draft-ietf-nemo-basic-support-03.txt   rfc3963.txt 
NEMO Working Group Vijay Devarapalli
INTERNET DRAFT Nokia Network Working Group V. Devarapalli
Category: Standards Track Ryuji Wakikawa Request for Comments: 3963 Nokia
Expires December 2004 Keio University Category: Standards Track R. Wakikawa
Alexandru Petrescu Keio University
A. Petrescu
Motorola Motorola
Pascal Thubert P. Thubert
Cisco Systems Cisco Systems
June 2004 January 2005
Network Mobility (NEMO) Basic Support Protocol Network Mobility (NEMO) Basic Support Protocol
draft-ietf-nemo-basic-support-03.txt
Status of This Memo Status of This Memo
By submitting this Internet-Draft, I certify that any applicable This document specifies an Internet standards track protocol for the
patent or other IPR claims of which I am aware have been disclosed, Internet community, and requests discussion and suggestions for
and any of which I become aware will be disclosed, in accordance with improvements. Please refer to the current edition of the "Internet
RFC 3667. Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
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http://www.ietf.org/ietf/1id-abstracts.txt
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Abstract Abstract
This document describes the Network Mobility (NEMO) Basic Support This document describes the Network Mobility (NEMO) Basic Support
protocol that enables mobile networks to attach to different points protocol that enables Mobile Networks to attach to different points
in the Internet. The protocol is an extension of Mobile IPv6 and in the Internet. The protocol is an extension of Mobile IPv6 and
allows for session continuity for every node in the mobile network as allows session continuity for every node in the Mobile Network as the
the network moves. It also allows every node in the mobile network network moves. It also allows every node in the Mobile Network to be
to be reachable while moving around. The Mobile Router, which reachable while moving around. The Mobile Router, which connects the
connects the network to the Internet, runs the NEMO Basic Support network to the Internet, runs the NEMO Basic Support protocol with
protocol with its Home Agent. The protocol is designed in such a way its Home Agent. The protocol is designed so that network mobility is
that network mobility is transparent to the nodes inside the mobile transparent to the nodes inside the Mobile Network.
network.
Contents
Status of This Memo 1
Abstract 1
1. Introduction 4
2. Terminology 5
3. Overview of the NEMO Protocol 6
4. Message Formats 9
4.1. Binding Update . . . . . . . . . . . . . . . . . . . . . 9
4.2. Binding Acknowledgement . . . . . . . . . . . . . . . . . 9
4.3. Mobile Network Prefix Option . . . . . . . . . . . . . . 10
5. Mobile Router Operation 12
5.1. Data Structures . . . . . . . . . . . . . . . . . . . . . 12
5.2. Sending Binding Updates . . . . . . . . . . . . . . . . . 13
5.3. Receiving Binding Acknowledgements . . . . . . . . . . . 13
5.4. Error Processing . . . . . . . . . . . . . . . . . . . . 14
5.4.1. Implicit Mode . . . . . . . . . . . . . . . . . . 14
5.4.2. Explicit Mode . . . . . . . . . . . . . . . . . . 14
5.5. Establishment of Bi-directional Tunnel . . . . . . . . . 15
5.6. Neighbor Discovery for Mobile Router . . . . . . . . . . 16
5.7. Multicast Groups for Mobile Router . . . . . . . . . . . 16
5.8. Returning Home . . . . . . . . . . . . . . . . . . . . . 16
6. Home Agent Operation 18
6.1. Data Structures . . . . . . . . . . . . . . . . . . . . . 18
6.1.1. Binding Cache . . . . . . . . . . . . . . . . . . 18
6.1.2. Prefix Table . . . . . . . . . . . . . . . . . . 18
6.2. Mobile Network Prefix Registration . . . . . . . . . . . 19
6.3. Advertising Mobile Network Reachability . . . . . . . . . 20
6.4. Establishment of Bi-directional Tunnel . . . . . . . . . 21
6.5. Forwarding Packets . . . . . . . . . . . . . . . . . . . 21
6.6. Sending Binding Acknowledgements . . . . . . . . . . . . 22
6.7. Mobile Network Prefix De-Registration . . . . . . . . . . 22
7. Modifications to Dynamic Home Agent Discovery 24
7.1. Modified Dynamic Home Agent Discovery Request . . . . . . 24
7.2. Modified Dynamic Home Agent Discovery Reply . . . . . . . 24
7.3. Modified Home Agent Information Option . . . . . . . . . 25
8. Support for Dynamic Routing Protocols 26
9. Security Considerations 28
10. IANA Considerations 29
11. Contributors 29
12. Acknowledgements 29
A. Examples of NEMO Basic Support Operation 32
B. Running Link State Routing Protocol with NEMO Basic Support 35 Table of Contents
B.1. Tunnel Interface Considerations . . . . . . . . . . . . . 35
B.2. OSPF Area Considerations . . . . . . . . . . . . . . . . 35
C. Changes from Previous Version 37 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology. . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of the NEMO Protocol. . . . . . . . . . . . . . . . 4
4. Message Formats. . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Binding Update. . . . . . . . . . . . . . . . . . . . . 7
4.2. Binding Acknowledgement . . . . . . . . . . . . . . . . 7
4.3. Mobile Network Prefix Option. . . . . . . . . . . . . . 8
5. Mobile Router Operation. . . . . . . . . . . . . . . . . . . 9
5.1. Data Structures . . . . . . . . . . . . . . . . . . . . 10
5.2. Sending Binding Updates . . . . . . . . . . . . . . . . 10
5.3. Receiving Binding Acknowledgements. . . . . . . . . . . 11
5.4. Error Processing . . . . . . . . . . . . . . . . . . . 12
5.4.1. Implicit Mode. . . . . . . . . . . . . . . . . . 12
5.4.2. Explicit Mode. . . . . . . . . . . . . . . . . . 12
5.5. Establishment of Bi-directional Tunnel . . . . . . . . 13
5.6. Neighbor Discovery for Mobile Router . . . . . . . . . 13
5.7. Multicast Groups for Mobile Router . . . . . . . . . . 14
5.8. Returning Home . . . . . . . . . . . . . . . . . . . . 14
6. Home Agent Operation . . . . . . . . . . . . . . . . . . . . 15
6.1. Data Structures . . . . . . . . . . . . . . . . . . . . 15
6.1.1. Binding Cache. . . . . . . . . . . . . . . . . . 15
6.1.2. Prefix Table . . . . . . . . . . . . . . . . . . 15
6.2. Mobile Network Prefix Registration . . . . . . . . . . 16
6.3. Advertising Mobile Network Reachability . . . . . . . . 17
6.4. Establishment of Bi-directional Tunnel . . . . . . . . 18
6.5. Forwarding Packets . . . . . . . . . . . . . . . . . . 18
6.6. Sending Binding Acknowledgements . . . . . . . . . . . 19
6.7. Mobile Network Prefix De-Registration . . . . . . . . . 19
7. Modifications to Dynamic Home Agent Address Discovery. . . . 20
7.1. Modified Dynamic Home Agent Discovery Request . . . . . 20
7.2. Modified Dynamic Home Agent Discovery Address Request . 20
7.3. Modified Home Agent Information Option . . . . . . . . 21
8. Support for Dynamic Routing Protocols. . . . . . . . . . . . 22
9. Security Considerations. . . . . . . . . . . . . . . . . . . 23
10. IANA Considerations. . . . . . . . . . . . . . . . . . . . . 24
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
A. Examples of NEMO Basic Support Operation. . . . . . . . . 27
B. Running Link State Routing Protocol with NEMO Basic
Support . . . . . . . . . . . . . . . . . . . . . . . . . 30
B.1. Tunnel Interface Considerations. . . . . . . . . . . 30
B.2. OSPF Area Considerations . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
Full Copyright Statement . . . . . . . . . . . . . . . . . . . . 33
1. Introduction 1. Introduction
This document describes protocol extensions to Mobile IPv6 (MIPv6) This document describes protocol extensions to Mobile IPv6 (MIPv6)
[1] to enable support for network mobility. The extensions are [1] to enable support for network mobility. The extensions are
backward compatible with Mobile IPv6. In particular, a NEMO backward compatible with Mobile IPv6. In particular, a NEMO-
compliant Home Agent can operate as a Mobile IPv6 Home Agent as well. compliant Home Agent can operate as a Mobile IPv6 Home Agent. The
solution described here satisfies the goals and requirements
identified in [11] for network mobility.
The NEMO Basic Support works in such a way that session continuity is The NEMO Basic Support ensures session continuity for all the nodes
ensured for all the nodes in the mobile network even as the Mobile in the Mobile Network, even as the Mobile Router changes its point of
Router changes its point of attachment to the Internet. It also attachment to the Internet. It also provides connectivity and
provides connectivity and reachability for all nodes in the mobile reachability for all nodes in the Mobile Network as it moves. The
network as the network moves. The solution supports both mobile solution supports both mobile nodes and hosts that do not support
nodes and hosts that do not support mobility in the mobile network. mobility in the Mobile Network.
Within the context of this document, the definition of a Mobile Within the context of this document, the definition of a Mobile
Router extends that of a Mobile IPv6 [1] Mobile Node, by adding Router extends that of a Mobile IPv6 [1] Mobile Node, by adding
the capability of routing between its point of attachment (Care-of routing capability routing between its point of attachment (Care-of
Address) and a subnet which moves with the Mobile Router. Address) and a subnet that moves with the Mobile Router.
The solution described in this document requires setting up a The solution described in this document proposes a bi-directional
bi-directional tunnel between the Mobile Router and its Home Agent. tunnel between the Mobile Router and its Home Agent. This tunnel is
This tunnel is set up when the Mobile Router sends a successful set up when the Mobile Router sends a successful Binding Update to
Binding Update to its Home Agent, informing the Home Agent of its its Home Agent, informing the Home Agent of its current point of
current point of attachment. attachment.
All traffic between the nodes in the mobile network and Correspondent All traffic between the nodes in the Mobile Network and Correspondent
Nodes passes through the Home Agent. This document does not describe Nodes passes through the Home Agent. This document does not describe
route optimization of this traffic. route optimization of this traffic.
The terminology document [10] describes Nested Mobility as a scenario The terminology document [10] describes Nested Mobility as a scenario
where a Mobile Router allows another Mobile Router to attach to its where a Mobile Router allows another Mobile Router to attach to its
mobile network. There could be arbitrary levels of nested mobility. Mobile Network. There could be arbitrary levels of nested mobility.
The operation of each Mobile Router remains the same whether the The operation of each Mobile Router remains the same whether the
Mobile Router attaches to another Mobile Router or to a fixed Access Mobile Router attaches to another Mobile Router or to a fixed Access
Router on the Internet. The solution described here does not place Router on the Internet. The solution described here does not place
any restriction on the number of levels for nested mobility. But it any restriction on the number of levels for nested mobility. But
should be noted that this might introduce significant overhead on the note that this might introduce significant overhead on the data
data packets as each level of nesting introduces another IPv6 header packets as each level of nesting introduces another IPv6 header
encapsulation. encapsulation.
This document does not discuss multihoming for Mobile Routers. This document does not discuss multihoming for Mobile Routers.
2. Terminology 2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [7]. document are to be interpreted as described in BCP 14, RFC 2119 [7].
Network Mobility related terminology is defined in [9] and [10]. Network Mobility - related terminology is defined in [9] and [10].
This document in addition defines the following terms. This document in addition defines the following terms.
Mobile Network Prefix Mobile Network Prefix
An IPv6 prefix that is delegated to a Mobile An IPv6 prefix delegated to a Mobile Router and advertised in
Router and advertised in the mobile network. There could the Mobile Network. More than one Mobile Network Prefix could
be more than one Mobile Network Prefix being advertised in be advertised in a Mobile Network.
a mobile network.
Prefix Table Prefix Table
It is a list of Mobile Network Prefixes indexed by A list of Mobile Network Prefixes indexed by the Home Address
the Home Address of a Mobile Router. The prefix table is of a Mobile Router. The Home Agent manages and uses Prefix
managed by the Home Agent and is used by the Home Agent Table to determine which Mobile Network Prefixes belong to a
to determine which Mobile Network Prefixes belong to a
particular Mobile Router. particular Mobile Router.
3. Overview of the NEMO Protocol 3. Overview of the NEMO Protocol
A Mobile Network is a network segment or subnet which can move and A Mobile Network is a network segment or subnet that can move and
attach to arbitrary points in the routing infrastructure. A mobile attach to arbitrary points in the routing infrastructure. A Mobile
network can only be accessed via specific gateways called Mobile Network can only be accessed via specific gateways called Mobile
Routers that manage its movement. Mobile networks have at least one Routers that manage its movement. Mobile Networks have at least one
Mobile Router serving them. A Mobile Router does not distribute Mobile Router serving them. A Mobile Router does not distribute the
the mobile network routes to the infrastructure at its point of Mobile Network routes to the infrastructure at its point of
attachment (i.e. in the visited network). Instead, it maintains a attachment (i.e., in the visited network). Instead, it maintains a
bidirectional tunnel to a Home Agent that advertises an aggregation bi-directional tunnel to a Home Agent that advertises an aggregation
of mobile networks to the infrasructure. The Mobile Router is also of Mobile Networks to the infrastructure. The Mobile Router is also
the default gateway for the mobile network. the default gateway for the Mobile Network.
