Internet DRAFT - draft-dhody-pce-srlg-collection
draft-dhody-pce-srlg-collection
PCE Working Group D. Dhody
Internet-Draft F. Zhang
Intended status: Standards Track X. Zhang
Expires: April 11, 2014 Huawei Technologies
October 08, 2013
PCEP Extensions for Receiving SRLG Information
draft-dhody-pce-srlg-collection-00
Abstract
The Path Computation Element (PCE) provides functions of path
computation in support of traffic engineering in networks controlled
by Multi-Protocol Label Switching (MPLS) and Generalized MPLS
(GMPLS).
This document provides extensions for the Path Computation Element
Protocol (PCEP) to support collection of Shared Risk Link Group
(SRLG) information during path computation and encoding this
information in the reply message.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 11, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 3
4. Extension to PCEP . . . . . . . . . . . . . . . . . . . . . . 4
4.1. The Extension of the RP Object . . . . . . . . . . . . . 4
4.2. SRLG Subobject in ERO . . . . . . . . . . . . . . . . . . 4
5. Other Considerations . . . . . . . . . . . . . . . . . . . . 5
5.1. Backward Compatibility . . . . . . . . . . . . . . . . . 5
5.2. Confidentiality via PathKey . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Manageability Considerations . . . . . . . . . . . . . . . . 5
7.1. Control of Function and Policy . . . . . . . . . . . . . 5
7.2. Information and Data Models . . . . . . . . . . . . . . . 5
7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 5
7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 6
7.5. Requirements On Other Protocols . . . . . . . . . . . . . 6
7.6. Impact On Network Operations . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8.1. New Subobjects for the ERO Object . . . . . . . . . . . . 6
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 8
1. Introduction
As per [RFC4655], PCE based path computation model is deployed in
large, multi-domain, multi-region, or multi-layer networks. In such
case PCEs may cooperate with each other to provide end to end optimal
path.
It is important to understand which TE links in the network might be
at risk from the same failures. In this sense, a set of links may
constitute a 'shared risk link group' (SRLG) if they share a resource
whose failure may affect all links in the set [RFC4202]. H-LSP
(Hierarchical LSP) or S-LSP (Stitched LSP) can be used for carrying
one or more other LSPs as described in [RFC4206] and [RFC6107].
H-LSP and S-LSP may be computed by PCE(s) and further form as a TE
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link. The SRLG information of such LSPs can be collected during path
computation itself and encoded in the PCEP Path Computation Reply
(PCRep) message. [I-D.zhang-ccamp-gmpls-uni-app] describes the use
of PCE for end to end User-Network Interface (UNI) path computation.
[I-D.farrel-interconnected-te-info-exchange] describes a scaling
problem with SRLGs in multi-layer environment and introduce a concept
of Macro SRLG. Lower layer SRLG collection at the time of path
computation can be used to generate such a Macro SRLG at the PCE.
Note that [I-D.ietf-ccamp-rsvp-te-srlg-collect] specifies a similar
extension to Resource ReserVation Protocol-Traffic Engineering (RSVP-
TE) where SRLG information is collected at the time of signaling.
1.1. Requirements Language
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. Terminology
The following terminology is used in this document.
CPS: Confidential Path Segment. A segment of a path that contains
nodes and links that the policy requires not to be disclosed
outside the domain.
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.
SRLG: Shared Risk Link Group.
UNI: User-Network Interface.
3. PCEP Requirements
Following key requirements are identified for PCEP to enable SRLG
information collection during path computation:
SRLG Collection Indication: The PCEP speaker must be capable of
indicating whether the SRLG information of the LSP should be
collected during the path computation procedure.
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SRLG Collection: If requested, the SRLG information should be
collected during the path computation and encoded in the PCRep
message.
4. Extension to PCEP
This document extends the existing RP (Request Parameters) object
[RFC5440] so that a PCEP speaker can request SRLG information
collection during path computation. The SRLG subobject maybe carried
inside the Explicit Route Object (ERO) in the PCRep message.
4.1. The Extension of the RP Object
This document adds the following flags to the RP Object:
S (SRLG - 1 bit): when set, in a PCReq message, this indicates that
the SRLG information of the Label switched path (LSP) should be
collected during the path computation procedure. Otherwise, when
cleared, this indicates that the SRLG information should not be
collected. In a PCRep message, when the S bit is set this
indicates that the returned path in ERO also carry the SRLG
information; otherwise (when the S bit is cleared), the returned
path does not carry SRLG information.
