draft-ietf-mobike-protocol-02.txt   draft-ietf-mobike-protocol-03.txt 
MOBIKE Working Group P. Eronen, Ed. MOBIKE Working Group P. Eronen, Ed.
Internet-Draft Nokia Internet-Draft Nokia
Expires: March 16, 2006 September 12, 2005 Expires: April 2, 2006 September 29, 2005
IKEv2 Mobility and Multihoming Protocol (MOBIKE) IKEv2 Mobility and Multihoming Protocol (MOBIKE)
draft-ietf-mobike-protocol-02.txt draft-ietf-mobike-protocol-03.txt
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Copyright Notice Copyright Notice
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Abstract Abstract
This document describes the MOBIKE protocol, a mobility and This document describes the MOBIKE protocol, a mobility and
multihoming extension to IKEv2. MOBIKE allows hosts to update the multihoming extension to Internet Key Exchange (IKEv2). MOBIKE
(outer) IP addresses associated with IKE and IPsec Security allows hosts to update the (outer) IP addresses associated with IKEv2
Associations (SAs). A mobile VPN client could use MOBIKE to keep the and IPsec Security Associations. A mobile VPN client could use
connection with the VPN gateway active while moving from one address MOBIKE to keep the connection with the VPN gateway active while
to another. Similarly, a multihomed host could use MOBIKE to move moving from one address to another. Similarly, a multihomed host
the traffic to a different interface if, for instance, the currently could use MOBIKE to move the traffic to a different interface if, for
used one stops working. instance, the currently used one stops working.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3
1.2 MOBIKE Protocol Overview . . . . . . . . . . . . . . . . . 4 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . 4
1.3 Terminology and Notations . . . . . . . . . . . . . . . . 5 3.1 Basic Operation . . . . . . . . . . . . . . . . . . . . . 4
2. MOBIKE Protocol Exchanges . . . . . . . . . . . . . . . . . . 6 3.2 Example Protocol Runs . . . . . . . . . . . . . . . . . . 5
2.1 Signaling Support for MOBIKE . . . . . . . . . . . . . . . 6 3.3 MOBIKE and Network Address Translation (NAT) . . . . . . . 8
2.2 Additional Addresses . . . . . . . . . . . . . . . . . . . 6 3.4 Limitations . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Changing Addresses in IPsec SAs . . . . . . . . . . . . . 7 4. Protocol Exchanges . . . . . . . . . . . . . . . . . . . . . 9
2.4 Updating Additional Addresses . . . . . . . . . . . . . . 10 4.1 Signaling Support for MOBIKE . . . . . . . . . . . . . . . 9
2.5 Return Routability Check . . . . . . . . . . . . . . . . . 11 4.2 Initial Tunnel Header Addresses . . . . . . . . . . . . . 9
2.6 Changes in NAT Mappings . . . . . . . . . . . . . . . . . 12 4.3 Additional Addresses . . . . . . . . . . . . . . . . . . . 9
2.7 NAT Prohibition . . . . . . . . . . . . . . . . . . . . . 12 4.4 Changing Addresses in IPsec SAs . . . . . . . . . . . . . 11
2.8 Failure Recovery and Timeouts . . . . . . . . . . . . . . 14 4.5 Updating Additional Addresses . . . . . . . . . . . . . . 14
3. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 15 4.6 Return Routability Check . . . . . . . . . . . . . . . . . 15
3.1 MOBIKE_SUPPORTED Notification Payload . . . . . . . . . . 15 4.7 Changes in NAT Mappings . . . . . . . . . . . . . . . . . 16
3.2 ADDITIONAL_IP4/6_ADDRESS Notification Payloads . . . . . . 15 4.8 NAT Prohibition . . . . . . . . . . . . . . . . . . . . . 16
3.3 NO_ADDITIONAL_ADDRESSES Notification Payload . . . . . . . 15 4.9 Path Testing . . . . . . . . . . . . . . . . . . . . . . . 17
3.4 UPDATE_SA_ADDRESSES Notification Payload . . . . . . . . . 15 4.10 Failure Recovery and Timeouts . . . . . . . . . . . . . 17
3.5 UNACCEPTABLE_ADDRESSES Notification Payload . . . . . . . 16 5. Payload Formats . . . . . . . . . . . . . . . . . . . . . . 19
3.6 COOKIE2 Notification Payload . . . . . . . . . . . . . . . 16 5.1 MOBIKE_SUPPORTED Notify Payload . . . . . . . . . . . . . 19
3.7 NO_NATS_ALLOWED Notification Payload . . . . . . . . . . . 16 5.2 ADDITIONAL_IP4/6_ADDRESS Notify Payloads . . . . . . . . . 19
3.8 UNEXPECTED_NAT_DETECTED Notification Payload . . . . . . . 16 5.3 NO_ADDITIONAL_ADDRESSES Notify Payload . . . . . . . . . . 19
4. Security Considerations . . . . . . . . . . . . . . . . . . . 17 5.4 UPDATE_SA_ADDRESSES Notify Payload . . . . . . . . . . . . 19
4.1 Traffic Redirection and Hijacking . . . . . . . . . . . . 17 5.5 UNACCEPTABLE_ADDRESSES Notify Payload . . . . . . . . . . 20
4.2 IPsec Payload Protection . . . . . . . . . . . . . . . . . 17 5.6 COOKIE2 Notify Payload . . . . . . . . . . . . . . . . . . 20
4.3 Denial-of-Service Attacks Against Third Parties . . . . . 18 5.7 NO_NATS_ALLOWED Notify Payload . . . . . . . . . . . . . . 20
4.4 Spoofing Network Connectivity Indications . . . . . . . . 19 5.8 UNEXPECTED_NAT_DETECTED Notify Payload . . . . . . . . . . 20
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 6. Security Considerations . . . . . . . . . . . . . . . . . . 21
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 6.1 Traffic Redirection and Hijacking . . . . . . . . . . . . 21
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.2 IPsec Payload Protection . . . . . . . . . . . . . . . . . 21
7.1 Normative References . . . . . . . . . . . . . . . . . . . 20 6.3 Denial-of-Service Attacks Against Third Parties . . . . . 22
7.2 Informative References . . . . . . . . . . . . . . . . . . 20 6.4 Spoofing Network Connectivity Indications . . . . . . . . 23
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 21 6.5 Address and Topology Disclosure . . . . . . . . . . . . . 23
A. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 22 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 24
Intellectual Property and Copyright Statements . . . . . . . . 23 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
9.1 Normative References . . . . . . . . . . . . . . . . . . . 25
9.2 Informative References . . . . . . . . . . . . . . . . . . 26
Author's Address . . . . . . . . . . . . . . . . . . . . . . 27
A. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . 27
Intellectual Property and Copyright Statements . . . . . . . 30
1. Introduction 1. Introduction
1.1 Motivation
IKEv2 is used for performing mutual authentication and establishing IKEv2 is used for performing mutual authentication and establishing
and maintaining IPsec security associations (SAs). In the current and maintaining IPsec Security Associations (SAs). In the current
specifications, the IPsec and IKE SAs are created implicitly between specifications, the IPsec and IKE SAs are created implicitly between
the IP addresses that are used when the IKE_SA is established. These the IP addresses that are used when the IKE_SA is established. These
IP addresses are then used as the outer (tunnel header) addresses for IP addresses are then used as the outer (tunnel header) addresses for
tunnel mode IPsec packets. Currently, it is not possible to change tunnel mode IPsec packets. Currently, it is not possible to change
these addresses after the IKE_SA has been created. these addresses after the IKE_SA has been created.
There are scenarios where these IP addresses might change. One There are scenarios where these IP addresses might change. One
example is mobility: a host changes its point of network attachment, example is mobility: a host changes its point of network attachment,
and receives a new IP address. Another example is a multihoming host and receives a new IP address. Another example is a multihoming host
that would like to change to a different interface if, for instance, that would like to change to a different interface if, for instance,
the currently used address stops working for some reason. the currently used interface stops working for some reason.
Although the problem can be solved by creating new IKE and IPsec SAs Although the problem can be solved by creating new IKE and IPsec SAs
when the addresses need to be changed, this may not be optimal for when the addresses need to be changed, this may not be optimal for
several reasons. In some cases, creating a new IKE_SA may require several reasons. In some cases, creating a new IKE_SA may require
user interaction for authentication (entering a code from a token user interaction for authentication (entering a code from a token
card, for instance). Creating new SAs often also involves expensive card, for instance). Creating new SAs often also involves expensive
calculations and possibly a large number of roundtrips. Due to these calculations and possibly a large number of roundtrips. Due to these
reasons, a mechanism for updating the IP addresses of existing IKE reasons, a mechanism for updating the IP addresses of existing IKE
and IPsec SAs is needed. The MOBIKE protocol described in this and IPsec SAs is needed. The MOBIKE protocol described in this
document provides such a mechanism. document provides such a mechanism.
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unchanged. Thus, mobility can be (mostly) invisible to applications unchanged. Thus, mobility can be (mostly) invisible to applications
and their connections using the VPN. and their connections using the VPN.
MOBIKE also supports more complex scenarios where the VPN gateway MOBIKE also supports more complex scenarios where the VPN gateway
also has several network interfaces: these interfaces could be also has several network interfaces: these interfaces could be
connected to different networks or ISPs, they may have may be a mix connected to different networks or ISPs, they may have may be a mix
of IPv4 and IPv6 addresses, and the addresses may change over time. of IPv4 and IPv6 addresses, and the addresses may change over time.
Furthermore, both parties could be VPN gateways relaying traffic for Furthermore, both parties could be VPN gateways relaying traffic for
other parties. other parties.
Note that this document does not claim to solve all the problems IETF 2. Terminology and Notation
MOBIKE working group has been chartered to work on. It is assumed
that issues such as transport mode (updating traffic selectors),
PFKEY extensions, and tunnel overhead reduction will be handled in
separate documents.
1.2 MOBIKE Protocol Overview When messages containing IKEv2 payloads are described, optional
payloads are shown in brackets (for instance, "[FOO]"), and a plus
sign indicates that a payload can be repeated one or more times (for
instance, "FOO+"). In some cases, the diagrams also show what
payloads defined in [IKEv2] would be typically included in, for
instance, the IKE_AUTH exchange. These payloads are shown for
illustrative purposes only; see [IKEv2] for an authoritative
description.
