draft-ietf-ipsecme-failure-detection-00.txt   draft-ietf-ipsecme-failure-detection-01.txt 
IPsecME Working Group Y. Nir, Ed. IPsecME Working Group Y. Nir, Ed.
Internet-Draft Check Point Internet-Draft Check Point
Intended status: Standards Track D. Wierbowski Intended status: Standards Track D. Wierbowski
Expires: March 7, 2011 IBM Expires: April 13, 2011 IBM
September 3, 2010 F. Detienne
P. Sethi
Cisco
October 10, 2010
A Quick Crash Detection Method for IKE A Quick Crash Detection Method for IKE
draft-ietf-ipsecme-failure-detection-00 draft-ietf-ipsecme-failure-detection-01
Abstract Abstract
This document describes an extension to the IKEv2 protocol that This document describes an extension to the IKEv2 protocol that
allows for faster detection of SA desynchronization using a saved allows for faster detection of SA desynchronization using a saved
token. token.
When an IPsec tunnel between two IKEv2 peers is disconnected due to a When an IPsec tunnel between two IKEv2 peers is disconnected due to a
restart of one peer, it can take as much as several minutes for the restart of one peer, it can take as much as several minutes for the
other peer to discover that the reboot has occurred, thus delaying other peer to discover that the reboot has occurred, thus delaying
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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 March 7, 2011. This Internet-Draft will expire on April 13, 2011.
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
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions Used in This Document . . . . . . . . . . . . 4 1.1. Conventions Used in This Document . . . . . . . . . . . . 4
2. RFC 4306 Crash Recovery . . . . . . . . . . . . . . . . . . . 5 2. RFC 4306 Crash Recovery . . . . . . . . . . . . . . . . . . . 5
3. Protocol Outline . . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Outline . . . . . . . . . . . . . . . . . . . . . . . 5
4. Formats and Exchanges . . . . . . . . . . . . . . . . . . . . 6 4. Formats and Exchanges . . . . . . . . . . . . . . . . . . . . 6
4.1. Notification Format . . . . . . . . . . . . . . . . . . . 6 4.1. Notification Format . . . . . . . . . . . . . . . . . . . 6
4.2. Passing a Token in the AUTH Exchange . . . . . . . . . . . 7 4.2. Passing a Token in the AUTH Exchange . . . . . . . . . . . 7
4.3. Replacing Tokens After Rekey or Resumption . . . . . . . . 8 4.3. Replacing Tokens After Rekey or Resumption . . . . . . . . 8
4.4. Replacing the Token for an Existing SA . . . . . . . . . . 9 4.4. Replacing the Token for an Existing SA . . . . . . . . . . 9
4.5. Presenting the Token in an INFORMATIONAL Exchange . . . . 9 4.5. Presenting the Token in an Unprotected Message . . . . . . 9
5. Token Generation and Verification . . . . . . . . . . . . . . 10 5. Token Generation and Verification . . . . . . . . . . . . . . 10
5.1. A Stateless Method of Token Generation . . . . . . . . . . 10 5.1. A Stateless Method of Token Generation . . . . . . . . . . 10
5.2. A Stateless Method with IP addresses . . . . . . . . . . . 11 5.2. A Stateless Method with IP addresses . . . . . . . . . . . 11
5.3. Token Lifetime . . . . . . . . . . . . . . . . . . . . . . 11 5.3. Token Lifetime . . . . . . . . . . . . . . . . . . . . . . 11
6. Backup Gateways . . . . . . . . . . . . . . . . . . . . . . . 11 6. Backup Gateways . . . . . . . . . . . . . . . . . . . . . . . 11
7. Alternative Solutions . . . . . . . . . . . . . . . . . . . . 12 7. Alternative Solutions . . . . . . . . . . . . . . . . . . . . 12
7.1. Initiating a new IKE SA . . . . . . . . . . . . . . . . . 12 7.1. Initiating a new IKE SA . . . . . . . . . . . . . . . . . 12
7.2. SIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.2. SIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.3. Birth Certificates . . . . . . . . . . . . . . . . . . . . 12 7.3. Birth Certificates . . . . . . . . . . . . . . . . . . . . 12
7.4. Reducing Liveness Check Length . . . . . . . . . . . . . . 13 7.4. Reducing Liveness Check Length . . . . . . . . . . . . . . 13
8. Interaction with Session Resumption . . . . . . . . . . . . . 13 8. Interaction with Session Resumption . . . . . . . . . . . . . 13
9. Operational Considerations . . . . . . . . . . . . . . . . . . 15 9. Operational Considerations . . . . . . . . . . . . . . . . . . 15
9.1. Who should implement this specification . . . . . . . . . 15 9.1. Who should implement this specification . . . . . . . . . 15
9.2. Response to unknown child SPI . . . . . . . . . . . . . . 16 9.2. Response to unknown child SPI . . . . . . . . . . . . . . 16
9.3. Using Tokens that Depend on IP Addresses . . . . . . . . . 16 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16
10. Security Considerations . . . . . . . . . . . . . . . . . . . 17
10.1. QCD Token Generation and Handling . . . . . . . . . . . . 17 10.1. QCD Token Generation and Handling . . . . . . . . . . . . 17
10.2. QCD Token Transmission . . . . . . . . . . . . . . . . . . 18 10.2. QCD Token Transmission . . . . . . . . . . . . . . . . . . 17
10.3. QCD Token Enumeration . . . . . . . . . . . . . . . . . . 18 10.3. QCD Token Enumeration . . . . . . . . . . . . . . . . . . 18
10.4. Selecting an Appropriate Token Generation Method . . . . . 18
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 19 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 19
13.1. Changes from draft-nir-ike-qcd-07 . . . . . . . . . . . . 19 13.1. Changes from draft-ietf-ipsecme-failure-detection-00 . . . 19
13.2. Changes from draft-nir-ike-qcd-03 and -04 . . . . . . . . 19 13.2. Changes from draft-nir-ike-qcd-07 . . . . . . . . . . . . 20
13.3. Changes from draft-nir-ike-qcd-02 . . . . . . . . . . . . 19 13.3. Changes from draft-nir-ike-qcd-03 and -04 . . . . . . . . 20
13.4. Changes from draft-nir-ike-qcd-01 . . . . . . . . . . . . 20 13.4. Changes from draft-nir-ike-qcd-02 . . . . . . . . . . . . 20