A mobile network can also consist of multiple and nested subnets. A A Mobile Network can also comprise of multiple and nested subnets. A
router with no support for mobility may be permanently attached to router without mobility support may be permanently attached to a
a mobile network for local distribution. Also, Mobile Routers may Mobile Network for local distribution. Also, Mobile Routers may be
be attached to mobile networks owned by different Mobile Routers and attached to Mobile Networks owned by different Mobile Routers and may
form a graph. In particular, with Basic NEMO Support, each Mobile form a graph. In particular, with Basic NEMO Support, each Mobile
Router is attached to another mobile network by a single interface, Router is attached to another Mobile Network by a single interface.
and if loops are avoided, the graph is a tree. If loops are avoided, the graph is a tree.
A Mobile Router has an unique Home Address through which it is A Mobile Router has a unique Home Address through which it is
reachable when it is registered with its Home Agent. The Home reachable when it is registered with its Home Agent. The Home
Address is configured from a prefix that is aggregated and advertised Address is configured from a prefix aggregated and advertised by its
by its Home Agent. The prefix could either be the prefix advertised Home Agent. The prefix could be either the prefix advertised on the
on the home link or the prefix delegated to the Mobile Router. home link or the prefix delegated to the Mobile Router. The Mobile
The Mobile Router can have more than one Home Address if there Router can have more than one Home Address if there are multiple
are multiple prefixes in the home link. The Mobile Router also prefixes in the home link. The Mobile Router also advertises one or
advertises one or more prefixes in the mobile network attached to it. more prefixes in the Mobile Network attached to it. The actual
The actual mechanism for assigning these prefixes to a given Mobile mechanism for assigning these prefixes to a given Mobile Router is
Router is outside the scope of this specification. outside the scope of this specification.
When the Mobile Router moves away from the home link and attaches to When the Mobile Router moves away from the home link and attaches to
a new access router, it acquires a Care-of Address from the visited a new access router, it acquires a Care-of Address from the visited
link. The Mobile Router can at any time act either as a Mobile Host link. The Mobile Router can at any time act either as a Mobile Host
or a Mobile Router. It acts as a Mobile Host as defined in [1] for or as a Mobile Router. It acts as a Mobile Host as defined in [1]
sessions originated by itself, while providing connectivity to the for sessions it originates and provides connectivity to the Mobile
Mobile Network. As soon as the Mobile Router acquires a Care-of Network. As soon as the Mobile Router acquires a Care-of Address, it
Address, it immediately sends a Binding Update to its Home Agent as immediately sends a Binding Update to its Home Agent as described in
described in [1]. When the Home Agent receives this Binding Update [1]. When the Home Agent receives this Binding Update, it creates a
it creates a binding cache entry binding the Mobile Router's Home cache entry binding the Mobile Router's Home Address to its Care-of
Address to its Care-of address at the current point of attachment. Address at the current point of attachment.
If the Mobile Router wishes to act as a Mobile Router and provide If the Mobile Router seeks to act as a Mobile Router and provide
connectivity to nodes in the mobile network, it indicates this to the connectivity to nodes in the Mobile Network, it indicates this to the
Home Agent by setting a flag (R) in the Binding Update. It MAY also Home Agent by setting a flag (R) in the Binding Update. It MAY also
include information about the Mobile Network Prefix in the Binding include information about the Mobile Network Prefix in the Binding
Update using one of the modes described in Section 5.2, so that the Update by using one of the modes described in section 5.2, so that
Home Agent can forward packets meant for nodes in the mobile network the Home Agent can forward packets meant for nodes in the Mobile
to the Mobile Router. A new Mobility Header Option is described in Network to the Mobile Router. A new Mobility Header Option for
this document to carry prefix information. This option is described carrying prefix information is described in section 4.3. If the
in Section 4.3. If the mobile network has more than one IPv6 prefix Mobile Network has more than one IPv6 prefix and wants the Home Agent
and wants the Home Agent to setup forwarding for all these prefixes, to setup forwarding for all of these prefixes, it includes multiple
it includes multiple prefix information options in a single Binding prefix information options in a single Binding Update. The Home
Update. The Home Agent sets up forwarding for each of these prefixes Agent sets up forwarding for each of these prefixes to the Mobile
to the Mobile Router's Care-of Address. In some scenarios the Router's Care-of Address. In some scenarios the Home Agent would
Home Agent already knows which prefixes belong to a Mobile Router already know which prefixes belong to a Mobile Router by an alternate
by an alternate mechanism such as static configuration. In these mechanism such as static configuration. In these scenarios, the
scenarios, the Mobile Router does not include any prefix information Mobile Router does not include any prefix information in the Binding
in the Binding Update. The Home Agent sets up forwarding for all Update. The Home Agent sets up forwarding for all prefixes owned by
prefixes owned by the Mobile Router, when it receives a Binding the Mobile Router when it receives a Binding Update from the Mobile
Update from the mobile router with the router flag (R) set. Router with the Mobile Router Flag (R) set.
The Home Agent acknowledges the Binding Update by sending a Binding The Home Agent acknowledges the Binding Update by sending a Binding
Acknowledgement to the Mobile Router. A positive acknowledgement Acknowledgement to the Mobile Router. A positive acknowledgement
means that the Home Agent has set up forwarding for the mobile with the Mobile Router Flag (R) set means that the Home Agent has set
network. Once the binding process completes, a bi-directional tunnel up forwarding for the Mobile Network. Once the binding process
is established between the Home Agent and the Mobile Router. The finishes, a bi-directional tunnel is established between the Home
tunnel end points are Mobile Router's Care-of Address and the Home Agent and the Mobile Router. The tunnel end points are the Mobile
Agent's address. If a packet with a source address belonging to Router's Care-of Address and the Home Agent's address. If a packet
the Mobile Network Prefix is received from the mobile network, the with a source address belonging to the Mobile Network Prefix is
Mobile Router reverse-tunnels the packet to the Home Agent through received from the Mobile Network, the Mobile Router reverse-tunnels
this tunnel. This reverse-tunneling is done by using IP-in-IP the packet to the Home Agent through this tunnel. This reverse-
encapsulation [3]. The Home Agent decapsulates this packet and tunneling is done by using IP-in-IP encapsulation [3]. The Home
forwards it to the Correspondent Node. For traffic originated by Agent decapsulates this packet and forwards it to the Correspondent
itself, the Mobile Router can use either reverse tunneling or route Node. For traffic originated by itself, the Mobile Router can use
optimization as specified in [1]. either reverse tunneling or route optimization, as specified in [1].
When a data packet is sent by a Correspondent Node to a node in the When a Correspondent Node sends a data packet to a node in the Mobile
mobile network, it gets routed to the Home Agent which currently Network, the packet is routed to the Home Agent that currently has
has the binding for the Mobile Router. It is expected that the the binding for the Mobile Router. The Mobile Router's network
Mobile Router's network prefix would be aggregated at the Home Agent, prefix would be aggregated at the Home Agent, which would advertise
which advertises the resulting aggregation. Alternatively, the Home the resulting aggregation. Alternatively, the Home Agent may receive
Agent may receive the data packets destined to the mobile network the data packets destined to the Mobile Network by advertising routes
by advertising routes to the Mobile Network Prefix. The actual to the Mobile Network Prefix. The actual mechanism by which these
mechanism by which these routes are advertised is outside the scope routes are advertised is outside the scope of this document. When
of this document. When the Home Agent receives a data packet meant the Home Agent receives a data packet meant for a node in the Mobile
for a node in the mobile network, it tunnels the packet to Mobile Network, it tunnels the packet to the Mobile Router's current Care-of
Router's current Care-of address. The Mobile Router decapsulates the Address. The Mobile Router decapsulates the packet and forwards it
packet and forwards it onto the interface where the mobile network onto the interface where the Mobile Network is connected. Before
is connected. The Mobile Router before decapsulating the tunneled decapsulating the tunneled packet, the Mobile Router has to check
packet, has to check if the Source address on the outer IPv6 header whether the Source address on the outer IPv6 header is the Home
is the Home Agent's address. However, this check is not necessary Agent's address. This check is not necessary if the packet is
if the packet is protected by IPsec in tunnel mode. The Mobile protected by IPsec in tunnel mode. The Mobile Router also has to
Router also has to make sure the destination address on the inner make sure that the destination address on the inner IPv6 header
IPv6 header belongs to a prefix used in the Mobile Network before belongs to a prefix used in the Mobile Network before forwarding the
forwarding the packet to the Mobile Network. Otherwise it should packet to the Mobile Network. If it does not, the Mobile Router
drop the packet. should drop the packet.
The mobile network could consist of nodes that do not support The Mobile Network could include nodes that do not support mobility
mobility and nodes that support mobility. A node in the mobile and nodes that do. A node in the Mobile Network can also be a fixed
network can also be a fixed or a mobile router. The protocol or a Mobile Router. The protocol described here ensures complete
described here ensures complete transparency of network mobility to transparency of network mobility to the nodes in the Mobile Network.
the nodes in the mobile network. Mobile Nodes that attach to the Mobile Nodes that attach to the Mobile Network treat it as a normal
mobile network treat it as a normal IPv6 access network and run the IPv6 access network and run the Mobile IPv6 protocol.
Mobile IPv6 protocol.
It is also possible for the Mobile Router and the Home Agent to run The Mobile Router and the Home Agent can run a routing protocol
a routing protocol through the bi-directional tunnel. In that case, through the bi-directional tunnel. In this case, the Mobile Router
the Mobile Router need not include prefix information in the Binding need not include prefix information in the Binding Update. Instead,
Update. Instead the Home Agent uses the routing protocol updates to the Home Agent uses the routing protocol updates to set up forwarding
setup forwarding for the mobile network. When running the routing for the Mobile Network. When the routing protocol is running, the
protocol it is required that the bi-directional tunnel be treated as bi-directional tunnel must be treated as a tunnel interface. The
a tunnel interface. The tunnel interface is included in the list of tunnel interface is included in the list of interfaces on which
interfaces on which routing protocol is active. The Mobile Router routing protocol is active. The Mobile Router should be configured
should be configured not to send any routing protocol messages on its not to send any routing protocol messages on its egress interface
egress interface when it is away from the home link and connected to when it is away from the home link and connected to a visited link.
a visited link.
Finally, the Home Agent may be configured with static routes to the Finally, the Home Agent may be configured with static routes to the
Mobile Network Prefix via the Mobile Router's Home Address. In that Mobile Network Prefix via the Mobile Router's Home Address. In this
case, the routes are set independently of the binding flows and case, the routes are set independently of the binding flows and the
the returning Home of a Mobile Router. The benefit is that such returning home of a Mobile Router. The benefit is that such movement
movement does not induce any additional signalling in the form of does not induce additional signalling in the form of routing updates
routing updates in the Home Network. The drawback of that model is in the home network. The drawback is that the routes are present
the routes are present even if the related Mobile Routers are not even if the related Mobile Routers are not reachable (at home or
reachable (at Home or bound) at a given point of time. bound) at a given point of time.
4. Message Formats 4. Message Formats
4.1. Binding Update 4.1. Binding Update
A new flag (R) is included in the Binding Update to indicate to the A new flag (R) is included in the Binding Update to indicate to the
Home Agent if the Binding Update is coming from a Mobile Router Home Agent whether the Binding Update is coming from a Mobile Router
and not from a mobile node. The rest of the Binding Update format and not from a mobile node. The rest of the Binding Update format
remains the same as defined in [1]. remains the same as defined in [1].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # | | Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|M|R| Reserved | Lifetime | |A|H|L|K|M|R| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. .
. Mobility options .
. .
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mobile Router Flag (R) Mobile Router Flag (R)
The Mobile Router Flag is set to indicate to the Home Agent The Mobile Router Flag is set to indicate to the Home Agent
that the Binding Update is from a Mobile Router. If the flag that the Binding Update is from a Mobile Router. If the flag
is set to 0, the Home Agent assumes that the Mobile Router is is set to 0, the Home Agent assumes that the Mobile Router is
just behaving as a Mobile Node, and MUST NOT forward packets behaving as a Mobile Node, and it MUST NOT forward packets
destined for the mobile network to the Mobile Router. destined for the Mobile Network to the Mobile Router.
Mobility Options Mobility Options
Variable length field which can include zero or more mobility A variable length field that can include zero or more mobility
options. This document defines a new mobility option in options. This document defines a new mobility option in
addition to what is defined in [1]. addition to what is defined in [1].
