MIP4 K. Leung
Internet-Draft G. Dommety
Intended status: Standards Track Cisco Systems
Expires: July 24, 2008 V. Narayanan
Qualcomm, Inc.
A. Petrescu
Motorola
January 21, 2008
Network Mobility (NEMO) Extensions for Mobile IPv4
draft-ietf-mip4-nemo-v4-base-08.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
This document describes a protocol for supporting Mobile Networks
between a Mobile Router and a Home Agent by extending the Mobile IPv4
protocol. A Mobile Router is responsible for the mobility of one or
more network segments or subnets moving together. The Mobile Router
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hides its mobility from the nodes on the mobile network. The nodes
on the Mobile Network may be fixed in relationship to the Mobile
Router and may not have any mobility function.
Extensions to Mobile IPv4 are introduced to support Mobile Networks.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Mobile Network Extensions . . . . . . . . . . . . . . . . . . 5
4.1. Mobile Network Request Extension . . . . . . . . . . . . . 5
4.2. Mobile Network Acknowledgement Extension . . . . . . . . . 6
5. Mobile Router Operation . . . . . . . . . . . . . . . . . . . 8
5.1. Error Processing . . . . . . . . . . . . . . . . . . . . . 9
6. Home Agent Operation . . . . . . . . . . . . . . . . . . . . . 9
6.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.2. Data Structures . . . . . . . . . . . . . . . . . . . . . 10
6.2.1. Registration Table . . . . . . . . . . . . . . . . . . 10
6.2.2. Prefix Table . . . . . . . . . . . . . . . . . . . . . 11
6.3. Mobile Network Prefix Registration . . . . . . . . . . . . 11
6.4. Advertising Mobile Network Reachability . . . . . . . . . 12
6.5. Establishment of Bi-directional Tunnel . . . . . . . . . . 13
6.6. Sending Registration Replies . . . . . . . . . . . . . . . 13
6.7. Mobile Network Prefix De-registration . . . . . . . . . . 13
7. Data Forwarding Operation . . . . . . . . . . . . . . . . . . 14
8. Nested Mobile Networks . . . . . . . . . . . . . . . . . . . . 14
9. Routing Protocol between Mobile Router and Home Agent . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10.1. Security when Dynamic Routing Protocol is Used . . . . . . 17
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
13.1. Normative References . . . . . . . . . . . . . . . . . . . 19
13.2. Informative References . . . . . . . . . . . . . . . . . . 19
Appendix A. ChangeLog . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Intellectual Property and Copyright Statements . . . . . . . . . . 25
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1. Introduction
This document describes protocol extensions to Mobile IPv4 as per
RFC 3344 [RFC3344] and its update [I-D.ietf-mip4-rfc3344bis], to
enable support for Mobile Networks. This draft addresses mainly the
co-located Care-of Address mode. Foreign Agent Care-of Address mode
(with 'legacy' Foreign Agents, RFC 3344 [RFC3344]) are supported but
without optimization, double encapsulation being used. For an
optimization of this mode, the gentle reader is directed to an
extension document [I-D.ietf-mip4-nemov4-fa].
A Mobile Network is defined as a network segment or subnet that can
change its point of attachment to the routing infrastructure. Such
movement is performed by a Mobile Router, which is the mobility
entity that provides connectivity and reachability as well as session
continuity for all the nodes in the Mobile Network. The Mobile
Router typically serves as the default gateway for the hosts on the
Mobile Network.
Mobility for the Mobile Network is supported by the Mobile Router
registering the point of attachment to its Home Agent. This
signaling sets up the tunnel between the two entities.
The Mobile Networks (either implicitly configured on the Home Agent
or explicitly identified by the Mobile Router) are advertised by the
Home Agent for route propagation. Traffic to and from nodes in the
Mobile Network are tunneled by the Home Agent to the Mobile Router,
and vice versa. Though packets from the Mobile Network can be
forwarded directly without tunneling (if reverse tunneling is not
used) packets will be dropped if ingress filtering is turned on.
This document specifies an additional tunnel between a Mobile
Router's Home Address and the Home Agent. This tunnel is
encapsulated within the normal tunnel between the Care-of Address
(CoA) and Home Agent. In Foreign Agent CoA mode, the tunnel between
the Mobile Router and Home Agent is needed to allow the Foreign Agent
to direct the decapsulated packet to the proper visiting Mobile
Router. However, in Collocated CoA mode, the additional tunnel is
not essential and could be eliminated because the Mobile Router is
the recipient of the encapsulated packets for the Mobile Network; a
proposal for this feature is in an extension document
[I-D.ietf-mip4-nemov4-fa].
All traffic between the nodes in the Mobile Network and Correspondent
Nodes passes through the Home Agent. This document does not cover
route optimization of this traffic.