13.5. Changes from draft-nir-ike-qcd-00 . . . . . . . . . . . . 20 13.5. Changes from draft-nir-ike-qcd-01 . . . . . . . . . . . . 20
13.6. Changes from draft-nir-qcr-00 . . . . . . . . . . . . . . 20 13.6. Changes from draft-nir-ike-qcd-00 . . . . . . . . . . . . 20
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 13.7. Changes from draft-nir-qcr-00 . . . . . . . . . . . . . . 20
14.1. Normative References . . . . . . . . . . . . . . . . . . . 20 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
14.2. Informative References . . . . . . . . . . . . . . . . . . 20 14.1. Normative References . . . . . . . . . . . . . . . . . . . 21
14.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
IKEv2, as described in [IKEv2bis] and its predecessor RFC 4306, has a IKEv2, as described in [RFC5996] and its predecessor RFC 4306, has a
method for recovering from a reboot of one peer. As long as traffic method for recovering from a reboot of one peer. As long as traffic
flows in both directions, the rebooted peer should re-establish the flows in both directions, the rebooted peer should re-establish the
tunnels immediately. However, in many cases the rebooted peer is a tunnels immediately. However, in many cases the rebooted peer is a
VPN gateway that protects only servers, or else the non-rebooted peer VPN gateway that protects only servers, or else the non-rebooted peer
has a dynamic IP address. In such cases, the rebooted peer will not has a dynamic IP address. In such cases, the rebooted peer will not
be able to re-establish the tunnels. Section 2 describes how be able to re-establish the tunnels. Section 2 describes how
recovery works under RFC 4306, and explains why it may take several recovery works under RFC 4306, and explains why it may take several
minutes. minutes.
The method proposed here, is to send an octet string, called a "QCD The method proposed here, is to send an octet string, called a "QCD
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database. A small non-volatile storage module is required for a database. A small non-volatile storage module is required for a
token maker, but a larger one can be used to enhance performance, as token maker, but a larger one can be used to enhance performance, as
described in Section 9.2. described in Section 9.2.
2. RFC 4306 Crash Recovery 2. RFC 4306 Crash Recovery
When one peer loses state or reboots, the other peer does not get any When one peer loses state or reboots, the other peer does not get any
notification, so unidirectional IPsec traffic can still flow. The notification, so unidirectional IPsec traffic can still flow. The
rebooted peer will not be able to decrypt it, however, and the only rebooted peer will not be able to decrypt it, however, and the only
remedy is to send an unprotected INVALID_SPI notification as remedy is to send an unprotected INVALID_SPI notification as
described in section 3.10.1 of [IKEv2bis]. That section also described in section 3.10.1 of [RFC5996]. That section also
describes the processing of such a notification: describes the processing of such a notification:
"If this Informational Message is sent outside the "If this Informational Message is sent outside the
context of an IKE_SA, it should be used by the recipient context of an IKE_SA, it should be used by the recipient
only as a "hint" that something might be wrong (because it only as a "hint" that something might be wrong (because it
could easily be forged)." could easily be forged)."
Since the INVALID_SPI can only be used as a hint, the non-rebooted Since the INVALID_SPI can only be used as a hint, the non-rebooted
peer has to determine whether the IPsec SA, and indeed the parent IKE peer has to determine whether the IPsec SA, and indeed the parent IKE
SA are still valid. The method of doing this is described in section SA are still valid. The method of doing this is described in section
2.4 of [IKEv2bis]. This method, called "liveness check" involves 2.4 of [RFC5996]. This method, called "liveness check" involves
sending a protected empty INFORMATIONAL message, and awaiting a sending a protected empty INFORMATIONAL message, and awaiting a
response. This procedure is sometimes referred to as "Dead Peer response. This procedure is sometimes referred to as "Dead Peer
Detection" or DPD. Detection" or DPD.
Section 2.4 does not mandate how many times the liveness check Section 2.4 does not mandate how many times the liveness check
message should be retransmitted, or for how long, but does recommend message should be retransmitted, or for how long, but does recommend
the following: the following:
"It is "It is
suggested that messages be retransmitted at least a dozen times over suggested that messages be retransmitted at least a dozen times over
a period of at least several minutes before giving up on an SA..." a period of at least several minutes before giving up on an SA..."
Those "at least several minutes" are a time during which both peers Those "at least several minutes" are a time during which both peers
are active, but IPsec cannot be used. are active, but IPsec cannot be used.
3. Protocol Outline 3. Protocol Outline
Supporting implementations will send a notification, called a "QCD Supporting implementations will send a notification, called a "QCD
token", as described in Section 4.1 in the last IKE_AUTH exchange token", as described in Section 4.1 in the first IKE_AUTH exchange
messages. These are the final IKE_AUTH request and final IKE_AUTH messages. These are the final IKE_AUTH request and final IKE_AUTH
response that contain the AUTH payloads. The generation of these response that contain the AUTH payloads. The generation of these
tokens is a local matter for implementations, but considerations are tokens is a local matter for implementations, but considerations are
described in Section 5. Implementations that send such a token will described in Section 5. Implementations that send such a token will
be called "token makers". be called "token makers".