For descriptions of the other fields in the message, see [1]. For descriptions of the other fields in the message, see [1].
4.2. Binding Acknowledgement 4.2. Binding Acknowledgement
A new flag (R) is included in the Binding Acknowledgement to indicate A new flag (R) is included in the Binding Acknowledgement to indicate
that the Home Agent which processed the corresponding Binding Update that the Home Agent that processed the corresponding Binding Update
supports Mobile Routers. The flag is set only if the corresponding supports Mobile Routers. The flag is set only if the corresponding
Binding Update had the Mobile Router flag (R) set to 1. The rest of Binding Update had the Mobile Router Flag (R) set to 1. The rest of
the Binding Acknowledgement format remains the same as defined in the Binding Acknowledgement format remains the same, as defined in
[1]. [1].
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status |K|R| Reserved | | Status |K|R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # | Lifetime | | Sequence # | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
. .
. Mobility options .
. .
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mobile Router Flag (R) Mobile Router Flag (R)
The Mobile Router Flag is set to indicate that the Home Agent The Mobile Router Flag is set to indicate that the Home Agent
which processed the Binding Update supports Mobile Routers. It that processed the Binding Update supports Mobile Routers. It
is set to 1 only if the corresponding Binding Update had the is set to 1 only if the corresponding Binding Update had the
Mobile Router flag set to 1. Mobile Router Flag set to 1.
For descriptions of the other fields in the message, see [1]. For descriptions of the other fields in the message, see [1].
This document also introduces the following new Binding This document also introduces the following new Binding
Acknowledgement status values. The values shown below are decimal Acknowledgement status values. The values shown below are decimal
values. values.
140 Mobile Router Operation not permitted 140 Mobile Router Operation not permitted
141 Invalid Prefix 141 Invalid Prefix
142 Not Authorized for Prefix 142 Not Authorized for Prefix
143 Forwarding Setup failed 143 Forwarding Setup failed (prefixes missing)
Status values less than 128 indicate that the Binding Update was Status values less than 128 indicate that the Binding Update was
processed successfully by the receiving nodes. Values greater than processed successfully by the receiving nodes. Values greater than
128 indicate that the Binding Update was rejected by the Home Agent. 128 indicate that the Binding Update was rejected by the Home Agent.
4.3. Mobile Network Prefix Option 4.3. Mobile Network Prefix Option
The Mobile Network Prefix Option is included in the Binding Update The Mobile Network Prefix Option is included in the Binding Update to
to indicate to the Home Agent the prefix information for the mobile indicate the prefix information for the Mobile Network to the Home
network. There could be multiple Mobile Network Prefix Options Agent. There could be multiple Mobile Network Prefix Options if the
if the Mobile Router has more than one IPv6 prefix in the mobile Mobile Router has more than one IPv6 prefix in the Mobile Network and
network and wants the Home Agent to forward packets for each of these wants the Home Agent to forward packets for each of these prefixes to
prefixes to the Mobile Router's current location. the Mobile Router's current location.
The Mobile Network Prefix Option has an alignment requirement of The Mobile Network Prefix Option has an alignment requirement of
8n+4. Its format is as follows. 8n+4. Its format is as follows.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | Prefix Length | | Type | Length | Reserved | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ Mobile Network Prefix + + Mobile Network Prefix +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type Type
TBA 6
Length Length
8 bit unsigned integer indicating the length in octets of the Eight-bit unsigned integer indicating the length in octets of
option excluding the type and length fields. Set to 18. the option, excluding the type and length fields. Set to 18.
Reserved Reserved
This field is unused for now. The value MUST be initialized to This field is unused for now. The value MUST be initialized to
zero by the sender, and MUST be ignored by the receiver. 0 by the sender and MUST be ignored by the receiver.
Prefix Length Prefix Length
8 bit unsigned integer indicating the prefix length of the IPv6 Eight-bit unsigned integer indicating the prefix length of the
prefix contained in the option. IPv6 prefix contained in the option.
Mobile Network Prefix Mobile Network Prefix
A 16 byte field contains the Mobile Network Prefix. A sixteen-byte field containing the Mobile Network Prefix
5. Mobile Router Operation 5. Mobile Router Operation
Mobile Router operation is derived largely from the combined Mobile Router operation is derived largely from the combined
behaviors of a Host, of a Router [5], and of a Mobile Node [1]. behaviors of a host, of a router [5], and of a Mobile Node [1].
A Mobile Node can act in two different ways: (1) as a Mobile Host A Mobile Node can act in two ways: (1) as a Mobile Host, in which
(in which case the Home Agent doesn't maintain any prefix information case the Home Agent doesn't maintain any prefix information related
related to the Mobile Host's Home Address, but does maintain a to the Mobile Host's Home Address but does maintain a binding cache
binding cache entry related to the Mobile Host's Home Address) and entry related to the Mobile Host's Home Address, and (2) as a Mobile
(2) as a Mobile Router (in which case, in addition to maintaining the Router, in which case, in addition to maintaining the binding cache
binding cache entry corresponding to the Mobile Router Home Address, entry corresponding to the Mobile Router Home Address, the Home Agent
the Home Agent also maintains forwarding information related to maintains forwarding information related to prefixes assigned to the
prefixes assigned to the mobile network). The distinction between Mobile Network. The distinction between the two modes is represented
the the two modes is represented by the value of the Mobile Router by the value of the Mobile Router Flag (R).
flag (R).
A Mobile Router MUST implement all requirements for IPv6 Mobile Nodes A Mobile Router MUST implement all requirements for IPv6 Mobile Nodes
as described in Section 8.5 of [1]. as described in section 8.5 of [1].
5.1. Data Structures 5.1. Data Structures
Like a Mobile Host, a Mobile Router also maintains a Binding Update Like a Mobile Host, a Mobile Router also maintains a Binding Update
List, described in Section 11.1 of Mobile IPv6 specification[1]. The List, described in section 11.1 of the Mobile IPv6 specification [1].
Binding Update list is a conceptual data structure which records The Binding Update list is a conceptual data structure that records
information that is sent in the Binding Updates. There is one entry information sent in the Binding Updates. There is one entry per each
per each destination that the Mobile Router is currently sending destination to which the Mobile Router is currently sending Binding
Binding Updates to. Updates.
This document introduces a new Prefix Information field in the This document introduces a new Prefix Information field in the
Binding Update list structure. This field is used to store any Binding Update list structure. This field is used to store any
prefix information that the Mobile Router includes in the Binding prefix information that the Mobile Router includes in the Binding
Update. If the Mobile Router sets the Mobile Router flag (R) in the Update. If the Mobile Router sets the Mobile Router Flag (R) in the
Binding Update, but does not include any prefix information in it Binding Update but does not include any prefix information in it this
this field is set to null. The Mobile Router does not include prefix field is set to null. The Mobile Router does not include prefix
information in the Binding Update in the implicit mode or when it information in the Binding Update in the implicit mode or when it,
runs a dynamic routing protocol with its Home Agent. runs a dynamic routing protocol with its Home Agent.
Similar to a Mobile Host, a Mobile Router stores the information As does a Mobile Host, a Mobile Router stores the information
regarding status of flags of the Binding Update, in the corresponding regarding status of flags of the Binding Update in the corresponding
Binding Update List entry. This document introduces a new mobile Binding Update List entry. This document introduces a new Mobile
router flag (R) for this entry. The status of this flag is stored in Router Flag (R) for this entry. The status of this flag is stored in
the Binding Update list whenever a Binding Update is sent. the Binding Update list whenever a Binding Update is sent.
A Mobile Router also maintains a Home Agent list populated according A Mobile Router also maintains a Home Agent list populated according
to the same procedure as a Mobile Host. to the same procedure as a Mobile Host.
5.2. Sending Binding Updates 5.2. Sending Binding Updates
A Mobile Router sends Binding Updates to its Home Agent as described A Mobile Router sends Binding Updates to its Home Agent, as described
in [1]. If the Mobile Router is not running a routing protocol in [1]. If the Mobile Router is not running a routing protocol as
as described in Section 8, it uses one of the following modes to described in section 8, it uses one of the following modes to tell
instruct the Home Agent to determine the prefixes that belong to the the Home Agent to determine which prefixes belong to the Mobile
Mobile Router. In all the modes, the Mobile Router sets the Mobile Router. In both modes, the Mobile Router sets the Mobile Router Flag
Router flag (R). (R).
Implicit: Implicit:
In this mode, the Mobile Router does not include a Mobile In this mode, the Mobile Router does not include a Mobile
Network Prefix Option in the Binding Update. The Home Agent Network Prefix Option in the Binding Update. The Home Agent
can use any mechanism (not defined in this document) to can use any mechanism (not defined in this document) to
determine the Mobile Network Prefix(es) owned by the Mobile determine the Mobile Network Prefix(es) owned by the Mobile
Router and setup forwarding for the mobile network. One Router and to set up forwarding for the Mobile Network. One
example would be manual configuration at the Home Agent mapping example would be manual configuration at the Home Agent mapping
the Mobile Router's Home Address to the information required the Mobile Router's Home Address to the information required
for setting up forwarding for the mobile network. for setting up forwarding for the Mobile Network.
Explicit: Explicit:
In this mode, the Mobile Router includes one or more Mobile In this mode, the Mobile Router includes one or more Mobile
Network Prefix Options in the Binding Update. These options Network Prefix Options in the Binding Update. These options
contain information about the Mobile Network Prefix(es) contain information about the Mobile Network Prefix(es)
configured on the mobile network. configured on the Mobile Network.
A Mobile Router MUST implement at least one mode and MAY implement A Mobile Router MUST implement at least one mode and MAY implement
both modes. If a Mobile Router implements both modes, local both. In the latter case, local configuration on the Mobile Router
configuration on the Mobile Router decides which mode to use. This decides which mode to use. This is out of scope for this document.
is out of scope for this document.
If the Mobile Router flag is set, Home Registration flag (H) MUST be If the Mobile Router Flag is set, the Home Registration Flag (H) MUST
set. be set.
If the Mobile Router has a valid binding cache entry at the Home If the Mobile Router has a valid binding cache entry at the Home
Agent, subsequent Binding Updates for the same Home Address should Agent, subsequent Binding Updates for the same Home Address should
have the same value for the Mobile Router Flag (R) as the value in have the same value as the value in the binding cache for the Mobile
the binding cache. Router Flag (R). In explicit mode, the Mobile Router MUST include
prefix information in all Binding Updates, including those sent to
refresh existing binding cache entries, if it wants forwarding
enabled for the corresponding Mobile Network Prefixes.
5.3. Receiving Binding Acknowledgements 5.3. Receiving Binding Acknowledgements
The Mobile Router receives Binding Acknowledgements from the Home The Mobile Router receives Binding Acknowledgements from the Home
Agent, corresponding to the Binding Updates it sent. If the Binding Agent corresponding to the Binding Updates it sent. If the Binding
Acknowledgement status is set to '0' (Binding Update accepted) and Acknowledgement status is set to 0 (Binding Update accepted) and the
the Mobile Router flag (R) is set to 1, the Mobile Router assumes Mobile Router Flag (R) is set to 1, the Mobile Router assumes that
that the Home Agent has successfully processed the Binding Update the Home Agent has successfully processed the Binding Update and has
and has set up forwarding for the mobile network. The Mobile Router set up forwarding for the Mobile Network. The Mobile Router can then
can then start using the bi-directional tunnel for reverse tunneling start using the bi-directional tunnel to reverse-tunnel traffic from
traffic from the mobile network. If the Mobile Router flag (R) is the Mobile Network. If the Mobile Router Flag (R) is not set, then
not set, then the Mobile Router concludes that its current Home the Mobile Router concludes that its current Home Agent does not
Agent does not support Mobile Routers and performs Dynamic Home support Mobile Routers and it performs Dynamic Home Agent Address
Agent Discovery again to discover Home Agents which support Mobile Discovery again to discover Home Agents that do. The Mobile Router
Routers. Additional the Mobile Router MUST also de-register with the MUST also de-register with the Home Agent that did not support it
Home Agent which did not support Mobile Routers before attempting before attempting registration with another.
registration with another Home Agent.
5.4. Error Processing 5.4. Error Processing
If the Binding Acknowledgement status is set to a value between 128 If the Binding Acknowledgement status is set to a value between 128
and 139, the Mobile Router takes necessary actions as described in and 139, the Mobile Router takes necessary actions as described in
the Mobile IPv6 specification [1]. For the Binding Acknowledgement the Mobile IPv6 specification [1]. For the Binding Acknowledgement
status values defined in this document, the following sections status values defined in this document, the following sections
explain the Mobile Router's behavior. explain the Mobile Router's behavior.