A similar protocol has been documented in RFC 3963 [RFC3963] for
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supporting IPv6 mobile networks with Mobile IPv6 extensions.
Multihoming for Mobile Routers is outside the scope of this document.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Terminology for network mobility support is defined in RFC 3344
[RFC3344] and its update [I-D.ietf-mip4-rfc3344bis]. In addition,
this document defines the following terms.
Mobile Network Prefix
The network prefix of the subnet delegated to a Mobile Router
as the Mobile Network.
Prefix Table
A list of Mobile Network Prefixes indexed by the Home Address
of a Mobile Router. The Home Agent manages and uses Prefix
Table to determine which Mobile Network Prefixes belong to a
particular Mobile Router.
3. Requirements
Although the original Mobile IPv4 specifications stated that Mobile
Networks can be supported by the Mobile Router and Home Agent using
static configuration or running a routing protocol (see Section 4.5
of RFC 3344 [RFC3344]), there is no solution for explicit
registration of the Mobile Networks served by the Mobile Router. A
solution needs to provide the Home Agent a means to ensure that a
Mobile Router claiming a certain Mobile Network Prefix is authorized
to do so. A solution would also expose the Mobile Network Prefixes
(and potentially other subnet-relevant information) in the exchanged
messages, to aid in network debugging.
The following requirements for Mobile Network support are enumerated:
o A Mobile Router should be able to operate in explicit or implicit
mode. A Mobile Router may explicitly inform the Home Agent which
Mobile Network(s) need to be propagated via a routing protocol. A
Mobile Router may also function in implicit mode, where the Home
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Agent may learn the mobile networks through other means, such as
from the AAA server, via pre-configuration, or via a dynamic
routing protocol.
o The Mobile Network should be supported using Foreign Agents that
are compliant to RFC 3344 [RFC3344] without any changes ('legacy'
Foreign Agents).
o The mobile network should allow Fixed Nodes, Mobile Nodes, or
Mobile Routers to be on it.
4. Mobile Network Extensions
4.1. Mobile Network Request Extension
For Explicit Mode, the Mobile Router informs the Home Agent about the
Mobile Network Prefixes during registration. The Registration
Request contains zero, one or several Mobile Network Request
extensions in addition to any other extensions defined by or in the
context of RFC 3344 [RFC3344]. When several Mobile Networks are
needed to be registered, each is included in a separate Mobile
Network Request extension, with its own Type, Length, Sub-Type,
Prefix Length and Prefix fields. A Mobile Network Request extension
is encoded in Type-Length-Value (TLV) format and respects the
following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Sub-Type | Prefix Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
Mobile Network Extension (skippable type range to be assigned
by IANA).
Length:
6
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Sub-Type:
TBA (Mobile Network Request)
Prefix Length:
8-bit unsigned integer indicating the number of bits covering
the network part of the address contained in the Prefix
field.
Prefix:
32-bit unsigned integer in network byte-order containing an
IPv4 address whose first Prefix Length bits make up the
Mobile Network Prefix.
4.2. Mobile Network Acknowledgement Extension
The Registration Reply contains zero, one or several Mobile Network
Acknowledgement extensions in addition to any other extensions
defined by or in the context of RFC 3344 [RFC3344] and its update
[I-D.ietf-mip4-rfc3344bis]. For Implicit Mode, the Mobile Network
Acknowledgement informs the Mobile Router the prefixes for which the
Home Agent sets up forwarding with respect to this Mobile Router.
Policies such as permitting only traffic from these Mobile Networks
to be tunneled to the Home Agent may be applied by the Mobile Router.
For Explicit Mode, when several Mobile Networks are needed to be
acknowledged explicitly, each is included in a separate Mobile
Network Acknowledgement extension, with its own Type, Sub-Type,
Length and Prefix Length fields. At least one Mobile Network
Acknowledgement extension MUST be in a successful Registration Reply
to indicate to the Mobile Router that the Mobile Network Request
extension was processed, thereby not skipped by the Home Agent.
A Registration Reply may contain any non-zero number of Explicit Mode
and Implicit Mode Acknowledgements sub-types. Both sub-types can be
present in a single Registration Reply. A Mobile Network
Acknowledgement extension is encoded in Type-Length-Value (TLV)
format. When the registration is denied with code HA_MOBNET_ERROR,
the Code field in the extension provides the reason for the failure.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Sub-Type | Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Reserved | Prefix
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type:
TBA Mobile Network Extension (skippable type range to be
assigned by IANA).
Length:
8
Sub-Type:
TBA (Explicit Mode Acknowledgement)
TBA (Implicit Mode Acknowledgement)
Code:
Value indicating success or failure:
TBA Success
TBA Invalid prefix (MOBNET_INVALID_PREFIX_LEN)
TBA Mobile Router is not authorized for prefix
(MOBNET_UNAUTHORIZED)
TBA Forwarding setup failed (MOBNET_FWDING_SETUP_FAILED)
Prefix Length:
8-bit unsigned integer indicating the number of bits covering
the network part of the address contained in the Prefix
field.