A supporting implementation receiving such a token MUST store it (or A supporting implementation receiving such a token MUST store it (or
a digest thereof) along with the IKE SA. Implementations that a digest thereof) along with the IKE SA. Implementations that
support this part of the protocol will be called "token takers". support this part of the protocol will be called "token takers".
Section 9.1 has considerations for which implementations need to be Section 9.1 has considerations for which implementations need to be
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When a token maker receives a protected IKE request message with When a token maker receives a protected IKE request message with
unknown IKE SPIs, it SHOULD generate a new token that is identical to unknown IKE SPIs, it SHOULD generate a new token that is identical to
the previous token, and send it to the requesting peer in an the previous token, and send it to the requesting peer in an
unprotected IKE message as described in Section 4.5. unprotected IKE message as described in Section 4.5.
When a token taker receives the QCD token in an unprotected When a token taker receives the QCD token in an unprotected
notification, it MUST verify that the TOKEN_SECRET_DATA matches the notification, it MUST verify that the TOKEN_SECRET_DATA matches the
token stored with the matching IKE SA. If the verification fails, or token stored with the matching IKE SA. If the verification fails, or
if the IKE SPIs in the message do not match any existing IKE SA, it if the IKE SPIs in the message do not match any existing IKE SA, it
SHOULD log the event. If it succeeds, it MUST silently delete the SHOULD log the event. If it succeeds, it MUST silently delete the
IKE SA associated with the IKE_SPI fields, and all dependant child IKE SA associated with the IKE_SPI fields, and all dependent child
SAs. This event MAY also be logged. The token taker MUST accept SAs. This event MAY also be logged. The token taker MUST accept
such tokens from any IP address and port combination, so as to allow such tokens from any IP address and port combination, so as to allow
different kinds of high-availability configurations of the token different kinds of high-availability configurations of the token
maker. maker.
A supporting token taker MAY immediately create new SAs using an A supporting token taker MAY immediately create new SAs using an
Initial exchange, or it may wait for subsequent traffic to trigger Initial exchange, or it may wait for subsequent traffic to trigger
the creation of new SAs. the creation of new SAs.
See Section 8 for a short discussion about this extensions's See Section 8 for a short discussion about this extensions's
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! ! ! !
~ TOKEN_SECRET_DATA ~ ~ TOKEN_SECRET_DATA ~
! ! ! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Protocol ID (1 octet) MUST be 1, as this message is related to an o Protocol ID (1 octet) MUST be 1, as this message is related to an
IKE SA. IKE SA.
o SPI Size (1 octet) MUST be zero, in conformance with section 3.10 o SPI Size (1 octet) MUST be zero, in conformance with section 3.10
of [IKEv2bis]. of [RFC5996].
o QCD Token Notify Message Type (2 octets) - MUST be xxxxx, the o QCD Token Notify Message Type (2 octets) - MUST be xxxxx, the
value assigned for QCD token notifications. TBA by IANA. value assigned for QCD token notifications. TBA by IANA.
o TOKEN_SECRET_DATA (16-128 octets) contains a generated token as o TOKEN_SECRET_DATA (16-128 octets) contains a generated token as
described in Section 5. described in Section 5.
4.2. Passing a Token in the AUTH Exchange 4.2. Passing a Token in the AUTH Exchange
For brevity, only the EAP version of an AUTH exchange will be For brevity, only the EAP version of an AUTH exchange will be
presented here. The non-EAP version is very similar. The figures presented here. The non-EAP version is very similar. The figures
below are based on appendix C.3 of [IKEv2bis]. below are based on appendix C.3 of [RFC5996].
first request --> IDi, first request --> IDi,
[N(INITIAL_CONTACT)], [N(INITIAL_CONTACT)],
[[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+], [[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
[IDr], [IDr],
[N(QCD_TOKEN)]
[CP(CFG_REQUEST)], [CP(CFG_REQUEST)],
[N(IPCOMP_SUPPORTED)+], [N(IPCOMP_SUPPORTED)+],
[N(USE_TRANSPORT_MODE)], [N(USE_TRANSPORT_MODE)],
[N(ESP_TFC_PADDING_NOT_SUPPORTED)], [N(ESP_TFC_PADDING_NOT_SUPPORTED)],
[N(NON_FIRST_FRAGMENTS_ALSO)], [N(NON_FIRST_FRAGMENTS_ALSO)],
SA, TSi, TSr, SA, TSi, TSr,
[V+] [V+]
first response <-- IDr, [CERT+], AUTH, first response <-- IDr, [CERT+], AUTH,
EAP, EAP,
[V+] [V+]
/ --> EAP / --> EAP
repeat 1..N times | repeat 1..N times |
\ <-- EAP \ <-- EAP
last request --> AUTH last request --> AUTH
[N(QCD_TOKEN)]
last response <-- AUTH, last response <-- AUTH,
[N(QCD_TOKEN)] [N(QCD_TOKEN)]
[CP(CFG_REPLY)], [CP(CFG_REPLY)],
[N(IPCOMP_SUPPORTED)], [N(IPCOMP_SUPPORTED)],
[N(USE_TRANSPORT_MODE)], [N(USE_TRANSPORT_MODE)],
[N(ESP_TFC_PADDING_NOT_SUPPORTED)], [N(ESP_TFC_PADDING_NOT_SUPPORTED)],
[N(NON_FIRST_FRAGMENTS_ALSO)], [N(NON_FIRST_FRAGMENTS_ALSO)],
SA, TSi, TSr, SA, TSi, TSr,
[N(ADDITIONAL_TS_POSSIBLE)], [N(ADDITIONAL_TS_POSSIBLE)],
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Note that the QCD_TOKEN notification is marked as optional because it Note that the QCD_TOKEN notification is marked as optional because it
is not required by this specification that every implementation be is not required by this specification that every implementation be
both token maker and token taker. If only one peer sends the QCD both token maker and token taker. If only one peer sends the QCD
token, then a reboot of the other peer will not be recoverable by token, then a reboot of the other peer will not be recoverable by
this method. This may be acceptable if traffic typically originates this method. This may be acceptable if traffic typically originates
from the other peer. from the other peer.
