draft-ietf-nemo-multihoming-issues-00.txt   draft-ietf-nemo-multihoming-issues-01.txt 
NEMO Working Group C. Ng NEMO Working Group C. Ng
Internet-Draft Panasonic Singapore Labs Internet-Draft Panasonic Singapore Labs
Expires: January 10, 2005 E. Paik Expires: April 25, 2005 E. Paik
Seoul National University KT
T. Ernst T. Ernst
WIDE at Keio University WIDE at Keio University
July 12, 2004 October 25, 2004
Analysis of Multihoming in Network Mobility Support Analysis of Multihoming in Network Mobility Support
draft-ietf-nemo-multihoming-issues-00 draft-ietf-nemo-multihoming-issues-01
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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). As there are many situations in which mobile mobility (NEMO). As there are many situations in which mobile
networks may be multihomed, a taxonomy is proposed to classify the networks may be multihomed, a taxonomy is proposed to classify the
possible configurations. We also describe possible deployment possible configurations. We also describe possible deployment
scenarios and we attempt to identify issues that arise when mobile scenarios and we attempt to identify issues that arise when mobile
networks are multihomed while mobility supports is taken care by NEMO networks are multihomed while mobility supports is taken care by NEMO
Basic Support. Basic Support.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Classification . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Classification . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1 (1,1,1): Single MR, Single HA, Single NEMO-Prefix . . . . 7 2.1 (1,1,1): Single MR, Single HA, Single MNP . . . . . . . . 7
2.2 (1,1,n): Single MR, Single HA, Multiple NEMO-Prefixes . . 7 2.2 (1,1,n): Single MR, Single HA, Multiple MNPs . . . . . . . 7
2.3 (1,n,1): Single MR, Multiple HAs, Single NEMO-Prefix . . . 8 2.3 (1,n,1): Single MR, Multiple HAs, Single MNP . . . . . . . 8
2.4 (1,n,n): Single MR, Multiple HAs, Multiple 2.4 (1,n,n): Single MR, Multiple HAs, Multiple MNPs . . . . . 8
NEMO-Prefixes . . . . . . . . . . . . . . . . . . . . . . 8 2.5 (n,1,1): Multiple MRs, Single HA, Single MNP . . . . . . . 9
2.5 (n,1,1): Multiple MRs, Single HA, Single NEMO-Prefix . . . 9 2.6 (n,1,n): Multiple MRs, Single HA, Multiple MNPs . . . . . 9
2.6 (n,1,n): Multiple MRs, Single HA, Multiple 2.7 (n,n,1): Multiple MRs, Multiple HAs, Single MNP . . . . . 10
NEMO-Prefixes . . . . . . . . . . . . . . . . . . . . . . 9 2.8 (n,n,n): Multiple MRs, Multiple HAs, Multiple MNPs . . . . 10
2.7 (n,n,1): Multiple MRs, Multiple HAs, Single NEMO-Prefix . 10
2.8 (n,n,n): Multiple MRs, Multiple HAs, Multiple
NEMO-Prefixes . . . . . . . . . . . . . . . . . . . . . . 11
3. Deployment Scenarios and Prerequisites . . . . . . . . . . . . 12 3. Deployment Scenarios and Prerequisites . . . . . . . . . . . . 12
3.1 Deployment Scenarios . . . . . . . . . . . . . . . . . . . 12 3.1 Deployment Scenarios . . . . . . . . . . . . . . . . . . . 12
3.2 Prerequisites . . . . . . . . . . . . . . . . . . . . . . 13 3.2 Prerequisites . . . . . . . . . . . . . . . . . . . . . . 13
4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 15 4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 15
4.1 Path Survival . . . . . . . . . . . . . . . . . . . . . . 15 4.1 Path Survival . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Path Selection . . . . . . . . . . . . . . . . . . . . . . 15 4.2 Path Selection . . . . . . . . . . . . . . . . . . . . . . 15
4.3 Ingress Filtering . . . . . . . . . . . . . . . . . . . . 16 4.3 Ingress Filtering . . . . . . . . . . . . . . . . . . . . 16
4.4 Failure Detection . . . . . . . . . . . . . . . . . . . . 17 4.4 Failure Detection . . . . . . . . . . . . . . . . . . . . 18
4.5 HA Synchronization . . . . . . . . . . . . . . . . . . . . 18 4.5 Media Detection . . . . . . . . . . . . . . . . . . . . . 19
4.6 MR Synchronization . . . . . . . . . . . . . . . . . . . . 18 4.6 HA Synchronization . . . . . . . . . . . . . . . . . . . . 19
4.7 Prefix Delegation . . . . . . . . . . . . . . . . . . . . 19 4.7 MR Synchronization . . . . . . . . . . . . . . . . . . . . 19
4.8 Multiple Bindings/Registrations . . . . . . . . . . . . . 19 4.8 Prefix Delegation . . . . . . . . . . . . . . . . . . . . 20
4.9 Source Address Selection . . . . . . . . . . . . . . . . . 19 4.9 Multiple Bindings/Registrations . . . . . . . . . . . . . 20
4.10 Impact on the Routing Infrastructure . . . . . . . . . . . 20 4.10 Source Address Selection . . . . . . . . . . . . . . . . . 20
4.11 Nested Mobile Networks . . . . . . . . . . . . . . . . . . 20 4.11 Impact on the Routing Infrastructure . . . . . . . . . . . 21
4.12 Split Mobile Networks . . . . . . . . . . . . . . . . . . 20 4.12 Nested Mobile Networks . . . . . . . . . . . . . . . . . . 21
4.13 Split Mobile Networks . . . . . . . . . . . . . . . . . . 21
5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 25
A. Alternative Classifications Approach . . . . . . . . . . . . . 25 A. Alternative Classifications Approach . . . . . . . . . . . . . 26
A.1 Ownership-Oriented Approach . . . . . . . . . . . . . . . 25 A.1 Ownership-Oriented Approach . . . . . . . . . . . . . . . 26
A.1.1 ISP Model . . . . . . . . . . . . . . . . . . . . . . 25 A.1.1 ISP Model . . . . . . . . . . . . . . . . . . . . . . 26
A.1.2 Subscriber/Provider Model . . . . . . . . . . . . . . 26 A.1.2 Subscriber/Provider Model . . . . . . . . . . . . . . 27
A.2 Problem-Oriented Approach . . . . . . . . . . . . . . . . 28 A.2 Problem-Oriented Approach . . . . . . . . . . . . . . . . 29
B. Nested Tunneling for Fault Tolerance . . . . . . . . . . . . . 29 B. Nested Tunneling for Fault Tolerance . . . . . . . . . . . . . 30
B.1 Detecting Presence of Alternate Routes . . . . . . . . . . 29 B.1 Detecting Presence of Alternate Routes . . . . . . . . . . 30
B.2 Re-Establishment of Bi-Directional Tunnels . . . . . . . . 29 B.2 Re-Establishment of Bi-Directional Tunnels . . . . . . . . 30
B.2.1 Using Alternate Egress Interface . . . . . . . . . . . 30 B.2.1 Using Alternate Egress Interface . . . . . . . . . . . 31
B.2.2 Using Alternate Mobile Router . . . . . . . . . . . . 30 B.2.2 Using Alternate Mobile Router . . . . . . . . . . . . 31
B.3 To Avoid Tunneling Loop . . . . . . . . . . . . . . . . . 31 B.3 To Avoid Tunneling Loop . . . . . . . . . . . . . . . . . 32
C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 32 C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Intellectual Property and Copyright Statements . . . . . . . . 33 Intellectual Property and Copyright Statements . . . . . . . . 35
1. Introduction 1. Introduction
The goals and objectives of Network Mobility Support (NEMO) are The goals and objectives of Network Mobility Support (NEMO) are
identified in [1] while the terminology is being described in [2] and identified in [1] while the terminology is being described in [2] and
[3]. NEMO Basic Support [4] is the solution proposed by the NEMO [3]. NEMO Basic Support [4] is the solution proposed by the NEMO
Working Group to provide continuous Internet connectivity to nodes Working Group to provide continuous Internet connectivity to nodes
located in a mobile network. This solutions basically solves the located in a mobile network. This solutions basically solves the
problem by setting up bi-directional tunnels between the mobile problem by setting up bi-directional tunnels between the mobile
routers (MRs) connecting the mobile network to the Internet and their routers (MRs) connecting the mobile network to the Internet and their
skipping to change at page 4, line 34 skipping to change at page 4, line 34
single node. Real-life scenarios as illustrated in [6] demonstrate single node. Real-life scenarios as illustrated in [6] demonstrate
that providing a permanent access to mobile networks such as vehicles that providing a permanent access to mobile networks such as vehicles
typically require the use of several interfaces and technologies typically require the use of several interfaces and technologies
since the mobile network may be moving in distant geographical since the mobile network may be moving in distant geographical
locations where different access technologies are provided and locations where different access technologies are provided and
governed by distinct access control policies. governed by distinct access control policies.
