draft-ietf-nemo-multihoming-issues-07.txt   rfc4980.txt 
NEMO Working Group C. Ng Network Working Group C. Ng
Internet-Draft Panasonic Singapore Labs Request for Comments: 4980 Panasonic Singapore Labs
Expires: August 9, 2007 T. Ernst Category: Informational T. Ernst
INRIA INRIA
E. Paik E. Paik
KT KT
M. Bagnulo M. Bagnulo
UC3M UC3M
February 5, 2007 October 2007
Analysis of Multihoming in Network Mobility Support Analysis of Multihoming in Network Mobility Support
draft-ietf-nemo-multihoming-issues-07
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Abstract Abstract
This document is an analysis of multihoming in the context of network This document is an analysis of multihoming in the context of network
mobility (NEMO) in IPv6. As there are many situations in which mobility (NEMO) in IPv6. As there are many situations in which
mobile networks may be multihomed, a taxonomy is proposed to classify mobile networks may be multihomed, a taxonomy is proposed to classify
the possible configurations. The possible deployment scenarios of the possible configurations. The possible deployment scenarios of
multihomed mobile networks are described together with the associated multihomed mobile networks are described together with the associated
issues when network mobility is supported by RFC 3963 (NEMO Basic issues when network mobility is supported by RFC 3963 (NEMO Basic
Support). Recommendations are offered on how to address these Support). Recommendations are offered on how to address these
issues. issues.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Classification . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Classification . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. (1,1,1): Single MR, Single HA, Single MNP . . . . . . . . 6
2.1. (1,1,1): Single MR, Single HA, Single MNP . . . . . . . . 7 2.2. (1,1,n): Single MR, Single HA, Multiple MNPs . . . . . . . 6
2.2. (1,1,n): Single MR, Single HA, Multiple MNPs . . . . . . . 8 2.3. (1,n,1): Single MR, Multiple HAs, Single MNP . . . . . . . 7
2.3. (1,n,1): Single MR, Multiple HAs, Single MNP . . . . . . . 8 2.4. (1,n,n): Single MR, Multiple HAs, Multiple MNPs . . . . . 8
2.4. (1,n,n): Single MR, Multiple HAs, Multiple MNPs . . . . . 9 2.5. (n,1,1): Multiple MRs, Single HA, Single MNP . . . . . . . 8
2.5. (n,1,1): Multiple MRs, Single HA, Single MNP . . . . . . . 10 2.6. (n,1,n): Multiple MRs, Single HA, Multiple MNPs . . . . . 9
2.6. (n,1,n): Multiple MRs, Single HA, Multiple MNPs . . . . . 10 2.7. (n,n,1): Multiple MRs, Multiple HAs, Single MNP . . . . . 9
2.7. (n,n,1): Multiple MRs, Multiple HAs, Single MNP . . . . . 11 2.8. (n,n,n): Multiple MRs, Multiple HAs, Multiple MNPs . . . . 10
2.8. (n,n,n): Multiple MRs, Multiple HAs, Multiple MNPs . . . . 12 3. Deployment Scenarios and Prerequisites . . . . . . . . . . . . 11
3.1. Deployment Scenarios . . . . . . . . . . . . . . . . . . . 11
3. Deployment Scenarios and Prerequisites . . . . . . . . . . . . 13 3.2. Prerequisites . . . . . . . . . . . . . . . . . . . . . . 13
3.1. Deployment Scenarios . . . . . . . . . . . . . . . . . . . 13 4. Multihoming Issues . . . . . . . . . . . . . . . . . . . . . . 14
3.2. Prerequisites . . . . . . . . . . . . . . . . . . . . . . 15 4.1. Fault Tolerance . . . . . . . . . . . . . . . . . . . . . 14
4.1.1. Failure Detection . . . . . . . . . . . . . . . . . . 15
4. Multihoming Issues . . . . . . . . . . . . . . . . . . . . . . 17 4.1.2. Path Exploration . . . . . . . . . . . . . . . . . . . 16
4.1. Fault Tolerance . . . . . . . . . . . . . . . . . . . . . 17 4.1.3. Path Selection . . . . . . . . . . . . . . . . . . . . 17
4.1.1. Failure Detection . . . . . . . . . . . . . . . . . . 17 4.1.4. Re-Homing . . . . . . . . . . . . . . . . . . . . . . 19
4.1.2. Path Exploration . . . . . . . . . . . . . . . . . . . 19 4.2. Ingress Filtering . . . . . . . . . . . . . . . . . . . . 19
4.1.3. Path Selection . . . . . . . . . . . . . . . . . . . . 20 4.3. HA Synchronization . . . . . . . . . . . . . . . . . . . . 21
4.1.4. Re-Homing . . . . . . . . . . . . . . . . . . . . . . 22 4.4. MR Synchronization . . . . . . . . . . . . . . . . . . . . 22
4.2. Ingress Filtering . . . . . . . . . . . . . . . . . . . . 22 4.5. Prefix Delegation . . . . . . . . . . . . . . . . . . . . 23
4.3. HA Synchronization . . . . . . . . . . . . . . . . . . . . 24 4.6. Multiple Bindings/Registrations . . . . . . . . . . . . . 23
4.4. MR Synchronization . . . . . . . . . . . . . . . . . . . . 24 4.7. Source Address Selection . . . . . . . . . . . . . . . . . 23
4.5. Prefix Delegation . . . . . . . . . . . . . . . . . . . . 25 4.8. Loop Prevention in Nested Mobile Networks . . . . . . . . 24
4.6. Multiple Bindings/Registrations . . . . . . . . . . . . . 26 4.9. Prefix Ownership . . . . . . . . . . . . . . . . . . . . . 24
4.7. Source Address Selection . . . . . . . . . . . . . . . . . 26 4.10. Preference Settings . . . . . . . . . . . . . . . . . . . 25
4.8. Loop Prevention in Nested Mobile Networks . . . . . . . . 26 5. Recommendations to the Working Group . . . . . . . . . . . . . 26
4.9. Prefix Ownership . . . . . . . . . . . . . . . . . . . . . 27 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.10. Preference Settings . . . . . . . . . . . . . . . . . . . 27 7. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 29
5. Recommendations to the Working Group . . . . . . . . . . . . . 29 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.1. Normative References . . . . . . . . . . . . . . . . . . . 29
9.2. Informative References . . . . . . . . . . . . . . . . . . 29
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 Appendix A. Alternative Classifications Approach . . . . . . . . 32
A.1. Ownership-Oriented Approach . . . . . . . . . . . . . . . 32
8. Security Considerations . . . . . . . . . . . . . . . . . . . 32 A.1.1. ISP Model . . . . . . . . . . . . . . . . . . . . . . 32
A.1.2. Subscriber/Provider Model . . . . . . . . . . . . . . 33
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32 A.2. Problem-Oriented Approach . . . . . . . . . . . . . . . . 34
Appendix B. Nested Tunneling for Fault Tolerance . . . . . . . . 35
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 33 B.1. Detecting Presence of Alternate Routes . . . . . . . . . . 35
10.1. Normative References . . . . . . . . . . . . . . . . . . . 33 B.2. Re-Establishment of Bi-Directional Tunnels . . . . . . . . 36
10.2. Informative References . . . . . . . . . . . . . . . . . . 33 B.2.1. Using Alternate Egress Interface . . . . . . . . . . . 36
B.2.2. Using Alternate Mobile Router . . . . . . . . . . . . 36
Appendix A. Alternative Classifications Approach . . . . . . . . 36 B.3. To Avoid Tunneling Loop . . . . . . . . . . . . . . . . . 37
A.1. Ownership-Oriented Approach . . . . . . . . . . . . . . . 36 B.4. Points of Considerations . . . . . . . . . . . . . . . . . 37
A.1.1. ISP Model . . . . . . . . . . . . . . . . . . . . . . 36
A.1.2. Subscriber/Provider Model . . . . . . . . . . . . . . 37
A.2. Problem-Oriented Approach . . . . . . . . . . . . . . . . 39
Appendix B. Nested Tunneling for Fault Tolerance . . . . . . . . 40
B.1. Detecting Presence of Alternate Routes . . . . . . . . . . 40
B.2. Re-Establishment of Bi-Directional Tunnels . . . . . . . . 41
B.2.1. Using Alternate Egress Interface . . . . . . . . . . . 41
B.2.2. Using Alternate Mobile Router . . . . . . . . . . . . 41
B.3. To Avoid Tunneling Loop . . . . . . . . . . . . . . . . . 42
B.4. Points of Considerations . . . . . . . . . . . . . . . . . 42
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 43
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 47
Intellectual Property and Copyright Statements . . . . . . . . . . 48
1. Introduction 1. Introduction
The design goals and objectives of Network Mobility Support (NEMO) in The design goals and objectives of Network Mobility (NEMO) support in
IPv6 are identified in [1] while the terminology is being described IPv6 are identified in [1], while the terminology is described in [2]
in [2] and [3]. NEMO Basic Support (RFC 3963) [4] is the solution and [3]. NEMO Basic Support (RFC 3963) [4] is the solution proposed
proposed by the NEMO Working Group to provide continuous Internet by the NEMO Working Group to provide continuous Internet connectivity
connectivity to nodes located in an IPv6 mobile network, e.g. like in to nodes located in an IPv6 mobile network, e.g., like in an in-
an in-vehicle embedded IP network. The NEMO Basic Support solution vehicle embedded IP network. The NEMO Basic Support solution does so
does so by setting up bi-directional tunnels between the mobile by setting up bi-directional tunnels between the mobile routers (MRs)
routers (MRs) connecting the mobile network to the Internet and their connecting the mobile network (NEMO) to the Internet and their
respective home agents (HAs), much like how this is done in Mobile respective home agents (HAs), much like how this is done in Mobile
IPv6 [5], the solution for host mobility support. NEMO Basic Support IPv6 [5], the solution for host mobility support. NEMO Basic Support
is transparent to nodes located behind the mobile router (i.e. the is transparent to nodes located behind the MR (i.e., the mobile
mobile network nodes, or MNNs) and as such does not require MNNs to network nodes, or MNNs), and as such, does not require MNNs to take
take any action in the mobility management. any action in the mobility management.
However, mobile networks are typically connected by means of wireless However, mobile networks are typically connected by means of wireless
and thus less reliable links; there could also be many nodes behind and thus less reliable links; there could also be many nodes behind
the MR. A loss of connectivity or a failure to connect to the the MR. A loss of connectivity or a failure to connect to the
Internet has thus a more significant impact than for a single mobile Internet has thus a more significant impact than for a single mobile
node. Scenarios illustrated in [6] demonstrate that providing a node. Scenarios illustrated in [6] demonstrate that providing a
permanent access to mobile networks such as vehicles typically permanent access to mobile networks typically require the use of
require the use of several interfaces and technologies since the several interfaces and technologies. For example, this is
mobile network may be moving in distant geographical locations where particularly useful for Intelligent Transport Systems (ITS)
different access technologies are provided and governed by distinct applications since vehicles are moving across distant geographical
access control policies. locations. Access would be provided through different access
technologies (e.g., Wimax, Wifi, 3G) and through different access
operators.
As specified in section 5 of the NEMO Basic Support Requirements [1] As specified in Section 5 of the NEMO Basic Support Requirements [1]
(R.12), the NEMO WG must ensure that NEMO Basic Support does not (R.12), the NEMO WG must ensure that NEMO Basic Support does not
prevent mobile networks to be multihomed, i.e. when there is more prevent mobile networks to be multihomed, i.e., when there is more
than one point of attachment between the mobile network and the than one point of attachment between the mobile network and the
Internet (see definitions in [3]). This arises either: Internet (see definitions in [3]). This arises either:
o when a MR has multiple egress interfaces, or o when an MR has multiple egress interfaces, or
o the mobile network has multiple MRs, or o the mobile network has multiple MRs, or
o the mobile network is associated with multiple HAs, or o the mobile network is associated with multiple HAs, or
o multiple global prefixes are available in the mobile network.--> o multiple global prefixes are available in the mobile network.
Using NEMO Basic Support, this would translate into having multiple Using NEMO Basic Support, this would translate into having multiple
bi-directional tunnels between the MR(s) and the corresponding HA, bi-directional tunnels between the MR(s) and the corresponding HA(s),
and may result into multiple MNPs available to the MNNs. However, and may result in multiple Mobile Network Prefixes (MNPs) available
NEMO Basic Support does not specify any particular mechanism to to the MNNs. However, NEMO Basic Support does not specify any
manage multiple bi-directional tunnels. The objectives of this memo particular mechanism to manage multiple bi-directional tunnels. The
are thus multifold: objectives of this memo are thus multifold:
o to determine all the potential multihomed configurations for a o to determine all the potential multihomed configurations for a
NEMO, and then to identify which of these may be useful in a real NEMO, and then to identify which of these may be useful in a real-
life scenario; life scenario;
o to capture issues that may prevent some multihomed configurations o to capture issues that may prevent some multihomed configurations
to be supported under the operation of NEMO Basic Support. It to be supported under the operation of NEMO Basic Support. It
doesn't necessarily mean that the ones not supported will not work does not necessarily mean that the ones not supported will not
with NEMO Basic Support, as it may be up to the implementors to work with NEMO Basic Support, as it may be up to the implementors
make it work (hopefully this memo will be helpful to these to make it work (hopefully this memo will be helpful to these
implementors); implementors);
o to decide which issues are worth solving and to determine which WG o to decide which issues are worth solving and to determine which WG
is the most appropriate to address these; is the most appropriate to address these;
o to identify potential solutions to the previously identified o to identify potential solutions to the previously identified
issues. issues.
In order to reach these objectives, a taxonomy for classifying the In order to reach these objectives, a taxonomy for classifying the
possible multihomed configurations is described in Section 2. possible multihomed configurations is described in Section 2.
skipping to change at page 5, line 36 skipping to change at page 4, line 39
issues are studied in Section 4. The issues are then summarized in a issues are studied in Section 4. The issues are then summarized in a
matrix for each of the deployment scenario, and recommendations are matrix for each of the deployment scenario, and recommendations are
made on which of the issues should be worked on and where in made on which of the issues should be worked on and where in
Section 5. This memo concludes with an evaluation of NEMO Basic Section 5. This memo concludes with an evaluation of NEMO Basic
Support for multihomed configurations. Alternative classifications Support for multihomed configurations. Alternative classifications
are outlined in the Appendix. are outlined in the Appendix.
The readers should note that this document considers multihoming only The readers should note that this document considers multihoming only
from the point of view of an IPv6 environment. In order to from the point of view of an IPv6 environment. In order to
understand this memo, the reader is expected to be familiar with the understand this memo, the reader is expected to be familiar with the
above cited documents, i.e. with the NEMO terminology as defined in above cited documents, i.e., with the NEMO terminology as defined in
[2] (section 3) and [3], Motivations and Scenarios for Multihoming [2] (Section 3) and [3], Motivations and Scenarios for Multihoming
[6], Goals and Requirements of Network Mobility Support [1], and the [6], Goals and Requirements of Network Mobility Support [1], and the
NEMO Basic Support specification [4]. Goals and benefits of NEMO Basic Support specification [4]. Goals and benefits of
multihoming as discussed in [6] are applicable to fixed nodes, mobile multihoming as discussed in [6], are applicable to fixed nodes,
nodes, fixed networks and mobile networks. mobile nodes, fixed networks, and mobile networks.
2. Classification 2. Classification
As there are several configurations in which mobile networks are As there are several configurations in which mobile networks are
multihomed, there is a need to classify them into a clearly defined multihomed, there is a need to classify them into a clearly defined
taxonomy. This can be done in various ways. A Configuration- taxonomy. This can be done in various ways. A Configuration-
Oriented taxonomy is described in this section. Two other Oriented taxonomy is described in this section. Two other
taxonomies, namely, the Ownership-Oriented Approach, and the Problem- taxonomies, namely, the Ownership-Oriented Approach and the Problem-
Oriented Approach are outlined in Appendix A.1 and Appendix A.2. Oriented Approach, are outlined in Appendix A.1 and Appendix A.2.
