draft-ietf-ipsecme-ipsec-ha-04.txt   draft-ietf-ipsecme-ipsec-ha-05.txt 
Network Working Group Y. Nir Network Working Group Y. Nir
Internet-Draft Check Point Internet-Draft Check Point
Intended status: Informational June 1, 2010 Intended status: Informational June 10, 2010
Expires: December 3, 2010 Expires: December 12, 2010
IPsec High Availability and Load Sharing Problem Statement IPsec Cluster Problem Statement
draft-ietf-ipsecme-ipsec-ha-04 draft-ietf-ipsecme-ipsec-ha-05
Abstract Abstract
This document describes a requirement from IKE and IPsec to allow for This document defines terminology, problem statement and requirements
more scalable and available deployments for VPNs. It defines for implementing IKE and IPsec on clusters. It also describes gaps
terminology for high availability and load sharing clusters in existing standards and their implementation that need to be
implementing IKE and IPsec, and describes gaps in the existing filled, in order to allow peers to interoperate with clusters from
standards. different vendors. An agreed terminology, problem statement and
requirements will allow the IPSECME WG to consider development of
IPsec/IKEv2 mechanisms to simplify cluster implementations.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 3, 2010. This Internet-Draft will expire on December 12, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 12 skipping to change at page 2, line 14
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The Problem Statement . . . . . . . . . . . . . . . . . . . . 5 3. The Problem Statement . . . . . . . . . . . . . . . . . . . . 5
3.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Lots of Long Lived State . . . . . . . . . . . . . . . . . 5 3.2. Lots of Long Lived State . . . . . . . . . . . . . . . . . 6
3.3. IKE Counters . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. IKE Counters . . . . . . . . . . . . . . . . . . . . . . . 6
3.4. Outbound SA Counters . . . . . . . . . . . . . . . . . . . 6 3.4. Outbound SA Counters . . . . . . . . . . . . . . . . . . . 6
3.5. Inbound SA Counters . . . . . . . . . . . . . . . . . . . 7 3.5. Inbound SA Counters . . . . . . . . . . . . . . . . . . . 7
3.6. Missing Synch Messages . . . . . . . . . . . . . . . . . . 7 3.6. Missing Synch Messages . . . . . . . . . . . . . . . . . . 7
3.7. Simultaneous use of IKE and IPsec SAs by Different 3.7. Simultaneous use of IKE and IPsec SAs by Different
Members . . . . . . . . . . . . . . . . . . . . . . . . . 8 Members . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.7.1. Outbound SAs using counter modes . . . . . . . . . . . 9 3.7.1. Outbound SAs using counter modes . . . . . . . . . . . 9
3.8. Different IP addresses for IKE and IPsec . . . . . . . . . 9 3.8. Different IP addresses for IKE and IPsec . . . . . . . . . 9
3.9. Allocation of SPIs . . . . . . . . . . . . . . . . . . . . 9 3.9. Allocation of SPIs . . . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Informative References . . . . . . . . . . . . . . . . . . . . 11 8. Informative References . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction 1. Introduction
IKEv2, as described in [RFC4306] and [IKEv2bis], and IPsec, as IKEv2, as described in [RFC4306] and [IKEv2bis], and IPsec, as
described in [RFC4301] and others, allows deployment of VPNs between described in [RFC4301] and others, allows deployment of VPNs between
different sites as well as from VPN clients to protected networks. different sites as well as from VPN clients to protected networks.
As VPNs become increasingly important to the organizations deploying As VPNs become increasingly important to the organizations deploying
them, there is a demand to make IPsec solutions more scalable and them, there is a demand to make IPsec solutions more scalable and
less prone to down time, by using more than one physical gateway to less prone to down time, by using more than one physical gateway to
either share the load or back each other up. Similar demands have either share the load or back each other up, forming a "cluster" (see
been made in the past for other critical pieces of an organizations's Section 2). Similar demands have been made in the past for other
infrastructure, such as DHCP and DNS servers, web servers, databases critical pieces of an organization's infrastructure, such as DHCP and
and others. DNS servers, web servers, databases and others.