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Reserved:
Sent as zero; ignored on reception.
Prefix:
32-bit unsigned integer in network byte-order containing an
IPv4 address whose first Prefix Length bits make up the
Mobile Network Prefix.
5. Mobile Router Operation
A Mobile Router's operation is generally derived from the behavior of
a Mobile Node, as set in RFC 3344 [RFC3344] and its update
[I-D.ietf-mip4-rfc3344bis]. In addition to maintaining mobility
bindings for its Home Address, the Mobile Router, together with the
Home Agent, maintains forwarding information for the Mobile Network
Prefix(es) assigned to the Mobile Router.
A Mobile Router SHOULD set the 'T' bit to 1 in all Registration
Request messages it sends to indicate the need for reverse tunnels
for all traffic. Without reverse tunnels, all the traffic from the
mobile network will be subject to ingress filtering in the visited
networks. Upon reception of a successful Registration Reply, the
Mobile Router processes the registration in accordance to RFC 3344
[RFC3344]. In addition, the following steps are taken:
o Check for Mobile Network Acknowledgement extension(s) in
Registration Reply
o Create tunnel to the Home Agent if registered in reverse tunneling
mode
o Set up default route via this tunnel or egress interface when
registered with or without reverse tunneling, respectively
In accordance with this specification, a Mobile Router may operate in
one of the following two modes: explicit and implicit. In explicit
mode, the Mobile Router includes Mobile Network Prefix information in
all Registration Requests (as Mobile Network Request extensions),
while in implicit mode it does not include this information in any
Registration Request. In this latter case, the Home Agent obtains
the Mobile Network Prefixes by other means than Mobile IP. One
example of obtaining the Mobile Network Prefix is through static
configuration on the Home Agent.
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A Mobile Router can obtain a Collocated or Foreign Agent Care-of
Address while operating in explicit or implicit modes.
For de-registration, the Mobile Router sends a registration request
with lifetime set to zero without any Mobile Network Request
extensions.
5.1. Error Processing
A Mobile Router interprets the values of the Code field in the Mobile
Network Acknowledgement Extension of the Registration Reply in order
to identify any error related to managing the Mobile Network Prefixes
by the Home Agent.
If the value of the Code field in the Registration Reply is set to
HA_MOBNET_DISALLOWED, then the Mobile Router MUST stop sending
Registration Requests with any Mobile Network Prefix extensions to
that Home Agent.
If the value of the Code field in the Registration Reply is set to
HA_MOBNET_ERROR then the Mobile Router MUST stop sending Registration
Requests that contain any of the Mobile Network Prefixes that are
defined by the values of the fields Prefix and Prefix Length in the
Mobile Network Acknowledgement extension. Note that the registration
is denied in this case and no forwarding for any Mobile Network
Prefixes would be set up by the Home Agent for the Mobile Router.
It is possible that the Mobile Router receives a Registration Reply
with no mobile network extensions if the registration was processed
by a Mobile IPv4 home agent that does not support this specification
at all. In that case, the absence of mobile network extensions must
be interpreted by the Mobile Router as the case where the Home Agent
does not support mobile networks.
All the error code values are TBA (To Be Assigned) subject to IANA
allocation.
6. Home Agent Operation
6.1. Summary
A Home Agent MUST support all the operations specified in RFC 3344
[RFC3344] and its update [I-D.ietf-mip4-rfc3344bis] for Mobile Node
support. The Home Agent MUST support both implicit and explicit
modes of operation for a Mobile Router.
The Home Agent processes the registration in accordance to RFC 3344
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[RFC3344], which includes route set up to the Mobile Router's Home
Address via the tunnel to the Care-of Address. In addition, for a
Mobile Router registering in explicit mode, the following steps are
taken:
1. Check that the Mobile Network Prefix information is valid
2. Ensure the Mobile Network Prefix(es) is or are authorized to be
on the Mobile Router
3. Create tunnel to the Mobile Router if it does not already exist
4. Set up route for the Mobile Network Prefix via this tunnel
5. Propagate Mobile Network Prefix routes via routing protocol if
necessary
6. Send the Registration Reply with the Mobile Network
Acknowledgement extension(s)
If there are any subnet routes via the tunnel to the Mobile Router
that are not specified in the Mobile Network extensions, these routes
are removed.
In the case where the Mobile Node is not permitted to act as a Mobile
Router, the Home Agent sends a registration denied message with error
code HA_MOBNET_DISALLOWED.
For a Mobile Router registering in implicit mode, the Home Agent
performs steps 3-6 above, once the registration request is processed
successfully.