Multihomed configurations can be classified depending on how many Multihomed configurations can be classified depending on how many MRs
mobile routers are present, how many egress interfaces, Care-of are present, how many egress interfaces, Care-of Address (CoA), and
Address (CoA) and Home Addresses (HoA) the mobile routers have, how Home Addresses (HoA) the MRs have, how many prefixes (MNPs) are
many prefixes (MNPs) are available to the mobile network nodes, etc. available to the mobile network nodes, etc. We use three key
We use three key parameters to differentiate the multihomed parameters to differentiate the multihomed configurations. Using
configurations. Using these parameters, each configuration is these parameters, each configuration is referred by the 3-tuple
referred by the 3-tuple (x,y,z), where 'x', 'y', 'z' are defined as (x,y,z), where 'x', 'y', 'z' are defined as follows:
follows:
o 'x' indicates the number of MRs where: o 'x' indicates the number of MRs where:
x=1 implies that a mobile network has only a single MR, x=1 implies that a mobile network has only a single MR,
presumably multihomed. presumably multihomed.
x=n implies that a mobile network has more than one MR. x=n implies that a mobile network has more than one MR.
o 'y' indicates the number of HAs associated with the entire mobile o 'y' indicates the number of HAs associated with the entire mobile
network, where: network, where:
y=1 implies that a single HA is assigned to the mobile network. y=1 implies that a single HA is assigned to the mobile network.
y=n implies that multiple HAs are assigned to the mobile network. y=n implies that multiple HAs are assigned to the mobile network.
o 'z' indicates the number of MNPs available within the NEMO, where: o 'z' indicates the number of MNPs available within the NEMO, where:
z=1 implies that a single MNP is available in the NEMO. z=1 implies that a single MNP is available in the NEMO.
z=N implies that multiple MNPs are available in the NEMO z=N implies that multiple MNPs are available in the NEMO.
It can be seen that the above three parameters are fairly orthogonal It can be seen that the above three parameters are fairly orthogonal
with one another. Thus different values of 'x', 'y' and 'z' result with one another. Thus, different values of 'x', 'y', and 'z' result
into different combinations of the 3-tuple (x,y,z). in different combinations of the 3-tuple (x,y,z).
As described in the sub-sections below, a total of 8 possible As will be described in the sub-sections below, a total of 8 possible
configurations can be identified. One thing the reader has to keep configurations can be identified. One thing the reader has to keep
in mind is that in each of the following 8 cases, the MR may be in mind is that in each of the following 8 cases, the MR may be
multihomed if either (i) multiple prefixes are available (on the home multihomed if either (i) multiple prefixes are available (on the home
link, or on the foreign link), or (ii) the MR is equipped with link, or on the foreign link), or (ii) the MR is equipped with
multiple interfaces. In such a case, the MR would have multiple HoA- multiple interfaces. In such a case, the MR would have multiple
CoA pairs. Issues pertaining to a multihomed MR are also addressed (HoA,CoA) pairs. Issues pertaining to a multihomed MR are also
in [7]. addressed in [7]. In addition, the readers should also keep in mind
that when "MNP(s) is/are available in the NEMO", the MNP(s) may
In addition, the readers should also keep in mind that when "MNP(s) either be explicitly announced by the MR via router advertisement, or
is/are available in the NEMO", the MNP(s) may either be explicitly made available through Dynamic Host Configuration Protocol (DHCP)
announced by the MR via router advertisement, or made available [8].
through Dynamic Host Configuration Protocol (DHCP).
2.1. (1,1,1): Single MR, Single HA, Single MNP 2.1. (1,1,1): Single MR, Single HA, Single MNP
The (1,1,1) configuration has only one MR, it is associated with a The (1,1,1) configuration has only one MR, it is associated with a
single HA, and a single MNP is available in the NEMO. To fall into a single HA, and a single MNP is available in the NEMO. The MR and the
multihomed configuration, at least one of the following conditions AR are connected to the Internet via a single Access Router (AR). To
must hold: fall into a multihomed configuration, at least one of the following
conditions must hold:
o The MR has multiple interfaces and thus it has multiple CoAs; o The MR has multiple interfaces and thus it has multiple CoAs;
o Multiple global prefixes are available on the foreign link, and o Multiple global prefixes are available on the foreign link, and
thus it has multiple CoAs; or thus it has multiple CoAs; or
o Multiple global prefixes are available on the home link, and thus
the MR has more than one path to reach the HA.
Note that the case where multiple prefixes are available on the Note that the case where multiple prefixes are available on the
foreign link does not have any bearing on the MNPs. MNPs are foreign link does not have any bearing on the MNPs. MNPs are
independent of prefixes available on the link where the MR is independent of prefixes available on the link where the MR is
attached to, thus prefixes available on the foreign link are not attached to, thus prefixes available on the foreign link are not
announced on the NEMO link. For the case where multiple prefixes are announced on the NEMO link. For the case where multiple prefixes are
available on the home link, these are only announced on the NEMO link available on the home link, these are only announced on the NEMO link
if the MR is configured to do so. In this configuration, only one if the MR is configured to do so. In the present (1,1,1)
MNP is announced. configuration, only one MNP is announced.
A bi-directional tunnel would then be established between each {HA A bi-directional tunnel would then be established between each
address,CoA} pair. (HoA,CoA) pair.
Regarding MNNs, they are (usually) not multihomed since they would Regarding MNNs, they are (usually) not multihomed since they would
configure a single global address from the single MNP available on configure a single global address from the single MNP available on
the link they are attached to. the link they are attached to.
_____ _____
_ p _ | | _ p _ | |
|_|-|<-_ |-|_|-| |-| _ |_|-|<-_ |-|_|-| |-| _
_ |-|_|=| |_____| | _ |-|_| _ |-|_|=| |_____| | _ |-|_|
|_|-| | |-|_|-| |_|-| | |-|_|-|
| |
MNNs MR AR Internet AR HA MNNs MR AR Internet AR HA
Figure 1: (1,1,1): 1 MR, 1 HA, 1 MNP Figure 1: (1,1,1): 1 MR, 1 HA, 1 MNP
2.2. (1,1,n): Single MR, Single HA, Multiple MNPs 2.2. (1,1,n): Single MR, Single HA, Multiple MNPs
The (1,1,n) configuration has only one MR, it is associated with a The (1,1,n) configuration has only one MR, it is associated with a
single HA and two or more MNPs are available in the NEMO. single HA, and two or more MNPs are available in the NEMO.
The MR may itself be multihomed, as detailed in Section 2.1. A bi- The MR may itself be multihomed, as detailed in Section 2.1. In such
directional tunnel would be established between each {HA address,CoA} a case, a bi-directional tunnel would be established between each
pair. (HoA,CoA) pair.
Regarding MNNs, they are multihomed because several MNPs are Regarding MNNs, they are multihomed because several MNPs are
available on the link they are attached to. The MNNs would then available on the link they are attached to. The MNNs would then
configure a global address from each MNP available on the link. configure a global address from each MNP available on the link.
_____ _____
_ p1,p2 _ | | _ p1,p2 _ | |
|_|-|<-_ |-|_|-| |-| _ |_|-|<-_ |-|_|-| |-| _
_ |-|_|=| |_____| | _ |-|_| _ |-|_|=| |_____| | _ |-|_|
|_|-| | |-|_|-| |_|-| | |-|_|-|
skipping to change at page 8, line 34 skipping to change at page 7, line 29
MNNs MR AR Internet AR HA MNNs MR AR Internet AR HA
Figure 2: (1,1,n): 1 MR, 1 HA, multiple MNPs Figure 2: (1,1,n): 1 MR, 1 HA, multiple MNPs
2.3. (1,n,1): Single MR, Multiple HAs, Single MNP 2.3. (1,n,1): Single MR, Multiple HAs, Single MNP
The (1,n,1) configuration has only one MR and a single MNP is The (1,n,1) configuration has only one MR and a single MNP is
available in the NEMO. The MR, however, is associated with multiple available in the NEMO. The MR, however, is associated with multiple
HAs. HAs.
The NEMO is multihomed since it has multiple HAs, but in addition the The NEMO is multihomed since it has multiple HAs, but in addition,
conditions detailed in Section 2.1 may also hold for the MR. A bi- the conditions detailed in Section 2.1 may also hold for the MR. A
directional tunnel would be established between each {HA address,CoA} bi-directional tunnel would then be established between each
pair. (HoA,CoA) pair.
Regarding MNNs, they are (usually) not multihomed since they would Regarding MNNs, they are (usually) not multihomed since they would
configure a single global address from the single MNP available on configure a single global address from the single MNP available on
the link they are attached to. the link they are attached to.
AR HA2 AR HA2
_ | _ |
|-|_|-| _ |-|_|-| _
_____ | |-|_| _____ | |-|_|
_ p _ | |-| _ p _ | |-|
skipping to change at page 9, line 25 skipping to change at page 8, line 11
MNNs MR AR Internet AR HA1 MNNs MR AR Internet AR HA1
Figure 3: (1,n,1): 1 MR, multiple HAs, 1 MNP Figure 3: (1,n,1): 1 MR, multiple HAs, 1 MNP
2.4. (1,n,n): Single MR, Multiple HAs, Multiple MNPs 2.4. (1,n,n): Single MR, Multiple HAs, Multiple MNPs
The (1,n,n) configuration has only one MR. However, the MR is The (1,n,n) configuration has only one MR. However, the MR is
associated with multiple HAs and more than one MNP is available in associated with multiple HAs and more than one MNP is available in
the NEMO. the NEMO.
The MR is multihomed since it has multiple HAs, but in addition the The MR is multihomed since it has multiple HAs, but in addition, the
conditions detailed in Section 2.1 may also hold. A bi-directional conditions detailed in Section 2.1 may also hold. A bi-directional
tunnel would be established between each {HA address,CoA} pair. tunnel would then be established between each (HoA,CoA) pair.
Regarding MNNs, they are multihomed because several MNPs are Regarding MNNs, they are multihomed because several MNPs are
available on the link they are attached to. The MNNs would then available on the link they are attached to. The MNNs would then
configure a global address with each MNP available on the link. configure a global address with each MNP available on the link.
AR HA2 AR HA2
_ | _ _ | _
_____ |-|_|-|-|_| _____ |-|_|-|-|_|
_ p1,p2 _ | |-| | _ p1,p2 _ | |-| |
|_|-|<-_ |-|_|-| | _ |_|-|<-_ |-|_|-| | _
_ |-|_|=| |_____|-| _ |-|_| _ |-|_|=| |_____|-| _ |-|_|
|_|-| | |-|_|-| |_|-| | |-|_|-|
| | | |
MNNs MR AR Internet AR HA1 MNNs MR AR Internet AR HA1
Figure 4: (1,n,n): 1 MR, multiple HAs, multiple MNPs Figure 4: (1,n,n): 1 MR, multiple HAs, multiple MNPs
2.5. (n,1,1): Multiple MRs, Single HA, Single MNP 2.5. (n,1,1): Multiple MRs, Single HA, Single MNP
The (n,1,1) configuration has more than one MR advertising global The (n,1,1) configuration has more than one MR advertising global
routes. However, the MR(s) are associated with as single HA, and routes. However, the MR(s) are associated with a single HA, and
there in a single MNP available in the NEMO. there is a single MNP available in the NEMO.
The NEMO is multihomed since it has multiple MRs, but in addition the The NEMO is multihomed since it has multiple MRs, but in addition the
conditions detailed in Section 2.1 may also hold for each MR. A bi- conditions detailed in Section 2.1 may also hold for each MR. A bi-
directional tunnel would be established between each {HA address,CoA} directional tunnel would then be established between each (HoA,CoA)
pair. pair.
Regarding MNNs, they are (usually) not multihomed since they would Regarding MNNs, they are (usually) not multihomed since they would
configure a single global address from the single MNP available on configure a single global address from the single MNP available on
the link they are attached to. the link they are attached to.
MR2 MR2
p<-_ | p<-_ |
_ |-|_|-| _____ _ |-|_|-| _____
|_|-| |-| | |_|-| |-| |
skipping to change at page 10, line 38 skipping to change at page 9, line 23
MNNs MR1 Internet AR HA MNNs MR1 Internet AR HA
Figure 5: (n,1,1): Multiple MRs, 1 HA, 1 MNP Figure 5: (n,1,1): Multiple MRs, 1 HA, 1 MNP
2.6. (n,1,n): Multiple MRs, Single HA, Multiple MNPs 2.6. (n,1,n): Multiple MRs, Single HA, Multiple MNPs
The (n,1,n) configuration has more than one MR; multiple global The (n,1,n) configuration has more than one MR; multiple global
routes are advertised by the MRs and multiple MNPs are available routes are advertised by the MRs and multiple MNPs are available
within the NEMO. within the NEMO.
The NEMO is multihomed since it has multiple MRs, but in addition the The NEMO is multihomed since it has multiple MRs, but in addition,
conditions detailed in Section 2.1 may also hold for each MR. A bi- the conditions detailed in Section 2.1 may also hold for each MR. A
directional tunnel would be established between each {HA address,CoA} bi-directional tunnel would then be established between each
pair. (HoA,CoA) pair.
Regarding MNNs, they are multihomed because several MNPs are Regarding MNNs, they are multihomed because several MNPs are
available on the link they are attached to. The MNNs would then available on the link they are attached to. The MNNs would then
configure a global address with each MNP available on the link. configure a global address with each MNP available on the link.
MR2 MR2
p2<-_ | p2<-_ |
_ |-|_|-| _____ _ |-|_|-| _____
|_|-| |-| | |_|-| |-| |
_ | | |-| _ _ | | |-| _
skipping to change at page 11, line 24 skipping to change at page 10, line 6
Figure 6: (n,1,n): Multiple MRs, 1 HA, multiple MNPs Figure 6: (n,1,n): Multiple MRs, 1 HA, multiple MNPs
2.7. (n,n,1): Multiple MRs, Multiple HAs, Single MNP 2.7. (n,n,1): Multiple MRs, Multiple HAs, Single MNP
The (n,n,1) configuration has more than one MR advertising multiple The (n,n,1) configuration has more than one MR advertising multiple
global routes. The mobile network is simultaneously associated with global routes. The mobile network is simultaneously associated with
multiple HAs and a single MNP is available in the NEMO. multiple HAs and a single MNP is available in the NEMO.
The NEMO is multihomed since it has multiple MRs and HAs, but in The NEMO is multihomed since it has multiple MRs and HAs, but in
addition the conditions detailed in Section 2.1 may also hold for addition, the conditions detailed in Section 2.1 may also hold for
each MR. A bi-directional tunnel would be established between each each MR. A bi-directional tunnel would then be established between
{HA address,CoA} pair. each (HoA,CoA) pair.
Regarding MNNs, they are (usually) not multihomed since they would Regarding MNNs, they are (usually) not multihomed since they would
configure a single global address from the single MNP available on configure a single global address from the single MNP available on
the link they are attached to. the link they are attached to.