4.2. SRLG Subobject in ERO
As per [RFC5440], ERO is used to encode the path of a TE LSP and is
carried within a PCRep message to provide the computed path when
computation was successful.
The SRLG of a path is the union of the SRLGs of the links in the LSP
[RFC4202]. The SRLG subobject is defined in
[I-D.ietf-ccamp-rsvp-te-srlg-collect], as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG ID 1 (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG ID n (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The meaning and description of Type, Length and SRLG ID can be found
in [I-D.ietf-ccamp-rsvp-te-srlg-collect]. Bits in the Flags field is
ignored.
The SRLG subobject should be encoded inside the ERO object in the
PCRep message when the S-Bit (SRLG) is set in the PCReq message.
5. Other Considerations
5.1. Backward Compatibility
If a PCE receives a request and the PCE does not understand the new
SRLG flag in the RP object, then the PCE SHOULD reject the request.
If PCEP speaker receives a PCRep message with SRLG subobject that it
does not support or recognize, it must act according to the existing
processing rules.
5.2. Confidentiality via PathKey
[RFC5520] defines a mechanism to hide the contents of a segment of a
path, called the Confidential Path Segment (CPS). The CPS may be
replaced by a path-key that can be conveyed in the PCEP and signaled
within in a RSVP-TE ERO.
When path-key confidentiality is used, collection of SRLG information
and encoding this information in PCRep along with the path-key could
be useful to compute a SRLG disjoint backup path at the later
instance.
6. Security Considerations
TBD.
7. Manageability Considerations
7.1. Control of Function and Policy
TBD.
7.2. Information and Data Models
TBD.
7.3. Liveness Detection and Monitoring
TBD.
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7.4. Verify Correct Operations
TBD.
7.5. Requirements On Other Protocols
TBD.
7.6. Impact On Network Operations
TBD.
8. IANA Considerations
IANA assigns values to PCEP parameters in registries defined in
[RFC5440]. IANA is requested to make the following additional
assignments.
8.1. New Subobjects for the ERO Object
IANA has previously assigned an Object-Class and Object-Type to the
ERO carried in PCEP messages [RFC5440]. IANA also maintains a list
of subobject types valid for inclusion in the ERO.
IANA is requested to assign one new subobject types for inclusion in
the ERO as follows:
Subobject Meaning Reference
34 (TBD) SRLG sub-object This document
9. Acknowledgments
TBD.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
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[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4874] Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
Extension to Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE)", RFC 4874, April 2007.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[RFC5520] Bradford, R., Vasseur, JP., and A. Farrel, "Preserving
Topology Confidentiality in Inter-Domain Path Computation
Using a Path-Key-Based Mechanism", RFC 5520, April 2009.
[RFC6107] Shiomoto, K. and A. Farrel, "Procedures for Dynamically
Signaled Hierarchical Label Switched Paths", RFC 6107,
February 2011.
[I-D.ietf-ccamp-rsvp-te-srlg-collect]
Zhang, F., Li, D., Dios, O., Margaria, C., and M. Hartley,
"RSVP-TE Extensions for Collecting SRLG Information",
draft-ietf-ccamp-rsvp-te-srlg-collect-03 (work in
progress), September 2013.
[I-D.farrel-interconnected-te-info-exchange]
Farrel, A., Drake, J., Bitar, N., Swallow, G., and D.
Ceccarelli, "Problem Statement and Architecture for
Information Exchange Between Interconnected Traffic
Engineered Networks", draft-farrel-interconnected-te-info-
exchange-01 (work in progress), July 2013.
[I-D.zhang-ccamp-gmpls-uni-app]
Zhang, F., Dios, O., Farrel, A., Zhang, X., and D.
Ceccarelli, "Applicability of Generalized Multiprotocol
Label Switching (GMPLS) User-Network Interface (UNI)",
draft-zhang-ccamp-gmpls-uni-app-04 (work in progress),
July 2013.
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Appendix A. Contributor Addresses
Udayasree Palle
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: udayasree.palle@huawei.com
Avantika
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: avantika.sushilkumar@huawei.com
Authors' Addresses
Dhruv Dhody
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: dhruv.ietf@gmail.com
Fatai Zhang
Huawei Technologies
Bantian, Longgang District
Shenzhen, Guangdong 518129
P.R.China
EMail: zhangfatai@huawei.com
Xian Zhang
Huawei Technologies
Bantian, Longgang District
Shenzhen, Guangdong 518129
P.R.China
EMail: zhang.xian@huawei.com
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