Networking Working Group R. Bradford
Internet-Draft JP. Vasseur
Intended Status: Standards Track Cisco Systems, Inc.
Created: May 14, 2008 A. Farrel
Expires: November 14, 2008 Old Dog Consulting
RSVP Extensions for Path Key Support
draft-ietf-ccamp-path-key-ero-01.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that
any applicable patent or other IPR claims of which he or she is
aware have been or will be disclosed, and any of which he or she
becomes aware will be disclosed, in accordance with Section 6 of
BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
Traffic Engineering (TE) Label Switched Paths (LSPs) may be
computed by Path Computation Elements (PCEs). Where the TE LSP
crosses multiple domains, such as Autonomous Systems (ASes), the
path may be computed by multiple PCEs that cooperate, with each
responsible for computing a segment of the path. To preserve
confidentiality of topology within each AS, the PCE supports a
mechanism to hide the contents of a segment of a path, called the
Confidential Path Segment (CPS), by encoding the contents as a
Path Key Subobject (PKS).
This document describes how to carry Path Key Subobjects in the
Resource Reservation Protocol (RSVP) Explicit Route Objects (EROs)
and Record Route Object (RROs) so facilitate confiedntiality in the
signaling of inter-domain TE LSPs.
Bradford, Vasseur, and Farrel [Page 1]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
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
RFC-2119 [RFC2119].
1. Introduction
Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
Traffic Engineering (TE) Label Switched Paths (LSPs) are signaled
using the TE extensions to the Resource Reservation Protocol
(RSVP-TE) [RFC3209], [RFC3473]. The routes followed by MPLS and
GMPLS TE LSPs may be computed by Path Computation Elements (PCEs)
[RFC4655].
Where the TE LSP crosses multiple domains [RFC4726], such as
Autonomous Systems (ASes), the path may be computed by multiple PCEs
that cooperate, with each responsible for computing a segment of the
path. To preserve confidentiality of topology with each AS, the
PCE Communications Protocol (PCEP) [PCEP] supports a mechanism to
hide the contents of a segment of a path, called the Confidential
Path Segment (CPS), by encoding the contents as a Path Key
Subobject (PKS) [PCE-PKS].
This document defines RSVP-TE protocol extensions necessary to
support the use of Path Key Segments in MPLS and GMPLS signaling.
1.1. Usage Scenario
Figure 1 shows a simple network constructed of two ASes. An LSP is
desired from the Ingress in Domain-1 to the Egress in Domain-2. As
described in [RFC4655], the Ingress Label Switching Router (LSR) acts
as a Path Computation Client (PCC) and sends a request to its PCE
(PCE-1). PCE-1 can compute the path within Domain-1, but has no
visiblity into Domain-2. So PCE-1 cooperates with PCE-2 to complete
the path computation.
However, PCE-2 does not want to share the information about the
path across Domain-2 with nodes outside the domain. So, as described
in [PCE-PKS], PCE-2 reports the Domain-2 path segment using a Path
Key Subobject rather than the details of the path.
PCE-1 can now return the path to be signaled to the Ingress LSR in a
path computation response with the Domain-2 segment still hidden as a
Path Key Segment.
In order to set up the LSP, the Ingress LSR signals using RSVP-TE and
encodes the path reported by PCE-1 in the Explicit Route Object
(ERO). This process is as normal for RSVP-TE, but requires that the
Bradford, Vasseur, and Farrel [Page 2]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
PKS is also included in the ERO using the mechanisms defined in this
document.
When the signaling message (the RSVP-TE Path message) reaches ASBR-2
it consults PCE-2 to 'decode' the PKS. (The information about which
PCE to use to decode the PKS is encoded within the PKS.) The PKS is
replaced in the ERO with the expanded information about the path.
----------------------------- ----------------------------
| Domain-1 | | Domain-2 |
| | | |
| ------- | | ------- |
| | PCE-1 |<---------------+--+-->| PCE-2 | |
| ------- | | ------- |
| ^ | | ^ |
| | | | | |
| v | | v |
| ------- ---- | | ---- |
| | PCC | - - |ASBR| | | |ASBR| - - ------ |
| |Ingress|--|A|--|B|--| 1 |-+--+-| 2 |--|C|--|D|--|Egress| |
| ------- - - ----- | | ---- - - ------ |
| | | |
----------------------------- ----------------------------
Figure 1 : A Simple network to demonstrate the use of the PKS
2. Terminology
CPS: Confidential Path Segment. A segment of a path that contains
nodes and links that the AS policy requires to not be disclosed
outside the AS.
PCE: Path Computation Element: an entity (component, application
or network node) that is capable of computing a network path or
route based on a network graph and applying computational
constraints.
PKS: Path Key Subobject. A subobject of an Explicit Route Object
which encodes a CPS, so as to preserve confidentiality.
3. RSVP-TE Path Key Subobject
The Path Key Subobject (PKS) may be carried in the Explicit Route
Object (ERO) of a RSVP-TE Path message [RFC3209]. The PKS is a fixed-
length subobject containing a Path-Key and a PCE-ID. The Path Key is
an identifier, or token used to represent the CPS within the context
of the PCE identified by the PCE-ID. The PCE-ID identifies the PCE
that can decode the Path Key using a reachable IPv4 or IPv6 address
Bradford, Vasseur, and Farrel [Page 3]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
of the PCE. In most cases, the decoding PCE is also the PCE that
computed the Path Key and the associated path. Because of the IPv4
and IPv6 variants, two subobjects are defined as follows.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Path Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PCE ID (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L
The L bit SHOULD NOT be set, so that the subobject represents a
strict hop in the explicit route.