MR2 AR HA2 MR2 AR HA2
p _ | p _ |
<-_ | |-|_|-| _ <-_ | |-|_|-| _
_ |-|_|-| _____ | |-|_| _ |-|_|-| _____ | |-|_|
|_|-| |-| |-| |_|-| |-| |-|
skipping to change at page 12, line 12 skipping to change at page 10, line 35
Figure 7: (n,n,1): Multiple MRs, Multiple HAs, 1 MNP Figure 7: (n,n,1): Multiple MRs, Multiple HAs, 1 MNP
2.8. (n,n,n): Multiple MRs, Multiple HAs, Multiple MNPs 2.8. (n,n,n): Multiple MRs, Multiple HAs, Multiple MNPs
The (n,n,n) configuration has multiple MRs advertising different The (n,n,n) configuration has multiple MRs advertising different
global routes. The mobile network is simultaneously associated with global routes. The mobile network is simultaneously associated with
more than one HA and multiple MNPs are available in the NEMO. more than one HA and multiple MNPs are available in the NEMO.
The NEMO is multihomed since it has multiple MRs and HAs, but in The NEMO is multihomed since it has multiple MRs and HAs, but in
addition the conditions detailed in Section 2.1 may also hold for addition, the conditions detailed in Section 2.1 may also hold for
each MR. A bi-directional tunnel would be established between each each MR. A bi-directional tunnel would then be established between
{HA address,CoA} pair. each (HoA,CoA) pair.
Regarding MNNs, they are multihomed because several MNPs are Regarding MNNs, they are multihomed because several MNPs are
available on the link they are attached to. The MNNs would then available on the link they are attached to. The MNNs would then
configure a global address with each MNP available on the link. configure a global address with each MNP available on the link.
MR2 AR HA2 MR2 AR HA2
p2 _ | p2 _ |
<-_ | |-|_|-| _ <-_ | |-|_|-| _
_ |-|_|-| _____ | |-|_| _ |-|_|-| _____ | |-|_|
|_|-| |-| |-| |_|-| |-| |-|
skipping to change at page 13, line 32 skipping to change at page 11, line 46
These benefits are now illustrated from a NEMO perspective with a These benefits are now illustrated from a NEMO perspective with a
typical instance scenario for each case in the taxonomy. We then typical instance scenario for each case in the taxonomy. We then
discuss the prerequisites to fulfill these. discuss the prerequisites to fulfill these.
3.1. Deployment Scenarios 3.1. Deployment Scenarios
x=1: Multihomed mobile networks with a single MR x=1: Multihomed mobile networks with a single MR
o Example 1: o Example 1:
MR with dual/multiple access interfaces (e.g. 802.11 and GPRS MR with dual/multiple access interfaces (e.g., 802.11 and GPRS
capabilities). This is a (1,1,*) if both accesses are capabilities). This is a (1,1,*) if a single HA is used for
performed with the same ISP. If the two accesses are offered both. If two independent HAs are used, this is a (1,n,n)
by independent ISPs, this is a (1,n,n) configuration. configuration.
Benefits: Ubiquitous Access, Reliability, Load Sharing, Benefits: Ubiquitous Access, Reliability, Load Sharing,
Preference Settings, Aggregate Bandwidth. Preference Settings, Aggregate Bandwidth.
x=N: Multihomed mobile networks with multiple MRs x=n: Multihomed mobile networks with multiple MRs
o Example 1: o Example 1:
Train with one MR in each car, all served by the same HA, thus Train with one MR in each car, all served by the same HA, thus
a (n,1,*) configuration. Alternatively, the train company a (n,1,*) configuration. Alternatively, the train company
might be forced to use different ISPs when the train crosses might use different HAs, in different countries, thus a (n,n,n)
different countries, thus a (n,n,n) configuration. configuration.
Benefits: Ubiquitous Access, Reliability, Load Sharing, Benefits: Ubiquitous Access, Reliability, Load Sharing,
Aggregate Bandwidth. Aggregate Bandwidth.
o Example 2: o Example 2:
W-PAN with a GPRS-enabled phone and a WiFi-enabled PDA. This Wireless personal area network with a GPRS-enabled phone and a
is a (n,n,n) configuration if the two access technologies are WiFi-enabled PDA. This is a (n,n,n) configuration if different
subscribed separately. HAs are also used.
Benefits: Ubiquitous Access, Reliability, Preference Settings, Benefits: Ubiquitous Access, Reliability, Preference Settings,
Aggregate Bandwidth. Aggregate Bandwidth.
y=1: Multihomed mobile networks with a single HA y=1: Multihomed mobile networks with a single HA
o Example: o Example:
Most single ISP cases in above examples. Most single HA cases in above examples.
y=N: Multihomed mobile networks with multiple HAs y=n: Multihomed mobile networks with multiple HAs
o Example 1: o Example 1:
Most multiple ISP cases in above examples. Most multiple HAs cases in above examples.
o Example 2: o Example 2:
Transatlantic flight with a HA in each continent. This is a Transatlantic flight with a HA in each continent. This is a
(1,n,1) configuration if there is only one MR. (1,n,1) configuration if there is only one MR.
Benefits: Ubiquitous Access, Reliability, Preference Settings Benefits: Ubiquitous Access, Reliability, Preference Settings
(reduced delay, shortest path). (reduced delay, shortest path).
z=1: Multihomed mobile networks with a single MNP z=1: Multihomed mobile networks with a single MNP
o Example: o Example:
Most single ISP cases in above examples. Most single HA cases in above examples.
z=N: Multihomed mobile networks with multiple MNPs z=n: Multihomed mobile networks with multiple MNPs
o Example 1: o Example 1:
Most multiple ISP cases in above examples. Most multiple HAs cases in above examples.
o Example 2: o Example 2:
Car with a prefix taken from home (personal traffic is Car with a prefix taken from home (personal traffic is
transmitted using this prefix and is paid by the owner) and one transmitted using this prefix and is paid by the owner) and one
that belongs to the car manufacturer (maintenance traffic is that belongs to the car manufacturer (maintenance traffic is
paid by the car manufacturer). This will typically be a paid by the car manufacturer). This will typically be a
(1,1,n) or a (1,n,n,) configuration. (1,1,n) or a (1,n,n,) configuration.
Benefits: Preference Settings Benefits: Preference Settings
skipping to change at page 16, line 10 skipping to change at page 14, line 12
Multiple tunnels must be maintained simultaneously. Multiple tunnels must be maintained simultaneously.
o Preference Settings: o Preference Settings:
Implicitly, multiple tunnels must be maintained simultaneously if Implicitly, multiple tunnels must be maintained simultaneously if
preferences are set for deciding which of the available bi- preferences are set for deciding which of the available bi-
directional tunnels should be used. To allow user/application to directional tunnels should be used. To allow user/application to
set the preference, a mechanism should be provided to the user/ set the preference, a mechanism should be provided to the user/
application for the notification of the availability of multiple application for the notification of the availability of multiple
bi-directional tunnels, and perhaps also to set preferences. bi-directional tunnels, and perhaps also to set preferences. A
Similar mechanism should also be provided to network similar mechanism should also be provided to network
administrators to manage preferences. administrators to manage preferences.
o Aggregate Bandwidth: o Aggregate Bandwidth:
Multiple tunnels must be maintained simultaneously in order to Multiple tunnels must be maintained simultaneously in order to
increase the total aggregated bandwidth available to the mobile increase the total aggregated bandwidth available to the mobile
network. network.
4. Multihoming Issues 4. Multihoming Issues
As discussed in the previous section, multiple bi-directional tunnels As discussed in the previous section, multiple bi-directional tunnels
need to be maintained either sequentially (e.g. for fault tolerance) need to be maintained either sequentially (e.g., for fault tolerance)
or simultaneously (e.g. for load sharing). or simultaneously (e.g., for load sharing).
In some cases, it may be necessary to divert packets from a (perhaps In some cases, it may be necessary to divert packets from a (perhaps
failed) bi-directional tunnel to an alternative (perhaps newly failed) bi-directional tunnel to an alternative (perhaps newly
established) bi-directional tunnel (i.e. for matters of fault established) bi-directional tunnel (i.e., for matters of fault
recovery, preferences), or to split traffic between multiple tunnels recovery, preferences), or to split traffic between multiple tunnels
(load sharing, load balancing). (load sharing, load balancing).
So, depending on the configuration under consideration, the issues So, depending on the configuration under consideration, the issues
discussed below may need to be addressed sometimes dynamically. For discussed below may need to be addressed sometimes dynamically. For
each issue, potential ways to solve the problem are investigated. each issue, potential ways to solve the problem are investigated.
4.1. Fault Tolerance 4.1. Fault Tolerance
One of the goals of multihoming is the provision of fault tolerance One of the goals of multihoming is the provision of fault tolerance
capabilities. In order to provide such features, a set of tasks need capabilities. In order to provide such features, a set of tasks need
to be performed, including: failure detection, alternative available to be performed, including: failure detection, alternative available
path exploration, path selection, re-homing of established path exploration, path selection, and re-homing of established
communications. These are also discussed in [8] and [8] by the Shim6 communications. These are also discussed in [9] by the Shim6 WG. In
WG. In the following sub-sections, we look at these issues in the the following sub-sections, we look at these issues in the specific
specific context of NEMO, rather than the general Shim6 perspective context of NEMO, rather than the general Shim6 perspective in [9].
in [8]. In addition, in some scenarios, it may also be required to In addition, in some scenarios, it may also be required to provide
provide the mechanisms for coordination between different HAs (see the mechanisms for coordination between different HAs (see
Section 4.3) and also the coordination between different MRs (see Section 4.3) and also the coordination between different MRs (see
Section 4.4). Section 4.4).
4.1.1. Failure Detection 4.1.1. Failure Detection
It is expected for faults to occur more readily at the edge of the It is expected for faults to occur more readily at the edge of the
network (i.e. the mobile nodes), due to the use of wireless network (i.e., the mobile nodes) due to the use of wireless
connections. Efficient fault detection mechanisms are necessary to connections. Efficient fault detection mechanisms are necessary to
recover in timely fashion. recover in timely fashion.
Depending on the NEMO configuration considered, the failure Depending on the NEMO configuration considered, the failure
protection domain greatly varies. In some configurations, the protection domain greatly varies. In some configurations, the
protection domain provided by NEMO multihoming is limited to the protection domain provided by NEMO multihoming is limited to the
links between the MR(s) and the HA(s). In other configurations, the links between the MR(s) and the HA(s). In other configurations, the
protection domain allows to recover from failures in other parts of protection domain allows to recover from failures in other parts of
the path, so an end to end failure detection mechanism is required. the path, so an end-to-end failure detection mechanism is required.
Below are detailed which failure detection capabilities are required The failure detection capabilities required for each configuration
for each configuration: are detailed below:
o For the (1,1,*) cases, multiple paths are available between a o For the (1,1,*) cases, multiple paths are available between a
single MR and a single HA. All the traffic from and to the NEMO single MR and a single HA. All the traffic to and from the NEMO
flows through these MR and HA. Failure detection mechanisms need flows through the MR and HA. Failure detection mechanisms need
only to be executed between these two devices. This is a NEMO/ only to be executed between these two devices. This is a NEMO-/
MIPv6 specific issue. MIPv6-specific issue.
o For the (n,1,*) cases, there is a single HA, so all the traffic o For the (n,1,*) cases, there is a single HA, so all the traffic to
from and to the NEMO will flow through it. The failure detection and from the NEMO will flow through it. The failure detection
mechanisms need to be able to detect failure in the path between mechanisms need to be able to detect failure in the path between
the used MR and the only HA. Hence, the failure detection the used MR and the only HA. Hence, the failure detection
mechanism needs only to involve the HA and the MRs. This is a mechanism needs only to involve the HA and the MRs. This is a
NEMO/MIPv6 specific issue. NEMO/MIPv6 specific issue.
o For the (n,n,*) cases, there are multiple paths between the o For the (n,n,*) cases, there are multiple paths between the
different HAs and the different MRs. Moreover, the HAs may be different HAs and the different MRs. Moreover, the HAs may be
located in different networks, and have different Internet access located in different networks, and have different Internet access
links. This implies that changing the HA used may not only allow links. This implies that changing the HA used may not only allow
recovering from failures in the link between the HA and the MR, recovering from failures in the link between the HA and the MR,
but also from other failure modes, affecting other parts of the but also from other failure modes, affecting other parts of the
path. In this case, an end-to-end failure detection mechanism path. In this case, an end-to-end failure detection mechanism
would provide additional protection. However, a higher number of would provide additional protection. However, a higher number of
failures is likely to occur in the link between the HA and the MR, failures is likely to occur in the link between the HA and the MR,
so it may be reasonable to provide optimized failure detection so it may be reasonable to provide optimized failure detection
mechanisms for this failure mode. The (n,n,n) case is hybrid, mechanisms for this failure mode. The (n,n,n) case is hybrid,
since selecting a different prefix results in a change of path. since selecting a different prefix results in a change of path.
For this case the Shim6 protocols (such as those discussed in [8]) For this case, the Shim6 protocols (such as those discussed in
may be useful. [9]) may be useful.
Most of the above cases involve the detection of tunnel failures Most of the above cases involve the detection of tunnel failures
between HA(s) and MR(s). This is no different from the case of between HA(s) and MR(s). This is no different from the case of
failure detection between a mobile host and its HA(s). As such, a failure detection between a mobile host and its HA(s). As such, a
solution for MIPv6 should apply to NEMO as well. For case (n,*,*), a solution for MIPv6 should apply to NEMO as well. For case (n,*,*),
MR synchronization solution (see Section 4.4) should be able to an MR synchronization solution (see Section 4.4) should be able to
complement a MIPv6 failure detection solution to achieve the desired complement a MIPv6 failure detection solution to achieve the desired
functionality for NEMO. functionality for NEMO.
In order for fault recovery to work, the MRs and HAs must first In order for fault recovery to work, the MRs and HAs must first
possess a means to detect failures: possess a means to detect failures:
o On the MR's side, the MR can rely on router advertisements from o On the MR's side, the MR can rely on router advertisements from
access routers, or other layer-2 trigger mechanisms to detect access routers, or other layer-2 trigger mechanisms to detect
faults, e.g. [9] and [10]. faults, e.g., [10] and [11].
o On the HA's side, it is more difficult to detect tunnel failures. o On the HA's side, it is more difficult to detect tunnel failures.
For an ISP deployment model, the HAs and MRs can use proprietary For an ISP deployment model, the HAs and MRs can use proprietary
methods (such as constant transmission of heartbeat signals) to methods (such as constant transmission of heartbeat signals) to
detect failures and check tunnel liveness. In the subscriber detect failures and check tunnel liveness. In the subscriber
model (see Appendix A.2: S/P model), a lack of standardized model (see Appendix A.2: S/P model), a lack of standardized
"tunnel liveness" protocol means that it is harder to detect "tunnel liveness" protocol means that it is harder to detect
failures. failures.
A possible method is for the MRs to send binding updates more A possible method is for the MRs to send binding updates more
regularly with shorter Lifetime values. Similarly, HAs can return regularly with shorter Lifetime values. Similarly, HAs can return
binding acknowledgment messages with smaller Lifetime values, thus binding acknowledgment messages with smaller Lifetime values, thus
forcing the MRs to send binding updates more frequently. These forcing the MRs to send binding updates more frequently. These
binding updates can be used to emulate "tunnel heartbeats". This binding updates can be used to emulate "tunnel heartbeats". This,
however may lead to more traffic and processing overhead, since however, may lead to more traffic and processing overhead, since
binding updates sent to HAs must be protected (and possibly binding updates sent to HAs must be protected (and possibly
encrypted) with security associations. encrypted) with security associations.
4.1.2. Path Exploration 4.1.2. Path Exploration
Once a failure in the currently used path is detected, alternative Once a failure in the currently used path is detected, alternative
paths have to be explored in order to identify an available one. paths have to be explored in order to identify an available one.
