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rfc:rfc7580

Internet Engineering Task Force (IETF) F. Zhang Request for Comments: 7580 Y. Lee Category: Standards Track J. Han ISSN: 2070-1721 Huawei

                                                          G. Bernstein
                                                     Grotto Networking
                                                                 Y. Xu
                                                                  CATR
                                                             June 2015
     OSPF-TE Extensions for General Network Element Constraints

Abstract

 Generalized Multiprotocol Label Switching (GMPLS) can be used to
 control a wide variety of technologies including packet switching
 (e.g., MPLS), time division (e.g., Synchronous Optical Network /
 Synchronous Digital Hierarchy (SONET/SDH) and Optical Transport
 Network (OTN)), wavelength (lambdas), and spatial switching (e.g.,
 incoming port or fiber to outgoing port or fiber).  In some of these
 technologies, network elements and links may impose additional
 routing constraints such as asymmetric switch connectivity, non-
 local label assignment, and label range limitations on links.  This
 document describes Open Shortest Path First (OSPF) routing protocol
 extensions to support these kinds of constraints under the control of
 GMPLS.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7580.

Zhang, et al. Standards Track [Page 1] RFC 7580 Generic Constraint OSPF-TE June 2015

Copyright Notice

 Copyright (c) 2015 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................3
    1.1. Conventions Used in This Document ..........................3
 2. Node Information ................................................3
    2.1. Connectivity Matrix ........................................4
 3. Link Information ................................................4
    3.1. Port Label Restrictions ....................................5
 4. Routing Procedures ..............................................5
 5. Scalability and Timeliness ......................................6
    5.1. Different Sub-TLVs into Multiple LSAs ......................6
    5.2. Decomposing a Connectivity Matrix into Multiple Matrices ...6
 6. Security Considerations .........................................7
 7. Manageability ...................................................7
 8. IANA Considerations .............................................8
    8.1. Node Information ...........................................8
    8.2. Link Information ...........................................8
 9. References ......................................................9
    9.1. Normative References .......................................9
    9.2. Informative References ....................................10
 Acknowledgments ...................................................11
 Contributors ......................................................11
 Authors' Addresses ................................................12

Zhang, et al. Standards Track [Page 2] RFC 7580 Generic Constraint OSPF-TE June 2015

1. Introduction

 Some data-plane technologies that require the use of a GMPLS control
 plane impose additional constraints on switching capability and label
 assignment.  In addition, some of these technologies should be
 capable of performing non-local label assignment based on the nature
 of the technology, e.g., wavelength continuity constraint in
 Wavelength Switched Optical Networks (WSONs) [RFC6163].  Such
 constraints can lead to the requirement for link-by-link label
 availability in path computation and label assignment.
 [RFC7579] provides efficient encodings of information needed by the
 routing and label assignment process in technologies such as WSON.
 These encodings are potentially applicable to a wider range of
 technologies as well.  The encoding provided in [RFC7579] is
 protocol-neutral and can be used in routing, signaling, and/or Path
 Computation Element communication protocol extensions.
 This document defines extensions to the OSPF routing protocol based
 on [RFC7579] to enhance the Traffic Engineering (TE) properties of
 GMPLS TE that are defined in [RFC3630], [RFC4202], and [RFC4203].
 The enhancements to the TE properties of GMPLS TE links can be
 advertised in OSPF-TE Link State Advertisements (LSAs).  The TE LSA,
 which is an opaque LSA with area flooding scope [RFC3630], has only
 one top-level Type-Length-Value (TLV) triplet and has one or more
 nested sub-TLVs for extensibility.  The top-level TLV can take one of
 three values: Router Address [RFC3630], Link [RFC3630], or Node
 Attribute [RFC5786].  In this document, we enhance the sub-TLVs for
 the Link TLV in support of the general network element constraints
 under the control of GMPLS.
 The detailed encoding of OSPF extensions is not defined in this
 document.  [RFC7579] provides encoding details.

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 RFC 2119 [RFC2119].

2. Node Information

 According to [RFC7579], the additional node information representing
 node switching asymmetry constraints includes device type and
 connectivity matrix.  Except for the device type, which is defined in
 [RFC7579], the other pieces of information are defined in this
 document.