5.4.1. Implicit Mode 5.4.1. Implicit Mode
In Implicit mode, the Mobile Router interprets only error In Implicit mode, the Mobile Router interprets only error statuses
status '140' (Mobile Router Operation not permitted) and '143' 140 (Mobile Router Operation not permitted) and 143 (Forwarding Setup
(Forwarding Setup failed). The Mobile Router MUST discard Binding failed). The Mobile Router MUST treat Binding Acknowledgements with
Acknowledgements with status '141' and '142'. statuses '141' and '142' as fatal errors, since they should not be
sent by the Home Agent in implicit mode.
If the Binding Acknowledgement from the Home Agent has the status If the Binding Acknowledgement from the Home Agent has the status
'140', the Mobile Router SHOULD send a Binding Update to another Home 140, the Mobile Router SHOULD send a Binding Update to another Home
Agent on the same home link. If no Home Agent replies positively Agent on the same home link. If no Home Agent replies positively,
the Mobile Router MUST refrain from sending Binding Updates with the the Mobile Router MUST refrain from sending Binding Updates with the
Mobile Router flag set to any Home Agent on the home link, and log Mobile Router Flag set to any Home Agent on the home link, and it
the information. must log the information.
If the Binding Acknowledgemnet has the status '143', the Mobile If the Binding Acknowledgement has the status 143, the Mobile Router
Router SHOULD send a Binding Update to another Home Agent on the same SHOULD send a Binding Update to another Home Agent on the same home
home link. If no Home Agent replies positively the Mobile Router link. If no Home Agent replies positively, the Mobile Router SHOULD
SHOULD refrain from sending this Binding Update to any Home Agent on refrain from sending this Binding Update to any Home Agent on the
the home link, and MAY send Binding Updates in Explicit mode to a home link, and MAY send Binding Updates in Explicit mode to a Home
Home Agent on the same home link. Agent on the same home link.
5.4.2. Explicit Mode 5.4.2. Explicit Mode
If the Mobile Router sent a Binding Update to Home Agent in explicit If the Mobile Router sent a Binding Update to the Home Agent in
mode then the Mobile Router interprets only error status '140' explicit mode, then the Mobile Router interprets only error statuses
(Mobile Router Operation not permitted), '141' (Invalid Prefix) and 140 (Mobile Router Operation not permitted), 141 (Invalid Prefix),
'142' (Not Authorized for Prefix). The Mobile Router MUST discard and 142 (Not Authorized for Prefix). The Mobile Router MUST treat
Binding Acknowledgements with status '143'. Binding Acknowledgements with status '143' as a fatal error, since it
should not be sent by the Home Agent in explicit mode.
If the Binding Acknowledgement from the Home Agent has the status If the Binding Acknowledgement from the Home Agent has the status
'140', the Mobile Router SHOULD send a Binding Update to another Home 140, the Mobile Router SHOULD send a Binding Update to another Home
Agent on the same home link. If no Home Agent replies positively Agent on the same home link. If no Home Agent replies positively,
then the Mobile Router MUST refrain from sending Binding Updates with then the Mobile Router MUST refrain from sending Binding Updates with
the Mobile Router flag set to any Home Agent on the home link, and the Mobile Router Flag set to any Home Agent on the home link, and it
log the information. must log the information.
If the Binding Acknowledgement has the status '141' or '142', the If the Binding Acknowledgement has the status 141 or 142, the Mobile
Mobile Router SHOULD send a Binding Update to another Home Agent Router SHOULD send a Binding Update to another Home Agent on the same
on the same home link. If no Home Agent replies positively then home link. If no Home Agent replies positively, then the Mobile
the Mobile Router SHOULD refrain from sending Binding Updates to Router SHOULD refrain from sending Binding Updates to any Home Agent
any Home Agent on the home link. The Mobile Router MUST also stop on the home link. The Mobile Router MUST also stop advertising the
advertising the prefix in the Mobile Network and try to obtain new prefix in the Mobile Network and try to obtain new IPv6 prefix
IPv6 prefix information for the Mobile Network by the same means information for the Mobile Network. It would do this by the same
that it initially got assigned the current Mobile Network Prefix. means that it initially got assigned the current Mobile Network
Alternatively, Mobile Router MAY send Binding Updates in Implicit Prefix. Alternatively, the Mobile Router MAY send Binding Updates in
mode to a Home Agent on the same home link. Implicit mode to a Home Agent on the same home link.
If at the end of this Error Processing procedure, as described in If by the end of this Error Processing procedure, as described in
Sections 5.4.1 and 5.4.2, the Mobile Router has tried every available sections 5.4.1 and 5.4.2, the Mobile Router has tried every available
modes of sending Binding Updates and still has not received a mode and still has not received a positive Binding Acknowledgement,
positive Binding Acknowledgement, the Mobile Router MUST stop sending the Mobile Router MUST stop sending Binding Updates with the Mobile
Binding Updates with the Mobile Router flag set for this Home Address Router Flag set for this Home Address and it must log the
and log the information. information.
In all the above cases, the Mobile Router MUST conclude that the Home In all cases above, the Mobile Router MUST conclude that the Home
Agent did not create a binding cache entry for the Mobile Router's Agent did not create a binding cache entry for the Mobile Router's
Home Address. Home Address.
5.5. Establishment of Bi-directional Tunnel 5.5. Establishment of Bi-directional Tunnel
When a successful Binding Acknowledgement is received, the Mobile When a successful Binding Acknowledgement is received, the Mobile
Router sets up its endpoint of the bi-directional tunnel. Router sets up its endpoint of the bi-directional tunnel.
The bi-directional tunnel between Mobile Router and Home Agent allows The bi-directional tunnel between the Mobile Router and the Home
packets to flow in both directions between these entities, while the Agent allows packets to flow in both directions, while the Mobile
Mobile Router is connected to a visited link. The bi-directional Router is connected to a visited link. The bi-directional tunnel is
tunnel is created by merging two unidirectional tunnels as described created by merging two unidirectional tunnels, as described in RFC
in RFC 2473 [3]. The tunnel from the Mobile Router to the Home Agent 2473 [3]. The tunnel from the Mobile Router to the Home Agent has
has the Care-of address of the Mobile Router as the tunnel entry the Care-of address of the Mobile Router as the tunnel entry point
point and the Home Agent's address as the tunnel exit point. The and the Home Agent's address as the tunnel exit point. The tunnel
tunnel from the Home Agent to the Mobile Router has the Home Agent's from the Home Agent to the Mobile Router has the Home Agent's address
address and the Mobile Router's Care-of address as the tunnel entry and the Mobile Router's Care-of Address as the tunnel entry point and
point and exit point respectively. All IPv6 traffic to and from the exit point, respectively. All IPv6 traffic to and from the Mobile
mobile network is sent through this bi-directional tunnel. Network is sent through this bi-directional tunnel.
A Mobile Router MAY limit the number of mobile routers that attach to
its mobile network (the number of levels in the nested aggregation)
by means of setting the Tunnel Encapsulation Limit field of the
Tunnel Encapsulation option.
A Mobile Router uses the Tunnel Hop Limit that is normally assigned A Mobile Router uses the Tunnel Hop Limit normally assigned to
to routers (not to hosts). Please refer to [3] for more details. routers (not to hosts). Please refer to [3] for more details.
5.6. Neighbor Discovery for Mobile Router 5.6. Neighbor Discovery for Mobile Router
When the Mobile Router is at home, it MAY be configured to send When the Mobile Router is at home, it MAY be configured to send
Router Advertisements and reply to Router Solicitations on the Router Advertisements and to reply to Router Solicitations on the
interface attached to the home link. The value of the Router interface attached to the home link. The value of the Router
Lifetime field MUST be set to zero to prevent other nodes from Lifetime field SHOULD be set to 0 to prevent other nodes from
configuring the Mobile Router as the default router. configuring the Mobile Router as the default router.
A Mobile Router SHOULD NOT send unsolicited Router Advertisements A Mobile Router SHOULD NOT send unsolicited Router Advertisements and
and SHOULD NOT reply to Router Solicitations on any egress interface SHOULD NOT reply to Router Solicitations on any egress interface when
when that interface is attached to a visited link. However, the that interface is attached to a visited link. However, the Mobile
Mobile Router SHOULD reply with Neighbor Advertisements to Neighbor Router SHOULD reply with Neighbor Advertisements to Neighbor
Solicitations received on the egress interface, for topologically Solicitations received on the egress interface, for addresses valid
correct addresses. on the visited link.
A router typically ignores router advertisements sent by other A router typically ignores Router Advertisements sent by other
routers on a link. However, a Mobile Router MUST NOT ignore Router routers on a link. However, a Mobile Router MUST NOT ignore Router
Advertisements received on the egress interface. The received Router Advertisements received on the egress interface. The received Router
Advertisements MAY be used for address configuration, default router Advertisements MAY be used for address configuration, default router
selection or movement detection. selection, or movement detection.
5.7. Multicast Groups for Mobile Router 5.7. Multicast Groups for Mobile Router
When at home, the Mobile Router joins the multicast group All Routers When at home, the Mobile Router joins the multicast group All Routers
Address with scopes '1' interface-local (on the home-advertising Address with scopes 1 interface-local (on the home-advertising
interface) and '2' link-local on any of its egress interfaces. When interface), and 2 link-local, on any of its egress interfaces. When
in a visited network, the Mobile Router MUST NOT join the above in a visited network, the Mobile Router MUST NOT join the above
multicast groups on the corresponding interface. multicast groups on the corresponding interface.
5.8. Returning Home 5.8. Returning Home
When the Mobile Router realizes it has returned to its home link When the Mobile Router detects that it has returned to its home link,
through movement detection mechanisms, it MUST de-register with it MUST de-register with its Home Agent. The Mobile Router MUST
its Home Agent. The Mobile Router MUST implement and follow the implement and follow the returning-home procedures defined for a
returning home procedures defined for a mobile node in [1]. In mobile node in [1]. In addition, the Mobile Router MAY start
addition, the Mobile Router MAY start behaving as a router on its behaving as a router on its egress interface, especially as follows:
egress interface. In particular,
- The Mobile Router MAY send router advertisements on its egress - The Mobile Router MAY send Router Advertisements on its egress
interfaces. But the router lifetime SHOULD be set to 0, so that interfaces, but the router lifetime SHOULD be set to 0 so that
hosts on the home link do not pick the Mobile Router as the hosts on the home link do not pick the Mobile Router as the
default router. default router.
- The Mobile Router MAY join the All Routers multicast group on the - The Mobile Router MAY join the All Routers Address multicast group
home link. on the home link.
- The Mobile Router MAY send routing protocol messages on its - The Mobile Router MAY send routing protocol messages on its egress
egress interface if it is configured to run a dynamic routing interface if it is configured to run a dynamic routing protocol.
protocol.
When the Mobile Router sends a de-registration Binding Update in When the Mobile Router sends a de-registration Binding Update in
Explicit mode, it SHOULD not include any Mobile Network Prefix Explicit mode, it SHOULD NOT include any Mobile Network Prefix
options in the Binding Update. When the Home Agent removes a binding options in the Binding Update. When the Home Agent removes a binding
cache entry, it deletes all the associated Mobile Network Prefix cache entry, it deletes all associated Mobile Network Prefix routes.
routes.
6. Home Agent Operation 6. Home Agent Operation
In order for a Mobile Router to operate correctly, the Home Agent For a Mobile Router to operate correctly, the Home Agent MUST satisfy
MUST satisfy all the requirements listed in Section 8.4 of [1]. The all the requirements listed in section 8.4 of [1]. The Home Agent
Home Agent MUST implement both modes described in Section 5.2 of this MUST implement both modes described in section 5.2 of this document.
document.
6.1. Data Structures 6.1. Data Structures
6.1.1. Binding Cache 6.1.1. Binding Cache
The Home Agent maintains Binding Cache Entries for each Mobile Router The Home Agent maintains Binding Cache Entries for each Mobile Router
that is currently registered with the Home Agent. The Binding Cache currently registered with the Home Agent. The Binding Cache is a
is a conceptual data structure described in detail in [1]. conceptual data structure described in detail in [1].
The Home Agent might need to store the Mobile Network Prefixes The Home Agent might need to store the Mobile Network Prefixes
associated with a Mobile Router in the corresponding Binding Cache associated with a Mobile Router in the corresponding Binding Cache
Entry. This is required if the Binding Update (that created the Entry. This is required if the Binding Update that created the
Binding Cache Entry) contained explicit prefix information. This Binding Cache Entry contained explicit prefix information. This
information can be used later to cleanup routes installed in explicit information can be used later to clean up routes installed in
mode, when the Binding Cache Entry is removed, and to maintain the explicit mode, when the Binding Cache Entry is removed, and to
routing table, for instance should the routes be manually removed. maintain the routing table, for instance, should the routes be
removed manually.
The Home Agent also stores the status of the Mobile Router Flag (R) The Home Agent also stores the status of the Mobile Router Flag (R)
in the Binding Cache entry. in the Binding Cache entry.