Since MOBIKE allows both parties to have several addresses, this When this document talks about updating the source/destination
leads us to an important question: there are up to N*M pairs of IP addresses of an IPsec SA, it means updating IPsec-related state so
addresses that could potentially be used. How to decide which of that outgoing ESP/AH packets use those addresses in the tunnel
these pairs should be used? The decision has to take into account header. Depending on how the nominal division between Security
Association Database (SAD), Security Policy Database (SPD), and Peer
Authorization Database (PAD) described in [IPsecArch] is actually
implemented, an implementation can have several different places that
have to be updated.
In this document, the term "initiator" means the party who originally
initiated the first IKE_SA (in a series of possibly several rekeyed
IKE_SAs); "responder" is the other peer. During the lifetime of the
IKE_SA, both parties may initiate INFORMATIONAL or CREATE_CHILD_SA
exchanges; in this case, the terms "exchange initiator" and "exchange
responder" are used. The term "original initiator" (which in [IKEv2]
refers to the party who started the latest IKE_SA rekeying) is not
used in this document.
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 [KEYWORDS].
3. Protocol Overview
3.1 Basic Operation
MOBIKE allows both parties to have several addresses, and there are
up to N*M pairs of IP addresses that could potentially be used. The
decision of which of these pairs to use has to take into account
several factors. First, the parties have may preferences about which several factors. First, the parties have may preferences about which
interface should be used, due to performance and cost reasons, for interface should be used, due to performance and cost reasons, for
instance. Second, the decision is constrained by the fact that some instance. Second, the decision is constrained by the fact that some
of the pairs may not work at all due to incompatible IP versions, of the pairs may not work at all due to incompatible IP versions,
outages somewhere in the network, problems at the local link at outages somewhere in the network, problems at the local link at
either end, and so on. either end, and so on.
MOBIKE solves this problem by taking a simple approach: the party MOBIKE solves this problem by taking a simple approach: the party
that initiated the IKE_SA (the "client" in remote access VPN that initiated the IKE_SA (the "client" in remote access VPN
scenario) is responsible for deciding which address pair is used for scenario) is responsible for deciding which address pair is used for
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downstream traffic. downstream traffic.
The details of exactly how the initiator makes the decision, what The details of exactly how the initiator makes the decision, what
information is used in making it, how the information is collected, information is used in making it, how the information is collected,
how preferences affect the decision, and when a decision needs to be how preferences affect the decision, and when a decision needs to be
changed, are largely beyond the scope of MOBIKE. This does not mean changed, are largely beyond the scope of MOBIKE. This does not mean
that these details are unimportant: on the contrary, they are likely that these details are unimportant: on the contrary, they are likely
to be crucial in any real system. However, MOBIKE is concerned with to be crucial in any real system. However, MOBIKE is concerned with
these details only to the extent that they are visible in IKEv2/IPsec these details only to the extent that they are visible in IKEv2/IPsec
messages exchanged between the peers (and thus need to be messages exchanged between the peers (and thus need to be
standardized to ensure interoperability). Issues such as mobility standardized to ensure interoperability).
detection and local policies are also not specific to MOBIKE, but
apply to existing mobility protocols such as Mobile IPv4 [MIP4] as
well.
MOBIKE also has to deal with situations where the network contains Many of these issues are also not specific to MOBIKE, but common with
NATs or stateful packet filters (for brevity, the rest of this the use of existing hosts in dynamic environments or with mobility
document talks simply about NATs). When the addresses used for IPsec protocols such as Mobile IP [MIP4] [MIP6]. A number of mechanisms
SAs are changed, MOBIKE can enable or disable IKEv2 NAT Traversal as already exist or are being developed to deal with these issues. For
needed. However, if the party "outside" the NAT changes its IP instance, link layer and IP layer mechanisms can be used to track the
address, it may no longer be able to send packets to the party status of connectivity within the local link [RFC2461], movement
"behind" the NAT, since the packets may not (depending on the exact detection is being specified in for both IPv4 and IPv6 [DNA4] [DNA6],
type of NAT) match the NAT mapping state. Here MOBIKE assumes that and so on.
the initiator is the party "behind" the NAT, and does not fully
support the case where the responder's addresses change when NATs are
present.
Updating the addresses of IPsec SAs naturally has to take into Updating the addresses of IPsec SAs naturally has to take into
account several security considerations. MOBIKE includes two account several security considerations. MOBIKE includes two
features designed to address these considerations. First, a "return features designed to address these considerations. First, a "return
routability" check can be used to verify the addresses provided by routability" check can be used to verify the addresses provided by
the peer. This makes it more difficult to flood third parties with the peer. This makes it more difficult to flood third parties with
large amounts of traffic. Second, a "NAT prohibition" feature large amounts of traffic. Second, a "NAT prohibition" feature
ensures that IP addresses have not been modified by NATs, IPv4/IPv6 ensures that IP addresses have not been modified by NATs, IPv4/IPv6
translation agents, or other similar devices. This feature is mainly translation agents, or other similar devices. This feature is mainly
intended for site-to-site VPNs where the administrators may know intended for site-to-site VPNs where the administrators may know
beforehand that NATs are not present, and thus any modification to beforehand that NATs are not present, and thus any modification to
the packet can be considered to be an attack. the packet can be considered to be an attack.
1.3 Terminology and Notations 3.2 Example Protocol Runs
When messages containing IKEv2 payloads are shown, optional payloads A simple MOBIKE exchange in a mobile scenario is illustrated below:
are shown in brackets (for instance, "[FOO]"), and a plus sign
indicates that a payload can be repeated one or more times (for
instance, "FOO+").
When this document talks about updating the source/destination Initiator Responder
addresses of an IPsec SA, it means updating IPsec-related state so ----------- -----------
that outgoing ESP/AH packets use those addresses in the tunnel 1) HDR, SAi1, KEi, Ni,
header. Depending on how the nominal division between Security N(NAT_DETECTION_*_IP) -->
Association Database (SAD), Security Policy Database (SPD), and Peer
Authorization Database (PAD) described in [IPsecArch] is actually
implemented, an implementation can have several different places that
have to be updated.
In this document, the term "initiator" means the party who originally <-- HDR, SAr1, KEr, Nr,
initiated the first IKE_SA (in a series of possibly several rekeyed N(NAT_DETECTION_*_IP)
IKE_SAs); "responder" is the other peer. During the lifetime of the
IKE_SA, both parties may initiate INFORMATIONAL or CREATE_CHILD_SA
exchanges; in this case, the terms "exchange initiator" and "exchange
responder" are used. The term "original initiator" (which in [IKEv2]
refers to the party who started the latest IKE_SA rekeying) is not
used in this document.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 2) HDR, SK { IDi, CERT, AUTH,
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this CP(CFG_REQUEST),
document are to be interpreted as described in [KEYWORDS]. SAi2, TSi, TSr,
N(MOBIKE_SUPPORTED) } -->
2. MOBIKE Protocol Exchanges <-- HDR, SK { IDr, CERT, AUTH,
CP(CFG_REPLY),
SAr2, TSi, TSr,
N(MOBIKE_SUPPORTED) }
2.1 Signaling Support for MOBIKE (Initiator gets information from lower layers that its attachment
point and address has changed.)
3) HDR, SK { N(UPDATE_SA_ADDRESSES),
N(NAT_DETECTION_*_IP) } -->
<-- HDR, SK { N(NAT_DETECTION_*_IP) }
(Responder verifies that the initiator has given it
a correct IP address.)
4) <-- HDR, SK { N(COOKIE2) }
HDR, SK { N(COOKIE2) } -->
Step 1 is the normal IKE_INIT exchange. In step 2, the peers inform
each other that they support MOBIKE. In step 3, the initiator
notices a change in its own address, and informs the responder about
this. At this point, it also starts to use the new address as a
source address in its own outgoing ESP traffic. The responder
records the new address, and if so required by policy, performs a
return routability check of the address. When this check completes,
the responder starts to use the new address as the destination for
its outgoing ESP traffic.
Another protocol run in multihoming scenario is illustrated below.
In this scenario the initiator has one address but the responder has
two.
Initiator Responder
----------- -----------
1) HDR, SAi1, KEi, Ni,
N(NAT_DETECTION_*_IP) -->
<-- HDR, SAr1, KEr, Nr,
N(NAT_DETECTION_*_IP)
2) HDR, SK { IDi, CERT, AUTH,
CP(CFG_REQUEST),
SAi2, TSi, TSr,
N(MOBIKE_SUPPORTED) } -->
<-- HDR, SK { IDr, CERT, AUTH,
CP(CFG_REPLY),
SAr2, TSi, TSr,
N(MOBIKE_SUPPORTED),
N(ADDITIONAL_IPV4_ADDRESS) }
(The initiator suspects a problem in the currently used address pair,
and probes its liveness.)
3) HDR, SK { N(NAT_DETECTION_*_IP) } -->
<-- HDR, SK { N(NAT_DETECTION_*_IP) }
(The initiator gives up on the current address pair, and tests the
other available address pair.)
4) HDR, SK { N(NAT_DETECTION_*_IP),
N(COOKIE2) } -->
<-- HDR, SK { N(NAT_DETECTION_*_IP),
N(COOKIE2) }
(This worked, and the initiator requests the peer to switch to new
addresses.)
5) HDR, SK { N(UPDATE_SA_ADDRESSES),
N(NAT_DETECTION_*_IP) } -->
<-- HDR, SK { N(NAT_DETECTION_*_IP) }
3.3 MOBIKE and Network Address Translation (NAT)
In some MOBIKE scenarios the network may contain NATs or stateful
packet filters (for brevity, the rest of this document talks simply
about NATs). The NAT Traversal feature specified in [IKEv2] allows
IKEv2 to work through NATs in many cases, and MOBIKE can leverage
this functionality: when the addresses used for IPsec SAs are
changed, MOBIKE can enable or disable IKEv2 NAT Traversal as needed.