IKE and IPsec are in particular less friendly to clustering than IKE and IPsec are in particular less friendly to clustering than
these other protocols, because they store more state, and that state these other protocols, because they store more state, and that state
is more volatile. Section 2 defines terminology for use in this is more volatile. Section 2 defines terminology for use in this
document, and in the envisioned solution documents. document, and in the envisioned solution documents.
In general, deploying IKE and IPsec in a cluster requires such a In general, deploying IKE and IPsec in a cluster requires such a
large amount of information to be synchronized among the members of large amount of information to be synchronized among the members of
the cluster, that it becomes impractical. Alternatively, if less the cluster, that it becomes impractical. Alternatively, if less
information is synchronized, failover would mean a prolonged and information is synchronized, failover would mean a prolonged and
skipping to change at page 3, line 50 skipping to change at page 3, line 50
"Single Gateway" is an implementation of IKE and IPsec enforcing a "Single Gateway" is an implementation of IKE and IPsec enforcing a
certain policy, as described in [RFC4301]. certain policy, as described in [RFC4301].
"Cluster" is a set of two or more gateways, implementing the same "Cluster" is a set of two or more gateways, implementing the same
security policy, and protecting the same domain. Clusters exist to security policy, and protecting the same domain. Clusters exist to
provide both high availability through redundancy, and scalability provide both high availability through redundancy, and scalability
through load sharing. through load sharing.
"Member" is one gateway in a cluster. "Member" is one gateway in a cluster.
"Availability" is a measure of a system's ability to perform the
service for which it was designed. It is measured as the percentage
of time a service is available, from the time it is supposed to be
available. Colloquially, availability is sometimes expressed in
"nines" rather than percentage, with 3 "nines" meaning 99.9%
availability, 4 "nines" meaning 99.99% availability, etc.
"High Availability" is a condition of a system, not a configuration "High Availability" is a condition of a system, not a configuration
type. A system is said to have high availability if its expected type. A system is said to have high availability if its expected
down time is low. High availability can be achieved in various ways, down time is low. High availability can be achieved in various ways,
one of which is clustering. All the clusters described in this one of which is clustering. All the clusters described in this
document achieve high availability. document achieve high availability. What "high" means depends on
application, but usually is 4 to 6 "nines" (at most 0.5-50 minutes of
down time per year in a system that is supposed to be available all
the time.
"Fault Tolerance" is a condition related to high availability, where "Fault Tolerance" is a condition related to high availability, where
a system maintains service availability, even when a specified set of a system maintains service availability, even when a specified set of
fault conditions occur. In clusters, we expect the system to fault conditions occur. In clusters, we expect the system to
maintain service availability, when one or more of the cluster maintain service availability, when one or more of the cluster
members fails. members fails.
"Completely Transparent Cluster" is a cluster where the occurence of "Completely Transparent Cluster" is a cluster where the occurence of
a fault is never visible to the peers. a fault is never visible to the peers.
"Partially Transparent Cluster" is a cluster where the occurence of a "Partially Transparent Cluster" is a cluster where the occurence of a
fault may be visible to the peers. fault may be visible to the peers.
"Hot Standby Cluster", or "HS Cluster" is a cluster where only one of "Hot Standby Cluster", or "HS Cluster" is a cluster where only one of
the members is active at any one time. This member is also referred the members is active at any one time. This member is also referred
to as the the "active", whereas the others are referred to as "stand- to as the the "active", whereas the other(s) are referred to as
bys". [VRRP] is one method of building such a cluster. "stand-bys". [VRRP] is one method of building such a cluster.
"Load Sharing Cluster", or "LS Cluster" is a cluster where more than "Load Sharing Cluster", or "LS Cluster" is a cluster where more than
one of the members may be active at the same time. The term "load one of the members may be active at the same time. The term "load
balancing" is also common, but it implies that the load is actually balancing" is also common, but it implies that the load is actually
balanced between the members, and we don't want to even imply that balanced between the members, and this is not a requirement.
this is a requirement.