In any case, the lack of a QCD_TOKEN notification MUST NOT be taken In any case, the lack of a QCD_TOKEN notification MUST NOT be taken
as an indication that the peer does not support this standard. as an indication that the peer does not support this standard.
Conversely, if a peer does not understand this notification, it will Conversely, if a peer does not understand this notification, it will
simply ignore it. Therefore a peer MAY send this notification simply ignore it. Therefore a peer may send this notification
freely, even if it does not know whether the other side supports it. freely, even if it does not know whether the other side supports it.
The QCD_TOKEN notification is related to the IKE SA and MUST follow The QCD_TOKEN notification is related to the IKE SA and MUST follow
the AUTH payload and precede the Configuration payload and all the AUTH payload and precede the Configuration payload and all
payloads related to the child SA. payloads related to the child SA.
4.3. Replacing Tokens After Rekey or Resumption 4.3. Replacing Tokens After Rekey or Resumption
After rekeying an IKE SA, the IKE SPIs are replaced, so the new SA After rekeying an IKE SA, the IKE SPIs are replaced, so the new SA
also needs to have a token. If only the responder in the rekey also needs to have a token. If only the responder in the rekey
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HDR, SK { N(COOKIE2), [N(QCD_TOKEN)] } HDR, SK { N(COOKIE2), [N(QCD_TOKEN)] }
(IP_I2:4500 -> IP_R1:4500) (IP_I2:4500 -> IP_R1:4500)
HDR, SK { N(COOKIE2), [N(QCD_TOKEN)] } --> HDR, SK { N(COOKIE2), [N(QCD_TOKEN)] } -->
A token taker MUST accept such gratuitous QCD_TOKEN notifications as A token taker MUST accept such gratuitous QCD_TOKEN notifications as
long as they are carried in protected exchanges. A token maker long as they are carried in protected exchanges. A token maker
SHOULD NOT generate them unless it is no longer able to generate the SHOULD NOT generate them unless it is no longer able to generate the
old QCD_TOKEN. old QCD_TOKEN.
4.5. Presenting the Token in an INFORMATIONAL Exchange 4.5. Presenting the Token in an Unprotected Message
This QCD_TOKEN notification is unprotected, and is sent as a response This QCD_TOKEN notification is unprotected, and is sent as a response
to a protected IKE request, which uses an IKE SA that is unknown. to a protected IKE request, which uses an IKE SA that is unknown.
request --> N(INVALID_IKE_SPI), N(QCD_TOKEN)+ request --> N(INVALID_IKE_SPI), N(QCD_TOKEN)+
If child SPIs are persistently mapped to IKE SPIs as described in If child SPIs are persistently mapped to IKE SPIs as described in
Section 9.2, a token taker may get the following unprotected message Section 9.2, a token taker may get the following unprotected message
in response to an ESP or AH packet. in response to an ESP or AH packet.
request --> N(INVALID_SPI), N(QCD_TOKEN)+ request --> N(INVALID_SPI), N(QCD_TOKEN)+
The QCD_TOKEN and INVALID_IKE_SPI notifications are sent together to The QCD_TOKEN and INVALID_IKE_SPI notifications are sent together to
support both implementations that conform to this specification and support both implementations that conform to this specification and
implementations that don't. Similar to the description in section implementations that don't. Similar to the description in section
2.21 of [IKEv2bis], The IKE SPI and message ID fields in the packet 2.21 of [RFC5996], the IKE SPI and message ID fields in the packet
headers are taken from the protected IKE request. headers are taken from the protected IKE request.
To support a periodic rollover of the secret used for token To support a periodic rollover of the secret used for token
generation, the token taker MUST support at least four QCD_TOKEN generation, the token taker MUST support at least four QCD_TOKEN
notifications in a single packet. The token is considered verified notifications in a single packet. The token is considered verified
if any of the QCD_TOKEN notifications matches. The token maker MAY if any of the QCD_TOKEN notifications matches. The token maker MAY
generate up to four QCD_TOKEN notifications, based on several generate up to four QCD_TOKEN notifications, based on several
generations of keys. generations of keys.
If the QCD_TOKEN verifies OK, an empty response MUST be sent. If the If the QCD_TOKEN verifies OK, the receiver MUST silently discard the
QCD_TOKEN cannot be validated, a response MUST NOT be sent. IKE SA and all associated child SAs. If the QCD_TOKEN cannot be
validated, a response MUST NOT be sent, and the event may be logged.
Section 5 defines token verification. Section 5 defines token verification.
5. Token Generation and Verification 5. Token Generation and Verification
No token generation method is mandated by this document. Two method No token generation method is mandated by this document. Two methods
are documented in the following sub-sections, but they only serve as are documented in the following sub-sections, but they only serve as
examples. examples.
The following lists the requirements from a token generation The following lists the requirements for a token generation
mechanism: mechanism:
o Tokens MUST be at least 16 octets long, and no more than 128 o Tokens MUST be at least 16 octets long, and no more than 128
octets long, to facilitate storage and transmission. Tokens octets long, to facilitate storage and transmission. Tokens
SHOULD be indistinguishable from random data. SHOULD be indistinguishable from random data.
o It should not be possible for an external attacker to guess the o It should not be possible for an external attacker to guess the
QCD token generated by an implementation. Cryptographic QCD token generated by an implementation. Cryptographic
mechanisms such as PRNG and hash functions are RECOMMENDED. mechanisms such as PRNG and hash functions are RECOMMENDED.
o The token maker, MUST be able to re-generate or retrieve the token o The token maker MUST be able to re-generate or retrieve the token
based on the IKE SPIs even after it reboots. based on the IKE SPIs even after it reboots.
o The method of token generation MUST be such, that a collision of o The method of token generation MUST be such that a collision of
QCD tokens between different pairs of IKE SPI will be highly QCD tokens between different pairs of IKE SPI will be highly
unlikely. unlikely.