For deregistration, the Home Agent removes the tunnel to the Mobile
Router and all routes using this tunnel. The Mobile Network
extensions are ignored.
6.2. Data Structures
6.2.1. Registration Table
The Registration Table in the Home Agent, in accordance with RFC 3344
[RFC3344] and its update [I-D.ietf-mip4-rfc3344bis], contains binding
information for every Mobile Node registered with it. RFC 3344
[RFC3344] and its update [I-D.ietf-mip4-rfc3344bis] define the format
of a Registration Table. In addition to all the parameters specified
by RFC 3344 [RFC3344] and its update [I-D.ietf-mip4-rfc3344bis], the
Home Agent MUST store the Mobile Network Prefixes associated with the
Mobile Router in the corresponding registration entry, when the
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corresponding registration was performed in explicit mode. When the
Home Agent is advertising reachability to Mobile Network Prefixes
served by a Mobile Router, the information stored in the Registration
Table can be used.
6.2.2. Prefix Table
The Home Agent must be able to authorize a Mobile Router for use of
Mobile Network Prefixes when the Mobile Router is operating in
explicit mode. Also, when the Mobile Router operates in implicit
mode, the Home Agent must be able to locate the Mobile Network
Prefixes associated with that Mobile Router. The Home Agent may
store the Home Address of the Mobile Router along with the mobile
network prefixes associated with that Mobile Router. If the Mobile
Router does not have a Home Address assigned, this table may store
the NAI RFC 2794 [RFC2794] of the Mobile Router that will be used in
dynamic Home Address assignment.
6.3. Mobile Network Prefix Registration
The Home Agent must process registration requests coming from Mobile
Routers in accordance with this section. The document RFC 3344
[RFC3344] and its update [I-D.ietf-mip4-rfc3344bis] specify that the
Home Address of a mobile node registering with a Home Agent must
belong to a prefix advertised on the home network. In accordance
with this specification, however, the Home Address must be configured
from a prefix that is served by the Home Agent, not necessarily the
one on the home network.
If the registration request is valid, the Home Agent checks to see if
there are any Mobile Network Prefix extensions included in the
Registration Request.
If so, the Mobile Network Prefix information is obtained from the
included extensions, and the Home Address from the Home Address field
of the Registration Request. For every Mobile Network Prefix
extension included in the registration request, the Home Agent MUST
perform a check against the Prefix Table. If the Prefix Table does
not contain at least one entry pairing that Home Address to that
Mobile Network Prefix then the check fails, otherwise it succeeds.
Following this check against the Prefix Table, the Home Agent MUST
construct a Registration Reply containing Mobile Network
Acknowledgement extensions. For a Mobile Network Prefix for which
the check was unsuccessfull the Code field in the corresponding
Mobile Network Acknowledgement extension should be set to
MOBNET_UNAUTHORIZED.
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For a Mobile Network Prefix for which the check was successfull the
Code field in the respective Mobile Network Acknowledgement
extensions should be set to 0.
The Home Agent MUST attempt to set up forwarding for each Mobile
Network Prefix extension for which the Prefix Table check was
successfull. If the forwarding setup fails for a particular Mobile
Network Prefix (for reasons like not enough memory available, or not
enough devices available, or other similar) the Code field in the
respective Mobile Network Acknowledgement extension should be set to
MOBNET_FWDING_SETUP_FAILED.
If forwarding and setup was successful for at least one Mobile
Network Prefix then the Code field of the Registration Reply message
should be set to 0. Otherwise that Code should be HA_MOBNET_ERROR.
If the registration request is sent in implicit mode, i.e., without
any Mobile Network Request extension, the Home Agent may use pre-
configured mobile network prefix information for the Mobile Router to
set up forwarding.
If the Home Agent is updating an existing binding entry for the
Mobile Router, it MUST check all the prefixes in the registration
table against the prefixes included in the registration request. If
one or more mobile network prefix is missing from the included
information in the registration request, it MUST delete those
prefixes from the registration table. Also, the Home Agent MUST
disable forwarding for those prefixes.
If all checks are successful, the Home Agent either creates a new
entry for the Mobile Router or updates an existing binding entry for
it and returns a successful registration reply back to the Mobile
Router or the Foreign Agent (if the registration request was received
from a Foreign Agent).
In accordance with RFC 3344 [RFC3344], the Home Agent does proxy ARP
for the Mobile Router Home Address, when the Mobile Router Home
Address is derived from the home network.
If the 'T' bit is set, the Home Agent creates a bi-directional tunnel
for the corresponding mobile network prefixes or updates the existing
bi-directional tunnel. This tunnel is maintained independent of the
reverse tunnel for the Mobile Router home address itself.
