Internet Draft Lou Berger (LabN)
Category: Standards Track Russ White (Cisco Systems)
Expiration Date: September 10, 2008 Eric Rosen (Cisco Systems)
March 10, 2008
BGP IPSec Tunnel Encapsulation Attribute
draft-ietf-softwire-encaps-ipsec-00.txt
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Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract
The BGP Encapsulation Subsequence Address Family Identifiers (SAFI)
provides a method for the dynamic exchange of encapsulation
information, and the indication of encapsulation protocol types to be
used for different next hops. Currently support for GRE and L2TPv3
tunnel types are defined. This document defines support for IPsec
tunnel types.
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Table of Contents
1 Introduction .............................................. 3
1.1 Conventions used in this document ......................... 3
2 IPsec Tunnel Encapsulation Types .......................... 3
3 Use of IPsec .............................................. 4
4 IPsec Tunnel Authenticator sub-TLV ........................ 4
4.1 Use of the IPsec Tunnel Authenticator sub-TLV ............. 5
5 Security Considerations ................................... 5
6 IANA Considerations ....................................... 6
7 References ................................................ 6
7.1 Normative References ...................................... 6
7.2 Informative References .................................... 7
8 Acknowledgments ........................................... 8
9 Authors' Addresses ........................................ 8
10 Full Copyright Statement .................................. 8
11 Intellectual Property ..................................... 9
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1. Introduction
The BGP [RFC4271] Encapsulation Subsequence Address Family
Identifiers (SAFI) allows for the communication of tunnel information
and the association of this information to a BGP next hop. The
Encapsulation SAFI can be used to support the mapping of prefixes to
next hops and tunnels of the same address family, IPv6 prefixes to
IPv4 next hops and tunnels using [RFC4798], and IPv4 prefixes to IPv6
next hops and tunnels using [V4NLRI-V6NH]. The Encapsulation SAFI
can also be used to support the mapping of VPN prefixes to tunnels
when VPN prefixes are advertised per [RFC4364] or [RFC4659].
[SOFTWIRES] provides useful context for the use of the Encapsulation
SAFI.
The Encapsulation SAFI is defined in [ENCAPS-SAFI]. [ENCAPS-SAFI]
also defines support for the GRE [RFC2784] and L2TPv3 [RFC3931]
tunnel types. This document builds on [ENCAPS-SAFI] and defines
support for IPsec tunnels. Support is defined for IP Authentication
Header in Tunnel-mode (AH), [RFC4302], and for IP Encapsulating
Security Payload in Tunnel-mode (ESP), [RFC4303]. Support for IP-in-
IP, [RFC2003], and MPLS-in-IP, [RFC4023] protected by IPsec Transport
Mode is also defined.
The Encapsulation NLRI Format is not modified by this document.
1.1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. IPsec Tunnel Encapsulation Types
Per [ENCAPS-SAFI], tunnel type is indicated in the Tunnel
Encapsulation attribute. This document defines the following tunnel
type values:
- AH in Tunnel-mode: Tunnel Type = 3
- ESP in Tunnel-mode: Tunnel Type = 4
- IP-in-IP Tunnel with IPsec Transport Mode: Tunnel Type = 5
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- MPLS-in-IP Tunnel with IPsec Transport Mode: Tunnel Type = 6
Note, see Section 4.3 of [ENCAPS-SAFI] for a discussion on the
advertisement and use of multiple tunnel types.
This document does not specify the use of the sub-TLV types defined
in [ENCAPS-SAFI] with these tunnel types. See below for the
definition of an IPsec tunnel type specific sub-TLV.
3. Use of IPsec
If a R1 is a BGP speaker that receives an Encapsulation SAFI update
from another BGP speaker, R2, then if R1 has any data packets for
which R2 is the BGP next hop, R1 MUST initiate an IPsec SA of the
specified "tunnel type", and all such data packets MUST be sent
through that SA.
Let R1 and R2 be two BGP speakers that may send data packets through
R3, such that the data packets from R1 and from R2 may be received by
R3 over the same interface. Then if R3 has sent an update containing
an Encapsulation SAFI, and if this update specifies an IPsec tunnel
type, and if this update is received by R2, and an Encapsulation-SAFI
with an IPsec tunnel type, MUST also be received by R1. That is, on
a given interface, if IPsec is required for any data packets, it MUST
be required for all. It does not necessarily need to be required for
control packets that are directly addressed to R3.
Security policy has the granularity of BGP speaker to BGP speaker.
The required security policies must be configured into the BGP
speakers, and the policy for each SA is negotiated via IKE.
4. IPsec Tunnel Authenticator sub-TLV
This document defines a new sub-TLV for use with the Tunnel
Encapsulation Attribute defined in [ENCAPS-SAFI]. The new sub-TLV is
referred to as the "IPsec Tunnel Authenticator sub-TLV" and MAY be
included in any Encapsulation SAFI NLRI ([ENCAPS-SAFI]) indicating a
Tunnel Type defined in this document. Support for the IPsec Tunnel
Authenticator sub-TLV" MUST be implemented whenever the tunnel types
defined in this document are implemented. However, its use is
OPTIONAL, and is a matter of policy.
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The sub-TLV type of the IPsec Tunnel Authenticator sub-TLV is 3. The
sub-TLV length is variable. The structure of the sub-TLV is as
follows:
- Authenticator Type: two octets
This document defines authenticator type 1, "SHA-1 hash of public
key", as defined in section 3.7 of RFC 4306.