The purpose of this memo is to investigate issues related to such a The purpose of this memo is to investigate issues related to such a
bi-directional tunneling mechanism when mobile networks are bi-directional tunneling mechanism when mobile networks are
multihomed, i.e. when there is more than one point of attachment multihomed, i.e. when there is more than one point of attachment
between the mobile network and the Internet. This arises when the between the mobile network and the Internet. This arises either when
mobile network is either associated with multiple HAs, when it has a MR has multiple egress interfaces, or the mobile network has
multiple MRs, or when an MR has multiple egress interfaces (see multiple MRs or is associated with multiple HAs, or multiple prefixes
definitions in [3]). are advertised down to the mobile network (see definitions in [3]).
As specified by R.12 in section 5 of [1], the NEMO WG must ensure As specified by R.12 in section 5 of [1], the NEMO WG must ensure
that NEMO Basic Support does not prevent mobile networks to be that NEMO Basic Support does not prevent mobile networks to be
multihomed. Using NEMO Basic Support, this translates into having multihomed. Using NEMO Basic Support, this translates into having
multiple bi-directional tunnels between the mobile network and its multiple bi-directional tunnels between the mobile network and its
HA(s), and may result into multiple NEMO-Prefixes being advertised to HA(s), and may result into multiple MNPs being advertised to the
the MNNs. However, NEMO Basic Support does not specify any MNNs. However, NEMO Basic Support does not specify any particular
particular mechanism to manage multiple bi-directional tunnels. The mechanism to manage multiple bi-directional tunnels. The objective
objective of this memo is thus three-folds: of this memo is thus three-folds:
o to capture issues for deploying a multihomed mobile network, o to capture issues for deploying a multihomed mobile network,
o to identify which multihoming configurations are useful, o to identify which multihoming configurations are useful,
o to identify issues that may prevent useful multihomed o to identify issues that may prevent useful multihomed
configurations to be supported under the operation of NEMO Basic configurations to be supported under the operation of NEMO Basic
Support. It doesn't mean that those not supported will not work Support. It doesn't mean that those not supported will not work
with NEMO Basic Support, just that it is up to the implementors to with NEMO Basic Support, just that it is up to the implementors to
make it work (hopefully issues discussed in this memo will be make it work (hopefully issues discussed in this memo will be
skipping to change at page 5, line 22 skipping to change at page 5, line 22
their benefits, and requirements to meet these benefits are their benefits, and requirements to meet these benefits are
illustrated in Section 3. Following this, we study the general illustrated in Section 3. Following this, we study the general
issues in Section 4, and we conclude with an evaluation of NEMO Basic issues in Section 4, and we conclude 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.
In order to understand this memo, the reader is expected to be In order to understand this memo, the reader is expected to be
familiar with the above cited documents, i.e. with the NEMO familiar with the above cited documents, i.e. with the NEMO
terminology as defined in [2] (section 3) and [3], Goals and Benefits terminology as defined in [2] (section 3) and [3], Goals and Benefits
of Multihoming [6], Goals and Requirements of Network Mobility of Multihoming [6], Goals and Requirements of Network Mobility
Support [1], and the NEMO Basic Support specification [4]. Support [1], and the NEMO Basic Support specification [4]. The
readers are reminded when describing the issues, we implicitly have
an IPv6 environment in mind (as NEMO Basic Support [4] is for IPv6),
though some of the issues are independent of IP version.
Note that goals and benefits for multihoming as discussed in [6] is Note that goals and benefits for multihoming as discussed in [6] is
applicable to fixed nodes, mobile nodes, fixed networks and mobile applicable to fixed nodes, mobile nodes, fixed networks and mobile
networks, so we won't re-state the motivations in the present memo. networks, so we won't re-state the motivations in the present memo.
2. Classification 2. Classification
Various discussions on the topic of multihoming issues in NEMO have Various discussions on the topic of multihoming issues in NEMO have
been carried out on the mailing list and at IETF meetings. As there been carried out on the mailing list and at IETF meetings. As there
are several configurations in which mobile networks are multihomed, are several configurations in which mobile networks are multihomed,
there is a need to classify them into a clearly defined taxonomy. there is a need to classify them into a clearly defined taxonomy.
This can be done in various ways. Three approaches have been This can be done in various ways. Three approaches have been
proposed on the NEMO mailing list. These are, namely, (i) the proposed on the NEMO mailing list. These are, namely, (i) the
Configuration-Oriented Approach, (ii) the Ownership-Oriented Configuration-Oriented Approach, (ii) the Ownership-Oriented
Approach, and (iii) the Problem-Oriented Approach. As the WG Approach, and (iii) the Problem-Oriented Approach. As the WG
consensus seems to have converged to the Configuration-Oriented consensus seems to have converged to the Configuration-Oriented
Approach, we only describe this approach here. The other two Approach, we only describe this approach here. The other two
approaches are outlined in Appendix A.1 and Appendix A.2. approaches are outlined in Appendix A.1 and Appendix A.2.
The Configuration-Oriented Approach
Multihomed configurations can be classified depending on how many Multihomed configurations can be classified depending on how many
mobile routers are present, how many egress interfaces, Care-of mobile routers are present, how many egress interfaces, Care-of
Address (CoA) and Home Addresses (HoA) the mobile routers have, how Address (CoA) and Home Addresses (HoA) the mobile routers have, how
many prefixes (NEMO-prefixes) are advertised to the mobile network many prefixes (MNPs) are advertised to the mobile network nodes, etc.
nodes, etc. For doing so, we use three key parameters For doing so, we use three key parameters differentiating different
differentiating different multihomed configurations. With these multihomed configurations. With these parameters, we can refer to
parameters, we can refer to each configuration by the 3-tuple each configuration by the 3-tuple (x,y,z), where 'x', 'y', 'z' are
(x,y,z), where 'x', 'y', 'z' are defined as follows: defined as follows:
o 'x' indicates the number of MRs where: o 'x' indicates the number of MRs where:
x=1 implies a mobile network has only a single MR, presumably x=1 implies a mobile network has only a single MR, presumably
multihomed. multihomed.
x=N implies a mobile network has more than one MR. x=N implies 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 (possibly in different y=N implies that multiple HAs (possibly in different
administrative domains) are assigned to the mobile network. administrative domains) are assigned to the mobile network.
o 'z' indicates the number of NEMO-prefixes announced to MNNs, o 'z' indicates the number of MNPs announced to MNNs, where:
where:
z=1 implies that a single NEMO-prefix is advertised to the MNNs. z=1 implies that a single MNP is advertised to the MNNs.
z=N implies that multiple NEMO-prefixes are advertised to the z=N implies that multiple MNPs are advertised to the MNNs.
MNNs.
It can be seen that the above three parameters are fairly orthogonal It can be seen that the above three parameters are fairly orthogonal
to one another. Thus different values of 'x', 'y' and 'z' give rise to one another. Thus different values of 'x', 'y' and 'z' give rise
to different combinations of the 3-tuple (x,y,z). As described in to different combinations of the 3-tuple (x,y,z). As described in
the sub-sections below, a total of 8 possible configurations can be the sub-sections below, a total of 8 possible configurations can be
identified. identified.
One thing the reader has to keep in mind is that in each of the One thing the reader has to keep in mind is that in each of the
following 8 cases, the MR may be multihomed if either (i) multiple following 8 cases, the MR may be multihomed if either (i) multiple
prefixes are advertised on the home link, (ii) multiple prefixes are prefixes are advertised on the home link, (ii) multiple prefixes are
advertised on the visited link, or (iii) the MR is equipped with advertised on the visited link, or (iii) the MR is equipped with
multiple interfaces. In such a case, the MR would have a combination multiple interfaces. In such a case, the MR would have a combination
of Home Address / Care-of Address pairs. Issues pertaining to a of Home Address / Care-of Address pairs. Issues pertaining to a
multihomed MR are also addressed in the companion document [7]. multihomed MR are also addressed in the companion document [7].
A simplified analysis of multihoming configuration in NEMO Basic A simplified analysis of multihoming configuration in NEMO Basic
Support using the same classification can be found in [8]. Support using the same classification can be found in [8].
2.1 (1,1,1): Single MR, Single HA, Single NEMO-Prefix 2.1 (1,1,1): Single MR, Single HA, Single MNP
The (1,1,1) mobile network has only one MR advertising a single The (1,1,1) mobile network has only one MR advertising a single MNP.