Nevertheless, there are some limitations since NATs usually introduce
an asymmetry in the network: only packets coming from the "inside"
cause state to be created. This asymmetry leads to restrictions on
what MOBIKE can do. To give a concrete example, consider a situation
where both peers have only a single address, and the initiator is
behind a NAT. If the responder's address now changes, it needs to
send a packet to the initiator using its new address. However, if
the NAT is, for instance, of the common "restricted cone" type (see
[STUN] for one description of different NAT types), this is not
possible: the NAT will drop packets sent from the new address (unless
the initiator has previously sent a packet to that address -- which
it cannot do until it knows the address).
For simplicity, MOBIKE does not attempt to handle all possible NAT-
related scenarios. Instead, MOBIKE assumes that if NATs are present,
the initiator is the party "behind" the NAT, and does not fully
support the case where the responder's addresses change.
"Does not fully support" means that no special effort is made to
support this functionality. However, if the alternative is losing
connectivity completely, the responder can still attempt to proceed
with the change, and depending on, e.g., the exact type of NAT, it
may succeed. However, analyzing the exact circumstances when this
will or will not work is not done in this document.
3.4 Limitations
This document focuses on the main scenario outlined in Section 1, and
supports only tunnel mode.
The base version of the MOBIKE protocol may not cover all potential
future use scenarios, such as transport mode, application to securing
SCTP or optimizations desirable in specific circumstances. Future
extensions may be defined later to support additional requirements.
4. Protocol Exchanges
4.1 Signaling Support for MOBIKE
Implementations that wish to use MOBIKE for a particular IKE_SA MUST Implementations that wish to use MOBIKE for a particular IKE_SA MUST
include a MOBIKE_SUPPORTED notification in the IKE_AUTH exchange (in include a MOBIKE_SUPPORTED notification in the IKE_AUTH exchange (in
case of multiple IKE_AUTH exchanges, in the message containing the SA case of multiple IKE_AUTH exchanges, in the message containing the SA
payload). payload).
The MOBIKE_SUPPORTED notification payload is described in Section 3. The format of the MOBIKE_SUPPORTED notification is described in
Section 5.
2.2 Additional Addresses 4.2 Initial Tunnel Header Addresses
When an IPsec SA is created, the tunnel header IP addresses (and port
if doing UDP encapsulation) are taken from the IKE_SA, not the IP
header of the IKEv2 message requesting the IPsec SA. The addresses
in the IKE_SA are initialized as follows: If the IKE_SA_INIT request
contains the NAT_DETECTION_*_IP notifications and the responder
supports NAT Traversal, the values are initialized from the IP header
of the first IKE_AUTH request. Otherwise, the values are initialized
from the IP header of the IKE_SA_INIT request.
The addresses are taken from the IKE_AUTH request when NAT Traversal
is being used because IKEv2 requires changing from port 500 to 4500
if a NAT is discovered. To simplify things, implementations that
support both this specification and NAT Traversal MUST change to port
4500 if the correspondent also supports both, even if no NAT was
detected between them (this way, there is no need to change the ports
later).
4.3 Additional Addresses
Both the initiator and responder MAY include one or more Both the initiator and responder MAY include one or more
ADDITIONAL_IP4_ADDRESS and/or ADDITIONAL_IP6_ADDRESS notification ADDITIONAL_IP4_ADDRESS and/or ADDITIONAL_IP6_ADDRESS notifications in
payloads in the IKE_AUTH exchange (in case of multiple IKE_AUTH the IKE_AUTH exchange (in case of multiple IKE_AUTH exchanges, in the
exchanges, in the message containing the SA payload). message containing the SA payload).
Initiator Responder Initiator Responder
----------- ----------- ----------- -----------
HDR, SK { IDi, [CERT], [IDr], AUTH, HDR, SK { IDi, [CERT], [IDr], AUTH,
[CP(CFG_REQUEST)] [CP(CFG_REQUEST)]
SAi2, TSi, TSr, SAi2, TSi, TSr,
N(MOBIKE_SUPPORTED), N(MOBIKE_SUPPORTED),
[N(ADDITIONAL_*_ADDRESS)+] --> [N(ADDITIONAL_*_ADDRESS)+] } -->
<-- HDR, SK { IDr, [CERT], AUTH, <-- HDR, SK { IDr, [CERT], AUTH,
[CP(CFG_REPLY)], [CP(CFG_REPLY)],
SAr2, TSi, TSr, SAr2, TSi, TSr,
N(MOBIKE_SUPPORTED) N(MOBIKE_SUPPORTED)
[N(ADDITIONAL_*_ADDRESS)+] } [N(ADDITIONAL_*_ADDRESS)+] }
The recipient stores this information, but no other action is taken The recipient stores this information, but no other action is taken
at this time. at this time.
Although both the initiator and responder maintain a set of peer Although both the initiator and responder maintain a set of peer
addresses (logically associated with the IKE_SA), it is important to addresses (logically associated with the IKE_SA), it is important to
note that they use this information for slightly different purposes. note that they use this information for slightly different purposes.
The initiator uses the set of responder addresses as an input to its The initiator uses the set of responder addresses as an input to its
address selection policy; it may at some later point decide to move address selection policy; it may at some later point decide to move
the IPsec traffic to one of these addresses using the procedure the IPsec traffic to one of these addresses using the procedure
described in Section 2.3. The responder normally does not use the described in Section 4.4. The responder normally does not use the
set of initiator addresses for anything: the addresses are used only set of initiator addresses for anything: the addresses are used only
when the responder's own addresses change. when the responder's own addresses change (see Section 4.5).
The set of addresses available to the peers can change during the The set of addresses available to the peers can change during the
lifetime of the IKE_SA. The procedure for updating this information lifetime of the IKE_SA. The procedure for updating this information
is described in Section 2.4. is described in Section 4.5.
Note that if some of the initiator's interfaces are behind a NAT Note that if some of the initiator's interfaces are behind a NAT
(from the responder's point of view), the addresses received by the (from the responder's point of view), the addresses received by the
responder will be incorrect. This means the procedure for changing responder will be incorrect. This means the procedure for changing
responder addresses described in Section 2.4 does not fully work when responder addresses described in Section 4.5 does not fully work when
the initiator is behind a NAT. For the same reason, the peers also the initiator is behind a NAT. For the same reason, the peers also
SHOULD NOT use this information for any other purposes than what is SHOULD NOT use this information for any other purposes than what is
explicitly described in this document. explicitly described in this document.
2.3 Changing Addresses in IPsec SAs 4.4 Changing Addresses in IPsec SAs
In MOBIKE, the initiator decides what addresses are used in the IPsec In MOBIKE, the initiator decides what addresses are used in the IPsec
SAs. That is, the responder usually never updates any IPsec SAs SAs. That is, the responder usually never updates any IPsec SAs
without receiving an explicit UPDATE_SA_ADDRESSES request from the without receiving an explicit UPDATE_SA_ADDRESSES request from the
initiator. (As described below, the responder can, however, update initiator. (As described below, the responder can, however, update
the IKE_SA in some circumstances.) the IKE_SA in some circumstances.)
The reasons why the initiator wishes to change the addresses are The reasons why the initiator wishes to change the addresses are
largely beyond the scope of MOBIKE. Typically triggers include largely beyond the scope of MOBIKE. Typically triggers include
information received from lower layers, such as changes in IP information received from lower layers, such as changes in IP
addresses or link-down indications. Some of this information can be addresses or link-down indications. Some of this information can be
unreliable: for instance, ICMP messages could be spoofed by an unreliable: for instance, ICMP messages could be spoofed by an
attacker. Such information itself MUST NOT be used to conclude than attacker. Unreliable information itself MUST NOT be used to conclude
an update is needed: instead, the initiator SHOULD trigger dead peer than an update is needed: instead, the initiator SHOULD trigger dead
detection. peer detection (that is, send an INFORMATIONAL request).
Changing addresses can also be triggered by events within IKEv2. At Changing addresses can also be triggered by events within IKEv2. At
least the following events can cause the initiator to re-evaluate its least the following events can cause the initiator to re-evaluate its
local address selection policy, possibly leading to changing the local address selection policy, possibly leading to changing the
addresses. addresses.
o An IKEv2 request has been re-transmitted several times, but no o An IKEv2 request has been re-transmitted several times, but no
valid reply has been received. This suggests the current path is valid reply has been received. This suggests the current path is
no longer working. no longer working.
o An INFORMATIONAL request containing ADDITIONAL_IP4/6_ADDRESS o An INFORMATIONAL request containing ADDITIONAL_IP4/6_ADDRESS
payloads is received. This means the peer's addresses may have notifications is received. This means the peer's addresses may
changed. have changed.
o An UNACCEPTABLE_ADDRESSES notification is received as a response o An UNACCEPTABLE_ADDRESSES notification is received as a response
to address update request (described below). to address update request (described below).
o The initiator receives a NAT_DETECTION_DESTINATION_IP payload that o The initiator receives a NAT_DETECTION_DESTINATION_IP notification
does not match the previous UPDATE_SA_ADDRESSES response (see that does not match the previous UPDATE_SA_ADDRESSES response (see
Section 2.6 for a more detailed description). Section 4.7 for a more detailed description).
The description in the rest of this section assumes that the The description in the rest of this section assumes that the
initiator has already decided what the new addresses should be. When initiator has already decided what the new addresses should be. When
this decision has been made, the initiator this decision has been made, the initiator:
o Updates the IKE_SA and the IPsec SAs associated with this IKE_SA o Updates the IKE_SA with the new addresses, and sets the
with the new addresses, and sets the "pending_update" flag in the "pending_update" flag in the IKE_SA.
