draft-ietf-ipsecme-ipsecha-protocol-06.txt   rfc6311.txt 
Network Working Group R. Singh, Ed. Internet Engineering Task Force (IETF) R. Singh, Ed.
Internet-Draft G. Kalyani Request for Comments: 6311 G. Kalyani
Intended status: Standards Track Cisco Category: Standards Track Cisco
Expires: November 7, 2011 Y. Nir ISSN: 2070-1721 Y. Nir
Check Point Check Point
Y. Sheffer Y. Sheffer
Porticor Porticor
D. Zhang D. Zhang
Huawei Huawei
May 6, 2011 July 2011
Protocol Support for High Availability of IKEv2/IPsec Protocol Support for High Availability of IKEv2/IPsec
draft-ietf-ipsecme-ipsecha-protocol-06
Abstract Abstract
The IPsec protocol suite is widely used for business-critical network The IPsec protocol suite is widely used for business-critical network
traffic. In order to make IPsec deployments highly available, more traffic. In order to make IPsec deployments highly available, more
scalable and failure-resistant, they are often implemented as IPsec scalable, and failure-resistant, they are often implemented as IPsec
High Availability (HA) clusters. However there are many issues in High Availability (HA) clusters. However, there are many issues in
IPsec HA clustering, and in particular in IKEv2 clustering. An IPsec HA clustering, and in particular in Internet Key Exchange
earlier document, "IPsec Cluster Problem Statement", enumerates the Protocol version 2 (IKEv2) clustering. An earlier document, "IPsec
issues encountered in the IKEv2/IPsec HA cluster environment. This Cluster Problem Statement", enumerates the issues encountered in the
document resolves these issues with the least possible change to the IKEv2/IPsec HA cluster environment. This document resolves these
protocol. issues with the least possible change to the protocol.
This document defines an extension to the IKEv2 protocol to solve the This document defines an extension to the IKEv2 protocol to solve the
main issues of "IPsec Cluster Problem Statement" in the commonly main issues of "IPsec Cluster Problem Statement" in the commonly
deployed hot-standby cluster, and provides implementation advice for deployed hot standby cluster, and provides implementation advice for
other issues. The main issues solved are the synchronization of other issues. The main issues solved are the synchronization of
IKEv2 Message ID counters, and of IPsec Replay Counters. IKEv2 Message ID counters, and of IPsec replay counters.
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This document is a product of the Internet Engineering Task Force
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working documents as Internet-Drafts. The list of current Internet- received public review and has been approved for publication by the
Drafts is at http://datatracker.ietf.org/drafts/current/. Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Internet-Drafts are draft documents valid for a maximum of six months Information about the current status of this document, any errata,
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This Internet-Draft will expire on November 7, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology .....................................................5
3. Issues Resolved from IPsec Cluster Problem Statement . . . . . 7 3. Issues Resolved from IPsec Cluster Problem Statement ............7
3.1. Large Amount of State . . . . . . . . . . . . . . . . . . 7 3.1. Large Amount of State ......................................8
3.2. Multiple Members Using the Same SA . . . . . . . . . . . . 8 3.2. Multiple Members Using the Same SA .........................9
3.3. Avoiding Collisions in SPI Number Allocation . . . . . . . 8 3.3. Avoiding Collisions in SPI Number Allocation ...............9
3.4. Interaction with Counter Modes . . . . . . . . . . . . . . 8 3.4. Interaction with Counter Modes .............................9
4. The IKEv2/IPsec SA Counter Synchronization Problem . . . . . . 9 4. The IKEv2/IPsec SA Counter Synchronization Problem .............10
5. SA Counter Synchronization Solution . . . . . . . . . . . . . 10 5. SA Counter Synchronization Solution ............................11
5.1. Processing Rules for IKE Message ID Synchronization . . . 12 5.1. Processing Rules for IKE Message ID Synchronization .......13
5.2. Processing Rules for IPsec Replay Counter 5.2. Processing Rules for IPsec Replay Counter
Synchronization . . . . . . . . . . . . . . . . . . . . . 13 Synchronization ...........................................14
6. IKEv2/IPsec Synchronization Notification Payloads . . . . . . 13 6. IKEv2/IPsec Synchronization Notification Payloads ..............14
6.1. The IKEV2_MESSAGE_ID_SYNC_SUPPORTED Notification . . . . . 14 6.1. The IKEV2_MESSAGE_ID_SYNC_SUPPORTED Notification ..........15
6.2. The IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED Notification . . . 14 6.2. The IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED Notification ......15
6.3. The IKEV2_MESSAGE_ID_SYNC Notification . . . . . . . . . . 15 6.3. The IKEV2_MESSAGE_ID_SYNC Notification ....................16
6.4. The IPSEC_REPLAY_COUNTER_SYNC Notification . . . . . . . . 15 6.4. The IPSEC_REPLAY_COUNTER_SYNC Notification ................16
7. Implementation Details . . . . . . . . . . . . . . . . . . . . 16 7. Implementation Details .........................................17
8. IKE SA and IPsec SA Message Sequencing . . . . . . . . . . . . 17 8. IKE SA and IPsec SA Message Sequencing .........................18
8.1. Handling of Pending IKE Messages . . . . . . . . . . . . . 17 8.1. Handling of Pending IKE Messages ..........................18
8.2. Handling of Pending IPsec Messages . . . . . . . . . . . . 17 8.2. Handling of Pending IPsec Messages ........................18
8.3. IKE SA Inconsistencies . . . . . . . . . . . . . . . . . . 17 8.3. IKE SA Inconsistencies ....................................19
9. Step by Step Details . . . . . . . . . . . . . . . . . . . . . 18 9. Step-by-Step Details ...........................................19
10. Interaction with other specifications . . . . . . . . . . . . 18 10. Interaction with Other Specifications .........................20
11. Security Considerations . . . . . . . . . . . . . . . . . . . 19 11. Security Considerations .......................................21
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 12. IANA Considerations ...........................................21
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20 13. Acknowledgements ..............................................22
14. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 20 14. References ....................................................22
14.1. Draft -06 . . . . . . . . . . . . . . . . . . . . . . . . 21 14.1. Normative References .....................................22
14.2. Draft -05 . . . . . . . . . . . . . . . . . . . . . . . . 21 14.2. Informative References ...................................22
14.3. Draft -04 . . . . . . . . . . . . . . . . . . . . . . . . 21 Appendix A. IKEv2 Message ID Sync Examples ........................24
14.4. Draft -03 . . . . . . . . . . . . . . . . . . . . . . . . 21 A.1. Normal Failover -- Example 1 ...............................24
14.5. Draft -02 . . . . . . . . . . . . . . . . . . . . . . . . 21 A.2. Normal Failover -- Example 2 ...............................24
14.6. Draft -01 . . . . . . . . . . . . . . . . . . . . . . . . 21 A.3. Normal Failover -- Example 3 ...............................25
14.7. Draft -00 . . . . . . . . . . . . . . . . . . . . . . . . 22 A.4. Simultaneous Failover ......................................25
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
15.1. Normative References . . . . . . . . . . . . . . . . . . . 22
15.2. Informative References . . . . . . . . . . . . . . . . . . 22
Appendix A. IKEv2 Message ID Sync Examples . . . . . . . . . . . 23
A.1. Normal Failover - Example 1 . . . . . . . . . . . . . . . 23
A.2. Normal Failover - Example 2 . . . . . . . . . . . . . . . 24
A.3. Normal Failover - Example 3 . . . . . . . . . . . . . . . 24
A.4. Simultaneous Failover . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction 1. Introduction
The IPsec protocol suite, including IKEv2, is a major building block The IPsec protocol suite, including the Internet Key Exchange
of virtual private networks (VPNs). In order to make such VPNs Protocol version 2 (IKEv2), is a major building block of virtual
highly available, more scalable and failure-resistant, these VPNs are private networks (VPNs). In order to make such VPNs highly
implemented as IKEv2/IPsec Highly Available (HA) clusters. However available, more scalable, and failure-resistant, these VPNs are
there are many issues with the IKEv2/IPsec HA cluster. Section 3 and implemented as IKEv2/IPsec Highly Available (HA) clusters. However,
Section 4 below expand on the issues around the IKEv2/IPsec HA there are many issues with the IKEv2/IPsec HA cluster. Sections 3
cluster solution, issues which were first described in the Problem and 4 below expand on the issues around the IKEv2/IPsec HA cluster
Statement [4]. solution, issues which were first described in the problem
statement [6].
In the case of a hot-standby cluster implementation of IKEv2/IPsec In the case of a hot standby cluster implementation of IKEv2/
based VPNs, the IKEv2/IPsec session is first established between the IPsec-based VPNs, the IKEv2/IPsec session is first established
peer and the active member of the cluster. Later, the active member between the peer and the active member of the cluster. Later, the
continuously syncs/updates the IKE/IPsec SA state to the standby active member continuously syncs/updates the IKE/IPsec security
member of the cluster. This primary SA state sync-up takes place association (SA) state to the standby member of the cluster. This
upon each SA bring-up and/or rekey. Performing the SA state primary SA state sync-up takes place upon each SA bring-up and/or
synchronization/update for every single IKE and IPsec message is very rekey. Performing the SA state synchronization/update for every
costly, so normally it is done periodically. As a result, when the single IKE and IPsec message is very costly, so normally it is done
failover event happens, this is first detected by the standby member periodically. As a result, when the failover event happens, this is
and, possibly after a considerable amount of time, it becomes the first detected by the standby member and, possibly after a
active member. During this failover process the peer is unaware of considerable amount of time, it becomes the active member. During
the failover event, and keeps sending IKE requests and IPsec packets this failover process, the peer is unaware of the failover event, and
to the cluster, as in fact it is allowed to do because of the IKEv2 keeps sending IKE requests and IPsec packets to the cluster, as in
windowing feature. After the newly-active member starts, it detects fact it is allowed to do because of the IKEv2 windowing feature.
the mismatch in IKE Message ID values and IPsec replay counters and After the newly active member starts, it detects the mismatch in IKE
needs to resolve this situation. Please see Section 4 for more Message ID values and IPsec replay counters and needs to resolve this
details of the problem. situation. Please see Section 4 for more details of the problem.