This process is closely related to failure detection in the sense This process is closely related to failure detection in the sense
that paths being explored need to be alternative paths to the one that paths being explored need to be alternative paths to the one
that has failed. There are, however, subtle but significant that has failed. There are, however, subtle but significant
differences between path exploration and failure detection. Failure differences between path exploration and failure detection. Failure
detection occurs on the currently used path while path exploration detection occurs on the currently used path while path exploration
occurs on the alternative paths (not on the one currently being used occurs on the alternative paths (not on the one currently being used
for exchanging packets). Although both path exploration and failure for exchanging packets). Although both path exploration and failure
detection are likely to rely on a reachability or keepalive test detection are likely to rely on a reachability or keepalive test
exchange, failure detection also relies on other information, such as exchange, failure detection also relies on other information, such as
upper layer information (e.g. positive or negative feedback form upper layer information (e.g., positive or negative feedback from
TCP), lower layer information (e.g. an interface is down), and TCP), lower layer information (e.g., an interface is down), and
network layer information (e.g. as an address being deprecated or network layer information (e.g., as an address being deprecated or
ICMP error message). ICMP error message).
Basically, the same cases as in the analysis of the failure detection Basically, the same cases as in the analysis of the failure detection
(Section 4.1.1) issue are identified: (Section 4.1.1) issue are identified:
o For the (1,1,*) cases, multiple paths are available between a o For the (1,1,*) cases, multiple paths are available between a
single MR and a single HA. The existing paths between the HA and single MR and a single HA. The existing paths between the HA and
the MR have to be explored to identify an available one. The the MR have to be explored to identify an available one. The
mechanism involves only the HA and the MR. This is a NEMO/MIPv6 mechanism involves only the HA and the MR. This is a NEMO-/
specific issue. MIPv6-specific issue.
o For the (n,1,*) cases, there is a single HA, so all the traffic o For the (n,1,*) cases, there is a single HA, so all the traffic to
from and to the NEMO will flow through it. The available and from the NEMO will flow through it. The available alternative
alternative paths are the different ones between the different MRs paths are the different ones between the different MRs and the HA.
and the HA. The path exploration mechanism only involves the HA The path-exploration mechanism only involves the HA and the MRs.
and the MRs. This is a NEMO/MIPv6 specific issue. This is a NEMO/MIPv6 specific issue.
o For the (n,n,*) cases, there are multiple paths between the o For the (n,n,*) cases, there are multiple paths between the
different HAs and the different MRs. In this case, alternative different HAs and the different MRs. In this case, alternative
paths may be routed completely independently one from one another. paths may be routed completely independent from one another. An
end-to-end path-exploration mechanism would be able to discover if
An end-to-end path exploration mechanism would be able to discover any of the end-to-end paths is available. The (n,n,1) case,
if any of the end-to-end paths is available. The (n,n,1) case,
however, seems to be pretty NEMO specific, because of the absence however, seems to be pretty NEMO specific, because of the absence
of multiple prefixes. The (n,n,n) case is hybrid, since selecting of multiple prefixes. The (n,n,n) case is hybrid, since selecting
a different prefix results in a change of path. For this case the a different prefix results in a change of path. For this case,
Shim6 protocols (such as those discussed in [8]) may be useful. the Shim6 protocols (such as those discussed in [9]) may be
useful.
Most of the above cases involve the path exploration of tunnels Most of the above cases involve the path exploration of tunnels
between HA(s) and MR(s). This is no different from the case of path between HA(s) and MR(s). This is no different from the case of path
exploration between a mobile host and its HA(s). As such, a solution exploration between a mobile host and its HA(s). As such, a solution
for MIPv6 should apply to NEMO as well. For case (n,*,*), a MR for MIPv6 should apply to NEMO as well. For case (n,*,*), an MR
synchronization solution (see Section 4.4) should be able to synchronization solution (see Section 4.4) should be able to
compliment a MIPv6 path exploration solution to achieve the desired complement an MIPv6 path-exploration solution to achieve the desired
functionality for NEMO. functionality for NEMO.
In order to perform path exploration, it is sometimes also necessary In order to perform path exploration, it is sometimes also necessary
for the mobile router to detect the availability of network media. for the MR to detect the availability of network media. This may be
This may be achieved using layer 2 triggers [9], or other mechanism achieved using layer 2 triggers [10], or other mechanism developed/
developed/recommended by the Detecting Network Attachment (DNA) recommended by the Detecting Network Attachment (DNA) Working Group
Working Group [10]. This is related to Section 4.1.1, since the [11]. This is related to Section 4.1.1, since the ability to detect
ability to detect media availability would often implies the ability media availability would often imply the ability to detect media
to detect media un-availability. unavailability.
4.1.3. Path Selection 4.1.3. Path Selection
A path selection mechanism is required to select among the multiple A path-selection mechanism is required to select among the multiple
available paths. Depending on the NEMO multihoming configuration available paths. Depending on the NEMO multihoming configuration
involved, the differences between the paths may affect only the part involved, the differences between the paths may affect only the part
between the HA and the MR, or they may affect the full end-to-end between the HA and the MR, or they may affect the full end-to-end
path. In addition, depending on the configuration, path selection path. In addition, depending on the configuration, path selection
may be performed by the HA(s), the MR(s) or the hosts themselves may be performed by the HA(s), the MR(s), or the hosts themselves
through address selection, as will be described in details next. through address selection, as will be described in detail next.
The multiple available paths may differ on the tunnel between the MR The multiple available paths may differ on the tunnel between the MR
and the HA used to carry traffic to/from the NEMO. In this case, and the HA used to carry traffic to/from the NEMO. In this case,
path selection is performed by the MR and the intra-NEMO routing path selection is performed by the MR and the intra-NEMO routing
system for traffic flowing from the NEMO, and path selection is system for traffic flowing from the NEMO, and path selection is
performed by the HA and intra-Home Network routing system for traffic performed by the HA and intra-Home Network routing system for traffic
flowing to the NEMO. flowing to the NEMO.
Alternatively, the multiple paths available may differ in more than Alternatively, the multiple paths available may differ in more than
just the tunnel between the MR and the HA, since the usage of just the tunnel between the MR and the HA, since the usage of
different prefixes may result in using different providers, hence in different prefixes may result in using different providers; hence, in
completely different paths between the involved endpoints. In this completely different paths between the involved endpoints. In this
case, besides the mechanisms presented in the previous case, case, besides the mechanisms presented in the previous case,
additional mechanisms for the end-to-end path selection may be additional mechanisms for the end-to-end path selection may be
needed. This mechanism may be closely related to source address needed. This mechanism may be closely related to source address
selection mechanisms within the hosts, since selecting a given selection mechanisms within the hosts, since selecting a given
address implies selecting a given prefix, which is associated with a address implies selecting a given prefix, which is associated with a
given ISP serving one of the home networks. given ISP serving one of the home networks.
A dynamic path selection mechanism is thus needed so that this path A dynamic path-selection mechanism is thus needed so that this path
could be selected by: could be selected by:
o The HA: it should be able to select the path based on some o The HA: it should be able to select the path based on some
information recorded in the binding cache. information recorded in the binding cache.
o The MR: it should be able to select the path based on router o The MR: it should be able to select the path based on router
advertisements received on both its egress interfaces or on its advertisements received on both its egress interfaces or on its
ingress interfaces for the (n,*,*) case. ingress interfaces for the (n,*,*) case.
o The MNN: it should be able to select the path based on "Default o The MNN: it should be able to select the path based on "Default
Router Selection" (see [Section 6.3.6. Default Router Selection] Router Selection" (see [Section 6.3.6 Default Router Selection]
[11]) in the (n,*,*) case or based on "Source Address Selection" [12]) in the (n,*,*) case or based on "Source Address Selection"
in the (*,*,n) cases (see Section 4.7 of the present memo). in the (*,*,n) cases (see Section 4.7 of the present memo).
o The user or the application: e.g. in case where a user wants to o The user or the application: e.g., in case where a user wants to
select a particular access technology among the available select a particular access technology among the available
technologies for reasons e.g. of cost or data rate. technologies for reasons, e.g., of cost or data rate.
o A combination of any of the above: a hybrid mechanism should be o A combination of any of the above: a hybrid mechanism should be
also available, e.g. one in which the HA, the MR, and/or the MNNs also available, e.g., one in which the HA, the MR, and/or the MNNs
are coordinated to select the path. are coordinated to select the path.
When multiple bi-directional tunnels are available and possibly used When multiple bi-directional tunnels are available and possibly used
simultaneously, the mode of operation may be either primary-secondary simultaneously, the mode of operation may be either primary-secondary
(one tunnel is precedent over the others and used as the default (one tunnel is precedent over the others and used as the default
tunnel, while the other serves as a back-up) or peer-to-peer (no tunnel, while the other serves as a backup) or peer-to-peer (no
tunnel has precedence over one another, they are used with the same tunnel has precedence over one another, they are used with the same
priority). This questions which of the bi-directional tunnels would priority). This questions which of the bi-directional tunnels would
be selected, and based on which of the parameters (e.g. type of flow be selected, and based on which of the parameters (e.g., type of flow
that goes into/out of the mobile network). that goes into/out of the mobile network).
The mechanisms for the selection among the different tunnels between The mechanisms for the selection among the different tunnels between
the MR(s) and the HA(s) seems to be quite NEMO/MIPv6 specific. the MR(s) and the HA(s) seem to be quite NEMO/MIPv6 specific.
For (1,*,*) cases, they are no different from the case of path For (1,*,*) cases, they are no different from the case of path
selection between a mobile host and its HA(s). As such, a solution selection between a mobile host and its HA(s). As such, a solution
for MIPv6 should apply to NEMO as well. For the (n,*,*) cases, a MR for MIPv6 should apply to NEMO as well. For the (n,*,*) cases, an MR
synchronization solution (see Section 4.4) should be able to synchronization solution (see Section 4.4) should be able to
compliment a MIPv6 path selection solution to achieve the desired complement an MIPv6 path-selection solution to achieve the desired
functionality for NEMO. functionality for NEMO.
The mechanisms for selecting among different end-to-end paths based The mechanisms for selecting among different end-to-end paths based
on address selection are similar to the ones used in other on address selection are similar to the ones used in other
multihoming scenarios, as those considered by Shim6 (e.g. [12]). multihoming scenarios, as those considered by Shim6 (e.g., [13]).
4.1.4. Re-Homing 4.1.4. Re-Homing
After an outage has been detected and an available alternative path After an outage has been detected and an available alternative path
has been identified, a re-homing event takes place, diverting the has been identified, a re-homing event takes place, diverting the
existing communications from one path to the other. Similar to the existing communications from one path to the other. Similar to the
previous items involved in this process, the re-homing procedure previous items involved in this process, the re-homing procedure
heavily varies depending on the NEMO multihoming configuration. heavily varies depending on the NEMO multihoming configuration.
o For the (*,*,1) configurations, the re-homing procedure involves o For the (*,*,1) configurations, the re-homing procedure involves
only the MR(s) and the HA(s). The re-homing procedure may involve only the MR(s) and the HA(s). The re-homing procedure may involve
the exchange of additional BU messages. These mechanisms are the exchange of additional BU messages. These mechanisms are
shared between NEMO Basic Support and MIPv6. shared between NEMO Basic Support and MIPv6.
o For the (*,*,n) cases, in addition to the previous mechanisms, end o For the (*,*,n) cases, in addition to the previous mechanisms,
to end mechanisms may be required. Such mechanisms may involve end-to-end mechanisms may be required. Such mechanisms may
some form of end to end signaling or may simply rely on using involve some form of end-to-end signaling or may simply rely on
different addresses for the communication. The involved using different addresses for the communication. The involved
mechanisms may be similar to those required for re-homing Shim6 mechanisms may be similar to those required for re-homing Shim6
communications (e.g. [12]). communications (e.g., [13]).
4.2. Ingress Filtering 4.2. Ingress Filtering
Ingress filtering mechanisms [13][14] may drop the outgoing packets Ingress filtering mechanisms [14][15] may drop the outgoing packets
when multiple bi-directional tunnels end up at different HAs. This when multiple bi-directional tunnels end up at different HAs. This
could particularly occur if different MNPs are handled by different could particularly occur if different MNPs are handled by different
HAs. If a packet with a source address configured from a specific HAs. If a packet with a source address configured from a specific
MNP is tunneled to a home agent that does not handle that specific MNP is tunneled to a HA that does not handle that specific MNP, the
MNP the packet may be discarded either by the home agent or by a packet may be discarded either by the HA or by a border router in the
border router in the home network. home network.
The ingress filtering compatibility issue is heavily dependent on the The ingress filtering compatibility issue is heavily dependent on the
particular NEMO multihoming configuration: particular NEMO multihoming configuration:
o For the (*,*,1) cases, there is not such an issue, since there is o For the (*,*,1) cases, there is not such an issue, since there is
a single MNP. a single MNP.
o For the (1,1,*) and (n,1,1) cases, there is not such a problem, o For the (1,1,*) and (n,1,1) cases, there is not such a problem,
since there is a single HA, accepting all the MNPs. since there is a single HA, accepting all the MNPs.
o For the (n,1,n) case, though ingress filtering would not occur at o For the (n,1,n) case, though ingress filtering would not occur at
the HA, it may occur at the MRs, when each MR is handling the HA, it may occur at the MRs, when each MR is handling
different MNPs. different MNPs.
o (*,n,n) are the cases where the ingress filtering presents some o (*,n,n) are the cases where the ingress filtering presents some
difficulties. In the (1,n,n) case, the problem is simplified difficulties. In the (1,n,n) case, the problem is simplified
because all the traffic from and to the NEMO is routed through a because all the traffic to and from the NEMO is routed through a
single MR. Such configuration allows the MR to properly route single MR. Such configuration allows the MR to properly route
packets respecting the constraints imposed by ingress filtering. packets respecting the constraints imposed by ingress filtering.
In this case, the single MR may face ingress filtering problems In this case, the single MR may face ingress filtering problems
that a multihomed mobile node may face, as documented in [7]. The that a multihomed mobile node may face, as documented in [7]. The
more complex case is the (n,n,n) case. A simplified case occurs more complex case is the (n,n,n) case. A simplified case occurs
when all the prefixes are accepted by all the HAs, so that no when all the prefixes are accepted by all the HAs, so that no
problems occur with the ingress filtering. However, this cannot problems occur with the ingress filtering. However, this cannot
be always assumed, resulting in the problem described below. be always assumed, resulting in the problem described below.
As an example of how this could happen, consider the deployment As an example of how this could happen, consider the deployment
scenario illustrated in Figure 9: the mobile network has two mobile scenario illustrated in Figure 9: the mobile network has two mobile
routers MR1 and MR2, with home agents HA1 and HA2 respectively. Two routers MR1 and MR2, with home agents HA1 and HA2, respectively. Two
bi-directional tunnels are established between the two pairs. Each bi-directional tunnels are established between the two pairs. Each
mobile router advertises a different MNP (P1 and P2 respectively). MR advertises a different MNP (P1 and P2 respectively). MNP P1 is
MNP P1 is registered to HA1, and MNP P2 is registered to HA2. Thus, registered to HA1, and MNP P2 is registered to HA2. Thus, MNNs
MNNs should be free to auto-configure their addresses on any of P1 or should be free to auto-configure their addresses on any of P1 or P2.
P2. Ingress filtering could thus happen in two cases: Ingress filtering could thus happen in two cases:
o If the two tunnels are available, MNN cannot forward packet with o If the two tunnels are available, MNN cannot forward packet with
source address equals P1.MNN to MR2. This would cause ingress source address equals P1.MNN to MR2. This would cause ingress
filtering at HA2 to occur (or even at MR2). This is contrary to filtering at HA2 to occur (or even at MR2). This is contrary to
normal Neighbor Discovery [11] practice that an IPv6 node is free normal Neighbor Discovery [12] practice that an IPv6 node is free
to choose any router as its default router regardless of the to choose any router as its default router regardless of the
prefix it chooses to use. prefix it chooses to use.
o If the tunnel to HA1 is broken, packets that would normally be o If the tunnel to HA1 is broken, packets that would normally be
sent through the tunnel to HA1 should be diverted through the sent through the tunnel to HA1 should be diverted through the
tunnel to HA2. If HA2 (or some border router in HA2's domain) tunnel to HA2. If HA2 (or some border router in HA2's domain)
performs ingress filtering, packets with source address configured performs ingress filtering, packets with source address configured
from MNP P1 may be discarded. from MNP P1 may be discarded.