Zhang, et al. Standards Track [Page 3] RFC 7580 Generic Constraint OSPF-TE June 2015

 Per [RFC7579], this document defines the Connectivity Matrix sub-TLV
 of the Node Attribute TLV defined in [RFC5786].  The new sub-TLV has
 Type 14.
 Depending on the control-plane implementation being used, the
 Connectivity Matrix sub-TLV may be optional in some specific
 technologies, e.g., WSON networks.  Usually, for example, in WSON
 networks, the Connectivity Matrix sub-TLV may be advertised in the
 LSAs since WSON switches are currently asymmetric.  If no
 Connectivity Matrix sub-TLV is included, it is assumed that the
 switches support symmetric switching.

2.1. Connectivity Matrix

 If the switching devices supporting certain data-plane technology are
 asymmetric, it is necessary to identify which input ports and labels
 can be switched to some specific labels on a specific output port.
 The connectivity matrix, which can represent either the potential
 connectivity matrix for asymmetric switches (e.g., Reconfigurable
 Optical Add/Drop Multiplexers (ROADMs) and such) or fixed
 connectivity for an asymmetric device such as a multiplexer as
 defined in [RFC7446], is used to identify these restrictions.
 The Connectivity Matrix is a sub-TLV of the Node Attribute TLV.  The
 length is the length of the value field in octets.  The meaning and
 format of this sub-TLV value field are defined in Section 2.1 of
 [RFC7579].  One sub-TLV contains one matrix.  The Connectivity Matrix
 sub-TLV may occur more than once to contain multiple matrices within
 the Node Attribute TLV.  In addition, a large connectivity matrix can
 be decomposed into smaller sub-matrices for transmission in multiple
 LSAs as described in Section 5.

3. Link Information

 The most common link sub-TLVs nested in the top-level Link TLV are
 already defined in [RFC3630] and [RFC4203].  For example, Link ID,
 Administrative Group, Interface Switching Capability Descriptor
 (ISCD), Link Protection Type, Shared Risk Link Group (SRLG), and
 Traffic Engineering Metric are among the typical link sub-TLVs.
 Per [RFC7579], this document defines the Port Label Restrictions sub-
 TLV of the Link TLV defined in [RFC3630].  The new sub-TLV has Type
 34.

Zhang, et al. Standards Track [Page 4] RFC 7580 Generic Constraint OSPF-TE June 2015

 Generally, all the sub-TLVs above are optional, depending on control-
 plane implementations being used.  The Port Label Restrictions sub-
 TLV will not be advertised when there are no restrictions on label
 assignment.

3.1. Port Label Restrictions

 Port label restrictions describe the label restrictions that the
 network element (node) and link may impose on a port.  These
 restrictions represent what labels may or may not be used on a link
 and are intended to be relatively static.  For increased modeling
 flexibility, port label restrictions may be specified relative to the
 port in general or to a specific connectivity matrix.
 For example, the port label restrictions describe the wavelength
 restrictions that the link and various optical devices such as
 Optical Cross-Connects (OXCs), ROADMs, and waveband multiplexers may
 impose on a port in WSON.  These restrictions represent which
 wavelengths may or may not be used on a link and are relatively
 static.  Detailed information about port label restrictions is
 provided in [RFC7446].
 The Port Label Restrictions sub-TLV is a sub-TLV of the Link TLV.
 The length is the length of value field in octets.  The meaning and
 format of this sub-TLV value field are defined in Section 2.2 of
 [RFC7579].  The Port Label Restrictions sub-TLV may occur more than
 once to specify a complex port constraint within the Link TLV.

4. Routing Procedures

 All sub-TLVs are nested in top-level TLV(s) and contained in Opaque
 LSAs.  The flooding rules of Opaque LSAs are specified in [RFC2328],
 [RFC5250], [RFC3630], and [RFC4203].
 Considering the routing scalability issues in some cases, the routing
 protocol should be capable of supporting the separation of dynamic
 information from relatively static information to avoid unnecessary
 updates of static information when dynamic information is changed.  A
 standards-compliant approach is to separate the dynamic information
 sub-TLVs from the static information sub-TLVs, each nested in a
 separate top-level TLV (see [RFC3630] and [RFC5786]), and advertise
 them in the separate OSPF-TE LSAs.
 For node information, since the connectivity matrix information is
 static, the LSA containing the Node Attribute TLV can be updated with
 a lower frequency to avoid unnecessary updates.