This document defines an extension to the IKEv2 protocol to solve the This document defines an extension to the IKEv2 protocol to solve the
main issues of IKE Message ID synchronization and IPsec SA replay main issues of IKE Message ID synchronization and IPsec SA replay
counter synchronization, and gives implementation advice to address counter synchronization, and gives implementation advice to address
other issues. Following is a summary of the solutions provided in other issues. Following is a summary of the solutions provided in
this document: this document:
o IKEv2 Message ID synchronization: this is done by syncing up the o IKEv2 Message ID synchronization: This is done by syncing up the
expected send and receive Message ID values with the peer, and expected send and receive Message ID values with the peer, and
updating the values at the newly active cluster member. updating the values at the newly active cluster member.
o IPsec Replay Counter synchronization: this is done by incrementing
o IPsec replay counter synchronization: This is done by incrementing
the cluster's outgoing SA replay counter values by a "large" the cluster's outgoing SA replay counter values by a "large"
number; in addition, the newly-active member requests the peer to number; in addition, the newly active member requests the peer to
increment the replay counter values it is using for the peer's increment the replay counter values it is using for the peer's
outgoing traffic. outgoing traffic.
Although this document describes the IKEv2 Message ID and IPsec Although this document describes the IKEv2 Message ID and IPsec
replay counter synchronization in the context of an IPsec HA cluster, replay counter synchronization in the context of an IPsec HA cluster,
the solution provided is generic and can be used in other scenarios the solution provided is generic and can be used in other scenarios
where IKEv2 Message ID or IPsec SA replay counter synchronization may where IKEv2 Message ID or IPsec SA replay counter synchronization may
be required. be required.
Implementations differ on the need to synchronize the IKEv2 Message Implementations differ on the need to synchronize the IKEv2 Message
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separately, using a separate notification for each capability. This separately, using a separate notification for each capability. This
provides the flexibility of implementing either or both of these provides the flexibility of implementing either or both of these
solutions. solutions.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [1]. document are to be interpreted as described in [1].
"SA Counter Synchronization Request/Response" are the request viz. "SA Counter Synchronization" is the informational exchange defined in
response of the informational exchange defined in this document to this document to synchronize the IKEv2/IPsec SA counter information
synchronize the IKEv2/IPsec SA counter information between one member between one member of the cluster and the peer.
of the cluster and the peer.
Some of the terms listed below are reused from [4] with further Some of the terms listed below are reused from [6] with further
clarification in the context of the current document. clarification in the context of the current document.
o "Hot Standby Cluster", or "HS Cluster" is a cluster where only one o "Hot Standby Cluster", or "HS Cluster", is a cluster where only
of the members is active at any one time. This member is also one of the members is active at any one time. This member is also
referred to as the "active" member, whereas the other(s) are referred to as the "active" member, whereas the other(s) are
referred to as "standby" members. VRRP [5] is one method of referred to as "standby" members. The Virtual Router Redundancy
building such a cluster. The goal of the Hot Standby Cluster is Protocol (VRRP) [7] is one method of building such a cluster. The
to create the illusion of a single virtual gateway to the peer(s). goal of the hot standby cluster is to create the illusion of a
o "Active Member" is the primary member in the Hot-Standby cluster. single virtual gateway to the peer(s).
o "Active Member" is the primary member in the hot standby cluster.
It is responsible for forwarding packets on behalf of the virtual It is responsible for forwarding packets on behalf of the virtual
gateway. gateway.
o "Standby Member" is the primary backup member. This member takes o "Standby Member" is the primary backup member. This member takes
control, i.e. becomes the active member, after the failover event. control, i.e., becomes the active member, after the failover
event.
o "Peer" is an IKEv2/IPsec endpoint that maintains an IPsec o "Peer" is an IKEv2/IPsec endpoint that maintains an IPsec
connection with the Hot-Standby cluster. The Peer identifies the connection with the hot standby cluster. The peer identifies the
cluster by the cluster's (single) IP address. If a failover event cluster by the cluster's (single) IP address. If a failover event
occurs, the standby member of the cluster becomes active, and the occurs, the standby member of the cluster becomes active, and the
peer normally doesn't notice that failover has taken place. peer normally doesn't notice that failover has taken place.
Although we treat the peer as a single entity, it may also be a Although we treat the peer as a single entity, it may also be a
cluster. cluster.
o "Multiple failover" is the situation where, in a cluster with o "Multiple failover" is the situation where, in a cluster with
three or more members, multiple failover events happen in rapid three or more members, multiple failover events happen in rapid
succession, e.g. from M1 to M2, and then to M3. It is our goal succession, e.g., from M1 to M2, and then to M3. It is our goal
that the implementation should be able to handle this situation, that the implementation should be able to handle this situation,
i.e. to handle the new failover event even if it is still i.e., to handle the new failover event even if it is still
processing the old failover. processing the old failover.
o "Simultaneous failover" is the situation where two clusters have o "Simultaneous failover" is the situation where two clusters have
an IPsec connection between them, and failover happens at both an IPsec connection between them, and failover happens at both
ends at the same time. It is our goal that implementations should ends at the same time. It is our goal that implementations should
be able to handle simultaneous failover. be able to handle simultaneous failover.
o "IPsec replay counter" is the Encapsulating Security Payload (ESP)
Sequence Number or Extended Sequence Number (Section 2.2 of [2]),
or the respective field in the Authentication Header (AH) protocol
(Section 2.5 of [3]).
The generic term "IKEv2/IPsec SA Counters" is used throughout this The generic term "IKEv2/IPsec SA Counters" is used throughout this
document. This term refers to both IKEv2 Message ID counters and document. This term refers to both IKEv2 Message ID counters and
IPsec replay counters. According to the IPsec standards, the IKEv2 IPsec replay counters. According to the IPsec standards, the IKEv2
Message ID counter is mandatory, and used to ensure reliable delivery Message ID counter is mandatory, and used to ensure reliable delivery
as well as to protect against message replay in IKEv2; the IPsec SA as well as to protect against message replay in IKEv2; the IPsec SA
replay counters are optional, and are used to provide the IPsec anti- replay counters are optional, and are used to provide the IPsec anti-
replay feature. replay feature.
Some of these terms are used in the following architectural diagram. Some of these terms are used in the following architectural diagram.
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| Cluster | | Cluster |
| | | |
| +---------+ | | +---------+ |
| | | | | | | |
| | Active | | | | Active | |
| | | | | | | |
| | Member | | | | Member | |
| | | | | | | |
| +---------+ | | +---------+ |
| ^ | | ^ |
+---------+ | Sync | | +---------+ | Synch | |
| | | Channel | | | | | Channel | |
| IPsec | IKE/IPsec Traffic | | | | IPsec | IKE/IPsec Traffic | | |
| | <=============================> | | | | | <=============================> | | |
| Peer | | | | | Peer | | | |
| | | | | | | | | |
+---------+ | | | +---------+ | | |
| v | | v |
| +---------+ | | +---------+ |
| | | | | | | |
| | Standby | | | | Standby | |
| | | | | | | |
| | Member | | | | Member | |
| | | | | | | |
| +---------+ | | +---------+ |
+---------------+ +---------------+
An IPsec Hot Standby Cluster An IPsec Hot Standby Cluster
3. Issues Resolved from IPsec Cluster Problem Statement 3. Issues Resolved from IPsec Cluster Problem Statement
The IPsec Cluster Problem Statement [4] enumerates the problems "IPsec Cluster Problem Statement" [6] enumerates the problems raised
raised by IPsec clusters. The following table lists the problem by IPsec clusters. The following table lists the problem statement's
statement's sections that are resolved by this document. sections that are resolved by this document.
o 3.2. Lots of Long Lived State
o 3.2. A Lot of Long-Lived State
o 3.3. IKE Counters o 3.3. IKE Counters
o 3.4. Outbound SA Counters o 3.4. Outbound SA Counters
o 3.5. Inbound SA Counters o 3.5. Inbound SA Counters
o 3.6. Missing Synchronization Messages o 3.6. Missing Synch Messages
o 3.7. Simultaneous use of IKE and IPsec SAs by Different Members o 3.7. Simultaneous Use of IKE and IPsec SAs by Different Members
* 3.7.1. Outbound SAs using counter modes * 3.7.1. Outbound SAs Using Counter Modes
o 3.8. Different IP addresses for IKE and IPsec o 3.8. Different IP Addresses for IKE and IPsec
o 3.9. Allocation of SPIs o 3.9. Allocation of SPIs
The main problem areas are solved using the protocol extension The main problem areas are solved using the protocol extension
defined below, starting with Section 5; additionally, this section defined below, starting with Section 5; additionally, this section
provides implementation advice for other issues in the following provides implementation advice for other issues in the following
subsections. Implementers should note that these subsections include subsections. Implementers should note that these subsections include
a number of new security-critical requirements. a number of new security-critical requirements.