IKE_SA.
o If NAT Traversal is not enabled, and the responder supports NAT o Updates the IPsec SAs associated with this IKE_SA with the new
Traversal (as indicated by NAT detection payloads in the addresses (unless the initiator's policy requires a return
IKE_SA_INIT exchange), and the initiator either suspects or knows routability check before updating the IPsec SAs, and the check has
that a NAT is likely to be present, enables NAT Traversal. not been done for this responder address yet).
o If the IPsec SAs were updated in the previous step: If NAT
Traversal is not enabled, and the responder supports NAT Traversal
(as indicated by NAT detection payloads in the IKE_SA_INIT
exchange), and the initiator either suspects or knows that a NAT
is likely to be present, enables NAT Traversal.
o If there are outstanding IKEv2 requests (requests for which the o If there are outstanding IKEv2 requests (requests for which the
initiator has not yet received a reply), continues retransmitting initiator has not yet received a reply), continues retransmitting
them using the addresses in the IKE_SA (the new addresses). them using the addresses in the IKE_SA (the new addresses).
o When the window size allows, sends an INFORMATIONAL request o When the window size allows, sends an INFORMATIONAL request
containing the UPDATE_SA_ADDRESSES notification payload (which containing the UPDATE_SA_ADDRESSES notification (which does not
does not contain any data), and clears the "pending_update" flag. contain any data), and clears the "pending_update" flag. The
request will be as follows:
Initiator Responder Initiator Responder
----------- ----------- ----------- -----------
HDR, SK { N(UPDATE_SA_ADDRESSES), HDR, SK { N(UPDATE_SA_ADDRESSES),
[N(NAT_DETECTION_*_IP)], [N(NAT_DETECTION_*_IP)],
[N(NO_NATS_ALLOWED)], [N(NO_NATS_ALLOWED)],
[N(COOKIE2)] } --> [N(COOKIE2)] } -->
o If a new address change occurs while waiting for the response, o If a new address change occurs while waiting for the response,
starts again from the first step (and ignores responses to this starts again from the first step (and ignores responses to this
UPDATE_SA_ADDRESSES request). UPDATE_SA_ADDRESSES request).
When processing an INFORMATIONAL request containing the When processing an INFORMATIONAL request containing the
UPDATE_SA_ADDRESSES notification, the responder UPDATE_SA_ADDRESSES notification, the responder:
o Determines whether it has already received a newer o Determines whether it has already received a newer
UPDATE_SA_ADDRESSES request than this one (if the responder uses a UPDATE_SA_ADDRESSES request than this one (if the responder uses a
window size greater than one, it is possible that requests are window size greater than one, it is possible that requests are
received out of order). If it has, a response message is sent, received out of order). If it has, a normal response message
but no other action is taken. (described below) is sent, but no other action is taken.
o If the NO_NATS_ALLOWED payload is present, processes it as o If the NO_NATS_ALLOWED notification is present, processes it as
described in Section 2.7. described in Section 4.8.
o Checks that the (source IP address, destination IP address) pair o Checks that the (source IP address, destination IP address) pair
in the IP header is acceptable according to local policy. If it in the IP header is acceptable according to local policy. If it
is not, replies with a message containing the is not, replies with a message containing the
UNACCEPTABLE_ADDRESSES notification (and possibly COOKIE2). UNACCEPTABLE_ADDRESSES notification (and possibly COOKIE2).
o Updates the IP addresses in the IKE_SA with the values from the IP o Updates the IP addresses in the IKE_SA with the values from the IP
header. (Using the address from the IP header is consistent with header. (Using the address from the IP header is consistent with
normal IKEv2, and allows IKEv2 to work with NATs without needing normal IKEv2, and allows IKEv2 to work with NATs without needing
unilateral self-address fixing [UNSAF].) unilateral self-address fixing [UNSAF].)
skipping to change at page 9, line 14 skipping to change at page 13, line 4
o Checks that the (source IP address, destination IP address) pair o Checks that the (source IP address, destination IP address) pair
in the IP header is acceptable according to local policy. If it in the IP header is acceptable according to local policy. If it
is not, replies with a message containing the is not, replies with a message containing the
UNACCEPTABLE_ADDRESSES notification (and possibly COOKIE2). UNACCEPTABLE_ADDRESSES notification (and possibly COOKIE2).
o Updates the IP addresses in the IKE_SA with the values from the IP o Updates the IP addresses in the IKE_SA with the values from the IP
header. (Using the address from the IP header is consistent with header. (Using the address from the IP header is consistent with
normal IKEv2, and allows IKEv2 to work with NATs without needing normal IKEv2, and allows IKEv2 to work with NATs without needing
unilateral self-address fixing [UNSAF].) unilateral self-address fixing [UNSAF].)
o Replies with an INFORMATIONAL response: o Replies with an INFORMATIONAL response:
Initiator Responder Initiator Responder
----------- ----------- ----------- -----------
<-- HDR, SK { [N(NAT_DETECTION_*_IP)], <-- HDR, SK { [N(NAT_DETECTION_*_IP)],
[N(COOKIE2)], } [N(COOKIE2)] }
o If necessary, initiates a return routability check for the new o If necessary, initiates a return routability check for the new
initiator address (see Section 2.5) and waits until the check is initiator address (see Section 4.6) and waits until the check is
completed. completed.
o Updates the IPsec SAs associated with this IKE_SA with the new o Updates the IPsec SAs associated with this IKE_SA with the new
addresses. addresses.
o If NAT Traversal is supported and NAT detection payloads were o If NAT Traversal is supported and NAT detection payloads were
included, enables or disables NAT Traversal. included, enables or disables NAT Traversal.
When the initiator receives the reply, it When the initiator receives the reply, it:
o If an address change has occured after the request was first sent, o If an address change has occurred after the request was first
no MOBIKE processing is done for the reply message, since a new sent, no MOBIKE processing is done for the reply message, since a
UPDATE_SA_ADDRESSES is going to be sent (or has already been sent, new UPDATE_SA_ADDRESSES is going to be sent (or has already been
if window size greater than one is in use). sent, if window size greater than one is in use).
o If the response contains the UNEXPECTED_NAT_DETECTED payload, o If the response contains the UNEXPECTED_NAT_DETECTED notification,
processes it as described in Section 2.7. processes it as described in Section 4.8.
o If the response contains an UNACCEPTABLE_ADDRESSES notification o If the response contains an UNACCEPTABLE_ADDRESSES notification,
payload, the initiator MAY select another addresses and retry the the initiator MAY select another addresses and retry the exchange,
exchange, keep on using the current addresses, or disconnect. keep on using the current addresses, or disconnect.
o Updates the IPsec SAs associated with this IKE_SA with the new
addresses (unless this was already done before sending the
request).
o If NAT Traversal is supported and NAT detection payloads were o If NAT Traversal is supported and NAT detection payloads were
included, enables or disables NAT Traversal. included, enables or disables NAT Traversal.
There is one exception to the rule that the responder never updates There is one exception to the rule that the responder never updates
any IPsec SAs without receiving an UPDATE_SA_ADDRESSES request. If any IPsec SAs without receiving an UPDATE_SA_ADDRESSES request. If
the source address the responder is currently using becomes the source address the responder is currently using becomes
unavailable (i.e., sending packets using that source address is no unavailable (i.e., sending packets using that source address is no
longer possible), the responder is allowed to update the IPsec SAs to longer possible), the responder is allowed to update the IPsec SAs to
use some other address (in addition to initiating the procedure use some other address (in addition to initiating the procedure
described in the next section). described in the next section).
2.4 Updating Additional Addresses 4.5 Updating Additional Addresses
As described in Section 2.2, both the initiator and responder can As described in Section 4.3, both the initiator and responder can
send a list of additional addresses in the IKE_AUTH exchange. This send a list of additional addresses in the IKE_AUTH exchange. This
information can be updated by sending an INFORMATIONAL exchange information can be updated by sending an INFORMATIONAL exchange
request message that contains either one or more ADDITIONAL_IP4/ request message that contains either one or more ADDITIONAL_IP4/
6_ADDRESS payloads or the NO_ADDITIONAL_ADDRESSES payload. 6_ADDRESS notifications or the NO_ADDITIONAL_ADDRESSES notification.
The message exchange will look as follows:
Initiator Responder Initiator Responder
----------- ----------- ----------- -----------
HDR, SK { [N(ADDITIONAL_*_ADDRESS)+], HDR, SK { [N(ADDITIONAL_*_ADDRESS)+],
[N(NO_ADDITIONAL_ADDRESSES)], [N(NO_ADDITIONAL_ADDRESSES)],
[N(NO_NATS_ALLOWED)], [N(NO_NATS_ALLOWED)],
[N(COOKIE2)] } --> [N(COOKIE2)] } -->
<-- HDR, SK { [N(COOKIE2)] } <-- HDR, SK { [N(COOKIE2)] }
When a request containing ADDITIONAL_*_ADDRESS or When a request containing ADDITIONAL_*_ADDRESS or
NO_ADDITIONAL_ADDRESSES payloads is received, the exchange responder NO_ADDITIONAL_ADDRESSES notification is received, the exchange
responder:
o Determines whether it has already received a newer request to o Determines whether it has already received a newer request to
update the addresses (if a window size greater than one is used, update the addresses (if a window size greater than one is used,
it is possible that the requests are received out of order). If it is possible that the requests are received out of order). If
it has, a response message is sent, but the address set is not it has, a response message is sent, but the address set is not
updated. updated.
o If the NO_NATS_ALLOWED payload is present, processes it as o If the NO_NATS_ALLOWED notification is present, processes it as
described in Section 2.7. described in Section 4.8.
o Updates the set of peer addresses based on the IP header and o Updates the set of peer addresses based on the IP header and
ADDITIONAL_IP4/6_ADDRESS or NO_ADDITIONAL_ADDRESS payloads. ADDITIONAL_IP4/6_ADDRESS or NO_ADDITIONAL_ADDRESS notifications.
o Sends a response. o Sends a response.
The initiator MAY include these payloads in the same request as The initiator MAY include these notifications in the same request as
UPDATE_SA_ADDRESSES. UPDATE_SA_ADDRESSES.
If the request to update the addresses is retransmitted using several If the request to update the addresses is retransmitted using several
different source addresses, a new INFORMATIONAL request MUST be sent. different source addresses, a new INFORMATIONAL request MUST be sent.
There is one additional complication: when the responder wants to There is one additional complication: when the responder wants to
update the address set, the currently used addresses may no longer update the address set, the currently used addresses may no longer
work. In this case, the responder uses the additional address list work. In this case, the responder uses the additional address list
received from the initiator and the list of its own addresses to received from the initiator and the list of its own addresses to
determine which addresses to use for sending the INFORMATIONAL determine which addresses to use for sending the INFORMATIONAL
request. This is the only time the responder uses the additional request. This is the only time the responder uses the additional
address list received from the initiator. address list received from the initiator.