"Failover" is the event where a one member takes over some load from "Failover" is the event where a one member takes over some load from
some other member. In a hot standby cluster, this hapens when a some other member. In a hot standby cluster, this hapens when a
standby member becomes active due to a failure of the former active standby member becomes active due to a failure of the former active
member, or because of an administrator command. In a load sharing member, or because of an administrator command. In a load sharing
cluster this usually happens because of a failure of one of the cluster, this usually happens because of a failure of one of the
members, but certain load-balancing technologies may allow a members, but certain load-balancing technologies may allow a
particular load (such as all the flows associated with a particular particular load (such as all the flows associated with a particular
child SA) to move from one member to another to even out the load, child SA) to move from one member to another to even out the load,
even without any failures. even without any failures.
"Tight Cluster" is a cluster where all the members share an IP "Tight Cluster" is a cluster where all the members share an IP
address. This could be accomplished using configured interfaces with address. This could be accomplished using configured interfaces with
specialized protocols or hardware, such as VRRP, or through the use specialized protocols or hardware, such as VRRP, or through the use
of multicast addresses, but in any case, peers need only be of multicast addresses, but in any case, peers need only be
configured with one IP address in the PAD. configured with one IP address in the PAD.
"Loose Cluster" is a cluster where each member has a different IP "Loose Cluster" is a cluster where each member has a different IP
address. Peers find the correct member using some method such as DNS address. Peers find the correct member using some method such as DNS
queries or [REDIRECT]. In some cases, members IP addresses may be queries or [REDIRECT]. In some cases, a member's IP address(es) may
allocated to other members at failover. be allocated to another member at failover.
"Synch Channel" is a communications channel among the cluster "Synch Channel" is a communications channel among the cluster
members, used to transfer state information. The synch channel may members, used to transfer state information. The synch channel may
or may not be IP based, may or may not be encrypted, and may work or may not be IP based, may or may not be encrypted, and may work
over short or long distances. The security and physical over short or long distances. The security and physical
characteristics of this channel are out of scope for this document, characteristics of this channel are out of scope for this document,
but it is a requirement that its use be minimized for scalability. but it is a requirement that its use be minimized for scalability.
3. The Problem Statement 3. The Problem Statement
skipping to change at page 6, line 4 skipping to change at page 6, line 14
3.2. Lots of Long Lived State 3.2. Lots of Long Lived State
IKE and IPsec have a lot of long lived state: IKE and IPsec have a lot of long lived state:
o IKE SAs last for minutes, hours, or days, and carry keys and other o IKE SAs last for minutes, hours, or days, and carry keys and other
information. Some gateways may carry thousands to hundreds of information. Some gateways may carry thousands to hundreds of
thousands of IKE SAs. thousands of IKE SAs.
o IPsec SAs last for minutes or hours, and carry keys, selectors and o IPsec SAs last for minutes or hours, and carry keys, selectors and
other information. Some gateways may carry hundreds of thousands other information. Some gateways may carry hundreds of thousands
such IPsec SAs. such IPsec SAs.
o SPD (Security Policy Database) Cache entries. While the SPD is
unchanging, the SPD cache changes on the fly due to narrowing.
Entries last at least as long as the SAD (Security Association
Database) entries, but tend to last even longer than that.
o SPD Cache entries. While the SPD is unchanging, the SPD cache A naive implementation of a cluster would have no synchronized state,
changes on the fly due to narrowing. Entries last at least as and a failover would produce an effect similar to that of a rebooted
long as the SAD entries, but tend to last even longer than that. gateway. [resumption] describes how new IKE and IPsec SAs can be
recreated in such a case.
A naive implementation of a high availability cluster would have no
synchronized state, and a failover would produce an effect similar to
that of a rebooted gateway. [resumption] describes how new IKE and
IPsec SAs can be recreated in such a case.
3.3. IKE Counters 3.3. IKE Counters
We can overcome the first problem described in Section 3.2, by We can overcome the first problem described in Section 3.2, by
synchronizing states - whenever an SA is created, we can synch this synchronizing states - whenever an SA is created, we can synch this
new state to all other members. However, those states are not only new state to all other members. However, those states are not only
long-lived, they are also ever changing. long-lived, they are also ever changing.
IKE has message counters. A peer may not process message n until IKE has message counters. A peer may not process message n until
after it has processed message n-1. Skipping message IDs is not after it has processed message n-1. Skipping message IDs is not
allowed. So a newly-active member needs to know the last message IDs allowed. So a newly-active member needs to know the last message IDs
both received and transmitted. both received and transmitted.
