Internet DRAFT - draft-hong-virtualif-mn-mipv6
draft-hong-virtualif-mn-mipv6
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
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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
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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
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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.
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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.
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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
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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.)
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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) | |
| +------------+ +------------+ |
+-------------------------------+
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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.
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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.
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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
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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
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