3.1. Large Amount of State 3.1. Large Amount of State
Section 3.2 of the Problem Statement mentions that a lot of state Section 3.2 of the problem statement [6] mentions that a lot of state
needs to be synchronized for a cluster to be transparent. The actual needs to be synchronized for a cluster to be transparent. The actual
volume of that data is very much implementation-dependent, and even volume of that data is very much implementation-dependent, and even
for the same implementation, the amounts of data may vary wildly. An for the same implementation, the amounts of data may vary wildly. An
IPsec gateway used for inter-domain VPN with a dozen other gateways, IPsec gateway used for inter-domain VPN with a dozen other gateways,
and having SAs that are rekeyed every 8 hours, will need a lot less and having SAs that are rekeyed every 8 hours, will need a lot less
synchronization traffic than a similar gateway used for remote synchronization traffic than a similar gateway used for remote
access, and supporting 10,000 clients. This is because counter access, and supporting 10,000 clients. This is because counter
synchronization is proportional to the number of SAs and requires synchronization is proportional to the number of SAs and requires
little data, and the setting up of an SA requires a lot of data. little data, and the setting up of an SA requires a lot of data.
Additionally, remote access IKE and IPsec SA setup tend to happen at Additionally, remote access IKE and IPsec SA setup tend to happen at
skipping to change at page 7, line 52 skipping to change at page 8, line 41
period of time. period of time.
If a large volume of traffic is necessary, it may be advisable to use If a large volume of traffic is necessary, it may be advisable to use
a dedicated high-speed network interface for synch traffic. When a dedicated high-speed network interface for synch traffic. When
packet loss can be made extremely low, it may be advisable to use a packet loss can be made extremely low, it may be advisable to use a
stateless transport such as UDP, to minimize network overhead. stateless transport such as UDP, to minimize network overhead.
If these methods are insufficient, it may be prudent that for some If these methods are insufficient, it may be prudent that for some
SAs the entire state is not synchronized. Instead, only an SAs the entire state is not synchronized. Instead, only an
indication of the SA's existence is synchronized. This, in indication of the SA's existence is synchronized. This, in
combination with a sticky solution (as described in section 3.7 of combination with a sticky solution (as described in Section 3.7 of
the problem statement) ensures that the traffic from a particular the problem statement [6]) ensures that the traffic from a particular
peer does not reach a different member before an actual failover peer does not reach a different member before an actual failover
happens. When that happens, the method described in [6] can be used happens. When that happens, the method described in [8] can be used
to quickly force the peer to set up a new SA. to quickly force the peer to set up a new SA.
3.2. Multiple Members Using the Same SA 3.2. Multiple Members Using the Same SA
In a load-sharing cluster of the "duplicate" variety (see section 3.7 In a load-sharing cluster of the "duplicate" variety (see Section 3.7
of the problem statement) multiple members may need to send traffic of the problem statement [6]), multiple members may need to send
with the same selectors. To actually use the same SA the cluster traffic with the same selectors. To actually use the same SA, the
would have to synchronize the Replay Counter after every packet, and cluster would have to synchronize the replay counter after every
that would impose unreasonable requirements on the synch connection. packet, and that would impose unreasonable requirements on the synch
connection.
A far better solution would be to not synchronize the outbound SA, A far better solution would be to not synchronize the outbound SA,
and create multiple outbound SAs, one for each member. The problem and create multiple outbound SAs, one for each member. The problem
with this option is that the peer might view these multiple parallel with this option is that the peer might view these multiple parallel
SAs as redundant, and tear down all but one of them. SAs as redundant, and tear down all but one of them.
Section 2.8 of [2] specifically allows multiple parallel SAs, but the Section 2.8 of [4] specifically allows multiple parallel SAs, but the
reason given for this is to have multiple SAs with different QoS reason given for this is to have multiple SAs with different Quality
attributes. So while this is not a new requirement of IKEv2 of Service (QoS) attributes. So while this is not a new requirement
implementations working with QoS, we re-iterate here that IPsec peers of IKEv2 implementations working with QoS, we re-iterate here that
MUST accept the long-term existence of multiple parallel SAs, even IPsec peers MUST accept the long-term existence of multiple parallel
when QoS mechanisms are not in use. SAs, even when QoS mechanisms are not in use.
3.3. Avoiding Collisions in SPI Number Allocation 3.3. Avoiding Collisions in SPI Number Allocation
Section 3.9 of the problem statement describes the problem of two Section 3.9 of the problem statement [6] describes the problem of two
cluster members allocating the same SPI number for two different SAs. cluster members allocating the same Security Parameter Index (SPI)
This would violate section 4.4.2.1 of [3]. There are several schemes number for two different SAs. This behavior would violate
to allow implementations to avoid such collisions, such as Section 4.4.2.1 of [5]. There are several schemes to allow
partitioning the SPI space, a request-response over the synch implementations to avoid such collisions, such as partitioning the
channel, and locking mechanisms. We believe that these are SPI space, a request-response over the synch channel, and locking
sufficiently robust and available so that we don't need to make an mechanisms. We believe that these are sufficiently robust and
exception to RFC 4301, and we can leave this problem for the available so that we don't need to make an exception to the rules in
implementations to solve. Cluster members must not generate multiple Section 4.4.2.1 of RFC 4301 [5], and we can leave this problem for
inbound SAs with the same SPI. the implementations to solve. Cluster members must not generate
multiple inbound SAs with the same SPI.
3.4. Interaction with Counter Modes 3.4. Interaction with Counter Modes
For SAs involving counter mode ciphers such as CTR [7] or GCM [8] For SAs involving counter mode ciphers such as Counter Mode (CTR) [9]
there is yet another complication. The initial vector for such modes or Galois/Counter Mode (GCM) [10], there is yet another complication.
MUST NOT be repeated, and senders may use methods such as counters or The initial vector for such modes MUST NOT be repeated, and senders
LFSRs to ensure this property. For an SA shared between multiple may use methods such as counters or linear feedback shift registers
active members (load sharing cases), implementations MUST ensure that (LFSRs) to ensure this property. For an SA shared between multiple
active members (load-sharing cases), implementations MUST ensure that
no initial vector is ever repeated. Similar concerns apply to an SA no initial vector is ever repeated. Similar concerns apply to an SA
failing over from one member to another. See [9] for a discussion of failing over from one member to another. See [11] for a discussion
this problem in another context. of this problem in another context.
Just as in the SPI collision problem, there are ways to avoid a Just as in the SPI collision problem, there are ways to avoid a
collision of initial vectors, and this is left up to implementations. collision of initial vectors, and this is left up to implementations.
In the context of load sharing, parallel SAs are a simple solution to In the context of load sharing, parallel SAs are a simple solution to
this problem as well. this problem as well.
4. The IKEv2/IPsec SA Counter Synchronization Problem 4. The IKEv2/IPsec SA Counter Synchronization Problem
The IKEv2 protocol [2] states that "An IKE endpoint MUST NOT exceed The IKEv2 protocol [4] states that "An IKE endpoint MUST NOT exceed
the peer's stated window size for transmitted IKE requests". the peer's stated window size for transmitted IKE requests".
All IKEv2 messages are required to follow a request-response All IKEv2 messages are required to follow a request-response
paradigm. The initiator of an IKEv2 request MUST retransmit the paradigm. The initiator of an IKEv2 request MUST retransmit the
request, until it has received a response from the peer. IKEv2 request, until it has received a response from the peer. IKEv2
introduces a windowing mechanism that allows multiple requests to be introduces a windowing mechanism that allows multiple requests to be
outstanding at a given point of time, but mandates that the sender's outstanding at a given point of time, but mandates that the sender's
window should not move until the oldest message it has sent is window should not move until the oldest message it has sent is
acknowledged. Loss of even a single message leads to repeated acknowledged. Loss of even a single message leads to repeated
retransmissions followed by an IKEv2 SA teardown if the retransmissions followed by an IKEv2 SA teardown if the
retransmissions remain unacknowledged. retransmissions remain unacknowledged.
An IPsec Hot Standby Cluster is required to ensure that in the case An IPsec hot standby cluster is required to ensure that in the case
of failover, the standby member becomes active immediately. The of failover, the standby member becomes active immediately. The
standby member is expected to have the exact value of the Message ID standby member is expected to have the exact value of the Message ID
counter as the active member had before failover. Even assuming the counter as the active member had before failover. Even assuming the
best effort to update the Message ID values from active to standby best effort to update the Message ID values from active to standby
member, the values at the standby member can still be stale due to member, the values at the standby member can still be stale due to
the following reasons: the following reasons:
o The standby member is unaware of the last message that was o The standby member is unaware of the last message that was
received and acknowledged by the previously active member, as the received and acknowledged by the previously active member, as the
failover event could have happened before the standby member could failover event could have happened before the standby member could
be updated. be updated.
o The standby member does not have information about on-going o The standby member does not have information about on-going
unacknowledged requests sent by the previously active member. As unacknowledged requests sent by the previously active member. As
a result after the failover event, the newly active member cannot a result, after the failover event, the newly active member cannot
retransmit those requests. retransmit those requests.
When a standby member takes over as the active member, it can only When a standby member takes over as the active member, it can only
initialize the Message ID values from the previously updated values. initialize the Message ID values from the previously updated values.
This would make it reject requests from the peer when these values This would make it reject requests from the peer when these values
are stale. Conversely, the standby member may end up reusing a stale are stale. Conversely, the standby member may end up reusing a stale
Message ID value which would cause the peer to drop the request. Message ID value, which would cause the peer to drop the request.