Often, it is feasible to synchronize the IKE message counters for In some cases, it is feasible to synchronize information about the
every IKE exchange. This way, the newly active member knows what IKE message counters after every IKE exchange. This way, the newly
messages it is allowed to process, and what message IDs to use on IKE active member knows what messages it is allowed to process, and what
requests, so that peers process them. message IDs to use on IKE requests, so that peers process them. We
leave it for future discussion to determine if it is always feasible
to do so.
3.4. Outbound SA Counters 3.4. Outbound SA Counters
ESP and AH have an optional anti-replay feature, where every ESP and AH have an optional anti-replay feature, where every
protected packet carries a counter number. Repeating counter numbers protected packet carries a counter number. Repeating counter numbers
is considered an attack, so the newly-active member must not use a is considered an attack, so the newly-active member MUST NOT use a
replay counter number that has already been used. The peer will drop replay counter number that has already been used. The peer will drop
those packets as duplicates and/or warn of an attack. those packets as duplicates and/or warn of an attack.
Though it may be feasible to synchronize the IKE message counters, it Though it may be feasible to synchronize the IKE message counters, it
is almost never feasible to synchronize the IPsec packet counters for is almost never feasible to synchronize the IPsec packet counters for
every IPsec packet transmitted. So we have to assume that at least every IPsec packet transmitted. So we have to assume that at least
for IPsec, the replay counter will not be up-to-date on the newly- for IPsec, the replay counter will not be up-to-date on the newly-
active member, and the newly-active member may repeat a counter. active member, and the newly-active member may repeat a counter.
A possible solution is to synch replay counter information, not for A possible solution is to synch replay counter information, not for
each packet emitted, but only at regular intervals, say, every 10,000 each packet emitted, but only at regular intervals, say, every 10,000
packets or every 0.5 seconds. After a failover, the newly-active packets or every 0.5 seconds. After a failover, the newly-active
member advances the counters for outbound SAs by 10,000. To the peer member advances the counters for outbound IPsec SAs by 10,000. To
this looks like up to 10,000 packets were lost, but this should be the peer this looks like up to 10,000 packets were lost, but this
acceptable, as neither ESP nor AH guarantee reliable delivery. should be acceptable, as neither ESP nor AH guarantee reliable
delivery.
3.5. Inbound SA Counters 3.5. Inbound SA Counters
An even tougher issue, is the synchronization of packet counters for An even tougher issue, is the synchronization of packet counters for
inbound SAs. If a packet arrives at a newly-active member, there is inbound IPsec SAs. If a packet arrives at a newly-active member,
no way to determine whether this packet is a replay or not. The there is no way to determine whether this packet is a replay or not.
periodic synch does not solve the problem at all, because suppose we The periodic synch does not solve the problem at all, because suppose
synchronize every 10,000 packets, and the last synch before the we synchronize every 10,000 packets, and the last synch before the
failover had the counter at 170,000. It is probable, though not failover had the counter at 170,000. It is probable, though not
certain, that packet number 180,000 has not yet been processed, but certain, that packet number 180,000 has not yet been processed, but
if packet 175,000 arrives at the newly- active member, it has no way if packet 175,000 arrives at the newly- active member, it has no way
of determining whether or not that packet has or has not already been of determining whether or not that packet has or has not already been
processed. The synchronization does prevent the processing of really processed. The synchronization does prevent the processing of really
old packets, such as those with counter number 165,000. Ignoring all old packets, such as those with counter number 165,000. Ignoring all
counters below 180,000 won't work either, because that's up to 10,000 counters below 180,000 won't work either, because that's up to 10,000
dropped packets, which may be very noticeable. dropped packets, which may be very noticeable.