5.1. A Stateless Method of Token Generation 5.1. A Stateless Method of Token Generation
This describes a stateless method of generating a token: This describes a stateless method of generating a token:
o At installation or immediately after the first boot of the token o At installation or immediately after the first boot of the token
maker, 32 random octets are generated using a secure random number maker, 32 random octets are generated using a secure random number
generator or a PRNG. generator or a PRNG.
o Those 32 bytes, called the "QCD_SECRET", are stored in non- o Those 32 bytes, called the "QCD_SECRET", are stored in non-
skipping to change at page 11, line 22 skipping to change at page 11, line 22
TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R) TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R)
5.2. A Stateless Method with IP addresses 5.2. A Stateless Method with IP addresses
This method is similar to the one in the previous section, except This method is similar to the one in the previous section, except
that the IP address of the token taker is also added to the block that the IP address of the token taker is also added to the block
being hashed. This has the disadvantage that the token needs to be being hashed. This has the disadvantage that the token needs to be
replaced (as described in Section 4.4) whenever the token taker replaced (as described in Section 4.4) whenever the token taker
changes its address. changes its address.
The reason to use this method is described in Section 9.3. When The reason to use this method is described in Section 10.4. When
using this method, the TOKEN_SECRET_DATA field is calculated as using this method, the TOKEN_SECRET_DATA field is calculated as
follows: follows:
TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R | IPaddr-T) TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R | IPaddr-T)
The IPaddr-T field specifies the IP address of the token taker. The IPaddr-T field specifies the IP address of the token taker.
Secret rollover considerations are similar to those in the previous Secret rollover considerations are similar to those in the previous
section. section.
5.3. Token Lifetime 5.3. Token Lifetime
skipping to change at page 11, line 44 skipping to change at page 11, line 44
The token is associated with a single IKE SA, and SHOULD be deleted The token is associated with a single IKE SA, and SHOULD be deleted
by the token taker when the SA is deleted or expires. More formally, by the token taker when the SA is deleted or expires. More formally,
the token is associated with the pair (SPI-I, SPI-R). the token is associated with the pair (SPI-I, SPI-R).
6. Backup Gateways 6. Backup Gateways
Making crash detection and recovery quick is a worthy goal, but since Making crash detection and recovery quick is a worthy goal, but since
rebooting a gateway takes a non-zero amount of time, many rebooting a gateway takes a non-zero amount of time, many
implementations choose to have a stand-by gateway ready to take over implementations choose to have a stand-by gateway ready to take over
as soon as the primary gateway fails for any reason. [cluster] as soon as the primary gateway fails for any reason. [cluster]
describes consideration for such clusters of gateways with describes considerations for such clusters of gateways with
synchronized state, but the rest of this section is relevant even synchronized state, but the rest of this section is relevant even
when there is no synchnorized state. when there is no synchronized state.
If such a configuration is available, it is RECOMMENDED that the If such a configuration is available, it is RECOMMENDED that the
stand-by gateway be able to generate the same token as the active stand-by gateway be able to generate the same token as the active
gateway. if the method described in Section 5.1 is used, this means gateway. if the method described in Section 5.1 is used, this means
that the QCD_SECRET field is identical in both gateways. This has that the QCD_SECRET field is identical in both gateways. This has
the effect of having the crash recovery available immediately. the effect of having the crash recovery available immediately.
Note that this refers to "high availability" configurations, where Note that this refers to "high availability" configurations, where
only one gateway is active at any given moment. This is different only one gateway is active at any given moment. This is different
from "load sharing" configurations where more than one gateway is from "load sharing" configurations where more than one gateway is
skipping to change at page 14, line 10 skipping to change at page 14, line 10
up a new IKE SA consume less computing resources. This is up a new IKE SA consume less computing resources. This is
particularly useful in the case of a remote access gateway that has particularly useful in the case of a remote access gateway that has
many tunnels. A failure of such a gateway would require all these many tunnels. A failure of such a gateway would require all these
many remote access clients to establish an IKE SA either with the many remote access clients to establish an IKE SA either with the
rebooted gateway or with a backup gateway. This tunnel re- rebooted gateway or with a backup gateway. This tunnel re-
establishment should occur within a short period of time, creating a establishment should occur within a short period of time, creating a
burden on the remote access gateway. Session Resumption addresses burden on the remote access gateway. Session Resumption addresses
this problem by having the clients store an encrypted derivative of this problem by having the clients store an encrypted derivative of
the IKE SA for quick re-establishment. the IKE SA for quick re-establishment.
What Session Resumption does not help, is the problem of detecting What Session Resumption does not help is the problem of detecting
that the peer gateway has failed. A failed gateway may go undetected that the peer gateway has failed. A failed gateway may go undetected
for as long as the lifetime of a child SA, because IPsec does not for as long as the lifetime of a child SA, because IPsec does not
have packet acknowledgement, and applications cannot signal the IPsec have packet acknowledgement, and applications cannot signal the IPsec
layer that the tunnel "does not work". Before establishing a new IKE layer that the tunnel "does not work". Before establishing a new IKE
SA using Session Resumption, a client should ascertain that the SA using Session Resumption, a client should ascertain that the
gateway has indeed failed. This could be done using either a gateway has indeed failed. This could be done using either a
liveness check (as in RFC 4306) or using the QCD tokens described in liveness check (as in RFC 4306) or using the QCD tokens described in
this document. this document.