Eventually there is a high probability of the IKEv2 and corresponding Eventually, there is a high probability of the IKEv2 and
IPsec SAs getting torn down simply because of a transitory Message ID corresponding IPsec SAs getting torn down simply because of a
mismatch and retransmission of requests, negating the benefits of the transitory Message ID mismatch and retransmission of requests,
high availability cluster despite the periodic update between the negating the benefits of the high-availability cluster despite the
cluster members. periodic update between the cluster members.
A similar issue is also observed with IPsec anti-replay counters if A similar issue is also observed with IPsec anti-replay counters if
anti-replay protection is enabled, which is commonly the case. anti-replay protection is enabled, which is commonly the case.
Regardless of how well the ESP and AH SA counters are synchronized Regardless of how well the ESP and AH SA counters are synchronized
from the active to the standby member, there is a chance that the from the active to the standby member, there is a chance that the
standby member would end up with stale counter values. The standby standby member would end up with stale counter values. The standby
member would then use those stale counter values when sending IPsec member would then use those stale counter values when sending IPsec
packets. The peer would drop such packets since when the anti-replay packets. The peer would drop such packets, since when the anti-
protection feature is enabled, duplicate use of counters is not replay protection feature is enabled, duplicate use of counters is
allowed. Note that IPsec allows the sender to skip some counter not allowed. Note that IPsec allows the sender to skip some counter
values and continue sending with higher counter values. values and continue sending with higher counter values.
We conclude that a mechanism is required to ensure that the standby We conclude that a mechanism is required to ensure that the standby
member has correct Message ID and IPsec counter values when it member has correct Message ID and IPsec counter values when it
becomes active, so that sessions are not torn down as a result of becomes active, so that sessions are not torn down as a result of
mismatched counters. mismatched counters.
5. SA Counter Synchronization Solution 5. SA Counter Synchronization Solution
This document defines two separate approaches to resolving the issues This document defines two separate approaches to resolving the issues
of mismatched IKE Message ID values and IPsec counter values. of mismatched IKE Message ID values and IPsec counter values.
o In the case of IKE Message ID values, the newly active cluster o In the case of IKE Message ID values, the newly active cluster
member and the peer negotiate a pair of new values so that future member and the peer negotiate a pair of new values so that future
IKE messages will not be dropped. IKE messages will not be dropped.
o For IPsec counter values, the newly-active member and the peer
o For IPsec counter values, the newly active member and the peer
both increment their respective counter values, "skipping forward" both increment their respective counter values, "skipping forward"
by a large number, to ensure that no IPsec counters are ever by a large number, to ensure that no IPsec counters are ever
reused. reused.
Although conceptually separate, the two synchronization processes Although conceptually separate, the two synchronization processes
would typically take place simultaneously. would typically take place simultaneously.
First, the peer and the active member of the cluster negotiate their First, the peer and the active member of the cluster negotiate their
ability to support IKEv2 Message ID synchronization and/or IPsec ability to support IKEv2 Message ID synchronization and/or IPsec
Replay Counter synchronization. This is done by exchanging one or replay counter synchronization. This is done by exchanging one or
both of the IKEV2_MESSAGE_ID_SYNC_SUPPORTED and both of the IKEV2_MESSAGE_ID_SYNC_SUPPORTED and
IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED notifications during the IKE_AUTH IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED notifications during the IKE_AUTH
exchange. When negotiating these capabilities, the responder MUST exchange. When negotiating these capabilities, the responder MUST
NOT assert support of a capability unless such support was asserted NOT assert support of a capability unless such support was asserted
by the initiator. Only a capability whose support was asserted by by the initiator. Only a capability whose support was asserted by
both parties can be used during the lifetime of the SA. The peer's both parties can be used during the lifetime of the SA. The peer's
capabilities with regard to this extension are part of the IKEv2 SA capabilities with regard to this extension are part of the IKEv2 SA
state, and thus MUST be shared between the cluster members. state, and thus MUST be shared between the cluster members.
This per-IKE SA information is shared with the other cluster members. This per-IKE SA information is shared with the other cluster members.
Peer Active Member Peer Active Member
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
HDR, SK {IDi, [CERT], [CERTREQ], [IDr], AUTH, HDR, SK {IDi, [CERT], [CERTREQ], [IDr], AUTH,
[N(IKEV2_MESSAGE_ID_SYNC_SUPPORTED),] [N(IKEV2_MESSAGE_ID_SYNC_SUPPORTED),]
[N(IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED),] [N(IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED),]
SAi2, TSi, TSr} ----------> SAi2, TSi, TSr} ---------->
<-------- HDR, SK {IDr, [CERT+], [CERTREQ+], AUTH, <-------- HDR, SK {IDr, [CERT+], [CERTREQ+], AUTH,
[N(IKEV2_MESSAGE_ID_SYNC_SUPPORTED),] [N(IKEV2_MESSAGE_ID_SYNC_SUPPORTED),]
[N(IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED),] SAr2, TSi, TSr} [N(IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED),]
SAr2, TSi, TSr}
After a failover event, the standby member MAY use the IKE Message ID After a failover event, the standby member MAY use the IKE Message ID
and/or IPsec Replay Counter synchronization capability when it and/or IPsec replay counter synchronization capability when it
becomes the active member, and provided support for the capabilities becomes the active member, and provided support for the capabilities
used has been negotiated. Following that, the peer MUST respond to used has been negotiated. Following that, the peer MUST respond to
any synchronization message it receives from the newly-active cluster any synchronization message it receives from the newly active cluster
member, subject to the rules noted below. member, subject to the rules noted below.
After the failover event, when the standby member becomes active, it After the failover event, when the standby member becomes active, it
has to synchronize its SA counters with the peer. There are now four has to synchronize its SA counters with the peer. There are now four
possible cases: possible cases:
1. The cluster member wishes to only perform IKE Message ID value 1. The cluster member wishes to only perform IKE Message ID value
synchronization. In this case it initiates an Informational synchronization. In this case, it initiates an Informational
exchange, with Message ID zero and the sole notification exchange, with Message ID zero and the sole notification
IKEV2_MESSAGE_ID_SYNC. IKEV2_MESSAGE_ID_SYNC.
2. If the newly-active member wishes to perform only IPsec replay
2. If the newly active member wishes to perform only IPsec replay
counter synchronization, it generates a regular IKEv2 counter synchronization, it generates a regular IKEv2
Informational exchange using the current Message ID values, and Informational exchange using the current Message ID values, and
containing the IPSEC_REPLAY_COUNTER_SYNC notification. containing the IPSEC_REPLAY_COUNTER_SYNC notification.
3. If synchronization of both counters is needed, the cluster member 3. If synchronization of both counters is needed, the cluster member
generates a zero-Message ID message as in case #1, and includes generates a zero-Message ID message as in case #1, and includes
both notifications in this message. both notifications in this message.
4. Lastly, the peer may not support this extension. This is known 4. Lastly, the peer may not support this extension. This is known
to the newly-active member (because the cluster members must to the newly active member (because the cluster members must
share this information, as noted earlier). This case is the share this information, as noted earlier). This case is the
existing IKEv2 behavior, and the IKE and IPsec SAs may or may not existing IKEv2 behavior, and the IKE and IPsec SAs may or may not
survive the failover, depending on the exact state on the peer survive the failover, depending on the exact state on the peer
and the cluster member. and the cluster member.
This figure contains the IKE message exchange used for SA counter This figure contains the IKE message exchange used for SA counter
synchronization. The following subsections describe the details of synchronization. The following subsections describe the details of
the sender and receiver processing of each message. the sender and receiver processing of each message.
Standby [Newly Active] Member Peer Standby [Newly Active] Member Peer
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
HDR, SK {N(IKEV2_MESSAGE_ID_SYNC), HDR, SK {N(IKEV2_MESSAGE_ID_SYNC),
[N(IPSEC_REPLAY_COUNTER_SYNC)]} --------> [N(IPSEC_REPLAY_COUNTER_SYNC)]} -------->
<--------- HDR, SK {N(IKEV2_MESSAGE_ID_SYNC)} <--------- HDR, SK {N(IKEV2_MESSAGE_ID_SYNC)}
Alternatively, if only IPsec Replay Counter synchronization is Alternatively, if only IPsec replay counter synchronization is
desired, a normal Informational exchange is used, where the Message desired, a normal Informational exchange is used, where the Message
ID is non-zero: ID is non-zero:
Standby [Newly Active] Member Peer Standby [Newly Active] Member Peer
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
HDR, SK{N(IPSEC_REPLAY_COUNTER_SYNC)} --------> HDR, SK{N(IPSEC_REPLAY_COUNTER_SYNC)} -------->
<--------- HDR <--------- HDR
5.1. Processing Rules for IKE Message ID Synchronization 5.1. Processing Rules for IKE Message ID Synchronization
The newly-active member sends a request containing two counter The newly active member sends a request containing two counter
values, one for the member (itself) and another for the peer, as well values, one for the member (itself) and another for the peer, as well
as a random nonce. We denote the values M1 and P1. The peer as a random nonce. We denote the values M1 and P1. The peer
responds with a message containing two counter values, M2 and P2 responds with a message containing two counter values, M2 and P2
(note that the values appear in the opposite order in the (note that the values appear in the opposite order in the
notification's payload). The goal of the rules below is to prevent notification's payload). The goal of the rules below is to prevent
an attacker from replaying a synchronization message, thereby an attacker from replaying a synchronization message and thereby
invalidating IKE messages that are currently in process. invalidating IKE messages that are currently in process.
o M1 is the next sender's Message ID to be used by the member. M1 o M1 is the next sender's Message ID to be used by the member. M1
MUST be chosen so that it is larger than any value known to have MUST be chosen so that it is larger than any value known to have
been used. It is RECOMMENDED to increment the known value at been used. It is RECOMMENDED to increment the known value at
least by the size of the IKE sender window. least by the size of the IKE sender window.