The easiest solution is to learn the replay counter from the incoming The easiest solution is to learn the replay counter from the incoming
traffic. This is allowed by the standards, because replay counter traffic. This is allowed by the standards, because replay counter
verification is an optional feature. The case can even be made that verification is an optional feature (see section 3.2 in [RFC4301]).
it is relatively secure, because non-attack traffic will reset the The case can even be made that it is relatively secure, because non-
counters to what they should be, so an attacker faces the dual attack traffic will reset the counters to what they should be, so an
challenge of a very narrow window for attack, and the need to time attacker faces the dual challenge of a very narrow window for attack,
the attack to a failover event. Unless the attacker can actually and the need to time the attack to a failover event. Unless the
cause the failover, this would be very difficult. It should be attacker can actually cause the failover, this would be very
noted, though, that although this solution is acceptable as far as difficult. It should be noted, though, that although this solution
RFC 4301 goes, it is a matter of policy whether this is acceptable. is acceptable as far as RFC 4301 goes, it is a matter of policy
whether this is acceptable.
Another possible solution to the inbound SA problem is to rekey all Another possible solution to the inbound IPsec SA problem is to rekey
child SAs following a failover. This may or may not be feasible all child SAs following a failover. This may or may not be feasible
depending on the implementation and the configuration. depending on the implementation and the configuration.
3.6. Missing Synch Messages 3.6. Missing Synch Messages
The synch channel is very likely not to be infallible. Before The synch channel is very likely not to be infallible. Before
failover is detected, some synchronization messages may have been failover is detected, some synchronization messages may have been
missed. For example, the active member may have created a new Child missed. For example, the active member may have created a new Child
SA using message n. The new information (entry in the SAD and update SA using message n. The new information (entry in the SAD and update
to counters of the IKE SA) is sent on the synch channel. Still, with to counters of the IKE SA) is sent on the synch channel. Still, with
every possible technology, the update may be missed before the every possible technology, the update may be missed before the
skipping to change at page 8, line 15 skipping to change at page 8, line 26
o The counters for the IKE SA show that only request n-1 has been o The counters for the IKE SA show that only request n-1 has been
sent. The next request will get the message ID n, but that will sent. The next request will get the message ID n, but that will
be rejected by the peer. After a sufficient number of be rejected by the peer. After a sufficient number of
retransmissions and rejections, the whole IKE SA with all retransmissions and rejections, the whole IKE SA with all
associated IPsec SAs will get dropped. associated IPsec SAs will get dropped.
The above scenario may be rare enough that it is acceptable that on a The above scenario may be rare enough that it is acceptable that on a
configuration with thousands of IKE SAs, a few will need to be configuration with thousands of IKE SAs, a few will need to be
recreated from scratch or using session resumption techniques. recreated from scratch or using session resumption techniques.
However, detecting this may take a long time (several minutes) and However, detecting this may take a long time (several minutes) and
this negates the goal of creating a high availability cluster in the this negates the goal of creating a cluster in the first place.
first place.
3.7. Simultaneous use of IKE and IPsec SAs by Different Members 3.7. Simultaneous use of IKE and IPsec SAs by Different Members
For load sharing clusters, all active members may need to use the For LS clusters, all active members may need to use the same SAs,
same SAs, both IKE and IPsec. This is an even greater problem than both IKE and IPsec. This is an even greater problem than in the case
in the case of HA, because consecutive packets may need to be sent by of HS clusters, because consecutive packets may need to be sent by
different members to the same peer gateway. different members to the same peer gateway.
The solution to the IKE SA issue is up to the application. It's The solution to the IKE SA issue is up to the application. It's
possible to create some locking mechanism over the synch channel, or possible to create some locking mechanism over the synch channel, or
else have one member "own" the IKE SA and manage the child SAs for else have one member "own" the IKE SA and manage the child SAs for
all other members. For IPsec, solutions fall into two broad all other members. For IPsec, solutions fall into two broad
categories. categories.
The first is the "sticky" category, where all communications with a The first is the "sticky" category, where all communications with a
single peer, or all communications involving a certain SPD cache single peer, or all communications involving a certain SPD cache
entry go through a single peer. In this case, all packets that match entry go through a single peer. In this case, all packets that match
any particular SA go through the same member, so no synchronization any particular SA go through the same member, so no synchronization
of the replay counter needs to be done. Inbound processing is a of the replay counter needs to be done. Inbound processing is a
"sticky" issue, because the packets have to be processed by the "sticky" issue, because the packets have to be processed by the
correct member based on peer and SPI. Another issue is that correct member based on peer and SPI. Another issue is that most
commodity load balancers will not be able to match the SPIs of the load balancers will not be able to match the SPIs of the encrypted
encrypted side to the clear traffic, and so the wrong member may get side to the clear traffic, and so the wrong member may get the the
the the other half of the flow. other half of the flow.