- Value: (variable)
A value used to authenticate the BGP speaker that generated this
NLRI. The length of this field is is not encoded explicitly, but
can be calculated as (sub-TLV length - 2).
In the case of authenticator type 1, this field contains the
20-octet value of the hash.
A BGP speaker which sends the IPsec Tunnel Authenticator sub-TLV with
authenticator type 1 MUST be configured with a certificate containing
the public key whose hash is sent in the value field of the sub-TLV.
This certificate MAY be self-signed.
4.1. Use of the IPsec Tunnel Authenticator sub-TLV
If a IPsec Tunnel Authenticator sub-TLV with authenticator type 1 is
present in the Encapsulation SAFI update, then R1 (as defined above
in Section 3) must use IKE to obtain a certificate from R2 (as
defined above in Section 3), and R2 must send a certificate
containing the public key whose hash occurred in the value field of
the IPsec Tunnel Authenticator sub-TLV. R1 MUST NOT attempt to
establish an SA to R2 UNLESS the public key in the certificate hashes
to the same value that occurs in the IPsec Tunnel Authenticator sub-
TLV.
5. Security Considerations
This document uses IP based tunnel technologies to support data plane
transport. Consequently, the security considerations of those tunnel
technologies apply. This document defines support for IPsec AH
[RFC4302] and ESP [RFC4303]. The security considerations from those
documents apply to the data plane aspects of this document.
As with [ENCAPS-SAFI], any modification of the information that is
used to form encapsulation headers, or to choose a tunnel type, or to
choose a particular tunnel for a particular payload type, user data
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packets may end up getting misrouted, misdelivered, and/or dropped.
Misdelivery is less of an issue when IPsec is used as such
misdelivery is likely to result in a failure of authentication or
decryption at the receiver. Furthermore, in environments where
authentication of BGP speakers is desired, the IPsec Tunnel
Authenticator sub-TLV defined in Section 4 may be used.
More broadly, the security considerations for the transport of IP
reachability information using BGP are discussed in [RFC4271] and
[RFC4272], and are equally applicable for the extensions described in
this document.
6. IANA Considerations
IANA is requested to administer assignment of new namespaces and new
values for namespaces defined in this document and reviewed in this
section.
Upon approval of this document, the IANA will make the assignment in
the Tunnel TLVs and sub-TLVs section of the registry.
Tunnel Type Reference
----------- ---------
AH: Type = 3 [This document]
ESP: Type = 4 [This document]
IP-in-IP tunnel
with IPsec Transport Mode: Type = 5 [This document]
MPLS-in-IP tunnel
with IPsec Transport Mode: Type = 6 [This document]
Tunnel Type Sub-TLV Type Reference
----------- ------------ ---------
3,4,5,6 IPsec Tunnel Authenticator: Type = 3 [This document]
7. References
7.1. Normative References
[ENCAPS-SAFI] Mohapatra, P., Rosen, E., "BGP Information SAFI
and BGP Tunnel Encapsulation Attribute", Work in
Progress, draft-ietf-softwire-encaps-safi-00.txt,
January 2008.
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[RFC4271] Rekhter, Y., Ed. et al, "A Border Gateway Protocol 4
(BGP-4)", RFC 4271, January 2006.
7.2. Informative References
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels," RFC 2119.
[RFC2784] Farinacci, D., et al, "Generic Routing Encapsulation
(GRE)", RFC 2784, March 2000.
[RFC3931] Lau, J., Ed., et al, "Layer Two Tunneling Protocol -
Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC4023] Worster, T., Rekhter, Y., Rosen, E., Ed.,
"Encapsulating MPLS in IP or Generic Routing
Encapsulation (GRE)", RFC 4023, March 2005.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, January 2006.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)"
RFC 4303, December 2005.
[RFC4364] Rosen, E., Rekhter, Y., "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC4659] De Clercq, J., et al, "BGP-MPLS IP Virtual Private
Network (VPN) Extension for IPv6 VPN", RFC 4659,
September 2006.
[RFC4798] J. De Clercq, D. Ooms, S. Prevost, F. Le Faucheur,
"Connecting IPv6 Islands over IPv4 MPLS using IPv6
Provider Edge Routers (6PE)", RFC 4798, February 2007.
[SOFTWIRES] Wu, J. et al, "Softwire Mesh Framework", Work in
Progress, draft-ietf-softwire-mesh-framework-03.txt,
January 2008.
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[V4NLRI-V6NH] F. Le Faucheur, E. Rosen, "Advertising an IPv4 NLRI
with an IPv6 Next Hop", Work in Progress,
draft-ietf-idr-v4nlri-v6nh-01.txt, October 2007.
8. Acknowledgments
The authors wish to thank Sam Hartman and Tero Kivinen for their help
with the security-related issues. However, it should be noted that
they have not reviewed this revision of the draft.
9. Authors' Addresses
Lou Berger
LabN Consulting, L.L.C.
Phone: +1-301-468-9228
Email: lberger@labn.net
Russ White
Cisco Systems
Email: riw@cisco.com
Eric C. Rosen
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA, 01719
Email: erosen@cisco.com
10. Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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11. Intellectual Property
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Acknowledgement
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Berger, et. al. Standards Track [Page 9]
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