6.4. Advertising Mobile Network Reachability
If the mobile network prefixes served by the Home Agent are
aggregated with the home network prefix and if the Home Agent is the
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default router on the home network, the Home Agent does not have to
advertise the Mobile Network Prefixes. The routes for the Mobile
Network Prefix are automatically aggregated into the home network
prefix (it is assumed that the Mobile Network Prefixes are
automatically aggregated into the home network prefix). If the
Mobile Router updates the mobile network prefix routes via a dynamic
routing protocol, the Home Agent SHOULD propagate the routes on the
appropriate networks.
6.5. Establishment of Bi-directional Tunnel
The Home Agent creates and maintains a bi-directional tunnel for the
mobile network prefixes of a Mobile Router registered with it. A
home agent supporting IPv4 Mobile Router operation MUST be able to
forward packets destined to the mobile network prefixes served by the
Mobile Router to its Care-of Address. Also, the Home Agent MUST be
able to accept packets tunneled by the Mobile Router with the source
address of the outer header set to the Care-of Address of the Mobile
Router and that of the inner header set to the Mobile Router's Home
Address or an address from one of the registered mobile network
prefixes.
6.6. Sending Registration Replies
The Home Agent MUST set the status code in the registration reply to
0 to indicate successful processing of the registration request and
successful set up of forwarding for all the mobile network prefixes
served by the Mobile Router. The registration reply MUST contain at
least one Mobile Network Acknowledgement extension.
If the Home Agent is unable to set up forwarding for one of more
mobile network prefixes served by the Mobile Router, it MUST set the
Mobile Network Acknowledgement Extension status code in the
registration reply to MOBNET_FWDING_SETUP_FAILED. When the prefix
length is zero or greater than 32, the status code MUST be set to
MOBNET_INVALID_PREFIX_LEN.
If the Mobile Router is not authorized to forward packets to one or
mobile network prefixes included in the request, the Home Agent MUST
set the code to MOBNET_UNAUTHORIZED_MR.
6.7. Mobile Network Prefix De-registration
If the received registration request is for de-registration of the
Care-of Address, the Home Agent, upon successful processing of it,
MUST delete the entry(ies) from its registration table. The home
agent tears down the bi-directional tunnel and stops forwarding any
packets to/from the Mobile Router. The Home Agent MUST ignore any
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included Mobile Network Request extension in a de-registration
request.
7. Data Forwarding Operation
For traffic to the nodes in the Mobile Network, the Home Agent MUST
perform double tunneling of the packet, if the Mobile Router had
registered with a Foreign Agent Care-of Address. In this case, the
Home Agent MUST encapsulate the packet with tunnel header (source IP
address set to Home Agent and destination IP address set to Mobile
Router's Home Address) and then encapsulate one more time with tunnel
header (source IP address set to Home Agent and destination IP
address set to CoA).
For optimization, the Home Agent SHOULD only encapsulate the packet
with the tunnel header (source IP address set to Home Agent and
destination IP address set to CoA) for Collocated CoA mode.
When a Home Agent receives a packet from the mobile network prefix in
the bi-directional tunnel, it MUST de-encapsulate the packet and
route it as a normal IP packet. It MUST verify that the incoming
packet has the source IP address set to the Care-of Address of the
Mobile Router. The packet MUST be dropped if the source address is
not set to the Care-of Address of the Mobile Router.
For traffic from the nodes in the Mobile Network, the Mobile Router
encapsulates the packet with a tunnel header (source IP address set
to Mobile Router's Home Address and destination IP address set to
Home Agent) if reverse tunnel is enabled. Otherwise, the packet is
routed directly to the Foreign Agent or access router.
In Collocated CoA mode, the Mobile Router MAY encapsulate one more
times with a tunnel header (source IP address set to the CoA and
destination IP address set to Home Agent).
8. Nested Mobile Networks
Nested Network Mobility is a scenario where a Mobile Router allows
another Mobile Router to attach to its Mobile Network. There could
be arbitrary levels of nested mobility. The operation of each Mobile
Router remains the same whether the Mobile Router attaches to another
Mobile Router or to a fixed Access Router on the Internet. The
solution described here does not place any restriction on the number
of levels for nested mobility. Two issues should be noted though.
First, whenever physical loops occur in a nested aggregation of
mobile networks this protocol does neither detect nor solve them -
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datagram forwarding may be blocked. Second, Mobile Routers in a deep
nested aggregation of mobile networks might introduce significant
overhead on the data packets as each level of nesting introduces
another tunnel header encapsulation.
9. Routing Protocol between Mobile Router and Home Agent
There are several benefits of running a dynamic routing protocol
between the Mobile Router and the Home Agent. If the mobile network
is relatively large, including several wireless subnets, then the
topology changes within the moving network can be exposed from the
Mobile Router to the Home Agent by using a dynamic routing protocol.
The purpose of the NEMOv4 protocol extensions to Mobile IPv4, as
defined in previous sections, is not to inform the Home Agent about
these topology changes, but to manage the mobility of the Mobile
Router.