Type
Subobject Type for a Path Key with 32-bit PCE ID as assigned by
IANA.
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The Length is always 8.
PCE ID
A 32-bit identifier of the PCE that can decode this key. The
identifier MUST be unique within the scope of the domain that the
CPS crosses, and MUST be understood by the LSR that will act as
PCC for the expansion of the PKS. The interpretation of the
PCE-ID is subject to domain-local policy. It MAY be an IPv4
address of the PCE that is always reachable, and MAY be an
address that is restricted to the domain in which the LSR that is
called upon to expand the CPS lies. Other values that have no
meaning outside the domain (for example, the Router ID of the
PCE) MAY be used to increase security or confidentiality.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Path Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PCE ID (16 bytes) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Bradford, Vasseur, and Farrel [Page 4]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
L
As above.
Type
Subobject Type for a Path Key with 128-bit PCE ID as assigned by
IANA.
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The Length is always 20.
PCE ID
A 128-bit identifier of the PCE that can decode this key. The
identifier MUST be unique within the scope of the domain that the
CPS crosses, and MUST be understood by the LSR that will act as
PCC for the expansion of the PKS. The interpretation of the
PCE-ID is subject to domain-local policy. It MAY be an IPv6
address of the PCE that is always reachable, but MAY be an
address that is restricted to the domain in which the LSR that is
called upon to expand the CPS lies. Other values that have no
meaning outside the domain (for example, the IPv6 TE Router ID)
MAY be used to increase security (see Section 5).
Note: The twins of these sub-objects are carried in PCEP messages
as defined in [PCE-PKS].
3.1. Explicit Route Object Processing Rules
This section to be completed in a future release.
3.2. Reporting Path Key Segments in Record Route Objects
This section to be completed in a future release.
4. Security Considerations
- Confidentiality of the CPS (can other network elements probe for
expansion of path-keys, possibly at random?).
- Authenticity of the path-key (resilience to alteration by
intermediaries, resilience to fake expansion of path-keys).
- Resilience from DNS attacks (insertion of spurious path-keys;
flooding of bogus path-key expansion requests).
Most of the interactions required by this extension are point to
Bradford, Vasseur, and Farrel [Page 5]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
point, can be authenticated and made secure as described in [PCEP]
and [RFC3209]. These interactions are listed in [PCE-PKS]
Thus, the major security issues can be dealt with using standard
techniques for securing and authenticating point-to-point
communications. In addition, it is recommended that the PCE
providing a decode response should check that the LSR that issued
the decode request is the head end of the decoded ERO segment.
Further protection can be provided by using a PCE ID to identify
the decoding PCE that is only meaningful within the domain that
contains the LSR at the head of the CPS. This may be an IP address
that is only reachable from within the domain, or some not-address
value. The former requires configuration of policy on the PCEs,
the latter requires domain-wide policy.
5. Manageability Considerations
5.1. Control of Function Through Configuration and Policy
The treatment of a path segment as a CPS, and its substitution in
a PCReq ERO with a PKS, is a function that SHOULD be under
operator and policy control where a PCE supports the function. The
operator SHOULD be given the ability to specify which path
segments are to be replaced and under what circumstances. For
example, an operator might set a policy that states that every
path segment for the operator's domain will be replaced by a PKS
when the PCReq has been issued from outside the domain.
6. IANA considerations
The IANA section will be detailed in further revision of this
document.
It will include code point requests for the three new ERO sub-
objects, and a new ErrorSpec Error Code.
Note: The twins of these sub-objects are be carried in PCEP
messages as defined in [PCE-PKS]. Ideally, IANA assignment of the
subobject types will be identical.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Bradford, Vasseur, and Farrel [Page 6]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., et al. "GMPLS Singlaling RSVP-TE extensions",
RFC3473, January 2003.
7.2. Informational References
[PCEP] Vasseur, J.P., Le Roux, J.L., Ayyangar, A., Oki, E.,
Ikejiri, A., Atlas, A., Dolganow, A., "Path Computation
Element (PCE) communication Protocol (PCEP)",
draft-ietf-pce-pcep, work in progress.
[PCE-PKS] Bradford, R., Vasseur, J.P., and Farrel, A., "Preserving
Topology Confidentiality in Inter-Domain Path Computation
Using a Key-Based Mechanism", draft-ietf-pce-path-key,
work in progress.
[RFC4655] Farrel, A., Vasseur, J.P., and Ash, J., "Path Computation
Element (PCE) Architecture", RFC 4655, August 2006.
[RFC4726] Farrel, A., Vasseur, J.P., and Ayyangar, A., "A Framework
for Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, November 2006.
8. Authors' Addresses:
Rich Bradford
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA - 01719
USA
Email: rbradfor@cisco.com
J.-P Vasseur
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA - 01719
USA
Email: jpv@cisco.com
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
Bradford, Vasseur, and Farrel [Page 7]
draft-ietf-ccamp-path-key-ero-01.txt May 2008
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.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Bradford, Vasseur, and Farrel [Page 8]