The other way, is to duplicate the child SAs, and have a pair of The second is the "duplicate" category, where the child SA is
IPsec SAs for each active member. Different packets for the same duplicated for each pair of IPsec SAs for each active member.
peer go through different members, and get protected using different Different packets for the same peer go through different members, and
SAs with the same selectors and matching the same entries in the SPD get protected using different SAs with the same selectors and
cache. This has some shortcomings: matching the same entries in the SPD cache. This has some
shortcomings:
o It requires multiple parallel SAs, which the peer has no use for. o It requires multiple parallel SAs, which the peer has no use for.
Section 2.8 or [RFC4306] specifically allows this, but some Section 2.8 or [RFC4306] specifically allows this, but some
implementation might have a policy against long term maintenance implementation might have a policy against long term maintenance
of redundant SAs. of redundant SAs.
o Different packets that belong to the same flow may be protected by o Different packets that belong to the same flow may be protected by
different SAs, which may seem "weird" to the peer gateway, different SAs, which may seem "weird" to the peer gateway,
especially if it is integrated with some deep inspection especially if it is integrated with some deep inspection
middleware such as a firewall. It is not known whether this will middleware such as a firewall. It is not known whether this will
cause problems with current gateways. It is also impossible to cause problems with current gateways. It is also impossible to
mandate against this, because the definition of "flow" varies from mandate against this, because the definition of "flow" varies from
one implementation to another. one implementation to another.
o Reply packets may arrive with an IPsec SA that is not "matched" to o Reply packets may arrive with an IPsec SA that is not "matched" to
the one used for the outgoing packets. Also, they might arrive at the one used for the outgoing packets. Also, they might arrive at
a different member. This problem is beyond the scope of this a different member. This problem is beyond the scope of this
skipping to change at page 9, line 22 skipping to change at page 9, line 32
o Reply packets may arrive with an IPsec SA that is not "matched" to o Reply packets may arrive with an IPsec SA that is not "matched" to
the one used for the outgoing packets. Also, they might arrive at the one used for the outgoing packets. Also, they might arrive at
a different member. This problem is beyond the scope of this a different member. This problem is beyond the scope of this
document and should be solved by the application, perhaps by document and should be solved by the application, perhaps by
forwarding misdirected packets to the correct gateway for deep forwarding misdirected packets to the correct gateway for deep
inspection. inspection.
3.7.1. Outbound SAs using counter modes 3.7.1. Outbound SAs using counter modes
For SAs involving counter mode ciphers such as [CTR] or [GCM] there For SAs involving counter mode ciphers such as [CTR] or [GCM] there
is yet another complication. The initial vector for such modes must is yet another complication. The initial vector for such modes MUST
never be repeated, and senders use methods such as counters or LFSRs NOT be repeated, and senders use methods such as counters or LFSRs to
to ensure this. An SA shared between more than one active member, or ensure this. An SA shared between more than one active member, or
even failing over from one member to another need to make sure that even failing over from one member to another need to make sure that
they do not generate the same initial vector. See [COUNTER_MODES] they do not generate the same initial vector. See [COUNTER_MODES]
for a discussion of this problem in another context. for a discussion of this problem in another context.
3.8. Different IP addresses for IKE and IPsec 3.8. Different IP addresses for IKE and IPsec
In many implementations there are separate IP addresses for the In many implementations there are separate IP addresses for the
cluster, and for each member. While the packets protected by tunnel cluster, and for each member. While the packets protected by tunnel
mode child SAs are encapsulated in IP headers with the cluster IP mode child SAs are encapsulated in IP headers with the cluster IP
address, the IKE packets originate from a specific member, and carry address, the IKE packets originate from a specific member, and carry
 End of changes. 28 change blocks. 
73 lines changed or deleted 87 lines changed or added

This html diff was produced by rfcdiff 1.38. The latest version is available from http://tools.ietf.org/tools/rfcdiff/