Similarly, topology changes in the home network can be exposed to the
Mobile Router by using a dynamic routing protocol. This may be
necessary when new fixed networks are added in the home network.
Here too, the purpose of NEMOv4 extensions is not to inform the
Mobile Router about topology changes at home.
Examples of dynamic routing protocol include but are not limited to
OSPF Version 2 RFC 2328 [RFC2328], BGP RFC 4271 [RFC4271] and RIP
RFC 2453 [RFC2453].
The recommendations are related to how the routing protocol and the
Mobile IPv4 implementation work in tandem on the Mobile Router and on
the Home Agent (1) without creating incoherent states in the
forwarding information bases at home and on the Mobile Router, (2)
without introducing topologically incorrect addressing information in
the visited domain and (3) efficiently avoid duplication of sent data
or over-provisioning of security.
The information exchanged between the Mobile Router and the Home
Agent is sent over the bi-directional tunnel established by the
Mobile IPv4 exchange Registration Request - Registration Reply (see
Section 6.5). If a network address and prefix about a subnet in the
moving network is sent by the Mobile Router within a routing protocol
message then they SHOULD NOT be sent in the Mobile IPv4 Registration
Request too, in order to avoid incoherencies in the forwarding
information bases. The Mobile Router SHOULD use NEMOv4 implicit mode
in this case (see Section 3).
The Mobile Router SHOULD NOT send routing protocol information
updates in the foreign network. The subnet addresses and prefixes
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valid in the moving network are topologically incorrect in the
visited network.
If the Mobile Router and the Home Agent use a dynamic routing
protocol over the tunnel interface, and if that protocol offers
security mechanisms to protect that protocol's messages, then the
security recommendations in Section 10.1 apply.
10. Security Considerations
The Mobile Network extension is protected by the same rules for
Mobile IP extensions in registration messages. See the Security
Considerations section in RFC 3344 [RFC3344].
The Home Agent MUST be able to verify that the Mobile Router is
authorized to provide mobility service for the Mobile Networks in the
registration request, before anchoring these Mobile Network Prefixes
on behalf of the Mobile Router. Forwarding for prefixes MUST NOT be
set up without successful authorization of the Mobile Router for
those prefixes. A registration failure MUST be notified to the
mobile router when it cannot be successfully authorized for prefixes
requested by it.
All registration requests and replies MUST be authenticated by the
MN-HA Authentication Extension as specified in RFC 3344 [RFC3344] and
its update [I-D.ietf-mip4-rfc3344bis]. When the registration request
is sent in explicit mode, i.e., with one or more Mobile Network
Prefix extensions, all the Mobile Network Prefix extensions MUST be
included before the MN-HA Authentication extension. Also, these
extensions MUST be included in the calculation of the MN-HA
authenticator value.
The Mobile Router should perform ingress filtering on all the packets
received on the mobile network prior to reverse tunneling them to the
Home Agent. The Mobile Router MUST drop any packets that do not have
a source address belonging to the mobile network.
The Mobile Router MUST also ensure that the source address of packets
arriving on the mobile network is not the same as the Mobile Router's
IP address on any interface. These checks will protect against nodes
attempting to launch IP spoofing attacks through the bi-directional
tunnel.
The Home Agent, upon receiving packets through the bi-directional
tunnel, MUST verify that the source addresses of the outer IP header
of the packets are set to the Mobile Router's care-of-address. Also,
it MUST ensure that the source address of the inner IP header is a
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topologically correct address on the mobile network. This will
prevent nodes from using the Home Agent to launch attacks inside the
protected network.
10.1. Security when Dynamic Routing Protocol is Used
If a dynamic routing protocol is used between the Mobile Router and
the Home Agent to propagate the mobile network information into the
home network, the routing updates SHOULD be protected with IPsec ESP
confidentiality between the Mobile Router and Home Agent, to prevent
information about home network topology from being visible to
eavesdroppers.
11. IANA Considerations
IANA to modify rules for the existing registry "Mobile IPv4 numbers -
per RFC 3344". The numbering space for Extensions that may appear in
Mobile IP control messages (those sent to and from UDP port number
434) should be modified.
The new Values and Names for the Type for Extensions appearing in
Mobile IP control messages are the following:
+-------+---------------------------------------------------+
| Value | Name |
+-------+---------------------------------------------------+
| TBA | Mobile Network Extension (To Be Assigned by IANA) |
+-------+---------------------------------------------------+
Table 1: New Values and Names for Extensions in Mobile IP Control
Messages
A new number space should be created for the Values and Names for the
Sub-Type for Mobile Network Extensions. This number space is
initially defined to hold the following entries, allocated by this
document:
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+-------+-----------------------------------------+
| Value | Name |
+-------+-----------------------------------------+
| TBA | Mobile Network Request Extension |
| TBA | Explicit Mode Acknowledgement Extension |
| TBA | Implicit Mode Acknowledgement Extension |
+-------+-----------------------------------------+
Table 2: New Values and Names for the Sub-Type for Mobile Network
Extensions
The policy of future assignments to this number space should be
following Standards Action or IESG Approval (see
[I-D.narten-iana-considerations-rfc2434bis]).
