IPv6 / Mobile IPv6 | |-------------------------------| | +------------------+ +--------+ | | Virtual Interface| | IFS | | | (VI) | +--------+ | +------------------+ | | / \ | | / \ | | +------------+ +------------+ | | | Interface 1| | Interface 2| | | | (I1) | | (I2) | | | +------------+ +------------+ | +-------------------------------+ Hong, et al. Expires April 17, 2006 [Page 7] Internet-Draft Virtual network interface model for a MN October 2005 Figure 1. Architecture of a virtual network interface model in a mobile nodeA mobile node with two interfaces 4.2. Operations of Mobile IPv6 in a mobile node with a virtual network interface model When a Mobile IPv6 or NEMO Basic Support module starts, the virtual network interface module is configured to send and receive packets. In the above figure, if the mobile node uses a network interface I1, the path between the virtual network interface VI and the real network interface I1 is made. When sending packets to another node, packets are delivered to VI and these packets are also flowed into I1 according to the path configuration. When receiving packets from another node, packets are delivered to I1 and these packets are also flowed into VI according to the path configuration. The packets which are delivered to VI are processed by Mobile IPv6 module. If a mobile node moves into another network and it chooses network interface I2, the path between the virtual network interface VI and the real network interface I2 is made. The IFS module updates the relation between a destination address and a network interface. When the mobile node is sending packets to another node, packets are delivered to VI and these packets are flowed into I2 according to the path configuration. When the mobile node is receiving packets from another node, packets are delivered to I2 and these packets are also flowed into VI according to the path configuration. Hong, et al. Expires April 17, 2006 [Page 8] Internet-Draft Virtual network interface model for a MN October 2005 5. Conclusions Mobile IPv6 and NEMO Basic Support are developed for a mobile node with s single network interface. In traditional TCP/IP network environments, a communication entity does not consider the change of network interfaces. To support multiple network interfaces in a mobile node used at traditional TCP/IP network environments, we propose a virtual network interface model. The proposed mechanism can solve the problems of multiple interfaces in a mobile node. Hong, et al. Expires April 17, 2006 [Page 9] Internet-Draft Virtual network interface model for a MN October 2005 6. References 6.1. Normative References [1] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [2] Devarapalli, V., Wakikawa, R., Petrescu, A. and Thubert, P., "Network Mobility (NEMO) Basic Support Protocol", RFC 3963, January 2005. 6.2. Informative References [3] Ernst, T., Montavont, N., Wakikawa, R., Paik, E., and K. Kuladinithi, "Goals and Benefits of Multihoming", draft-ernst-generic-goals-and-benefits-01 (work in progress), February 2005. [4] Montavont, N., Wakikawa, R., Ernst, T., Ng, C-W., and K. Kuladinithi, "Analysis of Multihoming in Mobile IPv6", draft-montavont-mobileip-multihoming-pb-statement-04 (work in progress), June 2005. [5] Montavont, N., Noel, T. and Kassi-Lahlou, M., "Mobile IPv6 for multiple interfaces (MMI)", draft-montavont-mip6-mmi-02. txt (work in progress), July 2005. [6] Y-G Hong, J-C Lee, J-S Park and H-J Kim, "Analysis of multiple interfaces in a Mobile Node", draft-hong-multipleif -mn-pb-statement-00.txt (work in progress), October 2005. [7] Alessandro Rubini, Linux Virtual Network Interfaces, http://www.linux-mag.com/2000-04/gear_01.html [8] MIPL Mobile IPv6 for Linux, http://www.mobile-ipv6.org Hong, et al. Expires April 17, 2006 [Page 10] Internet-Draft Virtual network interface model for a MN October 2005 Authors' Addresses Yong-Geun Hong ETRI 161 Gajeong-dong Yuseong-gu Daejeon, 305-350 Korea Phone: +82 42 860 6557 Email: yghong@etri.re.kr Joo-Chul Lee ETRI 161 Gajeong-dong Yuseong-gu Daejeon, 305-350 Korea Phone: +82 42 860 1021 Email: rune@etri.re.kr Jung-Soo Park ETRI 161 Gajeong-dong Yuseong-gu Daejeon, 305-350 Korea Phone: +82 42 860 6514 Email: pjs@etri.re.kr Hyoung-Jun Kim ETRI 161 Gajeong-dong Yuseong-gu Daejeon, 305-350 Korea Phone: +82 42 860 6576 Email: khj@etri.re.kr Hong, et al. Expires April 17, 2006 [Page 11] Internet-Draft Virtual network interface model for a MN October 2005 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. 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. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Hong, et al. Expires April 17, 2006 [Page 12]