Zhang, et al. Standards Track [Page 5] RFC 7580 Generic Constraint OSPF-TE June 2015

 For link information, a mechanism MAY be applied such that static
 information and dynamic information of one TE link are contained in
 separate Opaque LSAs.  For example, the Port Label Restrictions sub-
 TLV could be nested in separate top-level Link TLVs and advertised in
 the separate LSAs.
 As with other TE information, an implementation typically takes
 measures to avoid rapid and frequent updates of routing information
 that could cause the routing network to become swamped.  See
 Section 3 of [RFC3630] for related details.

5. Scalability and Timeliness

 This document defines two sub-TLVs for describing generic routing
 constraints.  The examples given in [RFC7579] show that very large
 systems, in terms of label count or ports, can be very efficiently
 encoded.  However, because there has been concern expressed that some
 possible systems may produce LSAs that exceed the IP Maximum
 Transmission Unit (MTU), methods should be given to allow for the
 splitting of general constraint LSAs into smaller LSAs that are under
 the MTU limit.  This section presents a set of techniques that can be
 used for this purpose.

5.1. Different Sub-TLVs into Multiple LSAs

 Two sub-TLVs are defined in this document:
 1.  Connectivity Matrix (carried in the Node Attribute TLV)
 2.  Port Label Restrictions (carried in the Link TLV)
 The Connectivity Matrix sub-TLV can be carried in the Node Attribute
 TLV (as defined in [RFC5786]), whereas the Port Label Restrictions
 sub-TLV can be carried in a Link TLV, of which there can be at most
 one in an LSA (as defined in [RFC3630]).  Note that the port label
 restrictions are relatively static, i.e., only would change with
 hardware changes or significant system reconfiguration.

5.2. Decomposing a Connectivity Matrix into Multiple Matrices

 In the highly unlikely event that a Connectivity Matrix sub-TLV by
 itself would result in an LSA exceeding the MTU, a single large
 matrix can be decomposed into sub-matrices.  Per [RFC7579], a
 connectivity matrix just consists of pairs of input and output ports
 that can reach each other; hence, this decomposition would be
 straightforward.  Each of these sub-matrices would get a unique
 matrix identifier per [RFC7579].

Zhang, et al. Standards Track [Page 6] RFC 7580 Generic Constraint OSPF-TE June 2015

 From the point of view of a path computation process, prior to
 receiving an LSA with a Connectivity Matrix sub-TLV, no connectivity
 restrictions are assumed, i.e., the standard GMPLS assumption of any
 port to any port reachability holds.  Once a Connectivity Matrix sub-
 TLV is received, path computation would know that connectivity is
 restricted and use the information from all Connectivity Matrix sub-
 TLVs received to understand the complete connectivity potential of
 the system.  Prior to receiving any Connectivity Matrix sub-TLVs,
 path computation may compute a path through the system when, in fact,
 no path exists.  In between the reception of an additional
 Connectivity Matrix sub-TLV, path computation may not be able to find
 a path through the system when one actually exists.  Both cases are
 currently encountered and handled with existing GMPLS mechanisms.
 Due to the reliability mechanisms in OSPF, the phenomena of late or
 missing Connectivity Matrix sub-TLVs would be relatively rare.
 In the case where the new sub-TLVs or their attendant encodings are
 malformed, the proper action would be to log the problem and ignore
 just the sub-TLVs in GMPLS path computations rather than ignoring the
 entire LSA.

6. Security Considerations

 This document does not introduce any further security issues other
 than those discussed in [RFC3630], [RFC4203], and [RFC5250].
 For general security aspects relevant to GMPLS-controlled networks,
 please refer to [RFC5920].

