Internet DRAFT - draft-lee-pce-pcep-ls-optical
draft-lee-pce-pcep-ls-optical
PCE Working Group Young Lee
Internet Draft Samsung
Intended Status: Experimental Haomian Zheng
Expires: September 2023 Huawei
Daniele Ceccarelli
Cisco
Wei Wang
Beijing Univ. of Posts and Telecom
Peter Park
KT
Bin Young Yoon
ETRI
March 9, 2023
PCEP Extension for Distribution of Link-State and TE Information for
Optical Networks
draft-lee-pce-pcep-ls-optical-13
Abstract
In order to compute and provide optimal paths, Path Computation
Elements (PCEs) require an accurate and timely Traffic Engineering
Database (TED). Traditionally this Link State and TE information has
been obtained from a link state routing protocol (supporting traffic
engineering extensions).
An existing experimental document extends the Path Computation
Element Communication Protocol (PCEP) with Link-State and Traffic
Engineering (TE) Information. This document provides further
experimental extensions to collect Link-State and TE information for
optical networks.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and 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.
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This Internet-Draft will expire on March 9, 2023.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction ................................................ 3
1.1. Requirements Language .................................. 3
2. Applicability ............................................... 3
3. Requirements for PCEP Extension ............................. 4
3.1. Reachable Source-Destination ........................... 5
3.2. Optical Latency......................................... 5
4. PCEP-LS Extensions for Optical Networks ..................... 6
4.1. Node Attributes TLV .................................... 6
4.2. Link Attributes TLV .................................... 6
4.3. PCEP-LS for Optical Network Extension .................. 7
5. Security Considerations ..................................... 8
6. IANA Considerations ......................................... 8
6.1. PCEP-LS Sub-TLV Type Indicators ........................ 8
7. References .................................................. 9
7.1. Normative References ................................... 9
7.2. Informative References ................................. 9
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Appendix A. Contributor's Address ............................. 11
Authors' Addresses ............................................ 11
1. Introduction
[PCEP-LS] describes an experimental mechanism by which Link State
(LS) and Traffic Engineering (TE) information can be collected from
packet networks and shared through the Path Computation Element
Communication Protocol (PCEP) with a Path Computation Element (PCE).
This approach is called PCEP-LS and uses a new PCEP message format.
Problems in the optical networks, such as Optical Transport Networks
(OTN), is becoming worse due to the growth of the network
scalability. Such growths are also challenging the requirement of
memory/storage on each equipment. The introduction of a PCEP-based
LS helps solving the problem, with equally capability and
functionalities.
This document describes an experimental extension to PCEP-LS for use
in optical networks, and explains how encodings defined in [PCEP-LS]
can be used in the optical network contexts.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Applicability
There are three main applicabilities of the mechanism described in
this document:
- Case 1: There is IGP running in optical network but there is a
need to collect LS and TE resource information at a PCE from
individual or specific optical nodes more frequently of more
rapidly than the IGP allows.
o A PCE may receive full information or an incremental
update (as opposed to the entire TE information of the
node/link).
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- Case 2: There is no IGP running in the optical network and
there is a need to collect link-state and TE resource
information from the optical nodes for use by the PCE.
- Case 3: There is a need to share abstract optical link-state
and TE information from child PCE to a parent PCE in a
hierarchical PCE (H-PCE) system per [RFC6805] and [RFC8751].
Alternatively, this requirement may exist between a Physical
Network Controller (PNC) and a Multi-Domain Service
Coordinator (MDSC) in the Abstraction and Control of TE
Networks (ACTN) architecture [RFC8453].
Note: The applicability for Case 3 may arise as a consequence
of Case 1 and Case 2. When TE information changes occur in the
optical network, this may also affect abstracted TE
information and thus needs to be updated to the parent
PCE/MSDC from each child PCE/PNC.
3. Requirements for PCEP Extension
The key requirements associated with link-state and TE information
distribution are identified for PCEP and listed in Section 4 of
[PCEP-LS]. These new functions introduced to PCEP to support
distribution of link-state (and TE) information are described in
Section 5 of [PCEP-LS]. Details of PCEP messages and related
Objects/TLVs are specified in Sections 8 and 9 of [PCEP-LS]. The key
requirements and new functions specified in [PCEP-LS] are equally
applicable to optical networks.
Besides the generic requirements specified in [PCEP-LS], optical
specific features also need to be considered. As a connection-based
network, there are specific parameters such as reachability table,
optical latency, wavelength consistency, and some other parameters
that need to be included during the topology collection. Without
these restrictions, the path computation may be inaccurate or
infeasible for deployment, therefore these information MUST be
included in the PCEP.
The procedure for using the optical parameters is described in
following sections.