Prefix: P1 +-----+ +----+ +----------+ +-----+ Prefix: P1 +-----+ +----+ +----------+ +-----+
skipping to change at page 23, line 49 skipping to change at page 21, line 26
P2.MNN +-----+ | | | Prefix: P2 P2.MNN +-----+ | | | Prefix: P2
| +-----+ +----+ | | +-----+ | +-----+ +----+ | | +-----+
+--| MR2 |--| AR |--| |---| HA2 | +--| MR2 |--| AR |--| |---| HA2 |
Prefix: P2 +-----+ +----+ +----------+ +-----+ Prefix: P2 +-----+ +----+ +----------+ +-----+
Figure 9: An (n,n,n) mobile network Figure 9: An (n,n,n) mobile network
Possible solutions to the ingress filtering incompatibility problem Possible solutions to the ingress filtering incompatibility problem
may be based on the following approaches: may be based on the following approaches:
o Some form of source address dependent routing, whether host-based o Some form of source address-dependent routing, whether host-based
and/or router-based where the prefix contained in the source and/or router-based where the prefix contained in the source
address of the packet is considered when deciding which exit address of the packet is considered when deciding which exit
router to use when forwarding the packet. router to use when forwarding the packet.
o The usage of nested tunnels for (*,n,n) cases. Appendix B o The usage of nested tunnels for (*,n,n) cases. Appendix B
describes one such approach. describes one such approach.
o Deprecating those prefixes associated to non-available exit o Deprecating those prefixes associated to non-available exit
routers. routers.
The ingress filtering incompatibilities problems that appear in some The ingress filtering incompatibilities problems that appear in some
NEMO multihoming configurations are similar to those considered in NEMO multihoming configurations are similar to those considered in
Shim6 (e.g. see [15]). Shim6 (e.g., see [16]).
4.3. HA Synchronization 4.3. HA Synchronization
In the (*,n,*) configuration, a single MNP would be registered at In the (*,n,*) configuration, a single MNP would be registered at
different HAs. This gives rise to the following cases: different HAs. This gives rise to the following cases:
o Only one HA may actively advertise a route to the MNP, o Only one HA may actively advertise a route to the MNP,
o Multiple HAs at different domains may advertise a route to the o Multiple HAs at different domains may advertise a route to the
same MNP. same MNP.
This may pose a problem in the routing infrastructure as a whole if This may pose a problem in the routing infrastructure as a whole if
the HAs are located in different administrative domains. The the HAs are located in different administrative domains. The
implications of this aspect needs further exploration. Certain level implications of this aspect needs further exploration. A certain
of HA co-ordination may be required. A possible approach is to adopt level of HA coordination may be required. A possible approach is to
a HA synchronization mechanism such as that described in [16] and adopt an HA synchronization mechanism such as that described in [17]
[17]. Such synchronization might also be necessary in a (*,n,*) and [18]. Such synchronization might also be necessary in a (*,n,*)
configuration, when a MR sends binding update messages to only one HA configuration, when an MR sends binding update messages to only one
(instead of all HAs). In such cases, the binding update information HA (instead of all HAs). In such cases, the binding update
might have to be synchronized between HAs. The mode of information might have to be synchronized between HAs. The mode of
synchronization may be either primary-secondary or peer-to-peer. In synchronization may be either primary-secondary or peer-to-peer. In
addition, when a MNP is delegated to the MR (see Section 4.5), some addition, when a MNP is delegated to the MR (see Section 4.5), some
level of co-ordination between the HAs may also be necessary. level of coordination between the HAs may also be necessary.
This issue is a general mobility issue that will also have to be This issue is a general mobility issue that will also have to be
dealt with by Mobile IPv6 as well as NEMO Basic Support. dealt with by Mobile IPv6 (see Section 6.2.3 in [7]) as well as NEMO
Basic Support.
4.4. MR Synchronization 4.4. MR Synchronization
In the (n,*,*) configurations, there are common decisions which may In the (n,*,*) configurations, there are common decisions that may
require synchronization among different MRs [18], such as: require synchronization among different MRs [19], such as:
o advertising the same MNP in the (n,*,1) configurations (see also o advertising the same MNP in the (n,*,1) configurations (see also
"prefix delegation" in Section 4.5); "prefix delegation" in Section 4.5);
o one MR relaying the advertisement of the MNP from another failed o one MR relaying the advertisement of the MNP from another failed
MR in the (n,*,n) configuration; and MR in the (n,*,n) configuration; and
o relaying between MRs everything that needs to be relayed, such as o relaying between MRs everything that needs to be relayed, such as
data packets, creating a tunnel from the ingress interface, etc, data packets, creating a tunnel from the ingress interface, etc.,
in the (n,*,*) configuration. in the (n,*,*) configuration.
However, there is no known standardized protocols for this kind of However, there is no known standardized protocol for this kind of
router-to-router synchronization. Without such synchronization, it router-to-router synchronization. Without such synchronization, it
may not be possible for a (n,*,*) configuration to achieve various may not be possible for a (n,*,*) configuration to achieve various
multihoming goals, such as fault tolerance. multihoming goals, such as fault tolerance.
Such a synchronization mechanism can be primary-secondary (i.e. a Such a synchronization mechanism can be primary-secondary (i.e., a
master MR, with the other MRs as backup) or peer-to-peer (i.e. there master MR, with the other MRs as backup) or peer-to-peer (i.e., there
is no clear administrative hierarchy between the MRs). The need for is no clear administrative hierarchy between the MRs). The need for
such mechanism is general in the sense that a multi-router site in such mechanism is general in the sense that a multi-router site in
the fixed network would require the same level of router the fixed network would require the same level of router
synchronization. synchronization.
Thus, this issue is not specific to NEMO Basic Support, though there Thus, this issue is not specific to NEMO Basic Support, though there
is a more pressing need to develop a MR to MR synchronization scheme is a more pressing need to develop an MR-to-MR synchronization scheme
for proving fault tolerances and failure recovery in NEMO for proving fault tolerances and failure recovery in NEMO
configurations due to the higher possibility of links failure. configurations due to the higher possibility of links failure.
In conclusion it is recommended to investigate a generic solution to In conclusion, it is recommended to investigate a generic solution to
this issue although the solution would first have to be developed for this issue although the solution would first have to be developed for
NEMO deployments. NEMO deployments.
4.5. Prefix Delegation 4.5. Prefix Delegation
In the (*,*,1) configurations, the same MNP must be advertised to the In the (*,*,1) configurations, the same MNP must be advertised to the
MNNs through different paths. There is, however, no synchronization MNNs through different paths. There is, however, no synchronization
mechanism available to achieve this. Without a synchronization mechanism available to achieve this. Without a synchronization
mechanism, MR may end up announcing incompatible MNPs. Particularly, mechanism, MR may end up announcing incompatible MNPs. Particularly,
o for the (*,n,1) cases, how can multiple HAs delegate the same MNP o for the (*,n,1) cases, how can multiple HAs delegate the same MNP
to the mobile network? For doing so, the HAs may be somehow to the mobile network? For doing so, the HAs may be somehow
configured to advertise the same MNP (see also "HA configured to advertise the same MNP (see also "HA
Synchronization" in Section 4.3). Synchronization" in Section 4.3).
o for the (n,*,1) cases, how can multiple MRs be synchronized to o for the (n,*,1) cases, how can multiple MRs be synchronized to
advertise the same MNP down the NEMO-link? For doing so, the MRs advertise the same MNP down the NEMO-link? For doing so, the MRs
may be somehow configured to advertise the same MNP (see also "MR may be somehow configured to advertise the same MNP (see also "MR
Synchronization" in Section 4.4). Synchronization" in Section 4.4).
Prefix delegation mechanisms [19][20][21] could be used to ensure all Prefix delegation mechanisms [20][21][22] could be used to ensure all
routers advertise the same MNP. Their applicability to a multihomed routers advertise the same MNP. Their applicability to a multihomed
mobile network should be considered. mobile network should be considered.
4.6. Multiple Bindings/Registrations 4.6. Multiple Bindings/Registrations
When a MR is configured with multiple Care-of Addresses, it is often When an MR is configured with multiple CoAs, it is often necessary
necessary for it to bind these Care-of Addresses to the same MNP. for it to bind these CoAs to the same MNP.
This is a generic mobility issue, since Mobile IPv6 nodes face a This is a generic mobility issue, since Mobile IPv6 nodes face a
similar problem. This issue is discussed in [7]. It is sufficient similar problem. This issue is discussed in [7]. It is sufficient
to note that solutions like [22] can solve this for both Mobile IPv6 to note that solutions like [23] can solve this for both Mobile IPv6
and NEMO Basic Support. This issue is being dealt with in the and NEMO Basic Support. This issue is being dealt with in the
Monami6 WG. Monami6 WG.
4.7. Source Address Selection 4.7. Source Address Selection
In the (*,*,n) configurations, MNNs would be configured with multiple In the (*,*,n) configurations, MNNs would be configured with multiple
addresses. Source address selection mechanisms are needed to decide addresses. Source address selection mechanisms are needed to decide
which address to choose from. which address to choose from.
However, currently available source address selection mechanisms do However, currently available source address selection mechanisms do
not allow MNNs to acquire sufficient information to select their not allow MNNs to acquire sufficient information to select their
source addresses intelligently (such as based on the traffic source addresses intelligently (such as based on the traffic
condition associated with the home network of each MNP). It may be condition associated with the home network of each MNP). It may be
desirable for MNNs to be able to acquire "preference" information on desirable for MNNs to be able to acquire "preference" information on
each MNP from the MRs. This would allow default address selection each MNP from the MRs. This would allow default address selection
mechanisms such as those specified in [23] to be used. Further mechanisms, such as those specified in [24], to be used. Further
exploration on setting such "preference" information in Router exploration on setting such "preference" information in Router
Advertisement based on performance of the bi-directional tunnel might Advertisement based on performance of the bi-directional tunnel might
prove to be useful. Note that source address selection may be prove to be useful. Note that source address selection may be
closely related to path selection procedures (see Section 4.1.3) and closely related to path selection procedures (see Section 4.1.3) and
re-homing techniques (see Section 4.1.4). re-homing techniques (see Section 4.1.4).
This is a general issue faced by any node when offered multiple This is a general issue faced by any node when offered multiple
prefixes. prefixes.
4.8. Loop Prevention in Nested Mobile Networks 4.8. Loop Prevention in Nested Mobile Networks
When a multihomed mobile network is nested within another mobile When a multihomed mobile network is nested within another mobile
network, it can result in very complex topologies. For instance, a network, it can result in very complex topologies. For instance, a
nested mobile network may be attached to two different root-MRs, thus nested mobile network may be attached to two different root-MRs, thus
the aggregated network no longer forms a simple tree structure. In the aggregated network no longer forms a simple tree structure. In
such a situation, infinite loop within the mobile network may occur. such a situation, infinite loop within the mobile network may occur.
This problem is specific to NEMO Basic Support. However, at the time This problem is specific to NEMO Basic Support. However, at the time
of writing, more research is recommended to assess the probability of of writing, more research is recommended to assess the probability of
loops occurring in a multihomed mobile network. For related work, loops occurring in a multihomed mobile network. For related work,
see [24] for a mechanism to avoid loops in nested NEMO. see [25] for a mechanism to avoid loops in nested NEMO.
4.9. Prefix Ownership 4.9. Prefix Ownership
When a (n,*,1) network splits, (i.e. the two MRs split themselves When a (n,*,1) network splits, (i.e., the two MRs split themselves
up), MRs on distinct links may try to register the only available up), MRs on distinct links may try to register the only available
MNP. This cannot be allowed, as the HA has no way to know which node MNP. This cannot be allowed, as the HA has no way to know which node
with an address configured from that MNP is attached to which MR. with an address configured from that MNP is attached to which MR.
Some mechanism must be present for the MNP to either be forcibly Some mechanism must be present for the MNP to either be forcibly
removed from one (or all) MRs, or the implementors must not allow a removed from one (or all) MRs, or the implementors must not allow a
(n,*,1) network to split. (n,*,1) network to split.
A possible approach to solving this problem is described in [25]. A possible approach to solving this problem is described in [26].
This problem is specific to NEMO Basic Support. However, it is This problem is specific to NEMO Basic Support. However, it is
unclear whether there is sufficient deployment scenario for this unclear whether there is a sufficient deployment scenario for this
problem to occur. problem to occur.
It is recommended that the NEMO WG standardizes a solution to solve It is recommended that the NEMO WG standardize a solution to solve
this problem if there is sufficient vendor/operator interest, or this problem if there is sufficient vendor/operator interest, or
specifies that the split of a (n,*,1) network cannot be allowed specify that the split of a (n,*,1) network cannot be allowed without
without a router renumbering. router renumbering.
4.10. Preference Settings 4.10. Preference Settings
When a mobile network is multihomed, the MNNs may be able to benefit When a mobile network is multihomed, the MNNs may be able to benefit
from this configuration, such as to choose among the available paths from this configuration, such as to choose among the available paths
based on cost, transmission delays, bandwidth, etc. However, in some based on cost, transmission delays, bandwidth, etc. However, in some
cases, such a choice is not made available to the MNNs. cases, such a choice is not made available to the MNNs.
Particularly: Particularly:
o In the (*,*,n) configuration, the MNNs can influence the path by o In the (*,*,n) configuration, the MNNs can influence the path by
source address selection (see Section 4.1.3, Section 4.7). source address selection (see Section 4.1.3 and Section 4.7).
o In the (n,*,*) configuration, the MNNs can influence the path by o In the (n,*,*) configuration, the MNNs can influence the path by
default router selection (see Section 4.1.3). default router selection (see Section 4.1.3).
o In the (1,*,1) configuration, the MNNs cannot influence the path o In the (1,n,1) configuration, the MNNs cannot influence the path
selection. selection.
A mechanism that allows the MNN to indicate its preference for a One aspect of preference setting is that the preference of the MNN
given traffic might be helpful. In addition, there may also be a (e.g., application or transport layer configuration) may not be the
need to exchange some information between the MRs and the MNNs. This same as the preference used by MR. Thus, forwarding choices made by
problem is general in the sense that any IPv6 nodes may wish to the MR may not be the best for a particular flow, and may even be
influence the routing decision done by the upstream routers. Such detrimental to some transport control loops (i.e., the flow control
algorithm for TCP may be messed up when MR unexpectedly performs load
balancing on a TCP flow). A mechanism that allows the MNN to
indicate its preference for a given traffic might be helpful here.
Another aspect of preference setting is that the MNN may not even be
aware of the existence of multiple forwarding paths, e.g., the
(1,n,1) configuration. A mechanism for the MR to advertise the
availability of multiple tunneling paths would allow the MNN to take
advantage of this, coupled with the previously mentioned mechanism
that allows the MNN to indicate its preference for a given traffic.
This problem is general in the sense that IPv6 nodes may wish to
influence the routing decision done by the upstream routers. Such a
mechanism is currently being explored by various WGs, such as the mechanism is currently being explored by various WGs, such as the
NSIS and IPFIX WGs. It is also possible that a Shim6 layer in the NSIS and IPFIX WGs. It is also possible that the Shim6 layer in the
MNNs may possess such capability. MNNs may possess such a capability. It is recommended for vendors or
operators to investigate into the solutions developed by these WGs
when providing multihoming capabilities to mobile networks.