Note that both peers can have their own policies about what addresses Note that both peers can have their own policies about what addresses
are acceptable to use. A minimal "mobile client" could have a policy are acceptable to use. A minimal "mobile client" could have a policy
that says that only the responder's address specified in local that says that only the responder's address specified in local
configuration is acceptable. This kind of client does not have to configuration is acceptable. This kind of client does not have to
send or process ADDITIONAL_*_ADDRESS notification payloads. send or process ADDITIONAL_*_ADDRESS notifications. Similarly, a
Similarly, a simple "VPN gateway" that has only a single address, and simple "VPN gateway" that has only a single address, and is not going
is not going to change it, does not need to send or understand to change it, does not need to send or understand
ADDITIONAL_*_ADDRESS notification payloads. ADDITIONAL_*_ADDRESS notifications.
2.5 Return Routability Check 4.6 Return Routability Check
Both parties can optionally verify that the other party can actually Both parties can optionally verify that the other party can actually
receive packets at the claimed address. This "return routability receive packets at the claimed address. This "return routability
check" can be done before updating the IPsec SAs, immediately after check" can be done before updating the IPsec SAs, immediately after
updating them, or continuously during the connection. updating them, or continuously during the connection.
By default, return routability check SHOULD be done before updating By default, return routability check SHOULD be done before updating
the IPsec SAs. In environments where the peer is expected to be the IPsec SAs. In environments where the peer is expected to be
well-behaving (many corporate VPNs, for instance), or the address can well-behaving (many corporate VPNs, for instance), or the address can
be verified by some other means (e.g., the address is included in the be verified by some other means (e.g., the address is included in the
peer's certificate), the return routability check MAY be skipped or peer's certificate), the return routability check MAY be omitted or
postponed until after the IPsec SAs have been updated. postponed until after the IPsec SAs have been updated.
Any INFORMATIONAL exchange can be used for return routability Any INFORMATIONAL exchange can be used for return routability
purposes (with one exception, described below): when a valid response purposes (with one exception, described below): when a valid response
is received, we know the other party can receive packets at the is received, we know the other party can receive packets at the
claimed address. claimed address.
To ensure that the peer cannot generate the correct INFORMATIONAL To ensure that the peer cannot generate the correct INFORMATIONAL
response without seeing the request, a new payload is added to response without seeing the request, a new payload is added to
INFORMATIONAL messages. The sender of an INFORMATIONAL request MAY INFORMATIONAL messages. The sender of an INFORMATIONAL request MAY
include a COOKIE2 notification payload, and if included, the include a COOKIE2 notification, and if included, the recipient of an
recipient of an INFORMATIONAL request MUST copy the payload as-is to INFORMATIONAL request MUST copy the notification as-is to the
the response. When processing the response, the original sender MUST response. When processing the response, the original sender MUST
verify that the value is the same one as sent. If the values do not verify that the value is the same one as sent. If the values do not
match, the IKE_SA MUST be closed. match, the IKE_SA MUST be closed.
There is one additional issue that must be taken into account. If If the same INFORMATIONAL request has been sent to several different
the INFORMATIONAL request has been sent to several different
addresses (i.e., the destination address in the IKE_SA has been addresses (i.e., the destination address in the IKE_SA has been
updated after the request was first sent), receiving the updated after the request was first sent), receiving the
INFORMATIONAL response does not tell which address is the working INFORMATIONAL response does not tell which address is the working
one. In this case, a new INFORMATIONAL request needs to be sent to one. In this case, a new INFORMATIONAL request needs to be sent to
check return routability. check return routability.
2.6 Changes in NAT Mappings 4.7 Changes in NAT Mappings
IKEv2 performs Dead Peer Detection (DPD) if there has recently been IKEv2 performs Dead Peer Detection (DPD) if there has recently been
only outgoing traffic on all of the SAs associated with the IKE_SA. only outgoing traffic on all of the SAs associated with the IKE_SA.
In MOBIKE, these messages can also be used to detect if NAT mappings In MOBIKE, these messages can also be used to detect if NAT mappings
have changed (for example, if the keepalive internal is too long, or have changed (for example, if the keepalive internal is too long, or
the NAT box is rebooted). More specifically, if both peers support the NAT box is rebooted). More specifically, if both peers support
both this specification and NAT Traversal, NAT_DETECTION_*_IP both this specification and NAT Traversal, NAT_DETECTION_*_IP
payloads MAY be included in any INFORMATIONAL request; if the request notifications MAY be included in any INFORMATIONAL request; if the
includes them, the responder MUST also include them in the response request includes them, the responder MUST also include them in the
(but no other action is taken, unless otherwise specified). response (but no other action is taken, unless otherwise specified).
When the initiator is behind a NAT, it SHOULD include these payloads
in DPD messages, and compare the received
NAT_DETECTION_DESTINATION_IP payload with the value from the previous
UPDATE_SA_ADDRESSES response (or the IKE_SA_INIT response). If the
values do not match, the IP address and/or port seen by the responder
has changed, and the initiator SHOULD send UPDATE_SA_ADDRESSES as
described in Section 2.3.
When MOBIKE is in use, the host not behind a NAT SHOULD NOT use the
dynamic updates specified in [IKEv2] Section 2.23 (where the peer
address and port are updated from the last valid authenticated
packet). This ensures that both peers have a consistent view of when
addresses are to be changed, and prevents conflicts between MOBIKE-
originated updates and NAT-T dynamic updates. It also means that an
INFORMATIONAL exchange that does not contain UPDATE_SA_ADDRESSES does
not cause any changes, allowing it to be used for, e.g., testing
whether a particular path works.
2.7 NAT Prohibition
IKEv2/IPsec implementations that do not support NAT Traversal can, in When the initiator is behind a NAT (as detected earlier using
fact, work across some types of one-to-one "basic" NATs and IPv4/IPv6 NAT_DETECTION_*_IP notifications), it SHOULD include these
translation agents in tunnel mode. This may be considered a problem notifications in DPD messages, and compare the received
in some circumstances, since in some sense any modification of the IP NAT_DETECTION_DESTINATION_IP notifications with the value from the
addresses can be considered to be an attack. previous UPDATE_SA_ADDRESSES response (or the IKE_SA_INIT response).
If the values do not match, the IP address and/or port seen by the
responder has changed, and the initiator SHOULD send
UPDATE_SA_ADDRESSES as described in Section 4.4.
The "NAT prohibition" feature allows the initiator to have a policy When MOBIKE is in use, the dynamic updates specified in [IKEv2]
that prevents the use of paths that contain NATs, IPv4/IPv6 Section 2.23 (where the peer address and port are updated from the
translation agents, or other nodes that modify the addresses in the last valid authenticated packet) work in a slightly different
IP header. This feature is mainly intended for site-to-site VPN fashion. The host not behind a NAT MUST NOT use these dynamic
cases, where the administrators may know beforehand that NATs are not updates for IKEv2 packets, but MAY use them for ESP packets. This
present, and thus any modification to the packet can be considered to ensures that an INFORMATIONAL exchange that does not contain
be an attack. UPDATE_SA_ADDRESSES does not cause any changes, allowing it to be
used for, e.g., testing whether a particular path works.
This specification addresses the issue as follows. When an IPsec SA 4.8 NAT Prohibition
is created, the tunnel header IP addresses (and port if doing UDP
encapsulation) are taken from the IKE_SA, not the message IP header.
The NO_NATS_ALLOWED payload is used to guarantee that NATs have not
modified the address used in IKE_SA. However, all response messages
are still sent to the address and port the corresponding request came
from.
An initiator who wishes to use this feature includes a Basic IKEv2/IPsec without NAT Traversal support may work across some
NO_NATS_ALLOWED payload in the IKE_SA_INIT request. The responder types of one-to-one "basic" NATs and IPv4/IPv6 translation agents in
then MUST calculate the expected value based on the values from the tunnel mode. This is because the IKEv2 integrity checksum does not
IP header, and compare this with the value in the NO_NATS_ALLOWED cover the addresses in the IP header. This may be considered a
payload. If they do not match, the responder replies with "HDR(A,0), problem in some circumstances, since in some sense any modification
N(UNEXPECTED_NAT_DETECTED)" and does not create any state. of the IP addresses can be considered to be an attack.
Initiator Responder This specification addresses the issue by protecting the IP addresses
----------- ----------- when NAT Traversal has not been explicitly enabled. This means that
HDR, [N(COOKIE)], MOBIKE without NAT Traversal support will not work if the paths
SAi1, KEi, Ni, contain NATs, IPv4/IPv6 translation agents, or other nodes that
[N(NO_NATS_ALLOWED)] --> modify the addresses in the IP header. This feature is mainly
intended for site-to-site VPN cases, where the administrators may
know beforehand that NATs are not present, and thus any modification
to the packet can be considered to be an attack.
<-- HDR, SAr1, KEr, Nr, More specifically, when NAT Traversal is not enabled, all messages
[CERTREQ] that can update the addresses associated with the IKE_SA and/or IPsec
SAs (the IKE_SA_INIT request and all INFORMATIONAL requests that
contain UPDATE_SA_ADDRESSES and/or ADDITIONAL_IP4/6_ADDRESS
notifications) MUST also include a NO_NATS_ALLOWED notification. The
exchange responder MUST verify that the contents of the
NO_NATS_ALLOWED notification match the addresses in the IP header.
If they do not match, a response containing an
UNEXPECTED_NAT_DETECTED notification is sent (and in the case of the
IKE_SA_INIT exchange, no state is created at the responder). The
response message is sent to the address and port the corresponding
request came from, not the address contained in the NO_NATS_ALLOWED
notification.
If the values do match, the responder initializes (local_address, If the exchange initiator receives an UNEXPECTED_NAT_DETECTION
local_port, peer_address, peer_port) in the to-be-created IKE_SA with notification in response to its request, it SHOULD retry the
values from the IP header. The same applies if neither operation several times using new IKE_SA_INIT/INFORMATIONAL requests.
NO_NATS_ALLOWED nor NAT_DETECTION_*_IP payloads were included, or if This ensures that an attacker who is able to modify only a single
the responder does not support NAT Traversal. packet does not unnecessarily cause a path to remain unused.
If the IKE_SA_INIT request included NAT_DETECTION_*_IP payloads but If an UNEXPECTED_NAT_DETECTED notification is sent, the exchange
no NO_NATS_ALLOWED payload, the situation is different since the responder MUST NOT use the contents of the NO_NATS_ALLOWED
initiator may at this point change from port 500 to 4500. In this notification for any other purpose than possibly logging the
case, the responder initializes (local_address, local_port, information for troubleshooting purposes.
peer_address, peer_port) from the first IKE_AUTH request.