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3.1. Reachable Source-Destination
The reachable source-destination node pair indicates that there are
some OCh paths between two nodes. The reachability is restricted by
impairment, wavelength consistency and so on. This information is
necessary at the PCE to ensure that the path computed between source
node and destination node is feasible. In this scenario, the PCE is
responsible for computing how many OCh paths are available to set up
connections between source and destination node. Moreover, if a set
of optical wavelengths is indicated in the path computation request,
the PCE also determines whether a wavelength from the set of
preselected optical wavelengths is available for the source-
destination pair connection.
To enable the PCE to complete the above functions, the reachable
relationship and OMS link information need to be reported to the
PCE. Once the PCE detects that any wavelength is available, the
corresponding OMS link is marked as a candidate link in the optical
network, which can then be used for path computation in the future.
Moreover, in a hierarchical PCE architecture, the information above
needs to be reported from child PCE to parent PCE, which acts as a
service coordinator.
3.2. Optical Latency
It is the usual case that the PCC indicates the latency when
requesting the path computation. In optical networks the latency is
a very sensitive parameter and there is stricter requirement on
latency. Given the number of OCh paths between source-destination
nodes, the PCE also need to determine how many OCh path satisfy the
indicated latency threshold.
There is usually an algorithm running on the PCE to guarantee the
performance of the computed path. During the computation, the delay
factor may be converted into a kind of link weight. After the
algorithm provides the candidate paths between the source and
destination nodes, the PCE selects the best path by computing the
total path propagation delay.
Optical PCEs contain optimization algorithms, e.g., shortest path
algorithm, to select the best-performing path.
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4. PCEP-LS Extensions for Optical Networks
This section provides the additional PCEP-LS extensions necessary to
support optical networks. All Objects/TLVs defined in [PCEP-LS] are
applicable to optical networks.
4.1. Node Attributes TLV
The Node-Attributed TLV is defined in Section 9.3.9.1 of [PCEP-LS].
This TLV is applicable for LS Node Object-Type as defined in [PCEP-
LS].
This TLV contains a number of Sub-TLVs. [PCEP-LS] defines that any
Node-Attribute defined for BGP-LS [BGP-LS] can be used as a Sub-TLV
of the PCEP Node-Attribute TLV. BGP-LS does not support optical
networks, so the Node-Attribute Sub-TLVs shown below are defined in
this document for use in PCEP-LS for optical networks.
TBD1 The Connectivity Matrix Sub-TLV is used as defined in
[RFC7579].
TBD2 The Resource Block Information Sub-TLV is used as defined in
[RFC7688].
TBD3 The Resource Block Accessibility Sub-TLV is used as defined in
[RFC7688].
TBD4 The Resource Block Wavelength Constraint Sub-TLV is used as
defined in [RFC7688].
TBD5 The Resource Block Pool State Sub-TLV is used as defined in
[RFC7688].
TBD6 The Resource Block Shared Access Wavelength Availability
Sub-TLV is used as defined in [RFC7688].
4.2. Link Attributes TLV
The Link-Attributes TLV is defined in Section 9.3.9.2 of [PCEP-LS].
This TLV is applicable for the LS Link Object-Type as defined in
[PCEP-LS].
This TLV contains a number of Sub-TLVs. [PCEP-LS] defines that any
Node-Attribute defined for BGP-LS [BGP-LS] can be used as a Sub-TLV
of the PCEP Link-Attribute TLV. BGP-LS does not support optical
networks, so the Link-Attribute Sub-TLVs shown below are defined in
this document for use in PCEP-LS for optical networks.
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TBD7 The ISCD Sub-TLV is used to describe the Interface Switching
Capability Descriptor as defined in [RFC4203].
TBD8 The OTN-TDM SCSI Sub-TLV is used to describe the Optical
Transport Network Time Division Multiplexing Switching
Capability Specific Information as defined in [RFC4203] and
[RFC7138].
TBD9 The WSON-LSC SCSI Sub-TLV is used to describe the Wavelength
Switched Optical Network Lambda Switch Capable Switching
Capability Specific Information as defined in [RFC4203] and
[RFC7688].
TBD10 The Flexi-grid SCSI Sub-TLV is used to describe the Flexi-grid
Switching Capability Specific Information as defined in
[RFC8363].
TBD11 The Port Label Restriction Sub-TLV is used as defined in
[RFC7579], [RFC7580], and [RFC8363].
4.3. PCEP-LS for Optical Network Extension
This section provides additional PCEP-LS extension necessary to
support the optical network parameters discussed in Sections 3.1 and
3.2.
Collection of link state and TE information is necessary before the
path computation processing can be done. The procedure can be
divided into: 1) link state collection by receiving the
corresponding topology information in periodically; 2) path
computation on the PCE, triggered by receiving a path computation
request message from a PCC, and completed by transmitting a path
computation reply with the path computation result, per [RFC4655].
For OTN networks, maximum bandwidth available may be per ODU 0/1/2/3
switching level or aggregated across all ODU switching levels (i.e.,
ODUj/k).