o P1 SHOULD be 1 more than the last Message ID value received from o P1 SHOULD be 1 more than the last Message ID value received from
the peer, but may be any higher value. the peer, but may be any higher value.
o The member SHOULD communicate the sent values to the other cluster o The member SHOULD communicate the sent values to the other cluster
members, so that if a second failover event takes place, the members, so that if a second failover event takes place, the
synchronization message is not replayed. Such a replay would synchronization message is not replayed. Such a replay would
result in the eventual deletion of the IKE SA (see below). result in the eventual deletion of the IKE SA (see below).
o The peer MUST silently drop any received synchronization message o The peer MUST silently drop any received synchronization message
if M1 is lower than or equal to the highest value it has seen from if M1 is lower than or equal to the highest value it has seen from
the cluster. This includes any previous received synchronization the cluster. This includes any previous received synchronization
messages. messages.
o M2 MUST be at least the higher of the received M1, and one more o M2 MUST be at least the higher of the received M1, and one more
than the highest sender value received from the cluster. This than the highest sender value received from the cluster. This
includes any previous received synchronization messages. includes any previous received synchronization messages.
o P2 MUST be the higher of the received P1 value, and one more than o P2 MUST be the higher of the received P1 value, and one more than
the highest sender value used by the peer. the highest sender value used by the peer.
o The request contains a Nonce field. This field MUST be returned o The request contains a Nonce field. This field MUST be returned
in the response, unchanged. A response MUST be silently dropped in the response, unchanged. A response MUST be silently dropped
if the received Nonce does not match the one that was sent. if the received nonce does not match the one that was sent.
o Both the request and the response MUST NOT contain any additional o Both the request and the response MUST NOT contain any additional
payloads, other than an optional IPSEC_REPLAY_COUNTER_SYNC payloads, other than an optional IPSEC_REPLAY_COUNTER_SYNC
notification in the request. notification in the request.
o The request and the response MUST both be sent with a Message ID o The request and the response MUST both be sent with a Message ID
value of zero. value of zero.
5.2. Processing Rules for IPsec Replay Counter Synchronization 5.2. Processing Rules for IPsec Replay Counter Synchronization
Upon failover, the newly-active member MUST increment its own Replay Upon failover, the newly active member MUST increment its own replay
Counter (the counter used for outgoing traffic), so as to prevent the counter (the counter used for outgoing traffic), so as to prevent the
case of its traffic being dropped by the peer as replay. We note case of its traffic being dropped by the peer as replay. We note
that IPsec allows the replay counter to skip forward by any amount. that IPsec allows the replay counter to skip forward by any amount.
The estimate is based on the outgoing IPsec bandwidth and the The estimate is based on the outgoing IPsec bandwidth and the
frequency of synchronization between cluster members. In those frequency of synchronization between cluster members. In those
implementations where it is difficult to estimate this value, the implementations where it is difficult to estimate this value, the
counter can be incremented by a very large number, e.g. 2**30. In counter can be incremented by a very large number, e.g., 2**30. In
the latter case, a rekey SHOULD follow shortly afterwards, to ensure the latter case, a rekey SHOULD follow shortly afterwards, to ensure
that the counter never wraps around. that the counter never wraps around.
Next, the cluster member estimates the number of incoming messages it Next, the cluster member estimates the number of incoming messages it
might have missed, using similar logic. The member sends out a might have missed, using similar logic. The member sends out an
IPSEC_REPLAY_COUNTER_SYNC notification, either stand-alone or IPSEC_REPLAY_COUNTER_SYNC notification, either stand-alone or
together with a IKEV2_MESSAGE_ID_SYNC notification. together with an IKEV2_MESSAGE_ID_SYNC notification.
If the IPSEC_REPLAY_COUNTER_SYNC is included in the same message as If the IPSEC_REPLAY_COUNTER_SYNC is included in the same message as
IKEV2_MESSAGE_ID_SYNC, the peer MUST process the Message ID IKEV2_MESSAGE_ID_SYNC, the peer MUST process the Message ID
notification first (which might cause the entire message to be notification first (which might cause the entire message to be
dropped as a replay). Then, it MUST increment the replay counters dropped as a replay). Then, it MUST increment the replay counters
for all Child SAs associated with the current IKE SA by the amount for all Child SAs associated with the current IKE SA by the amount
requested by the cluster member. requested by the cluster member.
6. IKEv2/IPsec Synchronization Notification Payloads 6. IKEv2/IPsec Synchronization Notification Payloads
skipping to change at page 14, line 21 skipping to change at page 15, line 25
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and
'Notify Message Type' fields are the same as described in Section 3 'Notify Message Type' fields are the same as described in Section 3
of [2]. The 'SPI Size' field MUST be set to 0 to indicate that the of [4]. The 'SPI Size' field MUST be set to 0 to indicate that the
SPI is not present in this message. The 'Protocol ID' MUST be set to SPI is not present in this message. The 'Protocol ID' MUST be set to
0, since the notification is not specific to a particular security 0, since the notification is not specific to a particular security
association. The 'Payload Length' field is set to the length in association. The 'Payload Length' field is set to the length in
octets of the entire payload, including the generic payload header. octets of the entire payload, including the generic payload header.
The 'Notify Message Type' field is set to indicate The 'Notify Message Type' field is set to indicate
IKEV2_MESSAGE_ID_SYNC_SUPPORTED, value TBD by IANA. There is no data IKEV2_MESSAGE_ID_SYNC_SUPPORTED (16420). There is no data associated
associated with this notification. with this notification.
6.2. The IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED Notification 6.2. The IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED Notification
This notification payload is included in the IKE_AUTH request/ This notification payload is included in the IKE_AUTH request/
response to indicate support for the IPsec SA Replay Counter response to indicate support for the IPsec SA replay counter
synchronization mechanism described in this document. synchronization mechanism described in this document.
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and
'Notify Message Type' fields are the same as described in Section 3 'Notify Message Type' fields are the same as described in Section 3
of [2] . The 'SPI Size' field MUST be set to 0 to indicate that the of [4] . The 'SPI Size' field MUST be set to 0 to indicate that the
SPI is not present in this message. The 'Protocol ID' MUST be set to SPI is not present in this message. The 'Protocol ID' MUST be set to
0, since the notification is not specific to a particular security 0, since the notification is not specific to a particular security
association. The 'Payload Length' field is set to the length in association. The 'Payload Length' field is set to the length in
octets of the entire payload, including the generic payload header. octets of the entire payload, including the generic payload header.
The 'Notify Message Type' field is set to indicate The 'Notify Message Type' field is set to indicate
IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED, value TBD by IANA. There is no IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED (16421). There is no data
data associated with this notification. associated with this notification.
6.3. The IKEV2_MESSAGE_ID_SYNC Notification 6.3. The IKEV2_MESSAGE_ID_SYNC Notification
This notification payload type (value TBD by IANA) is defined to This notification payload type (16422) is defined to synchronize the
synchronize the IKEv2 Message ID values between the newly-active IKEv2 Message ID values between the newly active (formerly standby)
(formerly standby) cluster member and the peer. cluster member and the peer.
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce Data | | Nonce Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EXPECTED_SEND_REQ_MESSAGE_ID | | EXPECTED_SEND_REQ_MESSAGE_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EXPECTED_RECV_REQ_MESSAGE_ID | | EXPECTED_RECV_REQ_MESSAGE_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
It contains the following data. It contains the following data.
o Nonce Data (4 octets): the random nonce data. The data should be
o Nonce Data (4 octets): The random nonce data. The data should be
identical in the synchronization request and response. identical in the synchronization request and response.
o EXPECTED_SEND_REQ_MESSAGE_ID (4 octets): this field is used by the
o EXPECTED_SEND_REQ_MESSAGE_ID (4 octets): This field is used by the
sender of this notification payload to indicate the Message ID it sender of this notification payload to indicate the Message ID it
will use in the next request that it will send to the other will use in the next request that it will send to the other
protocol peer. protocol peer.
o EXPECTED_RECV_REQ_MESSAGE_ID (4 octets): this field is used by the
o EXPECTED_RECV_REQ_MESSAGE_ID (4 octets): This field is used by the
sender of this notification payload to indicate the Message ID it sender of this notification payload to indicate the Message ID it
is expecting in the next request to be received from the other is expecting in the next request to be received from the other
protocol peer. protocol peer.
6.4. The IPSEC_REPLAY_COUNTER_SYNC Notification 6.4. The IPSEC_REPLAY_COUNTER_SYNC Notification
This notification payload type (value TBD by IANA) is defined to This notification payload type (16423) is defined to synchronize the
synchronize the IPsec SA Replay Counters between the newly-active IPsec SA replay counters between the newly active (formerly standby)
(formerly standby) cluster member and the peer. Since there may be cluster member and the peer. Since there may be numerous IPsec SAs
numerous IPsec SAs established under a single IKE SA, we do not established under a single IKE SA, we do not directly synchronize the
directly synchronize the value of each one. Instead, a delta value value of each one. Instead, a delta value is sent, and all replay
is sent and all Replay Counters for Child SAs of this IKE SA are counters for Child SAs of this IKE SA are incremented by the same
incremented by the same value. Note that this solution requires that value. Note that this solution requires that either all Child SAs
either all Child SAs use Extended Sequence Numbers or else that no use Extended Sequence Numbers (ESNs) or else that no Child SA uses
Child SA uses Extended Sequence Numbers [3]. This notification is ESNs. This notification is only sent by the cluster.
only sent by the cluster.