A remote access client conforming to both specifications will store A remote access client conforming to both specifications will store
skipping to change at page 15, line 50 skipping to change at page 15, line 50
of this protocol extension is reduced. For this reason critical of this protocol extension is reduced. For this reason critical
systems should implement backup gateways as described in Section 6. systems should implement backup gateways as described in Section 6.
Implementing the "token maker" side of QCD makes sense for IKE Implementing the "token maker" side of QCD makes sense for IKE
implementation where protected connections originate from the peer, implementation where protected connections originate from the peer,
such as inter-domain VPNs and remote access gateways. Implementing such as inter-domain VPNs and remote access gateways. Implementing
the "token taker" side of QCD makes sense for IKE implementations the "token taker" side of QCD makes sense for IKE implementations
where protected connections originate, such as inter-domain VPNs and where protected connections originate, such as inter-domain VPNs and
remote access clients. remote access clients.
To clarify the requirements: To clarify the this discussion:
o A remote-access client MUST be a token taker and MAY be a token o For remote-access clients it makes sense to implement the token
maker. taker role.
o A remote-access gateway MAY be a token taker and MUST be a token o For remote-access gateways it makes sense to implement the token
maker. maker role.
o An inter-domain VPN gateway MUST be both token maker and token o For inter-domain VPN gateway it makes sense to implement both
taker. roles, because it can't be known in advance where the traffic
originates.
o It is perfectly valid to implement both roles in any case, for
example when using a single library or a single gateway to perform
several roles.
In order to limit the effects of DoS attacks, a token taker SHOULD In order to limit the effects of DoS attacks, a token taker SHOULD
limit the rate of QCD_TOKENs verified from a particular source. limit the rate of QCD_TOKENs verified from a particular source.
If excessive amounts of IKE requests protected with unknown IKE SPIs If excessive amounts of IKE requests protected with unknown IKE SPIs
arrive at a token maker, the IKE module SHOULD revert to the behavior arrive at a token maker, the IKE module SHOULD revert to the behavior
described in section 2.21 of [IKEv2bis] and either send an described in section 2.21 of [RFC5996] and either send an
INVALID_IKE_SPI notification, or ignore it entirely. INVALID_IKE_SPI notification, or ignore it entirely.
9.2. Response to unknown child SPI 9.2. Response to unknown child SPI
After a reboot, it is more likely that an implementation receives After a reboot, it is more likely that an implementation receives
IPsec packets than IKE packets. In that case, the rebooted IPsec packets than IKE packets. In that case, the rebooted
implementation will send an INVALID_SPI notification, triggering a implementation will send an INVALID_SPI notification, triggering a
liveness check. The token will only be sent in a response to the liveness check. The token will only be sent in a response to the
liveness check, thus requiring an extra round-trip. liveness check, thus requiring an extra round-trip.
skipping to change at page 16, line 44 skipping to change at page 16, line 48
QCD token that arrives with an INVALID_SPI notification the same as QCD token that arrives with an INVALID_SPI notification the same as
if it arrived with the IKE SPIs of the parent IKE SA. if it arrived with the IKE SPIs of the parent IKE SA.
However, a persistent storage module might not be updated in a timely However, a persistent storage module might not be updated in a timely
manner, and could be populated with tokens relating to IKE SPIs that manner, and could be populated with tokens relating to IKE SPIs that
have already been rekeyed. A token taker MUST NOT take an invalid have already been rekeyed. A token taker MUST NOT take an invalid
QCD Token sent along with an INVALID_SPI notification as evidence QCD Token sent along with an INVALID_SPI notification as evidence
that the peer is either malfunctioning or attacking, but it SHOULD that the peer is either malfunctioning or attacking, but it SHOULD
limit the rate at which such notifications are processed. limit the rate at which such notifications are processed.
9.3. Using Tokens that Depend on IP Addresses
This section describes the rationale for token generation methods
such as the one described in Section 5.2. Note that this section
merely provides a possible rationale, and does not specify or
recommend any kind of configuration.
Some configurations of security gateway use a load-sharing cluster of
hosts, all sharing the same IP addresses, where the SAs (IKE and
child) are not synchronized between the cluster members. In such a
configuration, a single member does not know about all the IKE SAs
that are active for the configuration. A load balancer (usually a
networking switch) sends IKE and IPsec packets to the several members
based on source IP address.
In such a configuration, an attacker can send a forged protected IKE
packet with the IKE SPIs of an existing IKE SA, but from a different
IP address. This packet will likely be processed by a different
cluster member from the one that owns the IKE SA. Since no IKE SA
state is stored on this member, it will send a QCD token to the
attacker. If the QCD token does not depend on IP address, this token
can immediately be used to tell the token taker to tear down the IKE
SA using an unprotected QCD_TOKEN notification.
To thwart this possible attack, such configurations should use a
method that considers the taker's IP address, such as the method
described in Section 5.2.
10. Security Considerations 10. Security Considerations
10.1. QCD Token Generation and Handling 10.1. QCD Token Generation and Handling
Tokens MUST be hard to guess. This is critical, because if an Tokens MUST be hard to guess. This is critical, because if an
attacker can guess the token associated with an IKE SA, she can tear attacker can guess the token associated with an IKE SA, she can tear
down the IKE SA and associated tunnels at will. When the token is down the IKE SA and associated tunnels at will. When the token is
delivered in the IKE_AUTH exchange, it is encrypted. When it is sent delivered in the IKE_AUTH exchange, it is encrypted. When it is sent
again in an unprotected notification, it is not, but that is the last again in an unprotected notification, it is not, but that is the last
time this token is ever used. time this token is ever used.