IKEv2 requires that if an IPsec endpoint discovers a NAT between it 4.9 Path Testing
and its correspondent, it MUST send all subsequent traffic to and
from port 4500. To simplify things, implementations that support
both this specification and NAT Traversal MUST change to port 4500 if
the correspondent also supports both, even if no NAT was detected
between them (this way, there is no need to change the ports later).
NO_NATS_ALLOWED payloads can also be included when changing the IKEv2 Dead Peer Detection allows the peers to detect if the currently
addresses of IPsec SAs (see Section 2.3) and updating the additional used path has stopped working. However, if either of the peers has
addresses (see Section 2.4). An initiator using this "NAT several addresses, Dead Peer Detection alone does not tell which of
prohibition" feature includes a NO_NATS_ALLOWED payload in all the other paths might work.
address update messages.
If the initiator receives an UNEXPECTED_NAT_DETECTION notification in If required by its address selection policy, the initiator can use
response to its request, it SHOULD retry the operation several times normal IKEv2 INFORMATIONAL request/response messages to test whether
using new IKE_SA_INIT/INFORMATIONAL requests. This ensures that an a certain path works. Implementations MAY do path testing even if
attacker who is able to modify only a single packet does not the currenly used path is working to, for example, detect when a
unnecessarily cause a path to remain unused. better (but previously unavailable) path becomes available.
2.8 Failure Recovery and Timeouts 4.10 Failure Recovery and Timeouts
In MOBIKE, the initiator is responsible for detecting and recovering In MOBIKE, the initiator is responsible for detecting and recovering
from most failures. from most failures.
To give the initiator enough time to detect the error, the responder To give the initiator enough time to detect the error, the responder
SHOULD use relatively long timeout intervals when, for instance, SHOULD use relatively long timeout intervals when, for instance,
retransmitting IKEv2 requests or deciding whether to initiate dead retransmitting IKEv2 requests or deciding whether to initiate dead
peer detection. peer detection. While no specific timeout lengths are required, it
is suggested that responders continue retransmitting IKEv2 requests
for at least five minutes before giving up.
3. Payload Formats 5. Payload Formats
3.1 MOBIKE_SUPPORTED Notification Payload 5.1 MOBIKE_SUPPORTED Notify Payload
The MOBIKE_SUPPORTED notification payload is included in the IKE_AUTH The MOBIKE_SUPPORTED notification is included in the IKE_AUTH
exchange to indicate that the implementation supports this exchange to indicate that the implementation supports this
specification. specification.
The Notify Message Type for MOBIKE_SUPPORTED is TBD-BY- The Notify Message Type for MOBIKE_SUPPORTED is TBD-BY-IANA1. The
IANA(16396..40959). The Protocol ID and SPI Size fields are set to Protocol ID and SPI Size fields are set to zero. There is no data
zero. There is no data associated with this Notify type. associated with this Notify type.
3.2 ADDITIONAL_IP4/6_ADDRESS Notification Payloads 5.2 ADDITIONAL_IP4/6_ADDRESS Notify Payloads
Both parties can include ADDITIONAL_IP4_ADDRESS and/or Both parties can include ADDITIONAL_IP4_ADDRESS and/or
ADDITIONAL_IP6_ADDRESS payloads in the IKE_AUTH exchange and ADDITIONAL_IP6_ADDRESS notifications in the IKE_AUTH exchange and
INFORMATIONAL exchange request messages; see Section 2.2 and INFORMATIONAL exchange request messages; see Section 4.3 and
Section 2.4 for more detailed description. Section 4.5 for more detailed description.
The Notify Message Types for ADDITIONAL_IP4_ADDRESS and The Notify Message Types for ADDITIONAL_IP4_ADDRESS and
ADDITIONAL_IP6_ADDRESS are TBD-BY-IANA(16396..40959) and TBD-BY- ADDITIONAL_IP6_ADDRESS are TBD-BY-IANA2 and TBD-BY-IANA3,
IANA(16396..40959), respectively. The Protocol ID and SPI Size respectively. The Protocol ID and SPI Size fields are set to zero.
fields are set to zero. The data associated with these Notify types The data associated with these Notify types is either a four-octet
is either a four-octet IPv4 address or a 16-octet IPv6 address. IPv4 address or a 16-octet IPv6 address.
3.3 NO_ADDITIONAL_ADDRESSES Notification Payload 5.3 NO_ADDITIONAL_ADDRESSES Notify Payload
The NO_ADDITIONAL_ADDRESSES payload can be included in an The NO_ADDITIONAL_ADDRESSES notification can be included in an
INFORMATIONAL exchange request messages to indicate that the exchange INFORMATIONAL exchange request messages to indicate that the exchange
initiator does not have addresses beyond the one used in the exchange initiator does not have addresses beyond the one used in the exchange
(see Section 2.4 for more detailed description). (see Section 4.5 for more detailed description).
The Notify Message Type for NO_ADDITIONAL_ADDRESSES is TBD-BY- The Notify Message Type for NO_ADDITIONAL_ADDRESSES is TBD-BY-IANA4.
IANA(16396..40959). The Protocol ID and SPI Size fields are set to The Protocol ID and SPI Size fields are set to zero. There is no
zero. There is no data associated with this Notify type. data associated with this Notify type.
3.4 UPDATE_SA_ADDRESSES Notification Payload 5.4 UPDATE_SA_ADDRESSES Notify Payload
This payload is included in INFORMATIONAL exchange requests sent by This notification is included in INFORMATIONAL exchange requests sent
the initiator to update addresses of the IKE_SA and IPsec SAs (see by the initiator to update addresses of the IKE_SA and IPsec SAs (see
Section 2.3). Section 4.4).
The Notify Message Type for UPDATE_SA_ADDRESSES is TBD-BY- The Notify Message Type for UPDATE_SA_ADDRESSES is TBD-BY-IANA5. The
IANA(16396..40959). The Protocol ID and SPI Size fields are set to Protocol ID and SPI Size fields are set to zero. There is no data
zero. There is no data associated with this Notify type. associated with this Notify type.
3.5 UNACCEPTABLE_ADDRESSES Notification Payload 5.5 UNACCEPTABLE_ADDRESSES Notify Payload
The responder can include this notification payload in an The responder can include this notification in an INFORMATIONAL
INFORMATIONAL exchange response to indicate that the address change exchange response to indicate that the address change in the
in the corresponding request message (which contained an corresponding request message (which contained an UPDATE_SA_ADDRESSES
UPDATE_SA_ADDRESSES notification payload) was not carried out. notification) was not carried out.
The Notify Message Type for UNACCEPTABLE_ADDRESSES is TBD-BY- The Notify Message Type for UNACCEPTABLE_ADDRESSES is TBD-BY-IANA6.
IANA(40..8191). The Protocol ID and SPI Size fields are set to zero. The Protocol ID and SPI Size fields are set to zero. There is no
There is no data associated with this Notify type. data associated with this Notify type.
3.6 COOKIE2 Notification Payload 5.6 COOKIE2 Notify Payload
This payload MAY be included in any INFORMATIONAL request for return This notification MAY be included in any INFORMATIONAL request for
routability check purposes (see Section 2.5). If the INFORMATIONAL return routability check purposes (see Section 4.6). If the
request includes COOKIE2, the exchange responder MUST copy the INFORMATIONAL request includes COOKIE2, the exchange responder MUST
payload to the response message. copy the notification to the response message.
The data associated with this notification MUST be between 8 and 64 The data associated with this notification MUST be between 8 and 64
octets in length (inclusive), and MUST be chosen by the exchange octets in length (inclusive), and MUST be chosen by the exchange
initiator in a way that is unpredictable to the exchange responder. initiator in a way that is unpredictable to the exchange responder.
The Notify Message Type for this message is TBD-BY- The Notify Message Type for this message is TBD-BY-IANA7. The
IANA(16396..40959). The Protocol ID and SPI Size fields are set to Protocol ID and SPI Size fields are set to zero.
zero.
3.7 NO_NATS_ALLOWED Notification Payload 5.7 NO_NATS_ALLOWED Notify Payload
See Section 2.7 for a description of this payload. See Section 4.8 for a description of this notification.
The data associated with this notification is the SHA-1 hash The data field of this notification contains the following
[FIPS180-2] of the following data: IKE SPIs (in the order they appear information: the IP address and port from which the packet was sent,
in the header), the IP address and port from which the packet was and the IP address and port to which the packet was sent. The Notify
sent, and the IP address and port to which the packet was sent. The Message Type for this message is TBD-BY-IANA8. The Protocol ID and
Notify Message Type for this message is TBD-BY-IANA(16396..40959). SPI Size fields are set to zero.
The Protocol ID and SPI Size fields are set to zero.
3.8 UNEXPECTED_NAT_DETECTED Notification Payload 5.8 UNEXPECTED_NAT_DETECTED Notify Payload
See Section 2.7 for a description of this payload. See Section 4.8 for a description of this notification.
The Notify Message Type for UNEXPECTED_NAT_DETECTED is TBD-BY- The Notify Message Type for UNEXPECTED_NAT_DETECTED is TBD-BY-IANA9.
IANA(40..8191). The Protocol ID and SPI Size fields are set to zero. The Protocol ID and SPI Size fields are set to zero. There is no
There is no data associated with this Notify type. data associated with this Notify type.
4. Security Considerations 6. Security Considerations
The main goals of this specification are to not reduce the security The main goals of this specification are to not reduce the security
offered by usual IKEv2 procedures and to counter mobility related offered by usual IKEv2 procedures and to counter mobility related
threats in an appropriate manner. This section describes new threats in an appropriate manner. This section describes new
security considerations introduced by MOBIKE. See [IKEv2] for security considerations introduced by MOBIKE. See [IKEv2] for
security considerations for IKEv2 in general. security considerations for IKEv2 in general.
4.1 Traffic Redirection and Hijacking 6.1 Traffic Redirection and Hijacking
MOBIKE payload relating to updating addresses are encrypted, MOBIKE payloads relating to updating addresses are encrypted,
integrity protected, and replay protected using the IKE_SA. This integrity protected, and replay protected using the IKE_SA. This
assures that no one except the participants can, for instance, give a assures that no one except the participants can, for instance, give a
control message to change the addresses. control message to change the addresses.