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Incoming IPsec SA delta value | | Incoming IPsec SA delta value |
skipping to change at page 16, line 19 skipping to change at page 17, line 23
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Incoming IPsec SA delta value | | Incoming IPsec SA delta value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The notification payload contains the following data. The notification payload contains the following data.
o Incoming IPsec SA delta value (4 or 8 octets): The sender requests o Incoming IPsec SA delta value (4 or 8 octets): The sender requests
that the peer should increment all the Child SA Replay Counters that the peer should increment all the Child SA replay counters
for the sender's incoming (the peer's outgoing) traffic by this for the sender's incoming (the peer's outgoing) traffic by this
value. The size of this field depends on the ESN bit associated value. The size of this field depends on the ESN bit associated
with the Child SAs: if the ESN bit is 1, the field's size is 8 with the Child SAs: if the ESN bit is 1, the field's size is 8
octets, otherwise it is 4 octets. We note that this constrains octets; otherwise, it is 4 octets. We note that this constrains
the Child SAs of each IKE SA to either all have the ESN bit on or the Child SAs of each IKE SA to either all have the ESN bit on
off. or off.
7. Implementation Details 7. Implementation Details
This protocol does not change any of the existing IKEv2 rules This protocol does not change any of the existing IKEv2 rules
regarding Message ID values. regarding Message ID values.
The standby member can initiate the synchronization of IKEv2 Message The standby member can initiate the synchronization of IKEv2 Message
ID's under different circumstances. IDs under different circumstances.
o When it receives a problematic IKEv2/IPsec packet, i.e. a packet
o When it receives a problematic IKEv2/IPsec packet, i.e., a packet
outside its expected receive window. outside its expected receive window.
o When it has to send the first IKEv2/IPsec packet after a failover o When it has to send the first IKEv2/IPsec packet after a failover
event. event.
o When it has just received control from the active member and o When it has just received control from the active member and
wishes to update the values proactively, so that it need not start wishes to update the values proactively, so that it need not start
this exchange later, when sending or receiving the request. this exchange later, when sending or receiving the request.
To clarify the first alternative: the normal IKE behavior of To clarify the first alternative: the normal IKE behavior of
rejecting out-of-window messages is not changed, but such messages rejecting out-of-window messages is not changed, but such messages
can still be a valid trigger for the exchange defined in this can still be a valid trigger for the exchange defined in this
document. To avoid DoS attacks resulting from replayed messages, the document. To avoid denial-of-service (DoS) attacks resulting from
peer MUST NOT initiate counter synchronization for any particular IKE replayed messages, the peer MUST NOT initiate counter synchronization
SA more than once per failover event. for any particular IKE SA more than once per failover event.
The standby member can initiate the synchronization of IPsec SA The standby member can initiate the synchronization of IPsec SA
Replay Counters: replay counters:
o If there has been traffic using the IPsec SA in the recent past o If there has been traffic using the IPsec SA in the recent past
and the standby member suspects that its Replay Counter may be and the standby member suspects that its replay counter may be
stale. stale.
Since there can be a large number of sessions at the standby member, Since there can be a large number of sessions at the standby member,
and sending synchronization exchanges for all of them may result in and sending synchronization exchanges for all of them may result in
overload, the standby member can choose to initiate the exchange in a overload, the standby member can choose to initiate the exchange in a
"lazy" fashion: only when it has to send or expects to receive "lazy" fashion: only when it has to send or expects to receive
traffic from each peer. In general, the standby member is free to traffic from each peer. In general, the standby member is free to
initiate this exchange at its discretion. Implementation initiate this exchange at its discretion. Implementation
considerations include the ability to survive a certain amount of considerations include the ability to survive a certain amount of
traffic loss, and the capacity of a cluster member to initiate traffic loss, and the capacity of a cluster member to initiate
counter synchronization simultaneously with a large number of peers. counter synchronization simultaneously with a large number of peers.
8. IKE SA and IPsec SA Message Sequencing 8. IKE SA and IPsec SA Message Sequencing
The straightforward definitions of message sequence numbers, The straightforward definitions of message sequence numbers,
retransmissions and replay protection in IPsec and IKEv2 are strained retransmissions, and replay protection in IPsec and IKEv2 are
by the failover scenarios described in this document. This section strained by the failover scenarios described in this document. This
describes some policy choices that need to be made by implementations section describes some policy choices that need to be made by
in this setting. implementations in this setting.
8.1. Handling of Pending IKE Messages 8.1. Handling of Pending IKE Messages
After sending its "receive" counter, the cluster member MUST reject After sending its "receive" counter, the cluster member MUST reject
(silently drop) any incoming IKE messages that are outside its (silently drop) any incoming IKE messages that are outside its
declared window. A similar rule applies to the peer. Local policies declared window. A similar rule applies to the peer. Local policies
vary, and strict implementations will reject any incoming IKE message vary, and strict implementations will reject any incoming IKE message
arriving before Message ID synchronization is complete. arriving before Message ID synchronization is complete.
8.2. Handling of Pending IPsec Messages 8.2. Handling of Pending IPsec Messages
For IPsec, there is often a trade-off between security and For IPsec, there is often a trade-off between security and
reliability of the protected protocols. Here again there is some reliability of the protected protocols. Here again, there is some
leeway for local policy. Some implementations might accept incoming leeway for local policy. Some implementations might accept incoming
traffic that is outside the replay window for some time after the traffic that is outside the replay window for some time after the
failover event, and until the counters had been synchronized. Strict failover event, and until the counters had been synchronized. Strict
implementations will only accept traffic that's inside the "safe" implementations will only accept traffic that's inside the "safe"
window. window.
8.3. IKE SA Inconsistencies 8.3. IKE SA Inconsistencies
IKEv2 is normally a reliable protocol. As long as an IKE SA is IKEv2 is normally a reliable protocol. As long as an IKE SA is
valid, both peers share a single, consistent view of the IKE SA and valid, both peers share a single, consistent view of the IKE SA and
all associated Child SAs. Failover situations as described in this all associated Child SAs. Failover situations as described in this
document may involve forced deletion of IKE messages, resulting in document may involve forced deletion of IKE messages, resulting in
inconsistencies, such as Child SAs that exist on only one of the inconsistencies, such as Child SAs that exist on only one of the
peers. Such SAs might cause an INVALID_SPI to be returned when used peers. Such SAs might cause an INVALID_SPI to be returned when used
by that peer. Note that Sec. 1.5 of [2] allows but does not mandate by that peer. Note that Section 1.5 of [4] allows but does not
sending an INVALID_SPI notification in this case. mandate sending an INVALID_SPI notification in this case.
The Working Group discussed at some point a proposed set of rules for The IPsecME Working Group discussed at some point a proposed set of
dealing with such situations. However we believe that these rules for dealing with such situations. However, we believe that
situations should be rare in practice; as a result the "default" these situations should be rare in practice; as a result, the
behavior of tearing down the entire IKE SA is to be preferred over "default" behavior of tearing down the entire IKE SA is to be
the complexity of dealing with a multitude of edge cases. preferred over the complexity of dealing with a multitude of edge
cases.
9. Step by Step Details 9. Step-by-Step Details
This section goes through the sequence of steps of a typical failover This section goes through the sequence of steps of a typical failover
event, looking at a case where the IKEv2 Message ID values are event, looking at a case where the IKEv2 Message ID values are
synchronized. synchronized.
o The active cluster member and the peer device establish the o The active cluster member and the peer device establish the
session. They both announce the capability to synchronize counter session. They both announce the capability to synchronize counter
information by sending the IKEV2_MESSAGE_ID_SYNC_SUPPORTED information by sending the IKEV2_MESSAGE_ID_SYNC_SUPPORTED
notification in the IKE_AUTH Exchange. notification in the IKE_AUTH exchange.
o Some time later, the active member dies, and a standby member o Some time later, the active member dies, and a standby member
takes over. The standby member sends its own idea of the IKE takes over. The standby member sends its own idea of the IKE
Message IDs (both incoming and outgoing) to the peer in an Message IDs (both incoming and outgoing) to the peer in an
Informational message exchange with Message ID zero. Informational message exchange with Message ID zero.
o The peer first authenticates the message. The peer compares the o The peer first authenticates the message. The peer compares the
received values with the values available locally and picks the received values with the values available locally and picks the
higher value. It then updates its Message IDs with the higher higher value. It then updates its Message IDs with the higher
values and also propose the same values in its response. values and also proposes the same values in its response.
o The peer should not wait for any pending responses while o The peer should not wait for any pending responses while
responding with the new Message ID values. For example, if the responding with the new Message ID values. For example, if the
window size is 5 and the peer's window is 3-7, and if the peer has window size is 5 and the peer's window is 3-7, and if the peer has
sent requests 3, 4, 5, 6, 7 and received responses only for 4, 5, sent requests 3, 4, 5, 6, and 7 and received responses only for 4,
6, 7 but not for 3, then it should include the value 8 in its 5, 6, and 7 but not for 3, then it should include the value 8 in
EXPECTED_SEND_REQ_MESSAGE_ID payload and should not wait for a its EXPECTED_SEND_REQ_MESSAGE_ID payload and should not wait for a
response to message 3 anymore. response to message 3 any more.
o Similarly, the peer should also not wait for pending (incoming) o Similarly, the peer should also not wait for pending (incoming)
requests. For example if the window size is 5 and the peer's requests. For example, if the window size is 5 and the peer's
window is 3-7 and if the peer has received requests 4, 5, 6, 7 but window is 3-7, and if the peer has received requests 4, 5, 6, and
not 3, then it should send the value 8 in the 7 but not 3, then it should send the value 8 in the
EXPECTED_RECV_REQ_MESSAGE_ID payload, and should not expect to EXPECTED_RECV_REQ_MESSAGE_ID payload, and should not expect to
receive message 3 anymore. receive message 3 any more.