An aggregation of some tokens generated by one maker together with An aggregation of some tokens generated by one maker together with
skipping to change at page 18, line 24 skipping to change at page 17, line 50
an existing IKE SA. This implies that a conforming QCD token maker an existing IKE SA. This implies that a conforming QCD token maker
MUST be able to tell whether a particular pair of IKE SPIs represent MUST be able to tell whether a particular pair of IKE SPIs represent
a valid IKE SA. a valid IKE SA.
This requirement is obvious and easy in the case of a single gateway. This requirement is obvious and easy in the case of a single gateway.
However, some implementations use a load balancer to divide the load However, some implementations use a load balancer to divide the load
between several physical gateways. It MUST NOT be possible even in between several physical gateways. It MUST NOT be possible even in
such a configuration to trick one gateway into sending a QCD token such a configuration to trick one gateway into sending a QCD token
for an IKE SA which is valid on another gateway. for an IKE SA which is valid on another gateway.
This document does not specify how a load sharing sharing This document does not specify how a load sharing configuration of
configuration of IPsec gateways would work, but in order to support IPsec gateways would work, but in order to support this
this specification, all members MUST be able to tell whether a specification, all members MUST be able to tell whether a particular
particular IKE SA is active anywhere in the cluster. One way to do IKE SA is active anywhere in the cluster. One way to do it is to
it is to synchronize a list of active IKE SPIs among all the cluster synchronize a list of active IKE SPIs among all the cluster members.
members.
10.3. QCD Token Enumeration 10.3. QCD Token Enumeration
An attacker may try to attack QCD if the generation algorithm An attacker may try to attack QCD if the generation algorithm
described in Section 5.1 is used. The attacker will send several described in Section 5.1 is used. The attacker will send several
fake IKE requests to the gateway under attack, receiving and fake IKE requests to the gateway under attack, receiving and
recording the QCD Tokens in the responses. This will allow the recording the QCD Tokens in the responses. This will allow the
attacker to create a dictionary of IKE SPIs to QCD Tokens, which can attacker to create a dictionary of IKE SPIs to QCD Tokens, which can
later be used to tear down any IKE SA. later be used to tear down any IKE SA.
Three factors mitigate this threat: Three factors mitigate this threat:
o The space of all possible IKE SPI pairs is huge: 2^128, so making o The space of all possible IKE SPI pairs is huge: 2^128, so making
such a dictionary is impractical. Even if we assume that one such a dictionary is impractical. Even if we assume that one
implementation always generates predictable IKE SPIs, the space is implementation always generates predictable IKE SPIs, the space is
still at least 2^64 entries, so making the dictionary is extremely still at least 2^64 entries, so making the dictionary is extremely
hard. hard. To ensure this, token makers MUST use a good pseudo-random
number generator to generate the IKE SPIs.
o Throttling the amount of QCD_TOKEN notifications sent out, as o Throttling the amount of QCD_TOKEN notifications sent out, as
discussed in Section 9.1, especially when not soon after a crash discussed in Section 9.1, especially when not soon after a crash
will limit the attacker's ability to construct a dictionary. will limit the attacker's ability to construct a dictionary.
o The methods in Section 5.1 and Section 5.2 allow for a periodic o The methods in Section 5.1 and Section 5.2 allow for a periodic
change of the QCD_SECRET. Any such change invalidates the entire change of the QCD_SECRET. Any such change invalidates the entire
dictionary. dictionary.
10.4. Selecting an Appropriate Token Generation Method
This section describes the rationale for token generation methods
such as the one described in Section 5.2. Note that this section
merely provides a possible rationale, and does not specify or
recommend any kind of configuration.
Some configurations of security gateway use a load-sharing cluster of
hosts, all sharing the same IP addresses, where the SAs (IKE and
child) are not synchronized between the cluster members. In such a
configuration, a single member does not know about all the IKE SAs
that are active for the configuration. A load balancer (usually a
networking switch) sends IKE and IPsec packets to the several members
based on source IP address.
In such a configuration, an attacker can send a forged protected IKE
packet with the IKE SPIs of an existing IKE SA, but from a different
IP address. This packet will likely be processed by a different
cluster member from the one that owns the IKE SA. Since no IKE SA
state is stored on this member, it will send a QCD token to the
attacker. If the QCD token does not depend on IP address, this token
can immediately be used to tell the token taker to tear down the IKE
SA using an unprotected QCD_TOKEN notification.
To thwart this possible attack, such configurations should use a
method that considers the taker's IP address, such as the method
described in Section 5.2.
On the other hand, when using this method a change of address
invalidates the tokens, so this method has both advantages and
disadvantages.
11. IANA Considerations 11. IANA Considerations
IANA is requested to assign a notify message type from the status IANA is requested to assign a notify message type from the status
types range (16406-40959) of the "IKEv2 Notify Message Types" types range (16406-40959) of the "IKEv2 Notify Message Types"
registry with name "QUICK_CRASH_DETECTION". registry with name "QUICK_CRASH_DETECTION".
12. Acknowledgements 12. Acknowledgements
We would like to thank Hannes Tschofenig and Yaron Sheffer for their We would like to thank Hannes Tschofenig and Yaron Sheffer for their
comments about Session Resumption. comments about Session Resumption.
Frederic D'etienne and Pratima Sethi contributed the ideas in Frederic D'etienne and Pratima Sethi contributed the ideas in
Section 9.3 and Section 5.2. Section 10.4 and Section 5.2.
Others who have contrinuted valuable comments are, in alphabetical Others who have contrinuted valuable comments are, in alphabetical
order, Lakshminath Dondeti, Scott C Moonen and Dave Wierbowski. order, Lakshminath Dondeti and Scott C Moonen.