NEMO-prefix. In addition, the MR is associated with only one HA at In addition, the MR is associated with only one HA at any one time.
any one time. A bi-directional tunnel may be established between A bi-directional tunnel may be established between each pair of Home
each pair of Home Address / Care-of address if the MR is itself Address / Care-of address if the MR is itself multihomed.
multihomed.
The MR may be multihomed and MNNs are (usually) not multihomed since The MR may be multihomed and MNNs are (usually) not multihomed since
they would configure a single address on the single NEMO-prefix they would configure a single address on the single MNP announced on
announced 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 NEMO-prefix Figure 1: (1,1,1): 1 MR, 1 HA, 1 MNP
2.2 (1,1,n): Single MR, Single HA, Multiple NEMO-Prefixes 2.2 (1,1,n): Single MR, Single HA, Multiple MNPs
The (1,1,n) mobile network has only one MR, which is associated to The (1,1,n) mobile network has only one MR, which is associated to
only one HA at any one time. However, two or more NEMO-prefixes are only one HA at any one time. However, two or more MNPs are
advertised to the mobile network nodes. advertised to the mobile network nodes.
The MR may be itself multihomed, and MNNs are multihomed if several The MR may be itself multihomed, and MNNs are multihomed if several
NEMO-Prefixes are advertised on the link they are attached to. If MNPs are advertised on the link they are attached to. If that
that conditions holds, MNNs would configure an address with each conditions holds, MNNs would configure an address with each MNP
NEMO-prefix announced on the link. announced on the link.
_____ _____
_ p1,p2 _ | | _ p1,p2 _ | |
|_|-|<-_ |-|_|-| |-| _ |_|-|<-_ |-|_|-| |-| _
_ |-|_|=| |_____| | _ |-|_| _ |-|_|=| |_____| | _ |-|_|
|_|-| | |-|_|-| |_|-| | |-|_|-|
| |
MNNs MR AR Internet AR HA MNNs MR AR Internet AR HA
Figure 2: (1,1,n): 1 MR, 1 HA, multiple NEMO-prefixes Figure 2: (1,1,n): 1 MR, 1 HA, multiple MNPs
2.3 (1,n,1): Single MR, Multiple HAs, Single NEMO-Prefix 2.3 (1,n,1): Single MR, Multiple HAs, Single MNP
The (1,n,1) mobile network has only one MR advertising a single The (1,n,1) mobile network has only one MR advertising a single MNP.
NEMO-prefix. The MR, however, is associated to multiple HAs, The MR, however, is associated to multiple HAs, possibly one HA per
possibly one HA per Home Address, or one HA per egress interface. No Home Address, or one HA per egress interface.
assumption is made on whether or not the HAs belongs to the same
administrative domain (it may be justified to locate HAs in distinct
ISPs according to [Section 5.1.2. Possibly Multihomed, An Identical
Prefix from a Different Origin] [9])
The MR may be multihomed whereas MNNs are (usually) not multihomed The MR may be multihomed whereas MNNs are (usually) not multihomed
since they would configure a single address on the single NEMO-prefix since they would configure a single address on the single MNP
announced on the link they are attached to. announced on the link they are attached to.
AR HA2 AR HA2
_ | _ |
|-|_|-| _ |-|_|-| _
_____ | |-|_| _____ | |-|_|
_ p _ | |-| _ p _ | |-|
|_|-|<-_ |-|_|-| | |_|-|<-_ |-|_|-| |
_ |-|_|=| |_____|-| _ _ |-|_|=| |_____|-| _
|_|-| | | _ |-|_| |_|-| | | _ |-|_|
|-|_|-| |-|_|-|
| |
MNNs MR AR Internet AR HA1 MNNs MR AR Internet AR HA1
Figure 3: (1,n,1): 1 MR, multiple HAs, 1 NEMO-prefix Figure 3: (1,n,1): 1 MR, multiple HAs, 1 MNP
2.4 (1,n,n): Single MR, Multiple HAs, Multiple NEMO-Prefixes 2.4 (1,n,n): Single MR, Multiple HAs, Multiple MNPs
The (1,n,n) mobile network has only one MR. However, the MR is The (1,n,n) mobile network has only one MR. However, the MR is
associated with multiple HAs, possibly one per Home Address (or one associated with multiple HAs, possibly one per Home Address (or one
HA per egress interface), and the MR advertises more than one HA per egress interface), and the MR advertises more than one MNP on
NEMO-prefix on its ingress interfaces. No assumption is made on its ingress interfaces. No assumption is made on whether or not the
whether or not the HAs belongs to the same administrative domain. HAs belongs to the same administrative domain.
The MR may be multihomed, and the MNNs are generally multihomed since The MR may be multihomed, and the MNNs are generally multihomed since
they would configure an address on each NEMO-prefix announced on the they would configure an address on each MNP announced on the link
link they are attached to. they are attached to.
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 NEMO-prefixes Figure 4: (1,n,n): 1 MR, multiple HAs, multiple MNPs
2.5 (n,1,1): Multiple MRs, Single HA, Single NEMO-Prefix 2.5 (n,1,1): Multiple MRs, Single HA, Single MNP
The (n,1,1) mobile network has more than one MR advertising global The (n,1,1) mobile network has more than one MR advertising global
routes. These MRs, however, advertise the same NEMO-prefix and are routes. These MRs, however, advertise the same MNP and are
associated with the same HA. associated with the same HA.
Each MR may be itself multihomed, whereas MNNs are (usually) not Each MR may be itself multihomed, whereas MNNs are (usually) not
multihomed since they would configure a single address on the single multihomed since they would configure a single address on the single
NEMO-prefix announced on the link they are attached to. MNP announced on the link they are attached to.
MR2 MR2
p<-_ | p<-_ |
_ |-|_|-| _____ _ |-|_|-| _____
|_|-| |-| | |_|-| |-| |
_ | | |-| _ _ | | |-| _
|_|-| _ |-|_____| | _ |-|_| |_|-| _ |-|_____| | _ |-|_|
|-|_|-| |-|_|-| |-|_|-| |-|_|-|
p<- | | p<- | |
MNNs MR1 Internet AR HA MNNs MR1 Internet AR HA
Figure 5: (n,1,1): Multiple MRs, 1 HA, 1 NEMO-prefix Figure 5: (n,1,1): Multiple MRs, 1 HA, 1 MNP
2.6 (n,1,n): Multiple MRs, Single HA, Multiple NEMO-Prefixes 2.6 (n,1,n): Multiple MRs, Single HA, Multiple MNPs
The (n,1,n) mobile network has more than one MR advertising different The (n,1,n) mobile network has more than one MR advertising different
global routes and different NEMO-prefixes. However, these MRs are global routes and different MNPs. However, these MRs are associated
associated to the same HA. to the same HA.
Each MR may be itself multihomed, and MNNs are generally multihomed Each MR may be itself multihomed, and MNNs are generally multihomed
since they would configure an address on each NEMO-prefix announced since they would configure an address on each MNP announced on the
on the link they are attached to. link they are attached to.
MR2 MR2
p2<-_ | p2<-_ |
_ |-|_|-| _____ _ |-|_|-| _____
|_|-| |-| | |_|-| |-| |
_ | | |-| _ _ | | |-| _
|_|-| _ |-|_____| | _ |-|_| |_|-| _ |-|_____| | _ |-|_|
|-|_|-| |-|_|-| |-|_|-| |-|_|-|
p1<- | | p1<- | |
MNNs MR1 Internet AR HA MNNs MR1 Internet AR HA
Figure 6: (n,1,n): Multiple MRs, 1 HA, multiple NEMO-prefixes Figure 6: (n,1,n): Multiple MRs, 1 HA, multiple MNPs
2.7 (n,n,1): Multiple MRs, Multiple HAs, Single NEMO-Prefix 2.7 (n,n,1): Multiple MRs, Multiple HAs, Single MNP
The (n,n,1) mobile network has more than one MR advertising different The (n,n,1) mobile network has more than one MR advertising different
global routes. The mobile network is associated with multiple HAs at global routes. The mobile network is associated with multiple HAs at
any one time. No assumptions are made on whether or not the HAs any one time. No assumptions are made on whether or not the HAs
belongs to the same administrative domain. However, the MRs belongs to the same administrative domain. However, the MRs
advertises the same NEMO-prefix. advertises the same MNP.
Each MR may be itself multihomed whereas MNNs are (usually) not Each MR may be itself multihomed whereas MNNs are (usually) not
multihomed since they would configure a single address on the single multihomed since they would configure a single address on the single
NEMO-prefix announced on the link they are attached to. MNP announced on the link they are attached to.