The new Code Values for Mobile IP Registration Reply messages are the
following (for a registration denied by the Home Agent):
+-------+-----------------------------------------------------------+
| Value | Name |
+-------+-----------------------------------------------------------+
| TBA | Mobile Network Prefix operation error (HA_MOBNET_ERROR) |
| TBA | Mobile Router operation is not permitted |
| | (HA_MOBNET_DISALLOWED) |
+-------+-----------------------------------------------------------+
Table 3: New Code Values for Mobile IP Registration Reply
A new number space should be created for the Code Values for the
Mobile Network Acknowledgement Extension. This number space is
initially defined to hold the following entries, allocated by this
document (result of registration, as sent by the Home Agent):
+-----+-------------------------------------------------------------+
| TBA | Success |
| TBA | Invalid prefix length (MOBNET_INVALID_PREFIX_LEN) |
| TBA | Mobile Router is not authorized for prefix |
| | (MOBNET_UNAUTHORIZED) |
| TBA | Forwarding setup failed (MOBNET_FWDING_SETUP_FAILED) |
+-----+-------------------------------------------------------------+
Table 4: New Code Values for Mobile Network Acknowledgement Extension
The policy of future assignments to this number space should be
following Standards Action or IESG Approval (see
[I-D.narten-iana-considerations-rfc2434bis]).
The current non-modified numbering spaces could be consulted at the
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URL http://www.iana.org/assignments/mobileip-numbers (contents last
updated 2007-12-20 and last browsed 2008-01-04).
12. Acknowledgements
The authors would like to thank Christophe Janneteau, George
Popovich, Ty Bekiares, Ganesh Srinivasan, Alpesh Patel, Ryuji
Wakikawa, George Tsirtsis, and Henrik Levkowetz for their helpful
discussions, reviews and comments. Vijay Devarapalli extensively
reviewed one of the later versions of the draft. Hans Sjostrand
(Hans Sj\"ostrand) identified the last clarifications with respect to
Foreign Agent mode treatment. Pete McCann contributed necessary
refinements of many statements.
Mobile IPv4 versions as early as 1996 (RFC 2002) described Mobile
Networks and Mobile Routers support. Charles Perkins.
13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2453] Malkin, G., "RIP Version 2", STD 56, RFC 2453,
November 1998.
[RFC2794] Calhoun, P. and C. Perkins, "Mobile IP Network Access
Identifier Extension for IPv4", RFC 2794, March 2000.
[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
Protocol 4 (BGP-4)", RFC 4271, January 2006.
13.2. Informative References
[I-D.ietf-mip4-nemov4-fa]
Tsirtsis, G., Park, V., Narayanan, V., and K. Leung, "FA
extensions to NEMOv4 Base", draft-ietf-mip4-nemov4-fa-01
(work in progress), November 2007.
[I-D.ietf-mip4-rfc3344bis]
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Perkins, C., "IP Mobility Support for IPv4, revised",
draft-ietf-mip4-rfc3344bis-05 (work in progress),
July 2007.
[I-D.narten-iana-considerations-rfc2434bis]
Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs",
draft-narten-iana-considerations-rfc2434bis-08 (work in
progress), October 2007.
[RFC3963] Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
Thubert, "Network Mobility (NEMO) Basic Support Protocol",
RFC 3963, January 2005.
Appendix A. ChangeLog
The changes are listed in reverse chronological order, most recent
changes appearing at the top of the list.
From draft-ietf-mip4-nemo-v4-base-07.txt to
draft-ietf-mip4-nemo-v4-base-08.txt, following AD Review (Jari
Arkko):
o HA propagates Mobile Network Prefix only if necessary (previously
it was always doing it).
o emphasized that within nested mobile networks looping may occur
and this document doesn't do anything to address this.
o dropped a phrase which said that Mobile-Home auth extension
shouldn't be used when ESP protects the routing protocol message,
because that extension is only applied to Registration messages
(not tunneled data, which usually contains routing protocol
exchange).
o recommending "Standards Action or IESG Review" instead of "Expert
Review" for this numbering space, and added reference to a draft
for 2434bis.
o editorial: re-phrased about how Mobile IPv4 claimed mobile
networks support.
o editorial: added a necessary paragraph in the Acknowledgements
section.