However, just like with normal IKEv2, the actual IP addresses in the However, just like with normal IKEv2, the actual IP addresses in the
IP header are not covered by the integrity protection. This means IP header are not covered by the integrity protection. This means
that a NAT between the parties (or an attacker acting as a NAT) can that a NAT between the parties (or an attacker acting as a NAT) can
modify the addresses and cause incorrect tunnel header (outer) IP modify the addresses and cause incorrect tunnel header (outer) IP
addresses to be used for IPsec SAs. The scope of this attack is addresses to be used for IPsec SAs. The scope of this attack is
limited mainly to denial-of-service, since all traffic is protected limited mainly to denial-of-service, since all traffic is protected
using IPsec. using IPsec.
MOBIKE introduces the NO_NATS_ALLOWED payload that can be used to This attack can only be launched by on-path attackers that are
detect modification of the addresses in the IP header by outsiders capable of modifying IKEv2 messages carrying NAT detection payloads
When this payload is used, communication through NATs and other (such as Dead Peer Detection messages). By modifying the IP header
address translators is impossible. This feature is mainly intended of these packets, the attackers can lead the peers believe a new NAT
for site-to-site VPN cases, where the administrators may know or a changed NAT binding exists between them. The attack can
beforehand that valid NATs are not present, and thus any modification continue as long as the attacker is on the path, modifying the IKEv2
to the packet can be considered to be an attack. However, this messages. If this is no longer the case, IKEv2 and MOBIKE mechanisms
feature SHOULD NOT be enabled by default, since it creates a denial- designed to detect NAT mapping changes will eventually recognize that
of-service vulnerability even when no malicious attackers are the intended traffic is not getting through, and update the addresses
present: a misconfiguration or introduction of a (non-malicious) NAT appropriately.
can cause the connection to fail.
4.2 IPsec Payload Protection MOBIKE introduces the NO_NATS_ALLOWED notification that is used to
detect modification of the addresses in the IP header by outsiders.
When this notification is used, communication through NATs and other
address translators is impossible, so it is sent only when not doing
NAT Traversal. This feature is mainly intended for site-to-site VPN
cases, where the administrators may know beforehand that valid NATs
are not present, and thus any modification to the packet can be
considered to be an attack.
6.2 IPsec Payload Protection
The use of IPsec protection on payload traffic protects the The use of IPsec protection on payload traffic protects the
participants against disclosure of the contents of the traffic, participants against disclosure of the contents of the traffic,
should the traffic end up in an incorrect destination or be should the traffic end up in an incorrect destination or be
eavesdropped along the way. eavesdropped along the way.
However, security associations originally created for the protection However, security associations originally created for the protection
of a specific flow between specific addresses may be moved through of a specific flow between specific addresses may be updated by
MOBIKE. The level of required protection may be different in a new MOBIKE later on. This has to be taken into account if the level of
location of a VPN client, for instance. required protection depends on, for instance, the current location of
the VPN client.
It is recommended that security policies for peers that are allowed It is recommended that security policies for peers that are allowed
to use MOBIKE are configured in a manner that takes into account that to use MOBIKE are configured in a manner that takes into account that
a single security association can be used through different paths at a single security association can be used through paths of varying
different times. security properties at different times.
4.3 Denial-of-Service Attacks Against Third Parties 6.3 Denial-of-Service Attacks Against Third Parties
Traffic redirection may be performed not just to gain access to the Traffic redirection may be performed not just to gain access to the
traffic (not very interesting since it is encrypted) or deny service traffic (not very interesting since it is encrypted) or to deny
to the peers, but also to cause a denial-of-service attack for a service to the peers, but also to cause a denial-of-service attack
third party. For instance, a high-speed TCP session or a multimedia for a third party. For instance, a high-speed TCP session or a
stream may be redirected towards a victim host, causing its multimedia stream may be redirected towards a victim host, causing
communications capabilities to suffer. its communications capabilities to suffer.
The attackers in this threat can be either outsiders or even one of The attackers in this threat can be either outsiders or even one of
the participants. In usual VPN usage scenarios, attacks by the the IKEv2 peers. In usual VPN usage scenarios, attacks by the peers
participants can be easily dealt with if the authentication performed can be easily dealt with if the authentication performed in the
in the initial IKEv2 negotiation can be traced to persons who can be initial IKEv2 negotiation can be traced to persons who can be held
held responsible for the attack. This may not be the case in all responsible for the attack. This may not be the case in all
scenarios, particularly with opportunistic approaches to security. scenarios, particularly with opportunistic approaches to security.
Normally such attacks would expire in a short time frame due to the Normally such attacks would expire in a short time frame due to the
lack of responses (such as transport layer acknowledgements) from the lack of responses (such as transport layer acknowledgements) from the
victim. However, as described in [Aura02], malicious participants victim. However, as described in [Aura02], malicious participants
would typically be able to spoof such acknowledgements and maintain would typically be able to spoof such acknowledgements and maintain
the traffic flow for an extended period of time. For instance, if the traffic flow for an extended period of time. For instance, if
the attacker opened the TCP stream itself before redirecting it to the attacker opened the TCP stream itself before redirecting it to
the victim, the attacker becomes aware of the sequence number space the victim, the attacker becomes aware of the sequence number space
used in this particular session. used in this particular session.
It should also be noted, as shown in [Bombing], that without ingress It should also be noted, as shown in [Bombing], that without ingress
filtering in the attacker's network such attacks are already possible filtering in the attacker's network such attacks are already possible
simply by sending spoofed packets from the attacker to the victim simply by sending spoofed packets from the attacker to the victim
directly. Furthermore, if the attacker's network has ingress directly. Furthermore, if the attacker's network has ingress
filtering, this attack is largely prevented for MOBIKE as well. filtering, this attack is largely prevented for MOBIKE as well.
Consequently, it makes little sense to protect against attacks of Consequently, it makes little sense to protect against attacks of
similar nature in MOBIKE. However, it still makes sense to limit the similar nature in MOBIKE. However, it still makes sense to limit the
amplification capabilities provided to attackers, so that they cannot amplification capabilities provided to attackers, so that they cannot
use stream redirection to send 1000 packets to the victim by sending use stream redirection to send a large number of packets to the
just a few packets themselves. victim by sending just a few packets themselves.
This specification requires the use of return routability tests This specification includes return routability tests to limit the
(under certain conditions) to limit the duration of any "third party duration of any "third party bombing" attacks by off-path (relative
bombing" attacks by off-path (relative to the victim) attackers. The to the victim) attackers. The tests are authenticated messages that
tests are authenticated messages that the peer has to respond to, and the peer has to respond to, and can be performed either before the
can be performed either before the address change takes effect, address change takes effect, immediately afterwards, or even
immediately afterwards, or even periodically during the session. The periodically during the session. The tests contain unpredictable
tests contain unpredictable data, and only someone who has the keys data, and only someone who has the keys associated with the IKE SA
associated with the IKE SA and has seen the request packet can and has seen the request packet can properly respond to the test.
properly respond to the test.
4.4 Spoofing Network Connectivity Indications 6.4 Spoofing Network Connectivity Indications
Attackers may spoof various indications from lower layers and the Attackers may spoof various indications from lower layers and the
network in an effort to confuse the peers about which addresses are network in an effort to confuse the peers about which addresses are
or are not working. For example, attackers may spoof link-layer or are not working. For example, attackers may spoof link-layer
error messages in an effort to cause the parties to move their error messages in an effort to cause the parties to move their
traffic elsewhere or even to disconnect. Attackers may also spoof traffic elsewhere or even to disconnect. Attackers may also spoof
information related to network attachments, router discovery, and information related to network attachments, router discovery, and
address assignments in an effort to make the parties believe they address assignments in an effort to make the parties believe they
have Internet connectivity when in reality they do not. have Internet connectivity when in reality they do not.
This may cause use of non-preferred addresses or even denial-of- This may cause use of non-preferred addresses or even denial-of-
service. service.
MOBIKE does not provide any protection of its own for indications MOBIKE does not provide any protection of its own for indications
from other parts of the protocol stack. These vulnerabilities can be from other parts of the protocol stack. These vulnerabilities can be
mitigated through the use of techniques specific to the other parts mitigated through the use of techniques specific to the other parts
of the stack, such as properly dealing with ICMP errors of the stack, such as validation of ICMP errors [ICMPAttacks], link
[ICMPAttacks], link layer security, or the use of [SEND] to protect layer security, or the use of [SEND] to protect IPv6 Router and
IPv6 Router and Neighbor Discovery. Neighbor Discovery.
Ultimately MOBIKE depends on the delivery of IKEv2 messages to Ultimately MOBIKE depends on the delivery of IKEv2 messages to
determine which paths can be used. If IKEv2 messages sent using a determine which paths can be used. If IKEv2 messages sent using a
particular source and destination addresses reach the recipient and a particular source and destination addresses reach the recipient and a
reply is received, MOBIKE will usually consider the path working;if reply is received, MOBIKE will usually consider the path working;if
no reply is received even after retransmissions, MOBIKE will suspect no reply is received even after retransmissions, MOBIKE will suspect
the path is broken. An attacker who can consistently control the the path is broken. An attacker who can consistently control the
delivery or non-delivery of the IKEv2 messages in the network can delivery or non-delivery of the IKEv2 messages in the network can
thus influence which addresses actually get used. thus influence which addresses actually get used.
5. IANA Considerations 6.5 Address and Topology Disclosure
MOBIKE address updates and ADDITIONAL_IP4/6_ADDRESS notifications
reveal information about which networks the peers are connected to.
For example, consider a host A with two network interfaces: a
cellular connection and a wired Ethernet connection to a company LAN.
If host A now contacts host B using IKEv2/MOBIKE and sends
ADDITIONAL_IP4/6_ADDRESS notifications, host B receives additional
information it might not otherwise know. If host A used the cellular
connection for the IKEv2/MOBIKE traffic, host B can also see the
company LAN address (and perhaps further guess that host A is used by
an employee of that company). If host A used the company LAN to make
the connection, host B can see that host A has a subscription from
this particular cellular operator.