MR2 AR HA2 MR2 AR HA2
p _ | p _ |
<-_ | |-|_|-| _ <-_ | |-|_|-| _
_ |-|_|-| _____ | |-|_| _ |-|_|-| _____ | |-|_|
|_|-| |-| |-| |_|-| |-| |-|
_ | | | _ | | |
|_|-| _ |-|_____|-| _ |_|-| _ |-|_____|-| _
|-|_|-| | _ |-|_| |-|_|-| | _ |-|_|
<- | |-|_|-| <- | |-|_|-|
p | p |
MNNs MR1 Internet AR HA1 MNNs MR1 Internet AR HA1
Figure 7: (n,n,1): Multiple MRs, Multiple HAs, 1 NEMO-prefix Figure 7: (n,n,1): Multiple MRs, Multiple HAs, 1 MNP
2.8 (n,n,n): Multiple MRs, Multiple HAs, Multiple NEMO-Prefixes 2.8 (n,n,n): Multiple MRs, Multiple HAs, Multiple MNPs
The (n,n,n) mobile network has multiple MRs advertising different The (n,n,n) mobile network has multiple MRs advertising different
global routes and different NEMO-prefixes. The mobile network is global routes and different MNPs. The mobile network is associated
associated with more than one HA at any one time. No assumptions is with more than one HA at any one time. No assumptions is made on
made on whether or not the HA belongs to the same administrative whether or not the HA belongs to the same administrative domain.
domain.
Each MR may be itself multihomed and MNNs are generally multihomed Each MR may be itself multihomed and MNNs are generally multihomed
since they would configure an address on each NEMO-prefix announced since they would configure an address on each MNP announced on the
on the link they are attached to link they are attached to
MR2 AR HA2 MR2 AR HA2
p2 _ | p2 _ |
<-_ | |-|_|-| _ <-_ | |-|_|-| _
_ |-|_|-| _____ | |-|_| _ |-|_|-| _____ | |-|_|
|_|-| |-| |-| |_|-| |-| |-|
_ | | | _ | | |
|_|-| _ |-|_____|-| _ |_|-| _ |-|_____|-| _
|-|_|-| | _ |-|_| |-|_|-| | _ |-|_|
<- | |-|_|-| <- | |-|_|-|
p1 | p1 |
MNNs MR1 Internet AR HA1 MNNs MR1 Internet AR HA1
Figure 8: (n,n,n): Multiple MRs, HAs, and NEMO-prefixes Figure 8: (n,n,n): Multiple MRs, HAs, and MNPs
3. Deployment Scenarios and Prerequisites 3. Deployment Scenarios and Prerequisites
The following generic goals and benefits of multihoming are discussed The following generic goals and benefits of multihoming are discussed
in a companion document [6]: in a companion document [6]:
1. Permanent and Ubiquitous Access 1. Permanent and Ubiquitous Access
2. Redundancy/Fault-Recovery 2. Redundancy/Fault-Recovery
skipping to change at page 12, line 34 skipping to change at page 12, line 34
3.1 Deployment Scenarios 3.1 Deployment Scenarios
x=1: Multihomed mobile network with a single MR x=1: Multihomed mobile network with a single MR
o Example: an MR with dual/multiple access interfaces (e.g. o Example: an MR with dual/multiple access interfaces (e.g.
802.11 and GPRS capabilities). This is a S/P-(1,1,*) if both 802.11 and GPRS capabilities). This is a S/P-(1,1,*) if both
accesses are subscribed to the same ISP. If the two accesses accesses are subscribed to the same ISP. If the two accesses
are offered by independent ISPs, this is a S/mP-(1,n,n) [for are offered by independent ISPs, this is a S/mP-(1,n,n) [for
the meaning of this abbreviation, see Appendix A.1]. the meaning of this abbreviation, see Appendix A.1].
Benefits: Ubiquity, Redundancy/Fault-Recovery Benefits: Ubiquity, Redundancy/Fault-Recovery, Load Sharing,
Preference Settings
x=N: Multihomed mobile networks with multiple MRs x=N: Multihomed mobile networks with multiple MRs
o Example 1: a train with one MR in each car, all served by the o Example 1: a train with one MR in each car, all served by the
same HA, thus a (n,1,*). Alternatively, the train company same HA, thus a (n,1,*). Alternatively, the train company
might be forced to use different ISP when the train go to might be forced to use different ISP when the train go to
different locations, thus it is a (n,n,n). different locations, thus it is a (n,n,n).
Benefits: Load Sharing Benefits: Load Sharing, Redundancy/Fault-Recovery, Ubiquity
o Example 2: W-PAN with a GPRS_enabled phone and a WiFi-enabled o Example 2: W-PAN with a GPRS_enabled phone and a WiFi-enabled
PDA. This is a S/mP-(n,n,n) if the two access technologies are PDA. This is a S/mP-(n,n,n) if the two access technologies are
subscribed separately. subscribed separately.
Benefits: Ubiquity, Redundancy/Fault-Recovery Benefits: Ubiquity, Redundancy/Fault-Recovery, Preference
Settings
y=1: Multihomed mobile networks with a single HA y=1: Multihomed mobile networks with a single HA
o Most single ISP cases in above examples. o Most single ISP cases in above examples.
y=N: Multihomed mobile networks with multiple HAs y=N: Multihomed mobile networks with multiple HAs
o Most multiple ISP cases in above examples. o Most multiple ISP cases in above examples.
o Example: a transatlantic flight with a HA in each continent. o Example: a transatlantic flight with a HA in each continent.
This is a (1,n,1) network if there is only one MR. This is a (1,n,1) network if there is only one MR.
Benefits: Ubiquity (reduced delay, shortest path) Benefits: Ubiquity (reduced delay, shortest path)
z=1: Multihomed mobile networks with a single NEMO-prefix z=1: Multihomed mobile networks with a single MNP
o Most single ISP cases in above examples. o Most single ISP cases in above examples.
z=N: Multihomed mobile networks with multiple NEMO-prefixes z=N: Multihomed mobile networks with multiple MNPs
o Most multiple ISP cases in above examples. o Most multiple ISP cases in above examples.
o Example: a car with a prefix taken from home (personal traffic o Example: a car with a prefix taken from home (personal traffic
transit on this prefix and is paid by the owner) and one that transit on this prefix and is paid by the owner) and one that
belongs to the car manufacturer (maintenance traffic is paid by belongs to the car manufacturer (maintenance traffic is paid by
the car-manufacturer). This will typically be a (1,1,n). the car-manufacturer). This will typically be a (1,1,n).
Benefits: preference settings Benefits: preference settings
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Both the inbound and outbound traffic must be transmitted or Both the inbound and outbound traffic must be transmitted or
diverted over another bi-directional tunnel once a bi-directional diverted over another bi-directional tunnel once a bi-directional
tunnel is broken or disrupted. tunnel is broken or disrupted.
o Load Sharing and Load Balancing: o Load Sharing and Load Balancing:
Multiple tunnels must be maintained simultaneously. Multiple tunnels must be maintained simultaneously.
o Preference Settings: o Preference Settings:
A mechanism must be provided to the user or the application to Implicitly, multiple tunnels must be maintained simultaneously if
decide which of the available bi-directional tunnel should be preferences are set for deciding which of the available
used. bi-directional tunnels should be used. A mechanism must be
provided to the user/application about the availability of
multiple bi-direction tunnels, and perhaps also to set the
preference. The preference may reside in the mobile router or
mobile network nodes (using [9] for instance).
4. Problem Statement 4. Problem Statement
In order to reach the multihoming benefits, multiple tunnels may be In order to reach the multihoming benefits, multiple tunnels may be
maintained simultaneously (e.g. load balancing, load sharing) or not maintained simultaneously (e.g. load balancing, load sharing) or not
(e.g. redundancy) between the mobile network and the fixed network. (e.g. redundancy) between the mobile network and the fixed network.
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 tunnel recovery, preferences), or to split traffic between multiple tunnel
skipping to change at page 15, line 30 skipping to change at page 15, line 30
4.1 Path Survival 4.1 Path Survival
Internet connectivity is guaranteed for all MNNs as long as at least Internet connectivity is guaranteed for all MNNs as long as at least
one bi-directional tunnel is maintained between the mobile network one bi-directional tunnel is maintained between the mobile network
and the fixed Internet. When an alternative tunnel must be found to and the fixed Internet. When an alternative tunnel must be found to
substitute for the failed one, the loss of one tunnel to the Internet substitute for the failed one, the loss of one tunnel to the Internet
may result in broken sessions. In this case, new transport sessions may result in broken sessions. In this case, new transport sessions
will have to be established over the alternate tunnel if no mechanism will have to be established over the alternate tunnel if no mechanism
is provided to make this change transparent at layers above layer 3. is provided to make this change transparent at layers above layer 3.