From draft-ietf-mip4-nemo-v4-base-06.txt to
draft-ietf-mip4-nemo-v4-base-07.txt
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o encoded the draft into xml. Compiled with xml2rfc version
1.33pre4.
o checked against 'idnits' script version 2.05.03.
o substituted 'Care-of Address' for 'CoA'.
From draft-ietf-mip4-nemo-v4-base-05.txt to
draft-ietf-mip4-nemo-v4-base-06.txt
o substituted "TBA" for "1" in Sub-type of Mobile Network Request
Extension.
o substituted "TBA" for "0" in Code of Mobile Network
Acknowledgement Extension and in the IANA Section.
o modified the IANA section to request definition two new spaces
(instead of just defining new values) for Sub-Type of Mobile
Network Extensions and for Code Values for Mobile Network
Acknowledgement Extension, and to suggest "Expert Review" as
method of new assignments in these two spaces (and not necessarily
"IETF Consensus").
From draft-ietf-mip4-nemo-v4-base-04.txt to
draft-ietf-mip4-nemo-v4-base-05.txt
o updated the Acknowledgements section.
o capitalized all occurences of "Home Address", "Mobile Router" and
"Care-of Address".
o refined many statements.
o checked against 'idnits' script version 2.04.16.
From draft-ietf-mip4-nemo-v4-base-03.txt to
draft-ietf-mip4-nemo-v4-base-04.txt
o more changes in Introduction to say that with FA mode only the
non-optimized double-encapsulation operation is supported and
[I-D.ietf-mip4-nemov4-fa] proposes a optimization.
From draft-ietf-mip4-nemo-v4-base-02.txt to
draft-ietf-mip4-nemo-v4-base-03.txt
o changed a sentence in the Introduction to say that FA mode _is_
supported but unoptimized, and that a reference
[I-D.ietf-mip4-nemov4-fa] optimizes that mode.
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o added reference [I-D.ietf-mip4-rfc3344bis] to the rfc3344bis
draft.
From draft-ietf-mip4-nemo-v4-base-01.txt to
draft-ietf-mip4-nemo-v4-base-02.txt
o changed title from "IPv4 Network Mobility (NEMO) Protocol" to
"Network Mobility (NEMO) Extensions for Mobile IPv4".
From draft-ietf-mip4-nemo-v4-base-00.txt to
draft-ietf-mip4-nemo-v4-base-01.txt
o added a section on Routing Protocol between Mobile Router and Home
Agent.
o added a security subsection about running simultaneously a secure
routing protocol with secure Mobile IPv4.
o added a date tag on the IANA URL for Mobile IP numbering spaces.
o substituted 'Mobile Router' for 'MR' everywhere.
o updated reference to NEMOv4 FA draft.
From draft-ietf-nemo-v4-base-01.txt to
draft-ietf-mip4-nemo-v4-base-00.txt:
o changed draft name, headers and footers.
o changed title.
o a more coherent use of terms 'subnet', 'prefix' and 'mobile
network'.
o clarified only co-located CoA mode is supported (not FA CoA) for
Mobile Routers in this specification. And added reference to the
FA NEMO optimizations draft.
o changed 'devices' to 'hosts'.
o changed 'moving networks' to 'mobile networks'.
o clarified what 'reachability' in a certain context is: packets may
be dropped if ingress filtering is turned on.
o removed the MR-FA-CoA tunnel overhead optimization. There is
still an issue with text at HA doing optimization.
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This document was first presented as an individual contribution to
the NEMO Working Group, then adopted as a WG item to that group. The
01 version in the NEMO WG has been Last Called on the INFORMATIONAL
track. The evolution was:
From version draft-ietf-nemo-v4-base-00 to
draft-ietf-nemo-v4-base-01:
o removed error code HA_MOBNET_UNSUPPORTED.
o changed all values to be assigned by IANA, from specific numbers
to "TBA" (To Be Assigned).
o substituted "egress interface" for "roaming interface".
o changed HA behaviour upon reception of MNPs. In 00 the HA replied
positively only if all MNPs in RegReq were valid, in 01 a reply is
constructed specifying which MNP was valid and which not.
o clarified a 3-line paragraph saying that RegRep may contain both
implicit and explicit acknowledgements.
Authors' Addresses
Kent Leung
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
USA
Phone: +1 408-526-5030
Email: kleung@cisco.com
Gopal Dommety
Cisco Systems
170 W. Tasman Drive
San Jose, CA 95134
USA
Phone: +1 408-525-1404
Email: gdommety@cisco.com
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Vidya Narayanan
QUALCOMM, Inc.
5775 Morehouse Dr
San Diego, CA
USA
Phone: +1 858-845-2483
Email: vidyan@qualcomm.com
Alexandru Petrescu
Motorola
Parc les Algorithmes Saint Aubin
Gif-sur-Yvette, Essonne 91140
France
Phone: +33 169354827
Email: alexandru.petrescu@motorola.com
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