10. Interaction with other specifications 10. Interaction with Other Specifications
The usage scenario of this IKEv2/IPsec SA counter synchronization The usage scenario of this IKEv2/IPsec SA counter synchronization
solution is that an IKEv2 SA has been established between the active solution is that an IKEv2 SA has been established between the active
member of a hot-standby cluster and a peer, followed by a failover member of a hot standby cluster and a peer, followed by a failover
event occurring and the standby member becoming active. The solution event occurring and the standby member becoming active. The solution
further assumes that the IKEv2 SA state was continuously synchronized further assumes that the IKEv2 SA state was continuously synchronized
between the active and standby members of the cluster before the between the active and standby members of the cluster before the
failover event. failover event.
o Session resumption [10] assumes that a peer (client or initiator)
o Session resumption [12] assumes that a peer (client or initiator)
detects the need to re-establish the session. In IKEv2/IPsec SA detects the need to re-establish the session. In IKEv2/IPsec SA
counter synchronization, it is the newly-active member (a gateway counter synchronization, it is the newly active member (a gateway
or responder) that detects the need to synchronize the SA counter or responder) that detects the need to synchronize the SA counter
after the failover event. Also in a hot-standby cluster, the peer after the failover event. Also, in a hot standby cluster, the
establishes the IKEv2/IPsec session with a single IP address that peer establishes the IKEv2/IPsec session with a single IP address
represents the whole cluster, so the peer normally does not detect that represents the whole cluster, so the peer normally does not
the event of failover in the cluster unless the standby member detect the event of failover in the cluster unless the standby
takes too long to become active and the IKEv2 SA times out by use member takes too long to become active and the IKEv2 SA times out
of the IKEv2 liveness check mechanism. To conclude, session by use of the IKEv2 liveness check mechanism. To conclude,
resumption and SA counter synchronization after failover are session resumption and SA counter synchronization after failover
mutually exclusive: they are not expected to be used together, and are mutually exclusive: they are not expected to be used together,
both features can coexist within the same implementation without and both features can coexist within the same implementation
affecting each other. without affecting each other.
o The IKEv2 Redirect mechanism for load-balancing [11] can be used
o The IKEv2 Redirect mechanism for load balancing [13] can be used
either during the initial stages of SA setup (the IKE_SA_INIT and either during the initial stages of SA setup (the IKE_SA_INIT and
IKE_AUTH exchanges) or after session establishment. SA counter IKE_AUTH exchanges) or after session establishment. SA counter
synchronization is only useful after the IKE SA has been synchronization is only useful after the IKE SA has been
established and a failover event has occurred. So, unlike established and a failover event has occurred. So, unlike
Redirect, it is irrelevant during the first two exchanges. Redirect, it is irrelevant during the first two exchanges.
Redirect after the session has been established is mostly useful Redirect after the session has been established is mostly useful
for timed or planned shutdown/maintenance. A real failover event for timed or planned shutdown/maintenance. A real failover event
cannot be detected by the active member ahead of time, and so cannot be detected by the active member ahead of time, and so
using Redirect after session establishment is not possible in the using Redirect after session establishment is not possible in the
case of failover. So, Redirect and SA counter synchronization case of failover. So, Redirect and SA counter synchronization
after failover are mutually exclusive, in the sense described after failover are mutually exclusive, in the sense described
above. above.
o IKEv2 Failure Detection [6] solves a similar problem where the
o IKEv2 Failure Detection [8] solves a similar problem where the
peer can rapidly detect that a cluster member has crashed based on peer can rapidly detect that a cluster member has crashed based on
a token. It is unrelated to the current scenario because the goal a token. It is unrelated to the current scenario, because the
in failover is for the peer not to notice that a failure has goal in failover is for the peer not to notice that a failure has
occurred. occurred.
11. Security Considerations 11. Security Considerations
Since Message ID synchronization messages need to be sent with Since Message ID synchronization messages need to be sent with
Message ID zero, they are potentially vulnerable to replay attacks. Message ID zero, they are potentially vulnerable to replay attacks.
Because of the semantics of this protocol, these can only be denial- Because of the semantics of this protocol, these can only be denial-
of-service (DoS) attacks, and we are aware of two variants. of-service (DoS) attacks, and we are aware of two variants.
o Replay of Message ID synchronization request: This is countered by o Replay of Message ID synchronization request: This is countered by
the requirement that the Send counter sent by the cluster member the requirement that the Send counter sent by the cluster member
should always be monotonically increasing, a rule that the peer should always be monotonically increasing, a rule that the peer
enforces by silently dropping messages that contradict it. enforces by silently dropping messages that contradict it.
o Replay of the Message ID synchronization response: This is o Replay of the Message ID synchronization response: This is
countered by sending the nonce data along with the synchronization countered by sending the nonce data along with the synchronization
payload. The same nonce data has to be returned in the response. payload. The same nonce data has to be returned in the response.
Thus the standby member will accept a reply only for the current Thus, the standby member will accept a reply only for the current
request. After it receives a valid response, it MUST NOT process request. After it receives a valid response, it MUST NOT process
the same response again and MUST discard any additional responses. the same response again and MUST discard any additional responses.
As mentioned in Section 7, trigerring counter synchronization by out- As mentioned in Section 7, triggering counter synchronization by out-
of-window, potentially replayed messages, could open a DoS of-window, potentially replayed messages could open a DoS
vulnerability. This risk is mitigated by the solution described in vulnerability. This risk is mitigated by the solution described in
that section. that section.
12. IANA Considerations 12. IANA Considerations
This document introduces four new IKEv2 Notification Message types as This document introduces four new IKEv2 Notification Message types as
described in Section 6. The new Notify Message Types must be described in Section 6. The new Notify Message Types have been
assigned values between 16396 and 40959. assigned values as follows.
+-------------------------------------+-------------+ +-------------------------------------+-------+
| Name | Value | | Name | Value |
+-------------------------------------+-------------+ +-------------------------------------+-------+
| IKEV2_MESSAGE_ID_SYNC_SUPPORTED | TBD by IANA | | IKEV2_MESSAGE_ID_SYNC_SUPPORTED | 16420 |
| IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED | TBD by IANA | | IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED | 16421 |
| IKEV2_MESSAGE_ID_SYNC | TBD by IANA | | IKEV2_MESSAGE_ID_SYNC | 16422 |
| IPSEC_REPLAY_COUNTER_SYNC | TBD by IANA | | IPSEC_REPLAY_COUNTER_SYNC | 16423 |
+-------------------------------------+-------------+ +-------------------------------------+-------+
13. Acknowledgements 13. Acknowledgements
We would like to thank Pratima Sethi and Frederic Detienne for their We would like to thank Pratima Sethi and Frederic Detienne for their
review comments and valuable suggestions for the initial version of review comments and valuable suggestions for the initial version of
the document. the document.
We would also like to thank the following people (in alphabetical We would also like to thank the following people (in alphabetical
order) for their review comments and valuable suggestions: Dan order) for their review comments and valuable suggestions: Dan
Harkins, Paul Hoffman, Steve Kent, Tero Kivinen, David McGrew, and Harkins, Paul Hoffman, Steve Kent, Tero Kivinen, David McGrew, and
Pekka Riikonen. Pekka Riikonen.
14. Change Log 14. References
This section lists all the changes in this document.
NOTE TO RFC EDITOR: Please remove this section before publication.
14.1. Draft -06
Applied multiple review comments, from Pekka Riikonen, Alexey
Melnikov, Stephen Farrel, Robert Sparks, Pete Resnick, Russ Housley
and Adrian Farrel. Added an architectural reference diagram. Added
a MUST requirement for cluster members to share peers' support of
this protocol, which had been implicit in previous versions.
14.2. Draft -05
Applied Sean Turner's review comments.
14.3. Draft -04
Extended Sec. 3 for better coverage of other IPsec cluster-related
issues, and how they are resolved within the existing standards.
14.4. Draft -03
Clarified the rules for Message ID sync, so that replay attacks can
be avoided without a failover counter.
Added wording regarding inconsistent IKE state (basically choosing to
ignore the problem) and further rules dealing with pending traffic.
The IPsec replay counter delta value now refers to incoming traffic.
The associated notification is only sent from the cluster to the
peer, and not back.
14.5. Draft -02
Addressed comments by Yaron Sheffer posted on the WG mailing list.
Numerous editorial changes.
14.6. Draft -01
Added "Multiple and Simultaneous failover" scenarios as pointed out
by Pekka Riikonen.
Now document provides a mechanism to sync either IKEv2 message or
IPsec replay counter or both to cater different types of
implementations.
HA cluster's "failover count' is used to encounter replay of sync
requests by attacker.
The sync of IPsec SA replay counter optimized to to have just one
global bumped-up outgoing IPsec SA counter of ALL Child SAs under an
IKEv2 SA.
The examples added for IKEv2 Message ID sync to provide more clarity.
Some edits as per comments on mailing list to enhance clarity.
14.7. Draft -00
Version 00 is identical to
draft-kagarigi-ipsecme-ikev2-windowsync-04, started as WG document.
Added IPSECME WG HA design team members as authors.
Added comment in Introduction to discuss the window sync process on
WG mailing list to solve some concerns.
15. References
15.1. Normative References 14.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key [2] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303,
December 2005.
[3] Kent, S., "IP Authentication Header", RFC 4302, December 2005.