In the (1,1,1) case specifically, packets are always transmitted to/ In the (1,1,1) case specifically, packets are always transmitted
from the same MR's ingress interface, i.e. independently of MR's to/from the same MR's ingress interface, i.e. independently of MR's
links connectivity status. The tunnel can be changed transparently links connectivity status. The tunnel can be changed transparently
to the MNNs if mechanisms such as those studied in [10] are brought to the MNNs if mechanisms such as those studied in [10] are brought
to the MR. to the MR.
4.2 Path Selection 4.2 Path Selection
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 back-up) or peer-to-peer (no
skipping to change at page 16, line 12 skipping to change at page 16, line 12
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" [11]) in the (n,*,*) case or based on "Source Address Selection"
in the (*,*,n) cases (see Section 4.9 of the present memo). in the (*,*,n) cases (see Section 4.10 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 of cost or data rate. technologies for reasons 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.
4.3 Ingress Filtering 4.3 Ingress Filtering
Ingress filtering mechanisms may drop the outgoing packets when Ingress filtering mechanisms may drop the outgoing packets when
multiple bi-directional tunnels end up at different HAs. multiple bi-directional tunnels end up at different HAs. This could
occur if different MNPs are handled by different home agents. If
packet with a source address configured from a specific MNP is
tunnelled to a home agent that does not handle that specific MNP, the
packet may be discarded due to ingress filtering (either by the home
agent or by a border gateway in the home network).
This could occur when different NEMO-prefixes are handled by As an example of how this could happen, consider the deployment
different HAs such as the one illustrated in Figure 9. In Figure 9, scenario illustrated in Figure 9. In Figure 9, the mobile network
the mobile network has two mobile routers MR1 and MR2, with home has two mobile routers MR1 and MR2, with home agents HA1 and HA2
agents HA1 and HA2 respectively. Two bi-directional tunnels are respectively. Two bi-directional tunnels are established are
established are established between the two pairs. Each mobile established between the two pairs. Each mobile router advertises a
router advertises a different NEMO-prefix (P1 and P2). NEMO-prefix different MNP (P1 and P2). MNP P1 is registered to HA1, and MNP P2
P1 is registered to HA1, and NEMO-prefix P2 is registered to HA2. is registered to HA2. Thus, MNNs should be free to auto-configure
Thus, MNNs should be free to auto-configure their addresses on any of their addresses on any of P1 or P2. Ingress filtering could thus
P1 or P2. Ingress filtering could thus happen in two cases: 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 [11] 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. A simple solution is to require all prefix it chooses to use. A simple solution is to require all
MNNs to set their default router to the MR that advertises the MNNs to set their default router to the MR that advertises the MNP
NEMO-prefix the MNNs configured their addresses from. If such the MNNs configured their addresses from. If such requirement is
requirement is not placed on mobile network nodes, then a not placed on mobile network nodes, then a multihoming solution
multihoming solution for mobile networks must address this for mobile networks must address this problem. For a possible
problem. For a possible approach, see [12]. However, this is not approach, see [12]. However, this is not enough to maintain
enough to maintain connectivity if a tunnel fails (see Section 4.1 connectivity if a tunnel fails (see Section 4.1 for a discussion
for a discussion of this issue). of this issue).
o If the tunnel to HA1 is broken, packets would be sent through the o If the tunnel to HA1 is broken, packets would be sent through the
tunnel to HA1 are diverted through the tunnel to HA2. If HA2 (or tunnel to HA1 are diverted through the tunnel to HA2. If HA2 (or
some border gateway in the domain of HA2) performs ingress some border gateway in the domain of HA2) performs ingress
filtering, packets with source address configured from NEMO-Prefix filtering, packets with source address configured from MNP P1 may
P1 may be discarded. It should be noted that this problem may be be discarded. It should be noted that this problem may be faced
faced by any (*,n,n) mobile network, even if MR1 and MR2 are in by any (*,n,n) mobile network, even if MR1 and MR2 are in fact the
fact the same entity in Figure 9. same entity in Figure 9.
To avoid ingress filtering mechanisms dropping packets in such To avoid ingress filtering mechanisms dropping packets in such
situations, MR(s) can stop advertising P1. This would prevent MNNs situations, MR(s) can stop advertising P1. This would prevent MNNs
from using the address auto-configured on this prefix. However, such from using the address auto-configured on this prefix. However, such
a method suffers from the following two limitations: a method suffers from the following two limitations:
o Switching addresses is time consuming since nodes have to wait for o Switching addresses is time consuming since nodes have to wait for
addresses to get deprecated [13]. addresses to get deprecated [9].
o Switching addresses force transport sessions without multihoming o Switching addresses force transport sessions without multihoming
capabilities (such as TCP) to terminate, and be re-established capabilities (such as TCP) to terminate, and be re-established
using the alternative source address. Transport sessions with using the alternative source address. Transport sessions with
multihoming capabilities (such as SCTP) may be able to continue multihoming capabilities (such as SCTP) may be able to continue
without disruption (see also Section 4.1) without disruption (see also Section 4.1)
It is possible to overcome these limitations by using nested tunnels. Although one way to avoid the long wait for address deprecation by
Appendix B describes one such approach. sending a router advertisement with zero Lifetime, the
termination/disruption of transport sessions may render this solution
unattractive. It is possible to overcome these limitations by using
nested tunnels. Appendix B describes one such approach.
Prefix: P1 +-----+ +----+ +----------+ +-----+ Prefix: P1 +-----+ +----+ +----------+ +-----+
+--| MR1 |--| AR |--| |---| HA1 | +--| MR1 |--| AR |--| |---| HA1 |
| +-----+ +----+ | | +-----+ | +-----+ +----+ | | +-----+
IP: +-----+ | | | Prefix: P1 IP: +-----+ | | | Prefix: P1
P1.MNN or | MNN |--+ | Internet | P1.MNN or | MNN |--+ | Internet |
P2.MNN +-----+ | | | Prefix: P2 P2.MNN +-----+ | | | Prefix: P2
| +-----+ +----+ | | +-----+ | +-----+ +----+ | | +-----+
+--| MR2 |--| AR |--| |---| HA2 | +--| MR2 |--| AR |--| |---| HA2 |
Prefix: P2 +-----+ +----+ +----------+ +-----+ Prefix: P2 +-----+ +----+ +----------+ +-----+
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4.4 Failure Detection 4.4 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. In order for fault recovery to work, the recover in timely fashion. In order for fault recovery to work, the
MRs and HAs must first possess a means to detect failures: MRs and HAs must first possess a means to detect failures:
o On the MR's side, the MR can also rely on router advertisements o On the MR's side, the MR can also rely on router advertisements
from access routers, or other layer-2 trigger mechanisms to detect from access routers, or other layer-2 trigger mechanisms to detect
faults (e.g. [14] or [15]) . faults, e.g. [13] or [14]. (For a related issue, see Section
4.5.)
o On the HA's side, it is more difficult for HAs to detect tunnel o On the HA's side, it is more difficult for HAs to detect tunnel
failures. For an ISP deployment model, the HAs and MRs can use failures. For an ISP deployment model, the HAs and MRs can use
proprietary methods (such as constant transmission of heartbeat proprietary methods (such as constant transmission of heartbeat
signals) to detect failures and check tunnel liveness. In the S/P signals) to detect failures and check tunnel liveness. In the S/P
model (see Appendix A.2), a lack of standardized "tunnel liveness" model (see Appendix A.2), a lack of standardized "tunnel liveness"
protocol means that it is harder to detect failures. protocol means that it is harder to detect 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.
4.5 HA Synchronization There are other failure modes to consider as well, such as failure at
home agent, failure at access routers, or in general failure of a
link or node along the path from the mobile router to the home agent.
By the nature of the routing infrastructure, failure of intermediate
nodes or links are recovered by the the routing infrastructure by
choosing a different route. For those failures that can't be
receovered (such a failure of the access router), a heartbeadt
protocol or the use of small-lifetime binding updates described above
can also be used to detect tunnel failures.
In the (*,n,1) mobile networks, a single NEMO-prefix would be 4.5 Media Detection
registered at different HAs. This gives rise to the following
issues:
o Only one HA may actively advertise a route to the NEMO-prefix. In order to achieve benefits such as ubiquity or fault recovery, it
is necessary for mobile router to detect the availability of network
media. This may be achieved using layer 2 triggers [13], or other
mechanism developed/recommended by the Detecting Network Attachment
(DNA) Working Group.