6.1.2. Prefix Table 6.1.2. Prefix Table
The Home Agent SHOULD be able to prevent a Mobile Router from The Home Agent SHOULD be able to prevent a Mobile Router from
claiming Mobile Network Prefixes that belong to another Mobile claiming Mobile Network Prefixes belonging to another Mobile Router.
Router. The Home Agent can prevent such attacks if it maintains a The Home Agent can prevent such attacks if it maintains a Prefix
Prefix Table and verifies the Prefix Information provided by the Table and verifies the prefix information provided by the Mobile
Mobile Router against the entries in the Prefix Table. The Prefix Router against Prefix Table entries. The Prefix Table SHOULD be used
Table SHOULD be used by the Home Agent when it processes a Binding by the Home Agent when it processes a Binding Update in explicit
Update in explicit mode. It is not required when a dynamic routing mode. It is not required when a dynamic routing protocol is run
protocol is run between the Mobile Router and the Home Agent. between the Mobile Router and the Home Agent.
Each entry in the Prefix Table conceptually contains the following Each entry in the Prefix Table contains the following fields:
fields:
- The Home Address of the Mobile Router. This field is used as the - The Home Address of the Mobile Router. This field is used as the
key for searching the pre-configured prefix table. key for searching the pre-configured Prefix Table.
- The Mobile Network Prefix of the Mobile Router associated with - The Mobile Network Prefix of the Mobile Router associated with the
the Home Address. Home Address.
6.2. Mobile Network Prefix Registration 6.2. Mobile Network Prefix Registration
The Home Agent processes the Binding Update as described in Section The Home Agent processes the Binding Update as described in section
10.3.1 of the Mobile IPv6 specification [1]. This section describes 10.3.1 of the Mobile IPv6 specification [1]. This section describes
the processing of the Binding Update if the Mobile Router (R) flag is the processing of the Binding Update if the Mobile Router (R) Flag is
set. The Home Agent performs the following check in addition. set. The Home Agent performs the following check.
- The Home Registration (H) flag MUST be set. If not, the - The Home Registration (H) Flag MUST be set. If it is not, the
Home Agent MUST reject the Binding Update and send a Binding Home Agent MUST reject the Binding Update and send a Binding
Acknowledgement with status set to 140. Note: The basic support Acknowledgement with status set to 140. Note: The basic support
does not allow sending Binding Update for a Mobile Network Prefix does not allow sending a Binding Update for a Mobile Network
to correspondent nodes (for route optimization). Prefix to correspondent nodes (for route optimization).
- Mobile IPv6 specification [1] requires that the Home Address in - Mobile IPv6 specification [1] requires that the Home Address in
the Binding Update should be configured from a prefix advertised the Binding Update be configured from a prefix advertised on the
on the home link. Otherwise the Binding Update is rejected home link. Otherwise the Binding Update is rejected with status
with status value 132 [1]. This specification relaxes this value 132 [1]. This specification relaxes this requirement so
requirement so that the Home Agent rejects the Binding Update that the Home Agent rejects the Binding Update only if the Home
only if Home Address does not belong to the prefix that the Home Address does not belong to the prefix that the Home Agent is
Agent is configured to serve. configured to serve.
If the Home Agent has a valid binding cache entry for the Mobile If the Home Agent has a valid binding cache entry for the Mobile
Router and if the Binding Update has the Mobile Router Flag (R) Router, and if the Binding Update has the Mobile Router Flag (R) set
set to a value different from the value in the existing binding to a value different from that in the existing binding cache entry,
cache entry, the Home Agent MUST reject the Binding Update and send then the Home Agent MUST reject the Binding Update and send a Binding
a Binding Acknowledgement with status set to 139 (Registration Acknowledgement with status set to 139 (Registration type change
type change disallowed). However, if the Binding Update is a disallowed). However, if the Binding Update is a de-registration
de-registration Binding Update, the Home Agent ignores the value of Binding Update, the Home Agent ignores the value of the Mobile Router
the Mobile Router Flag (R). Flag (R).
If the Home Agent does not reject the Binding Update as described If the Lifetime specified in the Binding Update is 0 or the specified
above, and if a dynamic routing protocol is not being run between Care-of address matches the Home Address in the Binding Update, then
the Home Agent and the Mobile Router as described in Section 8, then this is a request to delete the cached binding for the home address
the Home Agent retrieves the Mobile Network Prefix information as and specified Mobile Network Prefixes. The Binding Update is
described below. processed as described in section 6.7.
If the Home Agent does not reject the Binding Update as invalid, and
if a dynamic routing protocol is not run between the Home Agent and
the Mobile Router as described in section 8, then the Home Agent
retrieves the Mobile Network Prefix information as described below.
- If a Mobile Network Prefix Option is present in the Binding - If a Mobile Network Prefix Option is present in the Binding
Update, the prefix information for the Mobile Network Prefix is Update, the prefix information for the Mobile Network Prefix is
retrieved from the Mobile Network Prefix field and the Prefix retrieved from the Mobile Network Prefix field and the Prefix
Length field of the option. If the Binding Update contains more Length field of the option. If the Binding Update contains more
than one option, the Home Agent MUST set up forwarding for all of than one option, the Home Agent MUST set up forwarding for all the
the Mobile Network Prefixes. If the Home Agent fails to setup Mobile Network Prefixes. If the Home Agent fails to set up
forwarding to all the prefixes listed in the Binding Update, then forwarding to all the prefixes listed in the Binding Update, then
it MUST NOT forward traffic to any of the prefixes, reject the it MUST NOT forward traffic to any of the prefixes. Furthermore,
Binding Update and send a Binding Acknowledgement with status set it MUST reject the Binding Update and send a Binding
to 141 (Invalid Prefix). Acknowledgement with status set to 141 (Invalid Prefix).
If the Home Agent verifies the prefix information with the Prefix If the Home Agent verifies the prefix information with the Prefix
Table and the check fails, the Home Agent MUST discard the Table and the check fails, the Home Agent MUST discard the Binding
Binding Update and send a Binding Acknowldegement with status set Update and send a Binding Acknowledgement with status set to 142
to 142 (Not Authorized for Prefix). (Not Authorized for Prefix).
- If there are is no option in the Binding Update carying - If there is no option in the Binding Update carrying prefix
prefix information, the Home Agent uses manual pre-configured information, the Home Agent uses manual pre-configured information
information to determine the prefixes assigned to the Mobile to determine the prefixes assigned to the Mobile Router and to set
Router and for setting up forwarding for the mobile network. If up forwarding for the Mobile Network. If there is no information
there is no information that the Home Agent can use, it MUST that the Home Agent can use, it MUST reject the Binding Update and
reject the Binding Update and send a Binding Acknowledgement with send a Binding Acknowledgement with status set to 143 (Forwarding
status set to 143 (Forwarding Setup failed). Setup failed).
If the Lifetime specified in the Binding Update is zero or the If the Home Agent has a valid binding cache entry for the Mobile
specified Care-of address matches the Home Address in the Binding Router, it should compare the list of prefixes in the Binding Update
Update, then this is a request to delete the cached binding for against the prefixes stored in the binding cache entry. If the
the home address and specified Mobile Network Prefixes. The binding cache entry contains prefixes that do not appear in the
Binding Update is processed according to the procedure described in Binding Update, the Home Agent MUST disable forwarding for these
Section 6.7. Mobile Network Prefixes.
If all checks are passed, the Home Agent creates a binding cache If all checks are passed, the Home Agent creates a binding cache
entry for Mobile Router's Home Address, or updates the binding cache entry for Mobile Router's Home Address or updates the entry if it
entry if it already exists. Otherwise, the Home Agent MUST NOT already exists. Otherwise, the Home Agent MUST NOT register the
register the binding of the Mobile Router's Home Address. binding of the Mobile Router's Home Address.
The Home Agent defends the Mobile Router's Home Address through Proxy The Home Agent defends the Mobile Router's Home Address through Proxy
Neighbor Discovery by multicasting onto the home link a Neighbor Neighbor Discovery by multicasting a Neighbor Advertisement message
Advertisement message on behalf of the mobile router. All fields in onto the home link on behalf of the Mobile Router. All fields in the
the Proxy Neighbor Advertisement message should be set in the same Proxy Neighbor Advertisement message should be set the same way they
way they would be set by the Mobile Router itself if sending this would be by the Mobile Router if it sent this Neighbor Advertisement
Neighbor Advertisement while at home, as described in [6], with the while at home, as described in [6]. There is an exception: If the
exception that the Router (R) bit in the Advertisement MUST be set if Mobile Router (R) Flag has been set in the Binding Update, the Router
the Mobile Router (R) flag has been set in the Binding Update. (R) bit in the Advertisement MUST be set.
The Home Agent also creates a bi-directional tunnel to the mobile The Home Agent also creates a bi-directional tunnel to the Mobile
router for the requested Mobile Network Prefix, or update an existing Router for the requested Mobile Network Prefix or updates an existing
bi-directional tunnel as described in Section 6.4. bi-directional tunnel as described in section 6.4.
6.3. Advertising Mobile Network Reachability 6.3. Advertising Mobile Network Reachability
In order to be able to receive packets meant for the mobile network, To receive packets meant for the Mobile Network, the Home Agent
the Home Agent advertises reachability to the mobile network. If advertises reachability to the Mobile Network. If the Home Link is
the Home Link is configured with a prefix that is an aggregation and configured with an aggregated prefix and the Mobile Network Prefix is
if the Mobile Network Prefix is aggregated under that prefix, then aggregated under that prefix, then the routing changes related to the
the routing changes related to the Mobile Network may be restricted Mobile Network may be restricted to the Home Link. If the Home Agent
to the Home Link. If the Home Agent is the only default router on is the only default router on the Home Link, routes to the Mobile
the Home Link, routes to the Mobile Network Prefix get aggregated Network Prefix are aggregated naturally under the Home Agent, which
naturally under the Home Agent and the Home Agent does not have to do does not have to do anything special.
anything special.
If the Home Agent receives routing updates through a dynamic routing If the Home Agent receives routing updates through a dynamic routing
protocol from the Mobile Router, it can be configured to propagate protocol from the Mobile Router, it can be configured to propagate
those routes on the relevant interfaces. those routes on the relevant interfaces.
6.4. Establishment of Bi-directional Tunnel 6.4. Establishment of Bi-directional Tunnel
The implementation of the bi-directional tunnels and the mechanism The implementation of the bi-directional tunnels and the mechanism
of attaching them to the IP stack are outside the scope of this for attaching them to the IP stack are outside the scope of this
specification. However, all implementations MUST be capable of the specification. However, all implementations MUST be capable of the
following operations. following operations:
- The Home Agent can tunnel packets meant for the mobile network - The Home Agent can tunnel packets meant for the Mobile Network
prefix to the Mobile Router's current location, the Care-of prefix to the Mobile Router's current location, the Care-of
Address of the Mobile Router. Address.
- The Home Agent can accept packets tunneled by the Mobile Router - The Home Agent can accept packets tunneled by the Mobile Router
with source address of the outer IPv6 header set to the Care-of with the source address of the outer IPv6 header set to the Mobile
Address of the Mobile Router. Router's Care-of Address.
6.5. Forwarding Packets 6.5. Forwarding Packets
When the Home Agent receives a data packet destined for the mobile When the Home Agent receives a data packet destined for the Mobile
network, it MUST forward the packet to the Mobile Router through the Network, it MUST forward the packet to the Mobile Router through the
bi-directional tunnel. The Home Agent either uses only the routing bi-directional tunnel. The Home Agent uses either the routing table,
table, only the Binding Cache or a combination of routing table the Binding Cache, or a combination to route packets to the Mobile
and Binding Cache to route packets to the mobile network. This is Network. This is implementation specific. Two examples are shown
implementation specific. Two examples are shown below. below.
1. The Home Agent maintains a route to the Mobile Network Prefix 1. The Home Agent maintains a route to the Mobile Network Prefix with
with the next hop set to the Mobile Router's Home Address. When the next hop set to the Mobile Router's Home Address. When the
the Home Agent tries to forward the packet to the next hop, it Home Agent tries to forward the packet to the next hop, it finds a
finds a binding cache entry for the home address. Then the Home binding cache entry for the home address. Then the Home Agent
Agent extracts the Mobile Router's Care-of address and tunnels extracts the Mobile Router's Care-of address and tunnels the
the packet to the Care-of address. packet to the Care-of address.
2. The Home Agent maintains a route to the Mobile Network Prefix 2. The Home Agent maintains a route to the Mobile Network Prefix with
with the outgoing interface set to the bi-directional tunnel the outgoing interface set to the bi-directional tunnel interface
interface between the Home Agent and the Mobile Router. For between the Home Agent and the Mobile Router. For this purpose,
this purpose, the Home Agent MUST treat this tunnel as a tunnel the Home Agent MUST treat this tunnel as a tunnel interface. When
interface. When the packets are forwarded through the tunnel the packets are forwarded through the tunnel interface, they are
interface, they get encapsulated automatically with the source encapsulated automatically, with the source address and
address and destination address in the outer IPv6 header set to destination address in the outer IPv6 header set to the Home
the Home Agent's address and the Mobile Router's Care-of address, Agent's address and the Mobile Router's Care-of address,
respectively. respectively.