It is recommended that vendors or operators to investigate into the In addition, the Monami6 WG is currently developing a flow filtering
solutions developed by these WGs when providing multihoming solution for mobile nodes to indicate how flows should be forwarded
capabilities to mobile networks. by a filtering agent [27] (such as HA and mobile anchor points). It
is recommended that the Monami6 WG consider the issues described here
so that flow filtering can be performed by the MNN to indicate how
flows should be forwarded by the MR.
5. Recommendations to the Working Group 5. Recommendations to the Working Group
Several issues that might impact the deployment of NEMO with Several issues that might impact the deployment of NEMO with
multihoming capabilities were identified in Section 4. These are multihoming capabilities were identified in Section 4. These are
shown in the matrix below, for each of the eight multihoming shown in the matrix below, for each of the eight multihoming
configurations, together with indications of from which WG(s) a configurations, together with indications from which WG(s) a solution
solution to each issue is most likely to be found. to each issue is most likely to be found.
+=================================================================+ +=================================================================+
| # of MRs: | 1 | 1 | 1 | 1 | n | n | n | n | | # of MRs: | 1 | 1 | 1 | 1 | n | n | n | n |
| # of HAs: | 1 | 1 | n | n | 1 | 1 | n | n | | # of HAs: | 1 | 1 | n | n | 1 | 1 | n | n |
| # of Prefixes: | 1 | n | 1 | n | 1 | n | 1 | n | | # of Prefixes: | 1 | n | 1 | n | 1 | n | 1 | n |
+=================================================================+ +=================================================================+
| Fault Tolerance | * | * | * | * | * | * | * | * | | Fault Tolerance | * | * | * | * | * | * | * | * |
+---------------------------------+---+---+---+---+---+---+---+---+ +---------------------------------+---+---+---+---+---+---+---+---+
| Failure Detection |N/M|N/M|N/M|N/M|N/M|N/M| N | S | | Failure Detection |N/M|N/M|N/M|N/M|N/M|N/M| N | S |
+---------------------------------+---+---+---+---+---+---+---+---+ +---------------------------------+---+---+---+---+---+---+---+---+
skipping to change at page 30, line 9 skipping to change at page 27, line 9
. - Not an Issue t - trivial . - Not an Issue t - trivial
* - Fault Tolerance is a combination of Failure Detection, Path * - Fault Tolerance is a combination of Failure Detection, Path
Exploration, Path Selection, and Re-Homing Exploration, Path Selection, and Re-Homing
Figure 10: Matrix of NEMO Multihoming Issues Figure 10: Matrix of NEMO Multihoming Issues
The above matrix serves to identify which issues are NEMO-specific, The above matrix serves to identify which issues are NEMO-specific,
and which are not. The readers are reminded that this matrix is a and which are not. The readers are reminded that this matrix is a
simplification of Section 4 as subtle details are not represented in simplification of Section 4 as subtle details are not represented in
Figure 10. Figure 10.
As can be seen from Figure 10, the following have some concerns which As can be seen from Figure 10, the following are some concerns that
are specific to NEMO: Failure Detection, Path Exploration, Path are specific to NEMO: Failure Detection, Path Exploration, Path
Selection, Re-Homing, Ingress Filtering, HA Synchronization, Prefix Selection, Re-Homing, Ingress Filtering, HA Synchronization, Prefix
Delegation, Loop Prevention in Nested NEMO, and Prefix Ownership. Delegation, Loop Prevention in Nested NEMO, and Prefix Ownership.
Based on the authors' best knowledge of the possible deployments of Based on the authors' best knowledge of the possible deployments of
NEMO, it is recommended that: NEMO, it is recommended that:
o A solution for Failure Detection, Path Exploration, Path o A solution for Failure Detection, Path Exploration, Path
Selection, and Re-Homing be solicited from other WGs. Selection, and Re-Homing be solicited from other WGs.
Although Path Selection is reflected in Figure 10 as NEMO- Although Path Selection is reflected in Figure 10 as NEMO-
Specific, the technical consideration of the problem is believed Specific, the technical consideration of the problem is believed
to be quite similar to the selection of multiple paths in mobile to be quite similar to the selection of multiple paths in mobile
nodes. As such, we would recommend vendors to solicit a solution nodes. As such, we would recommend vendors to solicit a solution
for these issues from other WGs in the IETF, for instance the for these issues from other WGs in the IETF; for instance, the
Monami6 or Shim6 WG. Monami6 or Shim6 WG.
o Ingress Filtering on the (n,n,n) configuration be solved by the o Ingress Filtering on the (n,n,n) configuration can be solved by
NEMO WG. the NEMO WG.
This problem is clearly defined, and can be solved by the WG. This problem is clearly defined, and can be solved by the WG.
Deployment of the (n,n,n) configuration can be envisioned on Deployment of the (n,n,n) configuration can be envisioned on
vehicles for mass transportation (such as buses, trains) where vehicles for mass transportation (such as buses, trains) where
different service providers may install their own mobile routers different service providers may install their own MRs on the
on the vehicle/vessel. vehicle/vessel.
It should be noted that the Shim6 WG may be developing a mechanism It should be noted that the Shim6 WG may be developing a mechanism
for overcoming ingress filtering in a more general sense. We thus for overcoming ingress filtering in a more general sense. We thus
recommend the NEMO WG to concentrate only on the (n,n,n) recommend that the NEMO WG concentrate only on the (n,n,n)
configuration should the WG decide to work on this issue. configuration should the WG decide to work on this issue.
o A solution for Home Agent Synchronization be looked at in a o A solution for HA Synchronization can be looked at in a mobility-
mobility specific WG and taking into consideration both mobile specific WG, taking into consideration both mobile hosts operating
hosts operating Mobile IPv6 and mobile routers operating NEMO Mobile IPv6 and MRs operating NEMO Basic Support.
Basic Support.
o A solution for Multiple Bindings/Registrations be presently looked o A solution for Multiple Bindings/Registrations is presently being
at by the Monami6 WG. developed by the Monami6 WG.
o Prefix Delegation be reviewed and checked by the NEMO WG. o Prefix Delegation should be reviewed and checked by the NEMO WG.
The proposed solutions [21] and [20] providing prefix delegation The proposed solutions [22] and [21] providing prefix delegation
functionality to NEMO Basic Support should be reviewed in order to functionality to NEMO Basic Support should be reviewed in order to
make sure concerns as discussed in Section 4.5 are properly make sure concerns, as discussed in Section 4.5, are properly
handled. handled.
o Loop Prevention in Nested NEMO be investigated. o Loop Prevention in Nested NEMO should be investigated.
Further research is recommended to assess the risk of having a Further research is recommended to assess the risk of having a
loop in the nesting of multihomed mobile networks. loop in the nesting of multihomed mobile networks.
o Prefix Ownership should be considered by the vendors and o Prefix Ownership should be considered by the vendors and
operators. operators.
The problem of Prefix Ownership only occurs when a mobile network The problem of Prefix Ownership only occurs when a mobile network
with multiple MRs and a single MNP can arbitrarily join and split. with multiple MRs and a single MNP can arbitrarily join and split.
Vendors and operators of mobile networks are encouraged to input Vendors and operators of mobile networks are encouraged to input
their views on the applicability of deploying such kind of mobile their views on the applicability of deploying such kind of mobile
networks. networks.
6. Conclusion 6. Conclusion
This memo presented an analysis of multihoming in the context of This memo presented an analysis of multihoming in the context of
network mobility under the operation of NEMO Basic Support (RFC network mobility under the operation of NEMO Basic Support (RFC
3963). The purpose was to investigate issues related to such a bi- 3963). The purpose was to investigate issues related to such a bi-
directional tunneling mechanism where mobile networks are multihomed directional tunneling mechanism where mobile networks are multihomed
and multiple bi-directional tunnels established between home agent and multiple bi-directional tunnels are established between Home
and mobile router pairs. For doing so, mobile networks were Agent and Mobile Router pairs. For doing so, mobile networks were
classified into a taxonomy comprising eight possible multihomed classified into a taxonomy comprising eight possible multihomed
configurations. Issues were explained one by one and then summarized configurations. Issues were explained one by one and then summarized
into a table showing the multihomed configurations where they apply into a table showing the multihomed configurations where they apply,
and suggesting the most relevant IETF working group where they could suggesting the most relevant IETF working group where they could be
be solved. This analysis will be helpful to extend the existing solved. This analysis will be helpful to extend the existing
standards to support multihoming and to implementors of NEMO Basic standards to support multihoming and to implementors of NEMO Basic
Support and multihoming-related mechanisms. Support and multihoming-related mechanisms.
7. IANA Considerations 7. Security Considerations
This is an informational document and as such does not require any
IANA action.
8. Security Considerations
This is an informational document where the multihoming This is an informational document where the multihoming
configurations under the operation of NEMO Basic Support are configurations under the operation of NEMO Basic Support are
analyzed. Security considerations of these multihoming analyzed. Security considerations of these multihoming
configurations, should they be different from those that concern NEMO configurations, should they be different from those that concern NEMO
Basic Support, must be considered by forthcoming solutions. Basic Support, must be considered by forthcoming solutions. For
instance, an attacker could try to use the multihomed device as a
means to access another network that would not be normally reachable
through the Internet. Even when forwarding to another network is
turned off by configuration, an attacker could compromise a system to
enable it.
9. Acknowledgments 8. Acknowledgments
The authors would like to thank people who have given valuable The authors would like to thank people who have given valuable
comments on various multihoming issues on the mailing list, and also comments on various multihoming issues on the mailing list, and also
those who have suggested directions in the 56th - 61st IETF Meetings. those who have suggested directions in the 56th - 61st IETF Meetings.
The initial evaluation of NEMO Basic Support on multihoming The initial evaluation of NEMO Basic Support on multihoming
configurations is a contribution from Julien Charbon. configurations is a contribution from Julien Charbon.
10. References 9. References
10.1. Normative References 9.1. Normative References
[1] Ernst, T., "Network Mobility Support Goals and Requirements", [1] Ernst, T., "Network Mobility Support Goals and Requirements",
draft-ietf-nemo-requirements-06 (work in progress), RFC 4886, July 2007.
November 2006.
[2] Manner, J. and M. Kojo, "Mobility Related Terminology", [2] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004. RFC 3753, June 2004.
[3] Ernst, T. and H. Lach, "Network Mobility Support Terminology", [3] Ernst, T. and H-Y. Lach, "Network Mobility Support
draft-ietf-nemo-terminology-06 (work in progress), Terminology", RFC 4885, July 2007.
November 2006.
[4] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert, [4] Devarapalli, V., Wakikawa, R., Petrescu, A., and P. Thubert,
"Network Mobility (NEMO) Basic Support Protocol", RFC 3963, "Network Mobility (NEMO) Basic Support Protocol", RFC 3963,
January 2005. January 2005.
[5] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in [5] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004. IPv6", RFC 3775, June 2004.
10.2. Informative References 9.2. Informative References
[6] Ernst, T., Montavont, N., Wakikawa, R., Ng, C., and K. [6] Ernst, T., Montavont, N., Wakikawa, R., Ng, C., and K.
Kuladinithi, "Motivations and Scenarios for Using Multiple Kuladinithi, "Motivations and Scenarios for Using Multiple
Interfaces and Global Addresses", Interfaces and Global Addresses", Work in Progress,
draft-ietf-monami6-multihoming-motivation-scenario-01 (work in October 2006.
progress), October 2006.
[7] Montavont, N., Wakikawa, R., Ernst, T., Ng, C., and K. [7] Montavont, N., Wakikawa, R., Ernst, T., Ng, C., and K.
Kuladinithi, "Analysis of Multihoming in Mobile IPv6", Kuladinithi, "Analysis of Multihoming in Mobile IPv6", Work
draft-ietf-monami6-mipv6-analysis-00 (work in progress), in Progress, February 2006.
February 2006.
[8] Arkko, J. and I. Beijnum, "Failure Detection and Locator Pair [8] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Exploration Protocol for IPv6 Multihoming", Carney, "Dynamic Host Configuration Protocol for IPv6
draft-ietf-shim6-failure-detection-07 (work in progress), (DHCPv6)", RFC 3315, July 2003.
[9] Arkko, J. and I. Beijnum, "Failure Detection and Locator Pair
Exploration Protocol for IPv6 Multihoming", Work in Progress,
December 2006. December 2006.
[9] Krishnan, S., Montavont, N., Yegin, A., Veerepalli, S., and A. [10] Krishnan, S., Montavont, N., Yegin, A., Veerepalli, S., and A.
Yegin, "Link-layer Event Notifications for Detecting Network Yegin, "Link-layer Event Notifications for Detecting Network
Attachments", draft-ietf-dna-link-information-05 (work in Attachments", Work in Progress, November 2006.
progress), November 2006.
[10] Narayanan, S., "Detecting Network Attachment in IPv6 Networks [11] Narayanan, S., "Detecting Network Attachment in IPv6 Networks
(DNAv6)", draft-ietf-dna-protocol-03.txt (work in progress), (DNAv6)", Work in Progress, October 2006.
October 2006.
[11] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery [12] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998. for IP Version 6 (IPv6)", RFC 2461, December 1998.
[12] Nordmark, E. and M. Bagnulo, "Level 3 multihoming shim [13] Nordmark, E. and M. Bagnulo, "Level 3 multihoming shim
protocol", draft-ietf-shim6-proto-07 (work in progress), protocol", Work in Progress, November 2006.
November 2006.
[13] Ferguson, P. and D. Senie, "Network Ingress Filtering: [14] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000. Address Spoofing", BCP 38, RFC 2827, May 2000.
[14] Baker, F. and P. Savola, "Ingress Filtering for Multihomed [15] Baker, F. and P. Savola, "Ingress Filtering for Multihomed
Networks", BCP 84, RFC 3704, March 2004. Networks", BCP 84, RFC 3704, March 2004.
[15] Huitema, C. and M. Marcelo, "Ingress filtering compatibility [16] Huitema, C. and M. Marcelo, "Ingress filtering compatibility
for IPv6 multihomed sites", for IPv6 multihomed sites", Work in Progress, October 2006.
draft-huitema-shim6-ingress-filtering-00 (work in progress),
October 2006.
[16] Wakikawa, R., Devarapalli, V., and P. Thubert, "Inter Home [17] Wakikawa, R., Devarapalli, V., and P. Thubert, "Inter Home
Agents Protocol (HAHA)", draft-wakikawa-mip6-nemo-haha-01 (work Agents Protocol (HAHA)", Work in Progress, February 2004.
in progress), February 2004.
[17] Koh, B., Ng, C., and J. Hirano, "Dynamic Inter Home Agent [18] Koh, B., Ng, C., and J. Hirano, "Dynamic Inter Home Agent
Protocol", draft-koh-mip6-nemo-dhap-00 (work in progress), Protocol", Work in Progress, July 2004.
July 2004.
[18] Tsukada, M., "Analysis of Multiple Mobile Routers Cooperation", [19] Tsukada, M., "Analysis of Multiple Mobile Routers Cooperation",
draft-tsukada-nemo-mr-cooperation-analysis-00 (work in Work in Progress, October 2005.
progress), October 2005.
[19] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix [20] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix
Delegation", RFC 3769, June 2004. Delegation", RFC 3769, June 2004.
[20] Droms, R. and P. Thubert, "DHCPv6 Prefix Delegation for NEMO", [21] Droms, R. and P. Thubert, "DHCPv6 Prefix Delegation for NEMO",
draft-ietf-nemo-dhcpv6-pd-02 (work in progress), Work in Progress, September 2006.
September 2006.