These additional addresses can also disclose more accurate location
information than just a single address. Suppose that host A uses its
cellular connection for IKEv2/MOBIKE traffic, but also sends an
ADDITIONAL_IP4_ADDRESS notification containing an IP address
corresponding to, say, a wireless LAN at a particular coffee shop
location. It is likely that host B can now make a much better guess
at A's location than would be possible based on the cellular IP
address alone.
Furthermore, as described in Section 4.3, some of the addresses could
also be private addresses behind a NAT.
In many environments, disclosing address information is not a problem
(and indeed it cannot be avoided if the hosts wish to use those
addresses for IPsec traffic). For instance, a remote access VPN
client could consider the corporate VPN gateway sufficiently
trustworthy for this purpose.
However, if MOBIKE is used in some more opportunistic approach, it
can be desirable to limit the information that is sent. The peers
naturally do not have to disclose any addresses they do not want to
use for IPsec traffic. Also, as noted in Section 4.5, an initiator
whose policy is to always use the locally configured responder
address does not have to send any ADDITIONAL_IP4/6_ADDRESS payloads.
7. IANA Considerations
This document does not create any new namespaces to be maintained by This document does not create any new namespaces to be maintained by
IANA, but it requires new values in namespaces that have been defined IANA, but it requires new values in namespaces that have been defined
in the IKEv2 base specification [IKEv2]. in the IKEv2 base specification [IKEv2].
This defines several new IKEv2 notification payloads whose values are This document defines several new IKEv2 notifications whose values
to be allocated from the "IKEv2 Notification Payload Types" are to be allocated from the "IKEv2 Notify Message Types" namespace.
namespace. These notification payloads are described in Section 3.
6. Acknowledgements Notify Message Value
--------------------------- -----
MOBIKE_SUPPORTED TBD-BY-IANA1 (16396..40959)
ADDITIONAL_IP4_ADDRESS TBD-BY-IANA2 (16396..40959)
ADDITIONAL_IP6_ADDRESS TBD-BY-IANA3 (16396..40959)
NO_ADDITIONAL_ADDRESSES TBD-BY-IANA4 (16396..40959)
UPDATE_SA_ADDRESSES TBD-BY-IANA5 (16396..40959)
UNACCEPTABLE_ADDRESSES TBD-BY-IANA6 (40..8191)
COOKIE2 TBD-BY-IANA7 (16396..40959)
NO_NATS_ALLOWED TBD-BY-IANA8 (16396..40959)
UNEXPECTED_NAT_DETECTED TBD-BY-IANA9 (40..8191)
These notifications are described in Section 5.
8. Acknowledgements
This document is a collaborative effort of the entire MOBIKE WG. We This document is a collaborative effort of the entire MOBIKE WG. We
would particularly like to thank Jari Arkko, Francis Dupont, Paul would particularly like to thank Jari Arkko, Francis Dupont, Paul
Hoffman, Tero Kivinen, and Hannes Tschofenig. This document also Hoffman, Tero Kivinen, and Hannes Tschofenig. This document also
incorporates ideas and text from earlier MOBIKE protocol proposals, incorporates ideas and text from earlier MOBIKE protocol proposals,
including [AddrMgmt], [Kivinen], [MOPO], and [SMOBIKE], and the including [AddrMgmt], [Kivinen], [MOPO], and [SMOBIKE], and the
MOBIKE design document [Design]. MOBIKE design document [Design].
7. References 9. References
7.1 Normative References
[FIPS180-2] 9.1 Normative References
National Institute of Standards and Technology,
"Specifications for the Secure Hash Standard", Federal
Information Processing Standard (FIPS) Publication 180-2,
August 2002.
[IKEv2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", [IKEv2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
draft-ietf-ipsec-ikev2-17 (work in progress), draft-ietf-ipsec-ikev2-17 (work in progress),
October 2004. October 2004.
[IPsecArch]
Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", draft-ietf-ipsec-rfc2401bis-06 (work
in progress), March 2005.
[KEYWORDS] [KEYWORDS]
Bradner, S., "Key words for use in RFCs to Indicate Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997. Requirement Levels", RFC 2119, March 1997.
[UDPEncap] [UDPEncap]
Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M. Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets", Stenberg, "UDP Encapsulation of IPsec ESP Packets",
RFC 3948, January 2005. RFC 3948, January 2005.
7.2 Informative References 9.2 Informative References
[AddrMgmt] [AddrMgmt]
Dupont, F., "Address Management for IKE version 2", Dupont, F., "Address Management for IKE version 2",
draft-dupont-ikev2-addrmgmt-07 (work in progress), draft-dupont-ikev2-addrmgmt-07 (work in progress),
May 2005. May 2005.
[Aura02] Aura, T., Roe, M., and J. Arkko, "Security of Internet [Aura02] Aura, T., Roe, M., and J. Arkko, "Security of Internet
Location Management", Proc. 18th Annual Computer Security Location Management", Proc. 18th Annual Computer Security
Applications Conference (ACSAC), December 2002. Applications Conference (ACSAC), December 2002.
[Bombing] Dupont, F., "A note about 3rd party bombing in Mobile [Bombing] Dupont, F., "A note about 3rd party bombing in Mobile
IPv6", draft-dupont-mipv6-3bombing-02 (work in progress), IPv6", draft-dupont-mipv6-3bombing-02 (work in progress),
June 2005. June 2005.
[DNA4] Aboba, B., "Detecting Network Attachment (DNA) in IPv4",
draft-ietf-dhc-dna-ipv4-15 (work in progress),
August 2005.
[DNA6] Narayanan, S., Daley, G., and N. Montavont, "Detecting
Network Attachment in IPv6 - Best Current Practices for
hosts", draft-ietf-dna-hosts-01 (work in progress),
June 2005.
[Design] Kivinen, T. and H. Tschofenig, "Design of the MOBIKE [Design] Kivinen, T. and H. Tschofenig, "Design of the MOBIKE
protocol", draft-ietf-mobike-design-02 (work in progress), protocol", draft-ietf-mobike-design-02 (work in progress),
February 2005. February 2005.
[ICMPAttacks] [ICMPAttacks]
Gont, F., "ICMP attacks against TCP", Gont, F., "ICMP attacks against TCP",
draft-gont-tcpm-icmp-attacks-03 (work in progress), draft-gont-tcpm-icmp-attacks-03 (work in progress),
December 2004. December 2004.
[IPsecArch]
Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", draft-ietf-ipsec-rfc2401bis-06 (work
in progress), March 2005.
[Kivinen] Kivinen, T., "MOBIKE protocol", [Kivinen] Kivinen, T., "MOBIKE protocol",
draft-kivinen-mobike-protocol-00 (work in progress), draft-kivinen-mobike-protocol-00 (work in progress),
February 2004. February 2004.
[MIP4] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, [MIP4] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002. August 2002.
[MIP6] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[MOPO] Eronen, P., "Mobility Protocol Options for IKEv2 (MOPO- [MOPO] Eronen, P., "Mobility Protocol Options for IKEv2 (MOPO-
IKE)", draft-eronen-mobike-mopo-02 (work in progress), IKE)", draft-eronen-mobike-mopo-02 (work in progress),
February 2005. February 2005.
[PseudoNAT] [RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Dupont, F. and J-J. Bernard, "Transient pseudo-NAT attacks Discovery for IP Version 6 (IPv6)", RFC 2461,
or how NATs are even more evil than you believed", December 1998.
draft-dupont-transient-pseudonat-04 (expired) (work in
progress), June 2004.
[SEND] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure [SEND] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005. Neighbor Discovery (SEND)", RFC 3971, March 2005.
[SMOBIKE] Eronen, P. and H. Tschofenig, "Simple Mobility and [SMOBIKE] Eronen, P. and H. Tschofenig, "Simple Mobility and
Multihoming Extensions for IKEv2 (SMOBIKE)", Multihoming Extensions for IKEv2 (SMOBIKE)",
draft-eronen-mobike-simple-00 (work in progress), draft-eronen-mobike-simple-00 (work in progress),
March 2004. March 2004.
[STUN] Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy,
"STUN - Simple Traversal of User Datagram Protocol (UDP)
Through Network Address Translators (NATs)", RFC 3489,
March 2003.
[UNSAF] Daigle, L., "IAB Considerations for UNilateral Self- [UNSAF] Daigle, L., "IAB Considerations for UNilateral Self-
Address Fixing (UNSAF) Across Network Address Address Fixing (UNSAF) Across Network Address
Translation", RFC 3424, November 2002. Translation", RFC 3424, November 2002.
Author's Address Author's Address
Pasi Eronen (editor) Pasi Eronen (editor)
Nokia Research Center Nokia Research Center
P.O. Box 407 P.O. Box 407
FIN-00045 Nokia Group FIN-00045 Nokia Group
Finland Finland
Email: pasi.eronen@nokia.com Email: pasi.eronen@nokia.com
Appendix A. Changelog Appendix A. Changelog
(This section should be removed by the RFC editor.) (This section should be removed by the RFC editor.)
Changes from -02 to -03:
o Editorial fixes and clarifications (issues 42 and 43).
o Clarified IANA considerations (issue 42).
o Added security considerations about address and topology
disclosure (issue 42).
o Added a suggestion about retransmission timeout (issue 42).
o Change dynamic address updates: MUST NOT do them based on IKEv2
packets, MAY do based on ESP (issue 34).
o Mandate NAT prohibition if not doing NAT traversal (issue 41).
o Clarified security considerations related to NATs (issue 41).
o Don't use SHA-1 in NO_NATS_ALLOWED, just send the addresses (issue
42).
o Added a short section about path testing.
o Added an example protocol run in Section 1.
Changes from -01 to -02: Changes from -01 to -02:
o Moved MOBIKE_SUPPORTED from IKE_SA_INIT to IKE_AUTH (issues 35, o Moved MOBIKE_SUPPORTED from IKE_SA_INIT to IKE_AUTH (issues 35,
37). 37).
o Changed terminology related to NAT prohibition (issues 22, 24). o Changed terminology related to NAT prohibition (issues 22, 24).
o Rewrote much of the ADDITIONAL_*_ADDRESS text, added o Rewrote much of the ADDITIONAL_*_ADDRESS text, added
NO_ADDITIONAL_ADDRESSES notification. NO_ADDITIONAL_ADDRESSES notification.
 End of changes. 126 change blocks. 
375 lines changed or deleted 621 lines changed or added

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