13. Change Log 13. Change Log
This section lists all changes in this document This section lists all changes in this document
NOTE TO RFC EDITOR : Please remove this section in the final RFC NOTE TO RFC EDITOR : Please remove this section in the final RFC
13.1. Changes from draft-nir-ike-qcd-07 13.1. Changes from draft-ietf-ipsecme-failure-detection-00
o Nits pointed out by Scott and Yaron.
o Pratima and Frederic are back on board.
o Changed IKEv2bis draft reference to RFC 5996.
o Resolved issues #189, #190, #191, and #192:
* Renamed section 4.5 and removed the requirement to send an
acknowledgement for the unprotected message.
* Moved the QCD token from the last to the first IKE_AUTH
request.
* Added a MUST to Section 10.3 to require that IKE SPIs be
randomly generated.
* Changed the language in Section 9.1, to not use RFC 2119
terminology.
* Moved the section describing why one would want the method
dependant on IP addresses (in Section 5.2 from operational
considerations to security considerations.
13.2. Changes from draft-nir-ike-qcd-07
o First WG version. o First WG version.
o Addressed Scott C Moonen's concern about collisions of QCD tokens. o Addressed Scott C Moonen's concern about collisions of QCD tokens.
o Updated references to point to IKEv2bis instead of RFC 4306 and o Updated references to point to IKEv2bis instead of RFC 4306 and
4718. Also converted draft reference for resumption to RFC 5723. 4718. Also converted draft reference for resumption to RFC 5723.
o Added Dave Wiebrowski as author, and removed Pratima and Frederic. o Added Dave Wiebrowski as author, and removed Pratima and Frederic.
13.2. Changes from draft-nir-ike-qcd-03 and -04 13.3. Changes from draft-nir-ike-qcd-03 and -04
Mostly editorial changes and cleaning up. Mostly editorial changes and cleaning up.
13.3. Changes from draft-nir-ike-qcd-02 13.4. Changes from draft-nir-ike-qcd-02
o Described QCD token enumeration, following a question by o Described QCD token enumeration, following a question by
Lakshminath Dondeti. Lakshminath Dondeti.
o Added the ability to replace the QCD token for an existing IKE SA. o Added the ability to replace the QCD token for an existing IKE SA.
o Added tokens dependant on peer IP address and their interaction o Added tokens dependent on peer IP address and their interaction
with MOBIKE. with MOBIKE.
13.4. Changes from draft-nir-ike-qcd-01 13.5. Changes from draft-nir-ike-qcd-01
o Removed stateless method. o Removed stateless method.
o Added discussion of rekeying and resumption. o Added discussion of rekeying and resumption.
o Added discussion of non-synchronized load-balanced clusters of o Added discussion of non-synchronized load-balanced clusters of
gateways in the security considerations. gateways in the security considerations.
o Other wording fixes. o Other wording fixes.
13.5. Changes from draft-nir-ike-qcd-00 13.6. Changes from draft-nir-ike-qcd-00
o Merged proposal with draft-detienne-ikev2-recovery o Merged proposal with draft-detienne-ikev2-recovery
o Changed the protocol so that the rebooted peer generates the o Changed the protocol so that the rebooted peer generates the
token. This has the effect, that the need for persistent storage token. This has the effect, that the need for persistent storage
is eliminated. is eliminated.
o Added discussion of birth certificates. o Added discussion of birth certificates.
13.6. Changes from draft-nir-qcr-00 13.7. Changes from draft-nir-qcr-00
o Changed name to reflect that this relates to IKE. Also changed o Changed name to reflect that this relates to IKE. Also changed
from quick crash recovery to quick crash detection to avoid from quick crash recovery to quick crash detection to avoid
confusion with IFARE. confusion with IFARE.
o Added more operational considerations. o Added more operational considerations.
o Added interaction with IFARE. o Added interaction with IFARE.
o Added discussion of backup gateways. o Added discussion of backup gateways.
14. References 14. References
14.1. Normative References 14.1. Normative References
[IKEv2bis]
Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol: IKEv2",
draft-ietf-ipsecme-ikev2bis-11 (work in progress),
May 2010.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol [RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol
(MOBIKE)", RFC 4555, June 2006. (MOBIKE)", RFC 4555, June 2006.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol: IKEv2", RFC 5996,
September 2010.
14.2. Informative References 14.2. Informative References
[RFC5723] Sheffer, Y. and H. Tschofenig, "IKEv2 Session Resumption", [RFC5723] Sheffer, Y. and H. Tschofenig, "IKEv2 Session Resumption",
RFC 5723, January 2010. RFC 5723, January 2010.
[cluster] Nir, Y., Ed., "IPsec Cluster Problem Statement", [cluster] Nir, Y., Ed., "IPsec Cluster Problem Statement",
draft-ietf-ipsecme-ipsec-ha (work in progress), July 2010. draft-ietf-ipsecme-ipsec-ha (work in progress), July 2010.
[recovery] [recovery]
Detienne, F., Sethi, P., and Y. Nir, "Safe IKE Recovery", Detienne, F., Sethi, P., and Y. Nir, "Safe IKE Recovery",
skipping to change at page 21, line 20 skipping to change at page 22, line 4
Authors' Addresses Authors' Addresses
Yoav Nir (editor) Yoav Nir (editor)
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
David Wierbowski David Wierbowski
International Business Machines International Business Machines
1701 North Street 1701 North Street
Endicott, New York 13760 Endicott, New York 13760
United States United States
Email: wierbows@us.ibm.com Email: wierbows@us.ibm.com
Frederic Detienne
Cisco Systems, Inc.
De Kleetlaan, 7
Diegem B-1831
Belgium
Phone: +32 2 704 5681
Email: fd@cisco.com
Pratima Sethi
Cisco Systems, Inc.
O'Shaugnessy Road, 11
Bangalore, Karnataka 560027
India
Phone: +91 80 4154 1654
Email: psethi@cisco.com
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