This is related to Section 4.4, since the ability to detect media
availability would often implies the ability to detect media
in-availability.
4.6 HA Synchronization
In the (*,n,1) mobile networks, a single MNP would be registered at
different HAs. This gives rise to the following issues:
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 NEMO-prefix same MNP
This may pose a problem in the routing infrastructure as a whole. This may pose a problem in the routing infrastructure as a whole.
The implications of this aspect needs further exploration. Certain The implications of this aspect needs further exploration. Certain
level of HA co-ordination may be required. A possible approach is to level of HA co-ordination may be required. A possible approach is to
adopt a HA synchronization mechanism such as that described in [16] adopt a HA synchronization mechanism such as that described in [15]
and [17]. Such synchronization might also be necessary in a (*,n,*) and [16]. Such synchronization might also be necessary in a (*,n,*)
mobile network, when a MR sends binding update messages to only one mobile network, when a MR sends binding update messages to only one
HA (instead of all HAs). In such cases, the binding update HA (instead of all HAs). In such cases, the binding update
information might have to be synchronized betweeen HAs. The mode of information might have to be synchronized betweeen HAs. The mode of
synchoronization may be either primary-secondary or peer-to-peer. synchoronization may be either primary-secondary or peer-to-peer.
See also Section 4.6. See also Section 4.7.
4.6 MR Synchronization 4.7 MR Synchronization
In the (n,*,*) mobile network, different MRs may need to be In the (n,*,*) mobile network, different MRs may need to be
synchronized in order to take common decisions. The mode of synchronized in order to take common decisions. The mode of
synchoronization may be either primary-secondary or peer-to-peer. synchoronization may be either primary-secondary or peer-to-peer.
This may include: This may include:
o In the (n,*,1) case, advertising the same NEMO-Prefix (see also o In the (n,*,1) case, advertising the same MNP (see also "prefix
"prefix delegation" in Section 4.7). delegation" in Section 4.8).
o In the (n,*,n) case, a MR relaying the advertisement of the o In the (n,*,n) case, a MR relaying the advertisement of the MNP
NEMO-Prefix from another failed MR. from another failed MR.
o In the (n,*,*) cases, relaying between MRs everything that needs o In the (n,*,*) cases, relaying between MRs everything that needs
to be relayed, such as data packets, creating a tunnel from the to be relayed, such as data packets, creating a tunnel from the
ingress interface, etc. ingress interface, etc.
4.7 Prefix Delegation 4.8 Prefix Delegation
In the (*,*,1) mobile network, the same NEMO-prefix must be In the (*,*,1) mobile network, the same MNP must be advertised to the
advertised to the MNNs through different paths. This questions how MNNs through different paths. This questions how to perform prefix
to perform prefix delegation: delegation:
o For the (*,n,1) mobile network, how multiple HAs would delegate o For the (*,n,1) mobile network, how multiple HAs would delegate
the same NEMO-prefix to the mobile network. For doing so, the HAs the same MNP to the mobile network. For doing so, the HAs may be
may be somehow configured to advertise the same NEMO-prefix. (see somehow configured to advertise the same MNP. (see also "HA
also "HA Synchronization" in Section 4.5). Synchronization" in Section 4.6).
o For the (n,*,n) mobile network, how multiple mobile routers would o For the (n,*,n) mobile network, how multiple mobile routers would
be synchronized to advertise the same NEMO-Prefix down the be synchronized to advertise the same MNP down the NEMO-link. For
NEMO-link. For doing so, the MRs may be somehow configured to doing so, the MRs may be somehow configured to advertise the same
advertise the same NEMO-prefix (see also "MR Synchronization" in MNP (see also "MR Synchronization" in Section 4.7).
Section 4.6).
This could be configured manually, or dynamically. Alternatively, This could be configured manually, or dynamically. Alternatively,
prefix delegation mechanisms [18][19] could be used to ensure all prefix delegation mechanisms [17][18] could be used to ensure all
routers advertise the same NEMO-prefix. routers advertise the same MNP.
4.8 Multiple Bindings/Registrations 4.9 Multiple Bindings/Registrations
When a MR is configured with multiple Care-of Addresses, it is often When a MR is configured with multiple Care-of Addresses, it is often
necessary for it to bind these Care-of Addresses to the same necessary for it to bind these Care-of Addresses to the same MNP.
NEMO-Prefix.
This is a generic issue, since Mobile IPv6 nodes face a similar This is a generic issue, since Mobile IPv6 nodes face a similar
problem if they wish to bind multiple Care-of Addresses to the same problem if they wish to bind multiple Care-of Addresses to the same
Home Address". This is better discussed in [7]. It is sufficient to Home Address". This is better discussed in [7]. It is sufficient to
note that solutions like [20] can solve this. note that solutions like [19] can solve this.
4.9 Source Address Selection 4.10 Source Address Selection
In the (*,*,n) mobile networks, MNNs would be configured with In the (*,*,n) mobile networks, MNNs would be configured with
multiple addresses. Source address selection mechanisms are needed multiple addresses. Source address selection mechanisms are needed
to decide which address to choose from. to decide which address to choose from.
It may be desirable for MNN to be able to acquire "preference" It may be desirable for MNN to be able to acquire "preference"
information on each NEMO-prefix from the MRs. This allows default information on each MNP from the MRs. This allows default address
address selection mechanism such as that specified in [13] to be selection mechanism such as that specified in [9] to be used.
used. Further exploration on setting such "preference" information Further exploration on setting such "preference" information in
in Router Advertisement based on performance of the bi-directional Router Advertisement based on performance of the bi-directional
tunnel might prove to be useful. tunnel might prove to be useful.
4.10 Impact on the Routing Infrastructure 4.11 Impact on the Routing Infrastructure
In the (1,n,1) case with HAs located in distinct ISPs/ASs, multiple In the (1,n,1) case with HAs located in distinct ISPs/ASs, multiple
routes directed to the mobile network may be advertised in the routes directed to the mobile network may be advertised in the
Internet. This may provide shorter paths, but this would add a Internet. Although this may provide shorter paths, it also adds
burden in routing tables as the route would be published in the burden to routing tables as multiple routes to the same prefix are
Internet Router Registry for multiple ASs. Such issues are injected into the routing infrastructure. Such issues are
investigated in the MULTI6 working group at the IETF. investigated in the MULTI6 working group at the IETF.
4.11 Nested Mobile Networks 4.12 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 two different root-MRs, thus nested mobile network may be attached two different root-MRs, thus
the aggregated network no longer forms a simple tree structure. As the aggregated network no longer forms a simple tree structure. As
such, a solution to prevent an infinite loop must be provided. such, a solution to prevent an infinite loop must be provided.
4.12 Split Mobile Networks 4.13 Split Mobile Networks
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), the only available NEMO-prefix will then be registered by two up), the only available MNP will then be registered by two different
different MRs on different links. This cannot be allowed, as the HA MRs on different links. This cannot be allowed, as the HA has no way
has no way to know which node with an address configured from that to know which node with an address configured from that MNP is
NEMO-prefix is attached to which MR. Some mechanism must be present attached to which MR. Some mechanism must be present for the MNP to
for the NEMO-prefix to either be forcibly removed from one (or all) either be forcibly removed from one (or all) MRs, or the implementors
MRs, or the implementors must not allow a (n,*,1) network to split. must not allow a (n,*,1) network to split.
A possible approach to solving this problem is described in [21]. A possible approach to solving this problem is described in [20].
5. Conclusion 5. Conclusion
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. The purpose of this memo is to investigate issues related mobility. The purpose of this memo is to investigate issues related
to such a bi-directional tunneling mechanism when mobile networks are to such a bi-directional tunneling mechanism when mobile networks are
multihomed. multihomed.
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. They include: multihoming capabilities were identified in Section 4. They include:
1. Path Survival 1. Path Survival
2. Path Availability 2. Path Availability
3. Ingress Filtering 3. Ingress Filtering
4. Failure Detection 4. Failure Detection
5. HA Synchronization 5. Media Detection
6. MR Synchronization 6. HA Synchronization
7. Prefix Delegation 7. MR Synchronization
8. Multiple Binding/Registrations 8. Prefix Delegation
9. Source Address Selection 9. Multiple Binding/Registrations
10. Imapct on the Routing Infrastructure 10. Source Address Selection
11. Nested Mobile Networks 11. Imapct on the Routing Infrastructure
12. Split Mobile Networks. 12. Nested Mobile Networks
13. Split Mobile Networks.
This study is a work in progress and need to be improved by a This study is a work in progress and need to be improved by a
thorough study of each individual issues. Particularly, this memo thorough study of each individual issues. Particularly, this memo
should be completed by a thorough threat analysis of multihoming should be completed by a thorough threat analysis of multihoming
configurations of mobile network. We will add security threat issues configurations of mobile network. We will add security threat issues
here as and when they are encountered, such as those described in here as and when they are encountered, such as those described in
[22]. We also encourage interested people to contribute to this [21]. We also encourage interested people to contribute to this
part. part.