[4] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, "Internet Key
Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010. Exchange Protocol Version 2 (IKEv2)", RFC 5996, September 2010.
[3] Kent, S. and K. Seo, "Security Architecture for the Internet [5] Kent, S. and K. Seo, "Security Architecture for the Internet
Protocol", RFC 4301, December 2005. Protocol", RFC 4301, December 2005.
15.2. Informative References 14.2. Informative References
[4] Nir, Y., "IPsec Cluster Problem Statement", RFC 6027, [6] Nir, Y., "IPsec Cluster Problem Statement", RFC 6027,
October 2010. October 2010.
[5] Nadas, S., "Virtual Router Redundancy Protocol (VRRP) Version 3 [7] Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP)
for IPv4 and IPv6", RFC 5798, March 2010. Version 3 for IPv4 and IPv6", RFC 5798, March 2010.
[6] Nir, Y., Wierbowski, D., Detienne, F., and P. Sethi, "A Quick [8] Nir, Y., Ed., Wierbowski, D., Detienne, F., and P. Sethi, "A
Crash Detection Method for IKE", Quick Crash Detection Method for the Internet Key Exchange
draft-ietf-ipsecme-failure-detection-08 (work in progress), Protocol (IKE)", RFC 6290, June 2011.
April 2011.
[7] Housley, R., "Using Advanced Encryption Standard (AES) Counter [9] Housley, R., "Using Advanced Encryption Standard (AES) Counter
Mode With IPsec Encapsulating Security Payload (ESP)", Mode With IPsec Encapsulating Security Payload (ESP)",
RFC 3686, January 2004. RFC 3686, January 2004.
[8] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode (GCM) [10] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode (GCM)
in IPsec Encapsulating Security Payload (ESP)", RFC 4106, in IPsec Encapsulating Security Payload (ESP)", RFC 4106,
June 2005. June 2005.
[9] McGrew, D. and B. Weis, "Using Counter Modes with Encapsulating [11] McGrew, D. and B. Weis, "Using Counter Modes with Encapsulating
Security Payload (ESP) and Authentication Header (AH) to Security Payload (ESP) and Authentication Header (AH) to
Protect Group Traffic", RFC 6054, November 2010. Protect Group Traffic", RFC 6054, November 2010.
[10] Sheffer, Y. and H. Tschofenig, "Internet Key Exchange Protocol [12] Sheffer, Y. and H. Tschofenig, "Internet Key Exchange Protocol
Version 2 (IKEv2) Session Resumption", RFC 5723, January 2010. Version 2 (IKEv2) Session Resumption", RFC 5723, January 2010.
[11] Devarapalli, V. and K. Weniger, "Redirect Mechanism for the [13] Devarapalli, V. and K. Weniger, "Redirect Mechanism for the
Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5685, Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 5685,
November 2009. November 2009.
Appendix A. IKEv2 Message ID Sync Examples Appendix A. IKEv2 Message ID Sync Examples
This (non-normative) section presents some examples that illustrate This (non-normative) section presents some examples that illustrate
how the IKEv2 Message ID values are synchronized. We use a tuple how the IKEv2 Message ID values are synchronized. We use a tuple
notation, denoting the two counters EXPECTED_SEND_REQ_MESSAGE_ID and notation, denoting the two counters EXPECTED_SEND_REQ_MESSAGE_ID and
EXPECTED_RECV_REQ_MESSAGE_ID on each protocol party as EXPECTED_RECV_REQ_MESSAGE_ID on each protocol party as
(EXPECTED_SEND_REQ_MESSAGE_ID, EXPECTED_RECV_REQ_MESSAGE_ID). (EXPECTED_SEND_REQ_MESSAGE_ID, EXPECTED_RECV_REQ_MESSAGE_ID).
Note that if the IKE message counters are already synchronized (as in Note that if the IKE message counters are already synchronized (as in
the first example), we expect the numbers to be reversed between the the first example), we expect the numbers to be reversed between the
two sides. If one protocol party intends to send the next request as two sides. If one protocol party intends to send the next request as
4, then the other expects the next received request to be 4. 4, then the other expects the next received request to be 4.
A.1. Normal Failover - Example 1 A.1. Normal Failover -- Example 1
Standby (Newly Active) Member Peer Standby (Newly Active) Member Peer
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Sync Request (0, 5) --------> Sync Request (0, 5) -------->
Peer has the values (5, 0) so it sends Peer has the values (5, 0), so it sends
<------------- (5, 0) as the Sync Response <------------- (5, 0) as the Sync Response
In this example, the peer has most recently sent an IKE request with In this example, the peer has most recently sent an IKE request with
Message ID 4, and has never received a request. So the peer's Message ID 4, and has never received a request. So the peer's
expected values for the next pair of messages are (5, 0). These are expected values for the next pair of messages are (5, 0). These are
the same values as received from the member and therefore they are the same values as received from the member, and therefore they are
sent as-is. sent as-is.
A.2. Normal Failover - Example 2 A.2. Normal Failover -- Example 2
Standby (Newly Active) Member Peer Standby (Newly Active) Member Peer
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Sync Request (2, 3) --------> Sync Request (2, 3) -------->
Peer has the values (4, 5) so it sends Peer has the values (4, 5), so it sends
<------------- (4, 5) as the Sync Response <------------- (4, 5) as the Sync Response
In this example, the peer has most recently sent an IKE message with In this example, the peer has most recently sent an IKE message with
the Message ID 3, and received one with ID 4. So the peer's expected the Message ID 3, and received one with ID 4. So the peer's expected
values for the next pair of messages are (4, 5). These are both values for the next pair of messages are (4, 5). These are both
higher than the corresponding values just received from the member higher than the corresponding values just received from the member
(the order of tuple members is reversed when doing this comparison!), (the order of tuple members is reversed when doing this comparison!),
and therefore they are sent as-is. and therefore they are sent as-is.
A.3. Normal Failover - Example 3 A.3. Normal Failover -- Example 3
Standby (Newly Active) Member Peer Standby (Newly Active) Member Peer
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Sync Request (2, 5) --------> Sync Request (2, 5) -------->
Peer has the values (2, 4) so it sends Peer has the values (2, 4), so it sends
<-------------(5, 4) as the Sync Response <-------------(5, 4) as the Sync Response
In this example, the newly active member expects to send the next IKE In this example, the newly active member expects to send the next IKE
message with ID 2. It sends an expected receive value of 5, which is message with ID 2. It sends an expected receive value of 5, which is
higher than the last ID value it has seen from the peer, because it higher than the last ID value it has seen from the peer, because it
believes some incoming messages may have been lost. The peer has believes some incoming messages may have been lost. The peer has
last sent a message with ID 1, and received one with ID 3, indicating last sent a message with ID 1, and received one with ID 3, indicating
that the a couple of messages sent by the previously active member that a couple of messages sent by the previously active member had
had not been synchronized into the other member. So the peer's next not been synchronized into the other member. So the peer's next
expected (send, receive) values are (2, 4). The peer replies with expected (send, receive) values are (2, 4). The peer replies with
the maximum of the received and the expected value for both send and the maximum of the received and the expected value for both send and
receive counters: (max(2, 5), max(4, 2)) = (5, 4). receive counters: (max(2, 5), max(4, 2)) = (5, 4).
A.4. Simultaneous Failover A.4. Simultaneous Failover
In the case of simultaneous failover, both sides send their In the case of simultaneous failover, both sides send their
synchronization requests simultaneously. The eventual outcome of synchronization requests simultaneously. The eventual outcome of
synchronization consists of the higher counter values. This is synchronization consists of the higher counter values. This is
demonstrated in the following figure. demonstrated in the following figure.
skipping to change at page 25, line 18 skipping to change at page 26, line 7
Sync Request (4,4) -----> Sync Request (4,4) ----->
<-------------- Sync Request (5,5) <-------------- Sync Request (5,5)
Sync Response (5,5) ----> Sync Response (5,5) ---->
<-------- Sync Response (5,5) <-------- Sync Response (5,5)
Authors' Addresses Authors' Addresses
Raj Singh (Editor) Raj Singh (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
Divyashree Chambers, B Wing, O'Shaugnessy Road Divyashree Chambers, B Wing, O'Shaugnessy Road
Bangalore, Karnataka 560025 Bangalore, Karnataka 560025
India India
Phone: +91 80 4301 3320 Phone: +91 80 4301 3320
Email: rsj@cisco.com EMail: rsj@cisco.com
Kalyani Garigipati Kalyani Garigipati
Cisco Systems, Inc. Cisco Systems, Inc.
Divyashree Chambers, B Wing, O'Shaugnessy Road Divyashree Chambers, B Wing, O'Shaugnessy Road
Bangalore, Karnataka 560025 Bangalore, Karnataka 560025
India India
Phone: +91 80 4426 4831 Phone: +91 80 4426 4831
Email: kagarigi@cisco.com EMail: kagarigi@cisco.com
Yoav Nir Yoav Nir
Check Point Software Technologies Ltd. Check Point Software Technologies Ltd.
5 Hasolelim St. 5 Hasolelim St.
Tel Aviv 67897 Tel Aviv 67897
Israel Israel
Email: ynir@checkpoint.com EMail: ynir@checkpoint.com
Yaron Sheffer Yaron Sheffer
Porticor Cloud Security Porticor Cloud Security
Email: yaronf.ietf@gmail.com EMail: yaronf.ietf@gmail.com
Dacheng Zhang Dacheng Zhang
Huawei Technologies Ltd. Huawei Technologies Ltd.
Email: zhangdacheng@huawei.com EMail: zhangdacheng@huawei.com
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