[21] Thubert, P. and TJ. Kniveton, "Mobile Network Prefix [22] Thubert, P. and TJ. Kniveton, "Mobile Network Prefix
Delegation", draft-ietf-nemo-prefix-delegation-01 (work in Delegation", Work in Progress, November 2006.
progress), November 2006.
[22] Wakikawa, R., "Multiple Care-of Addresses Registration", [23] Wakikawa, R., "Multiple Care-of Addresses Registration", Work
draft-ietf-monami6-multiplecoa-00 (work in progress), in Progress, June 2006.
June 2006.
[23] Draves, R., "Default Address Selection for Internet Protocol [24] Draves, R., "Default Address Selection for Internet Protocol
version 6 (IPv6)", RFC 3484, February 2003. version 6 (IPv6)", RFC 3484, February 2003.
[24] Thubert, P., Bontous, C., and N. Nicolas, "Nested Nemo Tree [25] Thubert, P., Bontous, C., and N. Nicolas, "Nested Nemo Tree
Discovery", draft-thubert-tree-discovery-04 (work in progress), Discovery", Work in Progress, November 2006.
November 2006.
[25] Kumazawa, M., "Token based Duplicate Network Detection for [26] Kumazawa, M., "Token based Duplicate Network Detection for
split mobile network (Token based DND)", split mobile network (Token based DND)", Work in Progress,
draft-kumazawa-nemo-tbdnd-02 (work in progress), July 2005. July 2005.
[27] Soliman, H., "Flow Bindings in Mobile IPv6 and NEMO Basic
Support", Work in Progress, March 2007.
Appendix A. Alternative Classifications Approach Appendix A. Alternative Classifications Approach
A.1. Ownership-Oriented Approach A.1. Ownership-Oriented Approach
An alternative approach to classifying multihomed mobile network is An alternative approach to classifying a multihomed mobile network
proposed by Erik Nordmark (Sun Microsystems) by breaking the was proposed by Erik Nordmark (Sun Microsystems) by breaking the
classification of multihomed network based on ownership. This is classification of multihomed network based on ownership. This is
more of a tree-like top-down classification. Starting from the more of a tree-like, top-down classification. Starting from the
control and ownership of the HA(s) and MR(s), there are two different control and ownership of the HA(s) and MR(s), there are two different
possibilities: either (i) the HA(s) and MR(s) are controlled by a possibilities: either (i) the HA(s) and MR(s) are controlled by a
single entity, or (ii) the HA(s) and MR(s) are controlled by separate single entity, or (ii) the HA(s) and MR(s) are controlled by separate
entities. We called the first possibility the 'ISP Model', and the entities. We called the first possibility the 'ISP Model', and the
second the 'Subscriber/Provider Model'. second the 'Subscriber/Provider Model'.
A.1.1. ISP Model A.1.1. ISP Model
The case of the HA(s) and MR(s) are controlled by the same entity can The case of the HA(s) and MR(s) are controlled by the same entity can
be best illustrated as an Internet Service Provider (ISP) installing be best illustrated as an Internet Service Provider (ISP) installing
mobile routers on trains, ships or planes. It is up to the ISP to MRs on trains, ships, or planes. It is up to the ISP to deploy a
deploy a certain configuration of mobile network; all 8 certain configuration of mobile network; all 8 configurations, as
configurations as described in the Configuration-Oriented Approach described in the Configuration-Oriented Approach, are possible. In
are possible. In the remaining portion of this document, when the remaining portion of this document, when specifically referring
specifically referring to a mobile network configuration that is to a mobile network configuration that is controlled by a single
controlled by a single entity, we will add an 'ISP' prefix: for entity, we will add an 'ISP' prefix; for example, ISP-(1,1,1) or ISP-
example: ISP-(1,1,1) or ISP-(1,N,N). (1,n,n).
When the HA(s) and MR(s) are controlled by a single entity (such as When the HA(s) and MR(s) are controlled by a single entity (such as
an ISP), the ISP can decide whether it wants to assign one or an ISP), the ISP can decide whether it wants to assign one or
multiple MNPs to the mobile network just like it can make the same multiple MNPs to the mobile network just like it can make the same
decision for any other link in its network (wired or otherwise). In decision for any other link in its network (wired or otherwise). In
any case, the ISP will make the routing between the mobile networks any case, the ISP will make the routing between the mobile networks
and its core routers (such as the HAs) work. This include not and its core routers (such as the HAs) work. This includes not
introducing any aggregation between the HAs which will filter out introducing any aggregation between the HAs, which will filter out
routing announcements for the MNP(es). routing announcements for the MNP(s).
To such ends, the ISP has various means and mechanisms. For one, the To such ends, the ISP has various means and mechanisms. For one, the
ISP can run its Interior Gateway Protocol (IGP) over bi-directional ISP can run its Interior Gateway Protocol (IGP) over bi-directional
tunnels between the MR(s) and HA(s). Alternatively, static routes tunnels between the MR(s) and HA(s). Alternatively, static routes
may be used with the tunnels. When static routes are used, a may be used with the tunnels. When static routes are used, a
mechanism to test "tunnel liveness" might be necessary to avoid mechanism to test "tunnel liveness" might be necessary to avoid
maintaining stale routes. Such "tunnel liveness" may be tested by maintaining stale routes. Such "tunnel liveness" may be tested by
sending heartbeats signals from MR(s) to the HA(s). A possibility is sending heartbeats signals from MR(s) to the HA(s). A possibility is
to simulate heartbeats using Binding Updates messages by controlling to simulate heartbeats using Binding Updates messages by controlling
the "Lifetime" field of the Binding Acknowledgment message to force the "Lifetime" field of the Binding Acknowledgment message to force
the MR to send Binding Update messages at regular interval. However, the MR to send Binding Update messages at regular intervals.
a more appropriate tool might be the Binding Refresh Request message, However, a more appropriate tool might be the Binding Refresh Request
though conformance to the Binding Refresh Request message may be less message, though conformance to the Binding Refresh Request message
strictly enforced in implementations since it serves a somewhat may be less strictly enforced in implementations since it serves a
secondary role when compared to Binding Update messages. somewhat secondary role when compared to Binding Update messages.
A.1.2. Subscriber/Provider Model A.1.2. Subscriber/Provider Model
The case of the HA(s) and MR(s) are controlled by the separate The case of the HA(s) and MR(s) controlled by the separate entities
entities can be best illustrated with a subscriber/provider model, can be best illustrated with a subscriber/provider model, where the
where the MRs belongs to a single subscriber and subscribes to one or MRs belongs to a single subscriber and subscribes to one or more ISPs
more ISPs for HA services. There is two sub-categories in this case: for HA services. There is two sub-categories in this case: when the
when the subscriber subscribes to a single ISP, and when the subscriber subscribes to a single ISP, and when the subscriber
subscriber subscribes to multiple ISPs. In the remaining portion of subscribes to multiple ISPs. In the remaining portion of this
this document, when specifically referring to a mobile network document, when specifically referring to a mobile network
configuration that is in the subscriber/provider model where the configuration that is in the subscriber/provider model where the
subscriber subscribes to only one ISP, we will add an 'S/P' prefix: subscriber subscribes to only one ISP, we will add an 'S/P' prefix;
for example: S/P-(1,1,1) or S/P-(1,n,n). When specifically referring for example, S/P-(1,1,1) or S/P-(1,n,n). When specifically referring
to a mobile network configuration that is in the subscriber/provider to a mobile network configuration that is in the subscriber/provider
model where the subscriber subscribes to multiple ISPs, we will add model where the subscriber subscribes to multiple ISPs, we will add
an 'S/mP' prefix: for example: S/mP-(1,1,1) or S/mP-(1,n,n). an 'S/mP' prefix; for example, S/mP-(1,1,1) or S/mP-(1,n,n).
Not all 8 configurations are likely to be deployed for the S/P and Not all 8 configurations are likely to be deployed for the S/P and
S/mP models. For instance, it is unlikely to foresee a S/mP-(*,1,1) S/mP models. For instance, it is unlikely to foresee a S/mP-(*,1,1)
mobile network where there is only a single HA. For the S/P model, mobile network where there is only a single HA. For the S/P model,
the following configurations are likely to be deployed: the following configurations are likely to be deployed:
o S/P-(1,1,1): Single Provider, Single MR, Single HA, Single MNP o S/P-(1,1,1): Single Provider, Single MR, Single HA, Single MNP
o S/P-(1,1,n): Single Provider, Single MR, Single HA, Multiple MNPs o S/P-(1,1,n): Single Provider, Single MR, Single HA, Multiple MNPs
skipping to change at page 38, line 15 skipping to change at page 34, line 17
o S/mP-(1,n,1): Multiple Providers, Single MR, Multiple HAs, Single o S/mP-(1,n,1): Multiple Providers, Single MR, Multiple HAs, Single
MNP MNP
o S/mP-(1,n,n): Multiple Providers, Single MR, Multiple HAs, o S/mP-(1,n,n): Multiple Providers, Single MR, Multiple HAs,
Multiple MNPs Multiple MNPs
o S/mP-(n,n,n): Multiple Providers, Multiple MRs, Multiple HAs, o S/mP-(n,n,n): Multiple Providers, Multiple MRs, Multiple HAs,
Multiple MNPs Multiple MNPs
When the HA(s) and MR(s) are controlled by different entities, it is When the HA(s) and MR(s) are controlled by different entities, it is
more likely the scenario where the MR is controlled by one entity more likely that the MR is controlled by one entity (i.e., the
(i.e. the subscriber), and the MR is establishing multiple bi- subscriber), and the MR is establishing multiple bi-directional
directional tunnels to one or more HA(s) provided by one or more tunnels to one or more HA(s) provided by one or more ISP(s). In such
ISP(s). In such case, it is unlikely for the ISP to run IGP over the cases, it is unlikely that the ISP will run IGP over the bi-
bi-directional tunnel, since ISP would most certainly wish to retain directional tunnel, since the ISP will most certainly wish to retain
full control of its routing domain. full control of its routing domain.
A.2. Problem-Oriented Approach A.2. Problem-Oriented Approach
A third approach is proposed by Pascal Thubert (Cisco System). This A third approach was proposed by Pascal Thubert (Cisco Systems).
focused on the problems of multihomed mobile networks rather than the This focused on the problems of multihomed mobile networks rather
configuration or ownership. With this approach, there is a set of 4 than the configuration or ownership. With this approach, there is a
categories based on two orthogonal parameters: the number of HAs, and set of 4 categories based on two orthogonal parameters: the number of
the number of MNPs advertised. Since the two parameters are HAs, and the number of MNPs advertised. Since the two parameters are
orthogonal, the categories are not mutually exclusive. The four orthogonal, the categories are not mutually exclusive. The four
categories are: categories are:
o Tarzan: Single HA for Different CoAs of Same MNP o Tarzan: Single HA for Different CoAs of Same MNP
This is the case where one MR registers different Care-of This is the case where one MR registers different CoAs to the same
Addresses to the same HA for the same subnet prefix. This is HA for the same subnet prefix. This is equivalent to the case of
equivalent to the case of y=1, i.e. the (1,1,*) mobile network. y=1, i.e., the (1,1,*) mobile network.
o JetSet: Multiple HAs for Different CoAs of Same MNP o JetSet: Multiple HAs for Different CoAs of Same MNP
This is the case where the MR registers different Care-of This is the case where the MR registers different CoAs to
Addresses to different HAs for the same subnet prefix. This is different HAs for the same subnet prefix. This is equivalent to
equivalent to the case of y=n, i.e. the (1,n,*) mobile network. the case of y=n, i.e., the (1,n,*) mobile network.
o Shinkansen: Single MNP Advertised by MR(s) o Shinkansen: Single MNP Advertised by MR(s)
This is the case where one MNP is announced by different MRs. This is the case where one MNP is announced by different MRs.
This is equivalent to the case of x=n and z=1, i.e. the (n,*,1) This is equivalent to the case of x=n and z=1, i.e., the (n,*,1)
mobile network. mobile network.
o DoubleBed: Multiple MNPs Advertised by MR(s) o DoubleBed: Multiple MNPs Advertised by MR(s)
This is the case where more than one MNPs are announced by the This is the case where more than one MNPs are announced by the
different MRs. This is equivalent to the case of x=n and z=n, different MRs. This is equivalent to the case of x=n and z=n,
i.e. the (n,*,n) mobile network. i.e., the (n,*,n) mobile network.
Appendix B. Nested Tunneling for Fault Tolerance Appendix B. Nested Tunneling for Fault Tolerance
In order to utilize the additional robustness provided by In order to utilize the additional robustness provided by
multihoming, MRs that employ bi-directional tunneling with their HAs multihoming, MRs that employ bi-directional tunneling with their HAs
should dynamically change their tunnel exit points depending on the should dynamically change their tunnel exit points depending on the
link status. For instance, if a MR detects that one of its egress link status. For instance, if an MR detects that one of its egress
interface is down, it should detect if any other alternate route to interface is down, it should detect if alternate routes to the global
the global Internet exists. This alternate route may be provided by Internet exists. This alternate route may be provided by any other
any other MRs connected to one of its ingress interfaces that has an MRs connected to one of its ingress interfaces that has an
independent route to the global Internet, or by another active egress independent route to the global Internet, or by another active egress
interface the MR itself possess. If such an alternate route exists, interface the MR itself possesses. If such an alternate route
the MR should re-establish the bi-directional tunnel using this exists, the MR should re-establish the bi-directional tunnel using
alternate route. this alternate route.
In the remaining part of this Appendix, we will attempt to In the remaining part of this Appendix, we will attempt to
investigate methods of performing such re-establishment of bi- investigate methods of performing such re-establishment of bi-
directional tunnels. This method of tunnel re-establishment is directional tunnels. This method of tunnel re-establishment is
particularly useful for the (*,n,n) NEMO configuration. The method particularly useful for the (*,n,n) NEMO configuration. The method
described is by no means complete and merely serves as a suggestion described is by no means complete and merely serves as a suggestion
on how to approach the problem. It is also not the objective to on how to approach the problem. It is also not the objective to
specify a new protocol specifically tailored to provide this form of specify a new protocol specifically tailored to provide this form of
re- establishments. Instead, we will limit ourselves to currently re- establishments. Instead, we will limit ourselves to currently
available mechanisms specified in Mobile IPv6 [5] and Neighbor available mechanisms specified in Mobile IPv6 [5] and Neighbor
Discovery in IPv6 [11]. Discovery in IPv6 [12].
B.1. Detecting Presence of Alternate Routes B.1. Detecting Presence of Alternate Routes
To actively utilize the robustness provided by multihoming, a MR must To actively utilize the robustness provided by multihoming, an MR
first be capable of detecting alternate routes. This can be manually must first be capable of detecting alternate routes. This can be
configured into the MR by the administrators if the configuration of manually configured into the MR by the administrators if the
the mobile network is relatively static. It is however highly configuration of the mobile network is relatively static. It is
desirable for MRs to be able to discover alternate routes however highly desirable for MRs to be able to discover alternate
automatically for greater flexibility. routes automatically for greater flexibility.
The case where a MR possesses multiple egress interface (bound to the The case where an MR possesses multiple egress interface (bound to
same HA or otherwise) should be trivial, since the MR should be able the same HA or otherwise) should be trivial, since the MR should be
to "realize" it has multiple routes to the global Internet. able to "realize" it has multiple routes to the global Internet.
In the case where multiple MRs are on the mobile network, each MR has In the case where multiple MRs are on the mobile network, each MR has
to detect the presence of other MR. A MR can do so by listening for to detect the presence of other MR. An MR can do so by listening for
Router Advertisement message on its *ingress* interfaces. When a MR Router Advertisement message on its *ingress* interfaces. When an MR
receives a Router Advertisement message with a non-zero Router receives a Router Advertisement message with a non-zero Router
Lifetime field from one of its ingress interfaces, it knows that Lifetime field from one of its ingress interfaces, it knows that
another MR which can provide an alternate route to the global another MR that can provide an alternate route to the global Internet
Internet is present in the mobile network. is present in the mobile network.