6. Acknowledgments 6. 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 - 59th IETF Meetings. those who have suggested directions in the 56th - 60th IETF Meetings.
Sincere gratitude is also extended to Marcelo Bagnulo Braun for his
The initial evaluation of NEMO Basic Support is a contribution from extensive review and comments on the -00 version of this draft. The
initial evaluation of NEMO Basic Support is a contribution from
Julien Charbon. Julien Charbon.
7 References 7 References
[1] Ernst, T., "Network Mobility Support Goals and Requirements", [1] Ernst, T., "Network Mobility Support Goals and Requirements",
draft-ietf-nemo-requirements-02 (work in progress), February draft-ietf-nemo-requirements-03 (work in progress), October
2004. 2004.
[2] Manner, J. and M. Kojo, "Mobility Related Terminology", RFC [2] Manner, J. and M. Kojo, "Mobility Related Terminology", RFC
3753, June 2004. 3753, June 2004.
[3] Ernst, T. and H. Lach, "Network Mobility Support Terminology", [3] Ernst, T. and H. Lach, "Network Mobility Support Terminology",
draft-ietf-nemo-terminology-01 (work in progress), February draft-ietf-nemo-terminology-02 (work in progress), October
2004. 2004.
[4] Devarapalli, V., "Network Mobility (NEMO) Basic Support [4] Devarapalli, V., "Network Mobility (NEMO) Basic Support
Protocol", draft-ietf-nemo-basic-support-03 (work in progress), Protocol", draft-ietf-nemo-basic-support-03 (work in progress),
June 2004. June 2004.
[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.
[6] Ernst, T., "Goals and Benefits of Multihoming", [6] Ernst, T., Montavont, N., Wakikawa, R. and E-K. Paik, "Goals
draft-multihoming-generic-goals-and-benefits-00 (work in and Benefits of Multihoming",
progress), February 2004. draft-ernst-generic-goals-and-benefits-00 (work in progress),
July 2004.
[7] Montavont, N., Wakikawa, R. and T. Ernst, "Analysis of [7] Montavont, N., Wakikawa, R. and T. Ernst, "Analysis of
Multihoming in Mobile IPv6", Multihoming in Mobile IPv6",
draft-montavont-mobileip-multihoming-pb-statement-01 (work in draft-montavont-mobileip-multihoming-pb-statement-01 (work in
progress), Feb 2004. progress), Feb 2004.
[8] Ernst, T. and J. Charbon, "Multihoming with NEMO Basic [8] Ernst, T. and J. Charbon, "Multihoming with NEMO Basic
Support", Proceedings First International Conference on Mobile Support", Proceedings First International Conference on Mobile
Computing and Ubiquitous Networking (ICMU), January 2004. Computing and Ubiquitous Networking (ICMU), January 2004.
[9] Savola, P., "Examining Site Multi-homing in Finnish Networks", [9] Draves, R., "Default Address Selection for Internet Protocol
Master's Thesis. , April 2003. version 6 (IPv6)", RFC 3484, February 2003.
[10] Montavont, N., Noel, T. and M. Kassi-Lahlou, "MIPv6 for [10] Montavont, N., Noel, T. and M. Kassi-Lahlou, "MIPv6 for
Multiple Interfaces", draft-montavont-mobileip-mmi-00 (work in Multiple Interfaces", draft-montavont-mobileip-mmi-02 (work in
progress), July 2002. progress), October 2003.
[11] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery [11] 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] Draves, R. and D. Thaler, "Default Router Preferences and [12] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", draft-ietf-ipv6-router-selection-04 More-Specific Routes", draft-ietf-ipv6-router-selection-06
(work in progress), June 2004. (work in progress), October 2004.
[13] Draves, R., "Default Address Selection for Internet Protocol
version 6 (IPv6)", RFC 3484, February 2003.
[14] Yegin, A., "Link-layer Hints for Detecting Network [13] Yegin, A., "Link-layer Hints for Detecting Network
Attachments", draft-yegin-dna-l2-hints-01 (work in progress), Attachments", draft-yegin-dna-l2-hints-01 (work in progress),
February 2004. February 2004.
[15] Yegin, A., "Supporting Optimized Handover for IP Mobility [14] Yegin, A., "Supporting Optimized Handover for IP Mobility
-Requirements for Underlying Systems", -Requirements for Underlying Systems",
draft-manyfolks-l2-mobilereq-02 (work in progress), July 2002. draft-manyfolks-l2-mobilereq-02 (work in progress), July 2002.
[16] Wakikawa, R., Devarapalli, V. and P. Thubert, "Inter Home [15] Wakikawa, R., Devarapalli, V. and P. Thubert, "Inter Home
Agents Protocol (HAHA)", draft-wakikawa-mip6-nemo-haha-01 (work Agents Protocol (HAHA)", draft-wakikawa-mip6-nemo-haha-01 (work
in progress), February 2004. in progress), February 2004.
[17] Koh, B., Ng, C. and J. Hirano, "Dynamic Inter Home Agent [16] Koh, B., Ng, C. and J. Hirano, "Dynamic Inter Home Agent
Protocol", draft-koh-mip6-nemo-dhap-00 (work in progress), July Protocol", draft-koh-mip6-nemo-dhap-00 (work in progress), July
2004. 2004.
[18] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix [17] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix
Delegation", RFC 3769, June 2004. Delegation", RFC 3769, June 2004.
[19] Droms, R. and P. Thubert, "DHCPv6 Prefix Delegation for NEMO", [18] Droms, R. and P. Thubert, "DHCPv6 Prefix Delegation for NEMO",
draft-droms-nemo-dhcpv6-pd-01 (work in progress), February draft-droms-nemo-dhcpv6-pd-01 (work in progress), February
2004. 2004.
[20] Wakikawa, R., "Multiple Care-of Addresses Registration", [19] Wakikawa, R., "Multiple Care-of Addresses Registration",
draft-wakikawa-mobileip-multiplecoa-02 (work in progress), draft-wakikawa-mobileip-multiplecoa-03 (work in progress), July
September 2003. 2004.
[21] Kumazawa, M., Watanabe, Y., Matsumoto, T. and S. Narayana, [20] Kumazawa, M., "Token based Duplicate Network Detection for
"Token based Duplicate Network Detection for split mobile split mobile network (Token based DND)",
network (Token based DND)", draft-kumazawa-nemo-tbdnd-00 (work draft-kumazawa-nemo-tbdnd-01 (work in progress), October 2004.
in progress), July 2004.
[22] Choi, S., "Threat for Multi-homed Mobile Networks", [21] Choi, S., "Threat for Multi-homed Mobile Networks",
draft-cho-nemo-threat-multihoming-00 (work in progress), draft-cho-nemo-threat-multihoming-00 (work in progress),
February 2004. February 2004.
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: cwng@psl.com.sg EMail: cwng@psl.com.sg
Paik, Eun Kyoung Eun Kyoung Paik
Seoul National University KT
Multimedia and Mobile communications Lab., Seoul National Univ. Portable Internet Team, Convergence Lab., KT
Shillim-dong, Kwanak-gu 17 Woomyeon-dong, Seocho-gu
Seoul 151-744 Seoul 137-792
Korea Korea
Phone: +82-2-880-1832 Phone: +82-2-526-5233
Fax: +82-2-872-2045 Fax: +82-2-526-5200
EMail: eun@mmlab.snu.ac.kr EMail: euna@kt.co.kr
URI: http://mmlab.snu.ac.kr/~eun/ URI: http://mmlab.snu.ac.kr/~eun/
Ernst Thierry Thierry Ernst
WIDE at Keio University WIDE at Keio University
Jun Murai Lab., Keio University. Jun Murai Lab., Keio University.