6.6. Sending Binding Acknowledgements 6.6. Sending Binding Acknowledgements
A Home Agent serving a Mobile Router sends Binding Acknowledgements A Home Agent serving a Mobile Router sends Binding Acknowledgements
according to the same rules it uses for sending Binding with the same rules it uses for sending Binding Acknowledgements to
Acknowledgements to Mobile Hosts [1], with the following Mobile Hosts [1], with the following enhancements.
enhancements.
The Home Agent sets the status code in the Binding Acknowledgement The Home Agent sets the status code in the Binding Acknowledgement to
to '0' (Binding Update accepted) in order to indicate to the Mobile 0 (Binding Update accepted) to indicate to the Mobile Router that it
Router that it successfully processed the Binding Update. It also successfully processed the Binding Update. It also sets the Mobile
sets the Mobile Router flag (R) to indicate to the Mobile Router that Router Flag (R) to indicate to the Mobile Router that it has set up
it has setup forwarding for the mobile network. forwarding for the Mobile Network.
If the Home Agent is configured not to support mobile routers, it If the Home Agent is not configured to support Mobile Routers, it
sets the status code in the Binding Acknowledgement to '140' (Mobile sets the status code in the Binding Acknowledgement to 140 (Mobile
Router Operation not permitted). Router Operation not permitted).
If one or more prefixes received in the Binding Update are invalid If one or more prefixes received in the Binding Update are invalid
and the Home Agent cannot setup forwarding for the prefixes, the Home and the Home Agent cannot set up forwarding for the prefixes, the
Agent sets the status code in the Binding Acknowledgement to '141' Home Agent sets the status code in the Binding Acknowledgement to 141
(Invalid Prefix) in order to indicate this to the Mobile Router. (Invalid Prefix) to indicate this to the Mobile Router.
If the Mobile Router is not authorized to use this Home Address to If the Mobile Router is not authorized to use this Home Address to
forward packets for one or more prefixes that are present in the forward packets for one or more prefixes present in the Binding
Binding Update, the Home Agent sets the status code in the Binding Update, the Home Agent sets the status code in the Binding
Acknowledgement to '142' (Not Authorized for Prefix) in order to Acknowledgement to 142 (Not Authorized for Prefix) to indicate this.
indicate this.
The Home Agent sets the status code to 143 (Forwarding Setup The Home Agent sets the status code to 143 (Forwarding Setup failed)
failed) if it is unable to determine the information needed to setup if it is unable to determine the information needed to set up
forwarding for the mobile network. This is used in the Implicit mode forwarding for the Mobile Network. This is used in the Implicit
where the Mobile Router does not include any prefix information in mode, in which the Mobile Router does not include any prefix
the Binding Update. information in the Binding Update.
6.7. Mobile Network Prefix De-Registration 6.7. Mobile Network Prefix De-registration
The Mobile Router de-registers with the Home Agent by sending a When the Home Agent successfully processes the de-registration BU, it
Binding Update with the lifetime set to zero. When the Home Agent deletes the Binding Cache Entry for the Mobile Router's Home Address
successfully processes the de-registration BU, it deletes the Binding and stops proxying the Home Address. This is described in detail in
Cache Entry for the Mobile Router's Home Address and stops proxying the Mobile IPv6 specification [1].
the Home Address. This is described in detail in the Mobile IPv6
specification [1].
In addition, the Home Agent also removes the bi-directional tunnel In addition, the Home Agent removes the bi-directional tunnel and
and stops forwarding packets to the mobile network. The Home Agent stops forwarding packets to the Mobile Network. The Home Agent
should keep all necessary information to clean up whichever routes it should keep all necessary information to clean up whichever routes it
installed, whether they come from implicit or explicit source. installed, whether they come from an implicit or explicit source.
In Explicit mode, the Home Agent MUST ignore any Mobile Network In Explicit mode, the Home Agent MUST ignore any Mobile Network
Prefix Options present in the de-registration Binding Update. Prefix Options present in the de-registration Binding Update.
7. Modifications to Dynamic Home Agent Discovery 7. Modifications to Dynamic Home Agent Address Discovery
This document extends the Dynamic Home Agent Discovery mechanism This document extends the Dynamic Home Agent Address Discovery
defined in [1], so that Mobile Routers attempt registration only with (DHAAD) defined in [1] so that Mobile Routers only attempt
Home Agents that support Mobile Routers. registration with Home Agents that support them.
7.1. Modified Dynamic Home Agent Discovery Request 7.1. Modified Dynamic Home Agent Discovery Address Request
A new flag (R) (Support for Mobile Routers) is introduced in the A new flag (R) (Support for Mobile Routers) is introduced in the
Dynamic Home Agent Discovery Reguest message defined in [1]. The DHAAD Request message, defined in [1]. The Mobile Router sets this
Mobile Router sets this flag to indicate that it wants to discover flag to indicate that it wants to discover Home Agents supporting
Home Agents that support Mobile Routers. Mobile Routers.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |R| Reserved | | Identifier |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mobile Router Support Flag (R) Mobile Router Support Flag (R)
A 1 bit flag which when set indicates that the Mobile Router A one-bit flag that when set indicates that the Mobile Router
wants to discover Home Agents that support Mobile Routers. wants to discover Home Agents supporting Mobile Routers.
For a description of the other fields in the message, see [1]. For a description of the other fields in the message, see [1].
7.2. Modified Dynamic Home Agent Discovery Reply 7.2. Modified Dynamic Home Agent Discovery Address Request
A new flag (R) (Support for Mobile Routers) is introduced in the A new flag (R) (Support for Mobile Routers) is introduced in the
Dynamic Home Agent Discovery Reply message defined in [1]. If a Home DHAAD Reply message, defined in [1]. If a Home Agent receives a
Agent receives a Dynamic Home Agent Discovery request message with Dynamic Home Agent Discovery request message with the Mobile Router
the Mobile Router Support flag set, it MUST reply with a list of Home Support Flag set, it MUST reply with a list of Home Agents supporting
Agents that support Mobile Routers. The Mobile Router Support flag Mobile Routers. The Mobile Router Support Flag MUST be set if there
MUST be set if there is at least one Home Agent that supports Mobile is at least one Home Agent supporting Mobile Routers. If none of the
Routers. If none of the Home Agents support Mobile Routers, the Home Home Agents support Mobile Routers, the Home Agent MAY reply with a
Agent MAY reply with a list of Home Agents that support just Mobile list of Home Agents that only support Mobile IPv6 Mobile Nodes. In
IPv6 Mobile Nodes. In this case, the Mobile Router Support flag MUST this case, the Mobile Router Support Flag MUST be set to 0.
be set to 0.
The modified message format is as follows. The modified message format is as follows.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Code | Checksum | | Type | Code | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |R| Reserved | | Identifier |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
. .
. Home Agent Addresses .
. .
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mobile Router Support Flag (R) Mobile Router Support Flag (R)
A 1 bit flag which when set indicates that the Home Agents A one-bit flag that when set indicates that the Home Agents
listed in this message support Mobile Routers. listed in this message support Mobile Routers.
For a description of the other fields in the message, see [1]. For a description of the other fields in the message, see [1].
7.3. Modified Home Agent Information Option 7.3. Modified Home Agent Information Option
A new flag (R) (Support for Mobile Routers) is introduced in the Home A new flag (R) (Support for Mobile Routers) is introduced in the Home
Agent Information Option defined in [1]. If a Home Agent supports Agent Information Option defined in [1]. If a Home Agent supports
Mobile Routers, it SHOULD set the flag. Mobile Routers, it SHOULD set the flag.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |R| Reserved | | Type | Length |R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Home Agent Preference | Home Agent Lifetime | | Home Agent Preference | Home Agent Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mobile Router Support Flag (R) Mobile Router Support Flag (R)
A 1-bit flag which when set indicates that the Home Agent A one-bit flag that when set indicates that the Home Agent
supports Mobile Routers. supports Mobile Routers.
For a description of the other fields in the message, see [1]. For a description of the other fields in the message, see [1].
8. Support for Dynamic Routing Protocols 8. Support for Dynamic Routing Protocols
In the solution described so far, forwarding to the mobile network In the solution described so far, forwarding to the Mobile Network at
at the Home Agent is set up when the Home Agent receives a Binding the Home Agent is set up when the Home Agent receives a Binding
Update from the Mobile Router. An alternative to this is for the Update from the Mobile Router. An alternative to this is for the
Home Agent and the Mobile Router to run an intra-domain routing Home Agent and the Mobile Router to run an intra-domain routing
protocol like RIPng [12] and OSPF [13] through the bi-directional protocol such as RIPng [12] and OSPF [13] through the bi-directional
tunnel. The Mobile Router can continue running the same routing tunnel. The Mobile Router can continue running the same routing
protocol that it was running when it was attached to the home link. protocol that it ran when attached to the home link.
Support for running a intra-domain routing protocol is optional and Support for running a intra-domain routing protocol is optional and
is governed by the configuration on the Mobile Router and the Home is governed by the configuration on the Mobile Router and the Home
Agent. Agent.
This feature is very useful when the mobile network is large with This feature is very useful when the Mobile Network is large with
multiple subnets containing different IPv6 prefixes. Routing changes multiple subnets containing different IPv6 prefixes. Routing changes
in the mobile network are propagated to the Home Agent quickly. in the Mobile Network are quickly propagated to the Home Agent.
Routing changes in the home link are also propagated to the Mobile Routing changes in the home link are quickly propagated to the Mobile
Router very quickly. Router.
When the Mobile Router is attached to the home link, it runs a When the Mobile Router is attached to the home link, it runs a
routing protocol by sending routing updates through its egress routing protocol by sending routing updates through its egress
interface. When the mobile router moves and attaches to a visited interface. When the Mobile Router moves and attaches to a visited
network, it MUST stop sending routing updates on the interface network, it should stop sending routing updates on the interface by
with which it attaches to the visited link. This is to reduce the which it attaches to the visited link. This reduces the chances that
chances that prefixes specific to the Mobile Network are leaked to prefixes specific to the Mobile Network will be leaked to the visited
the visited network in the case where routing protocol authentication network if routing protocol authentication is not enabled in the
is not enabled in the visited network and in the Mobile Network. It visited network and in the Mobile Network. It is expected that
is expected that normal deployment practices will include proper normal deployment practices will include proper authentication
authentication mechanisms to prevent unauthorized route announcements mechanisms to prevent unauthorized route announcements on both the
on both home and visited networks. The Mobile Router then starts home and visited networks. The Mobile Router then starts sending
sending routing protocol messages through the bi-directional tunnel routing protocol messages through the bi-directional tunnel toward
towards the Home Agent. Most routing protocols use link local the Home Agent. Most routing protocols use link-local addresses as
addresses as source addresses for the routing information messages. source addresses for the routing information messages. The Mobile
The Mobile Router is allowed to use link local addresses for the Router is allowed to use link-local addresses for the inner IPv6
inner IPv6 header of an encapsulated packet. But these routing header of an encapsulated packet. But these MUST NOT be forwarded to
protocol messages with link local address MUST NOT be forwarded to
another link by either the Mobile Router or the Home Agent. another link by either the Mobile Router or the Home Agent.
When the Home Agent receives the inner packet, it processes the When the Home Agent receives the inner packet, it processes the
encapsulated routing protocol messages and updates its routing table encapsulated routing protocol messages and updates its routing table
accordingly. As part of normal routing protocol operation, the next accordingly. As part of normal routing protocol operation, the next
hop information in these routing entries is filled with the Mobile hop information in these routing entries is filled with the Mobile
Router's link local address with the outgoing interface set to the Router's link-local address, with the outgoing interface set to the
bi-directional tunnel. bi-directional tunnel.
Similary, the Home Agent also sends routing updates through the Similarly, the Home Agent sends routing updates through the bi-
bi-directional tunnel to the Mobile Router. The Mobile Router directional tunnel to the Mobile Router. The Mobile Router processes
processes these routing protocol messages and updates its routing these routing protocol messages and updates its routing table. For
table. For all routes advertised by the Home Agent, the Mobile all routes advertised by the Home Agent, the Mobile Router sets the
Router sets the outgoing interface to the bi-directional tunnel to outgoing interface to the bi-directional tunnel to the Home Agent.
the Home Agent.
When the Mobile Router and the Home Agent exchange routes through When the Mobile Router and the Home Agent exchange routes through a
a dynamic routing protocol, the Mobile Router SHOULD NOT include dynamic routing protocol, the Mobile Router SHOULD NOT include Mobile
Mobile Network Prefixes in the Binding Update to the Home Agent. The Network Prefixes in the Binding Update to the Home Agent. Depending
Home Agent depending on its configuration might not add routes based on its configuration, the Home Agent might not add routes based on
on the prefix information in the Binding Updates at all, and might the prefix information in the Binding Updates and might use only the
use only the routing protocol updates. Moreover, including prefix routing protocol updates. Moreover, including prefix information in
information in both the Binding Updates and the routing protocol both the Binding Updates and the routing protocol updates is
updates is redundant. redundant.