For Wavelength Switched Optical Networks (WSON) , Routing and
Wavelength Assignment (RWA) information collected from Network
Elements (Nes) would be utilized to compute light paths. The list of
information collected can be found in [RFC7688]. More specifically,
the maximum bandwidth available may be per lambda/frequency level
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(OCh) or aggregated across all lambda/frequency levels. Per OCh
level abstraction gives more detailed data to the P-PCE at the
expense of more information processing. Either the OCh-level or the
aggregated level abstraction in the RWA constraint (i.e., wavelength
continuity) needs to be taken into account by the PCE during path
computation. Resource Block Accessibility (i.e., wavelength
conversion information) in [RFC7688] needs to be taken into account
in order to guarantee the reliability of optical path computation.
5. Security Considerations
This document extends PCEP for LS (and TE) distribution in optical
networks by including a set of Sub-TLVs to be carried in existing
TLVs of existing messages. Procedures and protocol extensions
defined in this document do not affect the overall PCEP security
model (see [RFC5440] and [RFC8253]). The PCE implementation SHOULD
provide mechanisms to prevent strains created by network flaps and
amount of LS (and TE) information as defined in [PCEP-LS]. Thus,
any mechanism used for securing the transmission of other PCEP
message SHOULD be applied here as well. As a general precaution, it
is RECOMMENDED that these PCEP extensions only be activated on
authenticated and encrypted sessions belonging to the same
administrative authority.
6. IANA Considerations
This document requests IANA actions to allocate code points for the
protocol elements defined in this document.
6.1. PCEP-LS Sub-TLV Type Indicators
PCEP-LS] requests IANA to create a registry of "PCEP-LS Sub-TLV Type
Indicators". IANA is requested to make the following allocations
from this registry using the range 1 to 255.
+-----------+--------------------------------------------------
| Sub-TLV | Meaning
+-----------+--------------------------------------------------
| TBD1 | Connectivity Matrix
| TBD2 | Resource Block Information
| TBD3 | Resource Block Accessibility
| TBD4 | Resource Block Wavelength Constraint
| TBD5 | Resource Block Pool State
| TBD6 | Resource Block Shared Access Wavelength Available
| TBD7 | ISCD
| TBD8 | OTN-TDM SCSI
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| TBD9 | WSON-LSC SCSI
| TBD10 | Flexi-grid SCSI
| TBD11 | Port Label Restriction
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.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
[RFC7688] Lee, Y., Ed., and G. Bernstein, Ed., "GMPLS OSPF
Enhancement for Signal and Network Element Compatibility
for Wavelength Switched Optical Networks", RFC 7688,
November 2015.
[RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119
Key Words", RFC 8174, May 2017.
7.2. Informative References
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, October 2008.
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[RFC7752] Gredler, H., Medved, J., Previdi, S., Farrel, A., and
S.Ray, "North-Bound Distribution of Link-State and TE
information using BGP", RFC 7752, March 2016.
[S-PCE-GMPLS] X. Zhang, et. al, "Path Computation Element (PCE)
Protocol Extensions for Stateful PCE Usage in GMPLS-
controlled Networks", draft-ietf-pce-pcep-stateful-pce-
gmpls, work in progress.
[RFC7399] A. Farrel and D. king, "Unanswered Questions in the Path
Computation Element Architecture", RFC 7399, October 2015.
[RFC8453] D.Ceccarelli, and Y. Lee (Editors), "Framework for
Abstraction and Control of TE Networks", RFC453, August,
2018.
[RFC6805] A. Farrel and D. King, "The Application of the Path
Computation Element Architecture to the Determination of a
Sequence of Domains in MPLS and GMPLS", RFC 6805, November
2012.
[PCEP-LS] D. Dhody, Y. Lee and D. Ceccarelli "PCEP Extension for
Distribution of Link-State and TE Information.", draft-
dhodylee-pce-pcep-ls, work in progress, July, 2020
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", RFC8231, September 2017.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., Dhody, D.,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC8253, October 2017.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", RFC8281, December 2017.
[RFC8751] D. Dhody, Y. Lee and D. Ceccarelli, "Hierarchical Stateful
Path Computation Element (PCE)", RFC8751, March 2020.
[RFC8363] X. Zhang, H. Zheng, R. Casellas, O. Gonzalez de Dios, D.
Ceccarelli, "GMPLS OSPF Extensions in support of Flexi-
grid DWDM networks", RFC8363, May 2018.
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Appendix A. Contributor's Address
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Authors' Addresses
Young Lee
Samsung
Email: younglee.tx@gmail.com
Haomian Zheng
Huawei Technologies Co., Ltd.
Email: zhenghaomian@huawei.com
Daniele Ceccarelli
Ericsson
Torshamnsgatan,48
Stockholm
Sweden
EMail: daniele.ceccarelli@ericsson.com
Wei Wang
Beijing University of Posts and Telecom
No. 10, Xitucheng Rd. Haidian District, Beijing 100876, China
Email: weiw@bupt.edu.cn
Peter Park
KT
Email: peter.park@kt.com
Bin Yeong Yoon
ETRI
Email: byyun@etri.re.kr
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