K-square Town Campus, 1488-8 Ogura, Saiwa-Ku K-square Town Campus, 1488-8 Ogura, Saiwa-Ku
Kawasaki, Kanagawa 212-0054 Kawasaki, Kanagawa 212-0054
Japan Japan
Phone: +81-44-580-1600 Phone: +81-44-580-1600
Fax: +81-44-580-1437 Fax: +81-44-580-1437
EMail: ernst@sfc.wide.ad.jp EMail: ernst@sfc.wide.ad.jp
URI: http://www.sfc.wide.ad.jp/~ernst/ URI: http://www.sfc.wide.ad.jp/~ernst/
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 multihomed mobile network is
proposed by Eric Nordmark (Sun Microsystems) by breaking the 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
skipping to change at page 25, line 33 skipping to change at page 26, line 33
mobile routers on trains, ships or planes. It is up to the ISP to mobile routers on trains, ships or planes. It is up to the ISP to
deploy a certain configuration of mobile network; all 8 deploy a certain configuration of mobile network; all 8
configurations as described in the Configuration-Oriented Approach configurations as described in the Configuration-Oriented Approach
are possible. In the remaining portion of this document, when are possible. In the remaining portion of this document, when
specifically referring to a mobile network configuration that is specifically referring to a mobile network configuration that is
controlled by a single entity, we will add an 'ISP' prefix: for controlled by a single entity, we will add an 'ISP' prefix: for
example: ISP-(1,1,1) or ISP-(1,N,N). example: ISP-(1,1,1) or ISP-(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 NEMO-prefixes to the mobile network just like it can make multiple MNPs to the mobile network just like it can make the same
the same decision for any other link in its network (wired or decision for any other link in its network (wired or otherwise). In
otherwise). In any case, the ISP will make the routing between the any case, the ISP will make the routing between the mobile networks
mobile networks and its core routers (such as the HAs) work. This and its core routers (such as the HAs) work. This include not
include not introducing any aggregation between the HAs which will introducing any aggregation between the HAs which will filter out
filter out routing announcements for the NEMO-prefix(es). routing announcements for the MNP(es).
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
skipping to change at page 26, line 22 skipping to change at page 27, line 22
when the subscriber subscribes to a single ISP, and when the when the subscriber subscribes to a single ISP, and when the
subscriber subscribes to multiple ISPs. In the remaining portion of subscriber subscribes to multiple ISPs. In the remaining portion of
this document, when specifically referring to a mobile network this 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 S/ Not all 8 configurations are likely to be deployed for the S/P and
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 o S/P-(1,1,1): Single Provider, Single MR, Single HA, Single MNP
NEMO-Prefix
o S/P-(1,1,n): Single Provider, Single MR, Single HA, Multiple o S/P-(1,1,n): Single Provider, Single MR, Single HA, Multiple MNPs
NEMO-Prefixes
o S/P-(1,n,1): Single Provider, Single MR, Multiple HAs, Single o S/P-(1,n,1): Single Provider, Single MR, Multiple HAs, Single MNP
NEMO-Prefix
o S/P-(1,n,n): Single Provider, Single MR, Multiple HAs, Multiple o S/P-(1,n,n): Single Provider, Single MR, Multiple HAs, Multiple
NEMO-Prefixes MNPs
o S/P-(n,n,1): Single Provider, Multiple MRs, Single HA, Single o S/P-(n,n,1): Single Provider, Multiple MRs, Single HA, Single MNP
NEMO-Prefix
o S/P-(n,1,n): Single Provider, Multiple MRs, Single HA, Multiple o S/P-(n,1,n): Single Provider, Multiple MRs, Single HA, Multiple
NEMO-Prefixes MNPs
o S/P-(n,n,1): Single Provider, Multiple MRs, Multiple HAs, Single o S/P-(n,n,1): Single Provider, Multiple MRs, Multiple HAs, Single
NEMO-Prefix MNP
o S/P-(n,n,n): Single Provider, Multiple MRs, Multiple HAs, Multiple o S/P-(n,n,n): Single Provider, Multiple MRs, Multiple HAs, Multiple
NEMO-Prefixes MNPs
For the S/mP model, the following configurations are likely to be For the S/mP model, the following configurations are likely to be
deployed: deployed:
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
NEMO-Prefix 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 NEMO-Prefixes 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 NEMO-Prefixes 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 the scenario where the MR is controlled by one entity
(i.e. the subscriber), and the MR is establishing multiple (i.e. the subscriber), and the MR is establishing multiple
bi-directional tunnels to one or more HA(s) provided by one or more bi-directional tunnels to one or more HA(s) provided by one or more
ISP(s). In such case, it is unlikely for the ISP to run IGP over the ISP(s). In such case, it is unlikely for the ISP to run IGP over the
bi-directional tunnel, since ISP would most certainly wish to retain bi-directional tunnel, since ISP would 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 is proposed by Pascal Thubert (Cisco System). This
focused on the problems of multihomed mobile networks rather than the focused on the problems of multihomed mobile networks rather than the
configuration or ownership. With this approach, there is a set of 4 configuration or ownership. With this approach, there is a set of 4
categories based on two orthogonal parameters: the number of HAs, and categories based on two orthogonal parameters: the number of HAs, and
the number of NEMO-prefixes advertised. Since the two parameters are 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 Care-of Addresses of Same o Tarzan: Single HA for Different Care-of Addresses of Same MNP
NEMO-Prefix
This is the case where one mobile router registers different This is the case where one mobile router registers different
Care-of Addresses to the same home agent for the same subnet Care-of Addresses to the same home agent for the same subnet
prefix. This is equivalent to the case of y=1, i.e. the (1,1,n) prefix. This is equivalent to the case of y=1, i.e. the (1,1,n)
mobile network. mobile network.
o JetSet: Multiple HAs for Different Care-of Addresses of Same o JetSet: Multiple HAs for Different Care-of Addresses of Same MNP
NEMO-Prefix
This is the case where the mobile router registers different This is the case where the mobile router registers different
Care-of Addresses to different home agents for the same subnet Care-of Addresses to different home agents for the same subnet
prefix. This is equivalent to the case of y=n, i.e. the (1,n,*) prefix. This is equivalent to the case of y=n, i.e. the (1,n,*)
mobile network. mobile network.
o Shinkansen: Single NEMO-Prefix Advertised by MR(s) o Shinkansen: Single MNP Advertised by MR(s)
This is the case where one NEMO-prefix is announced by different This is the case where one MNP is announced by different MRs.
MRs. This is equivalent to the case of z=n, i.e. the (1,*,n) This is equivalent to the case of z=n, i.e. the (1,*,n) mobile
mobile network. network.
o DoubleBed: Multiple NEMO-Prefixes Advertised by MR(s) o DoubleBed: Multiple MNPs Advertised by MR(s)
This is the case where more than one NEMO-prefixes are announced This is the case where more than one MNPs are announced by the
by the different MRs. This is equivalent to the case of z=n, i.e. different MRs. This is equivalent to the case of z=n, i.e. the
the (n,*,n) mobile network. (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 a 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 any other alternate route to
the global Internet exists. This alternate route may be provided by the global Internet exists. This alternate route may be provided by
any other MRs connected to one of its ingress interfaces that has an any other MRs connected to one of its ingress interfaces that has an
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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. A 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 a 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 which can provide an alternate route to the global
Internet is present in the mobile network. Internet 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 be which its current bi-directional When a 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 tunnel with its HA is using is down, it needs to re-establish the
bi-directional tunnel using an alternate route detected. We consider bi-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
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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).
Appendix C. Change Log Appendix C. Change Log
o This draft is an update of draft-ng-nemo-multihoming-issues-03.txt o This draft is an update of draft-ng-nemo-multihoming-issues-03.txt
which is itself a merge of 3 previous drafts which is itself a merge of 3 previous drafts
draft-ng-nemo-multihoming-issues-02.txt, draft-ng-nemo-multihoming-issues-02.txt,
draft-eun-nemo-multihoming-problem-statement-00.txt, and draft-eun-nemo-multihoming-problem-statement-00.txt, and
draft-charbon-nemo-multihoming-evaluation-00.txt draft-charbon-nemo-multihoming-evaluation-00.txt
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 Section 2.3: Removed text on assumption
* Addressed Issue #6 in Section 3.1: Added benefits
* Addressed Issue #7 in Section 3.2: Modified text
* Addressed Issue #9 in Section 4.3: Modified text
* Addressed Issue #10 in Section 4.4: Added paragraph on other
failure modes
* Addressed Issue #10: New Section 4.5 on media detection
* Addressed Issue #11 in Section 4.11: modified text
o Changes from draft-ng-multihoming-issues-03 to o Changes from draft-ng-multihoming-issues-03 to
draft-ietf-nemo-multihoming-issues-00: draft-ietf-nemo-multihoming-issues-00:
* Expanded "Problem Statement" (Section 4) * Expanded "Problem Statement" (Section 4)
* Merged "Evaluation" Section into "Problem Statement" (Section * Merged "Evaluation" Section into "Problem Statement" (Section
4) 4)
* Cleaned up description in "Classification" (Section 2), and * Cleaned up description in "Classification" (Section 2), and
 End of changes. 

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