Since the routing protocol messages from the Home Agent to the As the routing protocol messages from the Home Agent to the Mobile
Mobile Router could potentially contain information about the Router could potentially contain information about the internal
internal routing structure of the home network, these messages routing structure of the home network, these messages require
require authentication and confidentiality protection. Appropriate authentication and confidentiality protection. Appropriate
authentication and confidentiality protection mechanisms defined in authentication and confidentiality protection mechanisms, defined in
[14] MUST be used. For protecting routing protocol messages using [14], MUST be used. For protecting routing protocol messages by
ESP, the bi-directional tunnel between the Mobile Router and the using IPsec ESP [4], the bi-directional tunnel between the Mobile
Home Agent should be treated as the outgoing interface, with the Router and the Home Agent should be treated as the outgoing
Home Agent's and Mobile Router's addresses as source and destination interface, with the Home Agent and Mobile Router's addresses as
addresses for the inner encapsulated messages. source and destination addresses for the inner encapsulated messages.
If a link state routing protocol like OSPFv3 is run by the Mobile If a link state routing protocol such as OSPFv3 is run by the Mobile
Router and the Home Agent, the recommendations in Appendix B should Router and the Home Agent, the recommendations in Appendix B should
be followed. be followed.
9. Security Considerations 9. Security Considerations
All signaling messages between the Mobile Router and the Home Agent All signaling messages between the Mobile Router and the Home Agent
MUST be authenticated by IPsec [8]. The use of IPsec to protect MUST be authenticated by IPsec [8]. The use of IPsec to protect
Mobile IPv6 signaling messages is described in detail in the HA-MN Mobile IPv6 signaling messages is described in detail in the HA-MN
IPsec specification [2]. The signaling messages described in this IPsec specification [2]. The signaling messages described in this
document just extend Mobile IPv6 messages and do not require any document extend Mobile IPv6 messages and do not require any changes
changes to what is described in the HA-MN IPsec specification. to what is described in [2].
The Mobile Router has to perform ingress filtering on packets The Mobile Router has to perform ingress filtering on packets
received from the mobile network to ensure that nodes in the Mobile received from the Mobile Network to ensure that nodes in the Mobile
Network do not use the bi-directional tunnel to launch IP spoofing Network do not use the bi-directional tunnel to launch IP spoofing
attacks. In particular the Mobile Router SHOULD check that the IP attacks. In particular, the Mobile Router SHOULD check that the IP
source address in the packets received from the nodes in the Mobile source addresses in the packets received belong to the Mobile Network
Network belongs to the Mobile Network Prefix and is not the same as Prefix and are not the same as one of the addresses used by the
one of the addresses used by the Mobile Router. In case the Mobile Mobile Router. If the Mobile Router receives an IP-in-IP tunneled
Router receives a IP-in-IP tunneled packet from a node in the Mobile packet from a node in the Mobile Network and it has to forward the
Network and the Mobile Router has to forward the decapsulated packet, decapsulated packet, it SHOULD perform the above mentioned checks on
it SHOULD perform the above mentioned checks on the source address of the source address of the inner packet.
the inner packet.
The Home Agent has to verify that packets received through the The Home Agent has to verify that packets received through the bi-
bi-directional tunnel belong to the mobile network. This check is directional tunnel belong to the Mobile Network. This check is
necessary in order to prevent nodes from using the Home Agent to necessary to prevent nodes from using the Home Agent to launch
launch attacks that would have otherwise been prevented by ingress attacks that would have otherwise been prevented by ingress
filtering. The source address of the outer IPv6 header MUST be set filtering. The source address of the outer IPv6 header MUST be set
to the Mobile Router's current Care-of address. The source address to the Mobile Router's current Care-of Address. The source address
of the inner IPv6 header MUST be a topologically correct address with of the inner IPv6 header MUST be topologically correct with respect
respect to the IPv6 prefixes used in the mobile network. to the IPv6 prefixes used in the Mobile Network.
When the Mobile Router is running a dynamic routing protocol as If the Mobile Router sends a Binding Update with a one or more Mobile
described in Section 8, it injects routing update messages into Network Prefix options, the Home Agent MUST be able to verify that
the Home Link. Since the routing protocol message could contain the Mobile Router is authorized for the prefixes before setting up
information about the internal routing structure of the home network, forwarding for the prefixes.
these messages require confidentiality protection. Confidentiality
protection through IPsec ESP as described in [14] SHOULD be used. When the Mobile Router runs a dynamic routing protocol as described
in section 8, it injects routing update messages into the Home Link.
As the routing protocol message could contain information about the
internal routing structure of the home network, these messages
require confidentiality protection. The Mobile Router SHOULD use
confidentiality protection through IPsec ESP as described in [14].
If the bi-directional tunnel between the Mobile Router and the Home If the bi-directional tunnel between the Mobile Router and the Home
Agent is protected by ESP in tunnel mode for all IP traffic, then Agent is protected by ESP, in tunnel mode for all IP traffic, then no
no additional confidentiality protection specific to the routing additional confidentiality protection specific to the routing
protocol is required. protocol is required.
Home agents and mobile routers may use IPsec ESP to protect payload Home Agents and Mobile Routers may use IPsec ESP to protect payload
packets tunneled between themselves. This is useful to protect packets tunneled between themselves. This is useful to protect
communications against attackers on the path of the tunnel. communications against attackers on the path of the tunnel.
Please refer to the Mobile IPv6 specification [1] for security Please refer to the Mobile IPv6 specification [1] for security
considerations when the Mobile Router operates as a Mobile Host. considerations when the Mobile Router operates as a Mobile Host.
10. IANA Considerations 10. IANA Considerations
This document defines a new Mobility Header Option, the Mobile This document defines a new Mobility Header Option, the Mobile
Network Prefix Option. This option is described in Section 4.3. The Network Prefix Option as described in section 4.3. The type value
type value for this option needs to be assigned from the same space for this option MUST be assigned from the same space used by the
used by the mobility options defined in [1]. mobility options defined in [1].
This document also defines the following new Binding Acknowledgement This document also defines the following new Binding Acknowledgement
status values. These status values are defined in Section 4.2 status values. These status values are defined in section 4.2 and
and need to be assigned from the same space used for Binding MUST be assigned from the same space used for Binding Acknowledgement
Acknowledgement status values in [1]. status values in [1].
- Mobile Router Operation not permitted - Mobile Router Operation not permitted
- Invalid Prefix - Invalid Prefix
- Not Authorized for Prefix - Not Authorized for Prefix
- Forwarding Setup failed (prefixes missing)
- Forwarding Setup failed
11. Contributors 11. Contributors
We would like to acknowledge Ludovic Bellier, Claude Castelluccia, We would like to acknowledge Ludovic Bellier, Claude Castelluccia,
Thierry Ernst, Miguel Catalina-Gallego, Christophe Janneteau, T.J. Thierry Ernst [15], Miguel Catalina-Gallego, Christophe Janneteau,
Kniveton, Hong-Yon Lach, Jari T. Malinen, Koshiro Mitsuya, Alexis T.J. Kniveton, Hong-Yon Lach, Jari T. Malinen, Koshiro Mitsuya,
Olivereau, Charles E. Perkins and Keisuke Uehara, for their work on Alexis Olivereau, Charles E. Perkins, and Keisuke Uehara for their
earlier proposals for Network Mobility. This document inherits a lot work on earlier proposals for Network Mobility. This document has
of ideas from these proposals. inherited a lot of ideas from these proposals.
12. Acknowledgements 12. Acknowledgements
We thank all members of the NEMO Working Group, and of the preceding We thank all members of the NEMO Working Group, and of the preceding
MONET BoF for fruitful discussions on the mailing list and at IETF MONET BoF, for fruitful discussions on the mailing list and at IETF
meetings. meetings.
Kent Leung, Marco Molteni and Patrick Wetterwald for their work on Kent Leung, Marco Molteni, and Patrick Wetterwald are acknowledged
Network Mobility for IPv4 and IPv6. for their work on Network Mobility for IPv4 and IPv6.
Tim Leinmueller for many insightful remarks and for Section 7. Tim Leinmueller is acknowledged for many insightful remarks and for
section 7.
Jari Arkko, James Kempf and Chan-Wah Ng for their thorough review and Jari Arkko, James Kempf, Chan-Wah Ng, and Erik Nordmark are
comments. acknowledged for their thorough review and comments.
Normative References Souhwan Jung, Fan Zhao, S. Felix Wu, HyunGon Kim, and SungWon Sohn
are acknowledged for identifying threats related to tunneling between
the Mobile Network and the Home Agent.
[1] D. Johnson, C. Perkins and J. Arkko. Mobility Support in IPv6. 13. References
Internet Draft, IETF. draft-ietf-mobileip-ipv6-24.txt (work in
progress). June 2003.
[2] J. Arkko, V. Devarapalli and F. Dupont. Using IPsec to Protect 13.1. Normative References
Mobile IPv6 Signaling between Mobile Nodes and Home Agents.
Internet Draft, IETF. draft-ietf-mobileip-mipv6-ha-ipsec-06.txt
(work in progress). June 2003.
[3] A. Conta and S. Deering. Generic Packet Tunneling in IPv6 [1] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
Specification. RFC 2473, IETF. December 1998. IPv6", RFC 3775, June 2004.
[4] S. Kent and R. Atkinson. IP Encapsulating Security Payload [2] Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
(ESP). RFC 2402, IETF. November 1998. Protect Mobile IPv6 Signaling between Mobile Nodes and Home
Agents", RFC 3776, June 2004.
[5] S. Deering and R. Hinden. Internet Protocol, Version 6 (IPv6) [3] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
Specification. RFC 2460, IETF. December 1998. Specification", RFC 2473, December 1998.
[6] T. Narten, E. Nordmark and W. Simpson. Neighbour Discovery for [4] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload
IP Version 6 (IPv6). RFC 2461, IETF. December 1998. (ESP)", RFC 2406, November 1998.
[7] S. Bradner. Key words for use in RFCs to Indicate Requirement [5] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Levels. RFC 2119, IETF. March 1997. Specification", RFC 2460, December 1998.
Informative References [6] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
for IP Version 6 (IPv6)", RFC 2461, December 1998.
[8] S. Kent and R. Atkinson. Security Architecture for the Internet [7] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Protocol. RFC 2401, IETF. November 1998. Levels", BCP 14, RFC 2119, March 1997.
[9] J. Manner and M. Kojo. Mobility Related Terminology. Internet 13.2. Informative References
Draft, IETF. draft-ietf-seamoby-mobility-terminology-05.txt
(work in progress). November 2003.
[10] T. Ernst and H.-Y. Lach. Network Mobility Support Terminology. [8] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Draft, IETF. draft-ietf-nemo-terminology-00.txt (work Internet Protocol", RFC 2401, November 1998.
in progress). May 2003.
[11] T. Ernst. Network Mobility Support Goals and Requirements. [9] Manner, J. and M. Kojo, Eds., "Mobility Related Terminology",
Internet Draft, IETF. draft-ietf-nemo-requirements-01.txt (work RFC 3753, June 2004.
in progress). May 2003.
[12] G. Malkin and R. Minnear. RIPng for IPv6. RFC 2080, IETF. [10] Ernst, T., and H.-Y. Lach, "Network Mobility Support
January 1997. Terminology", Work in Progress, October 2004.
[13] R. Coltun, D. Ferguson and J. Moy. OSPF for IPv6. RFC 2470, [11] Ernst, T., "Network Mobility Support Goals and Requirements",
IETF. December 1999. Work in Progress, October 2004.
[14] M. Gupta and N. Melam. Authentication/Confidentiality for [12] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080, January
OSPFv3. Internet Draft, IETF. draft-ietf-ospf-ospfv3-auth-04.txt 1997.
(work in progress). December 2003.
[15] T. Ernst. Network Mobility Support in IPv6. PhD Thesis, [13] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC 2740,
University Joseph Fourier, Grenoble, France. October 2001. December 1999.
[16] T. Ernst, K, Mitsuya and K. Uehara. Network Mobility from the [14] Gupta, M. and N. Melam, "Authentication/Confidentiality for
InternetCAR perspective. Journal of Interconnection Networks OSPFv3", Work in Progress, December 2004.
(JOIN), Vol. 4, No. 3. September 2003.
[17] J. Moy. Extending OSPF to Support Demand Circuits. RFC 1793, [15] Ernst, T., "Network Mobility Support in IPv6", PhD Thesis,
IETF. April 1995. University Joseph Fourier, Grenoble, France. October 2001.