B.2. Re-Establishment of Bi-Directional Tunnels B.2. Re-Establishment of Bi-Directional Tunnels
When a MR detects that the link by which its current bi-directional When an MR detects that the link by which its current bi-directional
tunnel with its HA is using is down, it needs to re-establish the bi- tunnel with its HA is using is down, it needs to re-establish the bi-
directional tunnel using an alternate route detected. We consider directional tunnel using an alternate route detected. We consider
two separate cases here: firstly, the alternate route is provided by two separate cases here: firstly, the alternate route is provided by
another egress interface that belongs to the MR; secondly, the another egress interface that belongs to the MR; secondly, the
alternate route is provided by another MR connected to the mobile alternate route is provided by another MR connected to the mobile
network. We refer to the former case as an alternate route provided network. We refer to the former case as an alternate route provided
by an alternate egress interface, and the latter case as an alternate by an alternate egress interface, and the latter case as an alternate
route provided by an alternate MR. route provided by an alternate MR.
B.2.1. Using Alternate Egress Interface B.2.1. Using Alternate Egress Interface
When an egress interface of a MR loses the connection to the global When an egress interface of an MR loses the connection to the global
Internet, the MR can make use of its alternate egress interface Internet, the MR can make use of its alternate egress interface
should it possess multiple egress interfaces. The most direct way to should it possess multiple egress interfaces. The most direct way to
do so is for the MR to send a binding update to the HA of the failed do so is for the MR to send a binding update to the HA of the failed
interface using the CoA assigned to the alternate interface in order interface using the CoA assigned to the alternate interface in order
to re-establish the bi-directional tunneling using the CoA on the to re-establish the bi-directional tunneling using the CoA on the
alternate egress interface. After a successful binding update, the alternate egress interface. After a successful binding update, the
MR encapsulates outgoing packets through the bi-directional tunnel MR encapsulates outgoing packets through the bi-directional tunnel
using the alternate egress interface. using the alternate egress interface.
The idea is to use the global address (most likely a CoA) assigned to The idea is to use the global address (most likely a CoA) assigned to
an alternate egress interface as the new (back-up) CoA of the MR to an alternate egress interface as the new (back-up) CoA of the MR to
re-establish the bi-directional tunneling with its HA. re-establish the bi-directional tunneling with its HA.
B.2.2. Using Alternate Mobile Router B.2.2. Using Alternate Mobile Router
When the MR loses a connection to the global Internet, the MR can When the MR loses a connection to the global Internet, the MR can
utilize a route provided by an alternate MR (if one exists) to re- utilize a route provided by an alternate MR (if one exists) to re-
establish the bi-directional tunnel with its HA. First, the MR has establish the bi-directional tunnel with its HA. First, the MR has
to obtain a CoA from the alternate MR (i.e. attaches itself to the to obtain a CoA from the alternate MR (i.e., attach itself to the
alternate MR). Next, it sends binding update to its HA using the CoA alternate MR). Next, it sends binding update to its HA using the CoA
obtained from the alternate MR. From then on, the MR can obtained from the alternate MR. From then on, the MR can encapsulate
encapsulates outgoing packets through the bi-directional tunnel using outgoing packets through the bi-directional tunnel via the alternate
via the alternate MR. MR.
The idea is to obtain a CoA from the alternate MR and use this as the The idea is to obtain a CoA from the alternate MR and use this as the
new (back-up) CoA of the MR to re-establish the bi-directional new (back-up) CoA of the MR to re-establish the bi-directional
tunneling with its HA. tunneling with its HA.
Note that every packet sent between MNNs and their correspondent Note that every packet sent between MNNs and their correspondent
nodes will experience two levels of encapsulation. First level of nodes will experience two levels of encapsulation. The first level
tunneling occurs between a MR which the MNN uses as its default of tunneling occurs between an MR that the MNN uses as its default
router and the MR's HA. The second level of tunneling occurs between router and the MR's HA. The second level of tunneling occurs between
the alternate MR and its HA. the alternate MR and its HA.
B.3. To Avoid Tunneling Loop B.3. To Avoid Tunneling Loop
The method of re-establishing the bi-directional tunnel as described The method of re-establishing the bi-directional tunnel as described
in Appendix B.2 may lead to infinite loops of tunneling. This in Appendix B.2 may lead to infinite loops of tunneling. This
happens when two MRs on a mobile network lose connection to the happens when two MRs on a mobile network lose connection to the
global Internet at the same time and each MR tries to re-establish global Internet at the same time and each MR tries to re-establish
bi-directional tunnel using the other MR. We refer to this bi-directional tunnel using the other MR. We refer to this
phenomenon as tunneling loop. phenomenon as tunneling loop.
One approach to avoid tunneling loop is for a MR that has lost One approach to avoid tunneling loop is for an MR that has lost
connection to the global Internet to insert an option into the Router connection to the global Internet to insert an option into the Router
Advertisement message it broadcasts periodically. This option serves Advertisement message it broadcasts periodically. This option serves
to notify other MRs on the link that the sender no longer provides to notify other MRs on the link that the sender no longer provides
global connection. Note that setting a zero Router Lifetime field global connection. Note that setting a zero Router Lifetime field
will not work well since it will cause MNNs that are attached to the will not work well since it will cause MNNs that are attached to the
MR to stop using the MR as their default router too (in which case, MR to stop using the MR as their default router too (in which case,
things are back to square one). things are back to square one).
B.4. Points of Considerations B.4. Points of Considerations
This method of using tunnel re-establishments is by no means a This method of using tunnel re-establishments is by no means a
complete solution. There are still points to consider to develop it complete solution. There are still points to consider in order to
into a fully functional solution. For instance, in Appendix B.1, it develop it into a fully functional solution. For instance, in
was suggested that MR detects the presence of other MRs using Router Appendix B.1, it was suggested that MR detects the presence of other
Advertisements. However, Router Advertisements are link scoped, so MRs using Router Advertisements. However, Router Advertisements are
when there is more than one link, some information may be lost. For link scoped, so when there is more than one link, some information
instance, suppose a case where there is three MRs and three different may be lost. For instance, suppose a case where there are three MRs
prefixes and each MR is in a different link with regular routers in and three different prefixes and each MR is in a different link with
between. Suppose now that only a single MR is working, how do the regular routers in between. Suppose now that only a single MR is
other MRs identify which prefix they have to use to configure the new working; how do the other MRs identify which prefix they have to use
CoA? In this case, there are three prefixes being announced and a MR to configure the new CoA? In this case, there are three prefixes
whose link has failed, knows that his prefix is not to be used, but being announced, and an MR whose link has failed knows that its
it has not enough information to decide which one of the other two prefix is not to be used, but it does not have enough information to
prefixes to use to configure the new CoA. In such cases, a mechanism decide which one of the other two prefixes to use to configure the
is needed to allow a MR to withdraw its own prefix when it discovers new CoA. In such cases, a mechanism is needed to allow an MR to
that its link is no longer working. withdraw its own prefix when it discovers that its link is no longer
working.
Appendix C. Change Log
o Changes from draft-ietf-nemo-multihoming-issues-06 to -07:
* Removed in 2.1 the bullet "Multiple global prefixes are
available on the home link, and thus the MR has more than one
path to reach the home agent."
* In all 2.x sub-sections in the sentence similar to "A bi-
directional tunnel would then be established between each HoA-
CoA pair", replaced the part "HoA-CoA" pair with "{HA address,
CoA} pair."
* Removed in 2.3 ", possibly one HA per HoA, or one HA per egress
interface." and in 2.4 ", possibly one per Home Address (or one
HA per egress interface),"
* In 2.4 and 2.6 and 2.8, replaced "Regarding MNNs, they are
generally multihomed since they would configure a global
address from each MNP available on the link they are attached
to." with the better text in 2.2, i.e. "Regarding MNNs, they
are multihomed because several MNPs are available on the link
they are attached to. The MNNs would then configure a global
address with each MNP available on the link."
* In 4.1.1 and 4.1.2 3rd bullet, rephrased the complex sentence
"The (n,n,n) case is hybrid, since for those cases when[4.1.1]/
that[4.1.2] selecting a different prefix result in a change of
path, the Shim6 protocols (such as [9]) may be useful." into
"The (n,n,n) case is hybrid, since selecting a different prefix
results in a change of path. For this case the Shim6 protocols
(such as those discussed in [8]) may be useful."
* Probably due to a typo in the table in section 5 line "Path
Selection", changed "N |S/N| N |S/N| N |S/N| N |S/N|" to "M
|S/M| M |S/M| N |S/N| N |S/N|"
* Removed references to draft-yegin-dna-l2-hints-01 and
draft-manyfolks-l2-mobilereq-02. Should now be covered in
draft-ietf-dna-link-information-05.txt.
* Both draft-droms-nemo-dhcpv6-pd-02 and
draft-ietf-nemo-dhcpv6-pd-00 were cited. Removed the former.
* Replaced references to draft-ietf-dna-hosts-02 and
draft-ietf-dna-routers-01 with draft-ietf-dna-protocol-03.txt
where everything was merged.
* Replaced draft-ietf-shim6-reach-detect-01 with
draft-ietf-shim6-failure-detection
* Replaced draft-ietf-shim6-functional-dec with
draft-ietf-shim6-proto
* Rephrased paragraph about "Prefix Delegation" in section 5.
* Rephrased the conclusion.
* Replaced "visited link" with "foreign link" and "border
gateway" with "border router" in several places.
* Reordered author list.
* And, minor editorial corrections and reference update.
o Changes from draft-ietf-nemo-multihoming-issues-05 to -06:
* Minor editorial corrections and reference update
o Changes from draft-ietf-nemo-multihoming-issues-04 to -05:
* Addressed Issue #23: modified text in Sect 4.2: "Ingress
Filtering"
* Re-phrase statements in Sect 4 and 5 where we "... recommend
issue XXX to be worked on by Monami6/Shim6/IPv6/DNA WG" to
instead suggest that solution to the issue be solicited
elsewhere within the IETF.
o Changes from draft-ietf-nemo-multihoming-issues-03 to -04:
* Updated Section 3: "Deployment Scenarios and Prerequisites"
* Modifications to Section 4:
+ Removed "Media Detection" and moved the relevant concerns to
"Path Exploration"
+ Added new "Preference Settings" issue
+ Various text clean-ups in most of the sub-sections
* Modifications to Section 5:
+ Changed Section 5: "Matrix" to "Recommendations to the
Working Group"
+ Identifies which are the issues that are important, and made
recommendations as to how to resolve these multihoming
issues
* Addressed Issue #12: Added Appendix B.4: "Points of
Considerations" to document the concerns raised for this tunnel
re-establishment mechanism.
o Changes from draft-ietf-nemo-multihoming-issues-02 to -03:
* Enlisted Marcelo Bagnulo as co-author
* Restructuring of Section 4:
+ Re-named 'Path Survival' to 'Fault Tolerance'
+ Moved 'Path Failure Detection' and 'Path Selection' as sub-
issues of 'Fault Tolerance'
+ Added 'Path Exploration' and 'Re-homing' as sub-issues of
'Fault Tolerance'
+ Removed 'Impact on Routing Infrastructure'
* Breaking references into Normative and Informative
o Changes from draft-ietf-nemo-multihoming-issues-01 to -02:
* Added recommendations/suggestion of which WG each issue should
be addressed as pointed out in 61st IETF.
* Minor updates on references.
o Changes from draft-ietf-nemo-multihoming-issues-00 to -01:
* Replaced NEMO-Prefix with MNP as decided by the WG at 60th IETF
* Addressed Issue #1 in Section 1: Added a note to remind readers
that IPv6 is implicitly assumed
* Addressed Issue #3 in Sect 2.3: Removed text on assumption
* Addressed Issue #6 in Sect 3.1 "Deployment Scenarios": Added
benefits
* Addressed Issue #7 in Sect 3.2 "Prerequisites": Modified text
* Addressed Issue #9 in Sect 4.3 "Ingress Filtering": Modified
text
* Addressed Issue #10 in Sect 4.4: Added paragraph on other
failure modes
* Addressed Issue #10: New Sect 4.5 on media detection
* Addressed Issue #11 in Section 4.11: modified text
o Changes from draft-ng-multihoming-issues-03 to
draft-ietf-nemo-multihoming-issues-00:
* Expanded Section 4: "Problem Statement"
* Merged "Evaluation" Section into Section 4: "Problem Statement"
* Cleaned up description in Section 2: "Classification", and
clearly indicate in each classification, what are the
multihomed entities
* Re-organized Section 2: "Deployment Scenarios and
Prerequisites", and created the "Prerequisites" sub-section.
o Changes from draft-ng-multihoming-issues-02 to
draft-ng-multihoming-issues-03:
* Merged with draft-eun-nemo-multihoming-problem-statement (see
Section 4: "Problem Statement")
* Included conclusions from
draft-charbon-nemo-multihoming-evaluation-00
* Re-organized some part of "Benefits/Issues of Multihoming in
NEMO" to Section 4: "Problem Statement"
* Removed lots of text to be in sync with [6].
* Title changed from "Multihoming Issues in NEMO Basic Support"
to "Analysis of Multihoming in NEMO"
* Changed (w,x,y) to (x,y,z) in taxonomy.
* Moved alternative approaches of classification to Appendix
* Creation of this Change-Log itself ;-)
Authors' Addresses Authors' Addresses
Chan-Wah Ng Chan-Wah Ng
Panasonic Singapore Laboratories Pte Ltd Panasonic Singapore Laboratories Pte Ltd
Blk 1022 Tai Seng Ave #06-3530 Blk 1022 Tai Seng Ave #06-3530
Tai Seng Industrial Estate Tai Seng Industrial Estate
Singapore 534415 Singapore 534415
SG SG
Phone: +65 65505420 Phone: +65 65505420
Email: chanwah.ng@sg.panasonic.com EMail: chanwah.ng@sg.panasonic.com
Thierry Ernst Thierry Ernst
INRIA INRIA
INRIA Rocquencourt INRIA Rocquencourt
Domaine de Voluceau B.P. 105 Domaine de Voluceau B.P. 105
Le Chesnay, 78153 Le Chesnay 78153
France France
Phone: +33-1-39-63-59-30 Phone: +33-1-39-63-59-30
Fax: +33-1-39-63-54-91 Fax: +33-1-39-63-54-91
Email: thierry.ernst@inria.fr EMail: thierry.ernst@inria.fr
URI: http://www.nautilus6.org/~thierry URI: http://www.nautilus6.org/~thierry
Eun Kyoung Paik Eun Kyoung Paik
KT KT
Portable Internet Team, Convergence Lab., KT KT Research Center
17 Woomyeon-dong, Seocho-gu 17 Woomyeon-dong, Seocho-gu
Seoul 137-792 Seoul 137-792
Korea Korea
Phone: +82-2-526-5233 Phone: +82-2-526-5233
Fax: +82-2-526-5200 Fax: +82-2-526-5200
Email: euna@kt.co.kr EMail: euna@kt.co.kr
URI: http://mmlab.snu.ac.kr/~eun/ URI: http://mmlab.snu.ac.kr/~eun/
Marcelo Bagnulo Marcelo Bagnulo
Universidad Carlos III de Madrid Universidad Carlos III de Madrid
Av. Universidad, 30 Av. Universidad, 30
Leganes, Madrid 28911 Leganes, Madrid 28911
Spain Spain
Phone: +34 91624 8837 Phone: +34 91624 8837
Email: marcelo@it.uc3m.es EMail: marcelo@it.uc3m.es
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
skipping to change at page 48, line 44 skipping to change at line 1751
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
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specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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