[18] P. Thubert, et. al. NEMO Home Network models. Internet Draft, [16] Moy, J., "Extending OSPF to Support Demand Circuits", RFC 1793,
IETF. draft-ietf-home-network-models-00.txt (work in progress). April 1995.
April 2004.
A. Examples of NEMO Basic Support Operation [17] Thubert, P., et al., "NEMO Home Network models", Work in
Progress, October 2004.
This section tries to illustrate the NEMO protocol using a Mobile Appendix A. Examples of NEMO Basic Support Operation
This section tries to illustrate the NEMO protocol by using a Mobile
Router and a Mobile Node belonging to different administrative Router and a Mobile Node belonging to different administrative
domains. The Mobile Router's mobile network consists of a Local domains. The Mobile Router's Mobile Network consists of a Local
Fixed Node (LFN) and a Local Fixed Router (LFR) [10]. The LFR has Fixed Node (LFN) and a Local Fixed Router (LFR) [10]. The LFR has an
an access link to which other Mobile Nodes or Mobile Routers could access link to which other Mobile Nodes or Mobile Routers could
attach to. attach.
Figure 1 depicts the scenario where both the Mobile Router and the Figure 1 depicts the scenario where both the Mobile Router and the
Mobile Node are at home. Mobile Node are at home.
+----+ +-------+ +----+ +-------+
| MN | | HA_MN | | MN | | HA_MN |
+--+-+ 1:: +---+---+ +--+-+ 1:: +---+---+
2+-------------+3 2+-------------+3
| |
| |
skipping to change at page 32, line 41 skipping to change at page 27, line 41
+--+-+ +-------+ +--+-+ +-------+
5:: |1 5:: |1
---------- ----------
2| |3 2| |3
+--+-+ +--+-+ +--+-+ +--+-+
| LFN| | LFR| | LFN| | LFR|
+--+-+ +--+-+ +--+-+ +--+-+
6:: |1 6:: |1
---------- ----------
Figure 1: Mobile Router and Mobile Node at home. Figure 1. Mobile Router and Mobile Node at home.
The Mobile Router then moves away from the home link and attaches to The Mobile Router then moves away from the home link and attaches to
a visited link. This is shown in Figure 2. The Mobile Router sends a visited link. This is shown in Figure 2. The Mobile Router sends
a Binding Update to HA_MR when it attaches to a visited link and a Binding Update to HA_MR when it attaches to a visited link and
configures a Care-of Addres. HA_MR creates a binding cache entry for configures a Care-of Address. HA_MR creates a binding cache entry
the Mobile Router's Home Address and also sets up forwarding for the for the Mobile Router's Home Address and also sets up forwarding for
prefixes on the mobile network. the prefixes on the Mobile Network.
+----+ +-------+ +----+ +-------+
| MN | | HA_MN | | MN | | HA_MN |
+--+-+ 1:: +---+---+ +--+-+ 1:: +---+---+
2+-------------+3 2+-------------+3
| |
| |
+-------+2 2:: +-------------------+ 3:: 2+-------+ +-------+2 2:: +-------------------+ 3:: 2+-------+
| CN_MN |------| Internet |------| CN_MR | | CN_MN |------| Internet |------| CN_MR |
+-------+ ++------------------+ +-------+ +-------+ ++------------------+ +-------+
skipping to change at page 33, line 36 skipping to change at page 28, line 36
+--+-+ +-------+ 5::/prefixlen -> forward +--+-+ +-------+ 5::/prefixlen -> forward
5:: |1 to MR 5:: |1 to MR
---------- 6::/prefixlen -> forward ---------- 6::/prefixlen -> forward
2| |3 to MR 2| |3 to MR
+--+-+ +--+-+ +--+-+ +--+-+
| LFN| | LFR| | LFN| | LFR|
+--+-+ +--+-+ +--+-+ +--+-+
6:: |1 6:: |1
---------- ----------
Figure 2: Mobile Router on a Visited Link. Figure 2. Mobile Router on a visited link.
Figure 3 shows the Mobile Node moving away from its home link and Figure 3 shows the Mobile Node moving away from its home link and
attaching to the Mobile Router. The Mobile Node configures a Care-of attaching to the Mobile Router. The Mobile Node configures a Care-of
Address from the prefix advertised on the mobile network and sends a Address from the prefix advertised on the Mobile Network and sends a
Binding Update to its Home Agent (HA_MN) and its Correspondent Node Binding Update to its Home Agent (HA_MN) and to its Correspondent
(CN_MN). Both HA_MN and CN_MN create binding cache entries for the Node (CN_MN). Both HA_MN and CN_MN create binding cache entries for
Mobile Node's Home Address. the Mobile Node's Home Address.
+-------+ +-------+
| HA_MN | 1::2->6::2 | HA_MN | 1::2->6::2
1:: +---+---+ 1:: +---+---+
---------|3 ---------|3
| |
| |
+-------+2 2:: +-------------------+ 3:: 2+-------+ +-------+2 2:: +-------------------+ 3:: 2+-------+
| CN_MN |------| Internet |------| CN_MR | | CN_MN |------| Internet |------| CN_MR |
+-------+ ++------------------+ +-------+ +-------+ ++------------------+ +-------+
skipping to change at page 34, line 40 skipping to change at page 29, line 40
+--+-+ +--+-+ +--+-+ +--+-+
| LFN| | LFR| | LFN| | LFR|
+--+-+ +--+-+ +--+-+ +--+-+
6:: |1 6:: |1
--------+- --------+-
|2 |2
+--+-+ +--+-+
| MN | | MN |
+----+ +----+
Figure 3: Mobile Node attached to Mobile Figure 3. Mobile Node attached to Mobile
Router on a Visited Link Router on a visited link
B. Running Link State Routing Protocol with NEMO Basic Support Appendix B. Running Link State Routing Protocol with NEMO Basic Support
The bi-directional tunnel between the Mobile Router and the Home The bi-directional tunnel between the Mobile Router and the Home
Agent is used a virtual interface over which routing protocol Agent is used as a virtual interface over which routing protocol
messages are exchanged. When a link state routing protocol is run messages are exchanged. When a link state routing protocol is run,
the following recommendations should be followed. the following recommendations should be followed.
B.1. Tunnel Interface Considerations B.1. Tunnel Interface Considerations
If the tunnel interface goes up and down every time the Mobile Router If the tunnel interface goes up and down every time the Mobile Router
moves to a new visited network, with high level of mobility and moves to a new visited network with a high level of mobility and a
sufficient number of mobile routers, the amount of interface state sufficient number of Mobile Routers, the amount of interface state
changes will adversely affect the Home Agent performance. This also changes will adversely affect the Home Agent's performance. This
introduces a high level of instability in the home network. To also introduces a high level of instability in the home network. To
avoid this, the following should be considered when implementing the avoid this, the following should be considered when the bi-
bi-directional tunnel. directional tunnel is implemented:
- A tunnel inteface is consistently assigned to each Mobile Router - A tunnel interface is consistently assigned to each Mobile Router,
as long as it has a valid binding cache at the Home Agent as long as it has a valid binding cache at the Home Agent.
- Everytime the Mobile Router moves and updates the binding cache - Everytime the Mobile Router moves and updates the binding cache
entry, the bi-directional tunnel should not be torn down and entry, the bi-directional tunnel should not be torn down and set
setup again. The tunnel end points should be updated dynamically up again. The tunnel end points should be updated dynamically
with the Mobile Router's current care-of address. with the Mobile Router's current Care-of Address.
- With a large number of interfaces, Hello packet processing may - With a large number of interfaces, Hello packet processing may
become a burden. Therefore the tunnel interface should be become a burden. Therefore, the tunnel interface should be
treated as On-Demand circuits for OSPF [17]. treated as On-Demand circuits for OSPF [16].
B.2. OSPF Area Considerations B.2. OSPF Area Considerations
The following should be considered when the Home Network is The following should be considered when the Home Network is
configured for running OSPF. configured for running OSPF:
- The entire Home domain SHOULD NOT be configured as a single area - The entire Home domain SHOULD NOT be configured as a single area
if a Home Agent supports Mobile Routers. At least the Home if a Home Agent supports Mobile Routers. At least the home
Network should be configured as a separate area. network should be configured as a separate area.
- The bi-directional tunnel interfaces to the Mobile Routers should - The bi-directional tunnel interfaces to the Mobile Routers should
never be included in the same area as the backbone links. never be included in the same area as the backbone links.
For a more detailed discussion on configuring a Home Network for NEMO For a more detailed discussion on configuring a home network for NEMO
Basic Support, please see [18]. Basic Support, please see [17].
One disadvantage of running OSPFv3 with NEMO Basic Support is that One disadvantage of running OSPFv3 with NEMO Basic Support is the
there is a possibility that the Mobile Networks will be told of the possibility that the Mobile Networks will be told of the topology of
topology of the entire Home Network, including all the fixed and the entire home network, including all the fixed and Mobile Routers.
mobile routers, while the only thing the Mobile Routers might really The only thing the Mobile Routers might really need is a default
need is a default route through the Home Agent. route through the Home Agent.
To reduce the amount of routing protocol messages received by a To reduce the amount of routing protocol messages received by a
Mobile Router, one can configure each bi-directional tunnel to a Mobile Router, one can configure each bi-directional tunnel to a
Mobile Router as a separate area. But this requires that the Home Mobile Router as a separate area. But this requires that the Home
Agent support a large number of OSPF areas if it supports a large Agent support a large number of OSPF areas if it supports a large
number of Mobile Routers and might not be possible with most router number of Mobile Routers, and it might not be possible with most
implementations. router implementations.
Another option is to configure multiple areas on the Home Link and Another option is to configure multiple areas on the Home Link and
group a number of Mobile Routers into each area. This reduces the group a number of Mobile Routers into each area. This reduces the
number of areas that a Home Agent needs to support, but at the same number of areas that a Home Agent needs to support but also reduces
time reduces the amount of routing protocol traffic that a Mobile the amount of routing protocol traffic that a Mobile Router receives.
Router receives.
C. Changes from Previous Version
The following changes have been made to this document from version 02
- Clarified that Mobile Network Prefix Options should be ignored in
de-registration binding updates. (Issue #30)
- Addressed tunnel interface concerns when dynamic routing
protocols are used. Added section B.1. (Issue #31)
- Addressed OSPF Area configuration considerations. Added section
B.2. (Issue #31)
- Clarified the use of link local addresses on the inner
encapsulated packets when routing protocol messages are exchanged
between the Mobile Router and the Home Agent. (Issue #31)
- Clarified that binding acknowledgement status values are in
decimal. (Issue #32)
- Clarifed that the Home Agent does not have to check the source
address of the outer IPv6 header against the binding cache if the
tunneled packet is protected by ESP in tunneled mode. (Issue
#33)
- Fixed the text which says Mobile Router does not process binding
acknowledgement with status value 140. (Issue #33)
- Added text to clarify the relationship between the use of a
Prefix Table and running a dynamic routing protocol. (Issue #33)
- Clarified the terminology used in describing bi-directional
tunnel setup. (Issue #34)
- Added text to specify that the Mobile Router has to implement
atleast one mode and may implement both. (Issue #34)
- Re-wrote section 5.4 for better clarity. (Issue #34)
- Mobile Router Flag in Binding Update conflicts with HMIPv6's M
flag. Moved the flag to a new position. (Issue #35)
- Clarified Binding Acknowledgement status value 139 and the Mobile
Router Flag. (Issue #38)
Authors' Address Authors' Addresses
Vijay Devarapalli Vijay Devarapalli
Nokia Research Center Nokia Research Center
313 Fairchild Drive 313 Fairchild Drive
Mountain View, CA 94043 Mountain View, CA 94043
USA USA
Email: vijay.devarapalli@nokia.com
EMail: vijay.devarapalli@nokia.com
Ryuji Wakikawa Ryuji Wakikawa
Keio University and WIDE Keio University and WIDE
5322 Endo Fujisawa Kanagawa 5322 Endo Fujisawa Kanagawa
252-8520 Japan 252-8520
Email: ryuji@sfc.wide.ad.jp Japan
EMail: ryuji@sfc.wide.ad.jp
Alexandru Petrescu Alexandru Petrescu
Motorola Labs Motorola Labs
Parc les Algorithmes Saint Aubin Parc les Algorithmes Saint Aubin
Gif-sur-Yvette 91193 Gif-sur-Yvette 91193
France France
Email: Alexandru.Petrescu@motorola.com
EMail: Alexandru.Petrescu@motorola.com
Pascal Thubert Pascal Thubert
Cisco Systems Technology Center Cisco Systems Technology Center
Village d'Entreprises Green Side Village d'Entreprises Green Side
400, Avenue Roumanille 400, Avenue Roumanille
Biot - Sophia Antipolis 06410 Biot - Sophia Antipolis 06410
France France
Email: pthubert@cisco.com
Intellectual Property Statement EMail: pthubert@cisco.com
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Internet Society. Internet Society.
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