7. Manageability

 No existing management tools handle the additional TE parameters as
 defined in this document and distributed in OSPF-TE.  The existing
 MIB module contained in [RFC6825] allows the TE information
 distributed by OSPF-TE to be read from a network node; this MIB
 module could be augmented (possibly by a sparse augmentation) to
 report this new information.
 The current environment in the IETF favors the Network Configuration
 Protocol (NETCONF) [RFC6241] and YANG [RFC6020] over SNMP and MIB
 modules.  Work is in progress in the TEAS working group to develop a
 YANG module to represent the generic TE information that may be
 present in a Traffic Engineering Database (TED).  This model may be
 extended to handle the additional information described in this
 document to allow that information to be read from network devices or
 exchanged between consumers of the TED.  Furthermore, links state

Zhang, et al. Standards Track [Page 7] RFC 7580 Generic Constraint OSPF-TE June 2015

 export using BGP [BGP-LS] enables the export of TE information from a
 network using BGP.  Work could realistically be done to extend BGP-LS
 to also carry the information defined in this document.
 It is not envisaged that the extensions defined in this document will
 place substantial additional requirements on Operations,
 Administration, and Maintenance (OAM) mechanisms currently used to
 diagnose and debug OSPF systems.  However, tools that examine the
 contents of opaque LSAs will need to be enhanced to handle these new
 sub-TLVs.

8. IANA Considerations

 IANA has allocated new sub-TLVs as defined in Sections 2 and 3 as
 follows:

8.1. Node Information

 IANA maintains the "Open Shortest Path First (OSPF) Traffic
 Engineering TLVs" registry with a sub-registry called "Types for sub-
 TLVs of TE Node Attribute TLV (Value 5)".  IANA has assigned a new
 code point as follows:
       Type   |  Sub-TLV                      |  Reference
       -------+-------------------------------+------------
        14    |  Connectivity Matrix          |  [RFC7580]

8.2. Link Information

 IANA maintains the "Open Shortest Path First (OSPF) Traffic
 Engineering TLVs" registry with a sub-registry called "Types for sub-
 TLVs of TE Link TLV (Value 2)".  IANA has assigned a new code point
 as follows:
       Type   |  Sub-TLV                      |  Reference
       -------+-------------------------------+------------
         34   |  Port Label Restrictions      |  [RFC7580]

Zhang, et al. Standards Track [Page 8] RFC 7580 Generic Constraint OSPF-TE June 2015

9. References

9.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
            DOI 10.17487/RFC2328, April 1998,
            <http://www.rfc-editor.org/info/rfc2328>.
 [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
            (TE) Extensions to OSPF Version 2", RFC 3630,
            DOI 10.17487/RFC3630, September 2003,
            <http://www.rfc-editor.org/info/rfc3630>.
 [RFC4202]  Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
            Extensions in Support of Generalized Multi-Protocol Label
            Switching (GMPLS)", RFC 4202, DOI 10.17487/RFC4202,
            October 2005, <http://www.rfc-editor.org/info/rfc4202>.
 [RFC4203]  Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
            in Support of Generalized Multi-Protocol Label Switching
            (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
            <http://www.rfc-editor.org/info/rfc4203>.
 [RFC5250]  Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
            OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250,
            July 2008, <http://www.rfc-editor.org/info/rfc5250>.
 [RFC5786]  Aggarwal, R. and K. Kompella, "Advertising a Router's
            Local Addresses in OSPF Traffic Engineering (TE)
            Extensions", RFC 5786, DOI 10.17487/RFC5786, March 2010,
            <http://www.rfc-editor.org/info/rfc5786>.
 [RFC7579]  Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and
            J. Han, "General Network Element Constraint Encoding for
            GMPLS-Controlled Networks", RFC 7579,
            DOI 10.17487/RFC7579, June 2015,
            <http://www.rfc-editor.org/info/rfc7579>.

Zhang, et al. Standards Track [Page 9] RFC 7580 Generic Constraint OSPF-TE June 2015

9.2. Informative References

 [BGP-LS]   Gredler, H., Medved, J., Previdi, S., Farrel, A., and S.
            Ray, "North-Bound Distribution of Link-State and TE
            Information using BGP", Work in Progress,
            draft-ietf-idr-ls-distribution-11, June 2015.
 [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
            the Network Configuration Protocol (NETCONF)", RFC 6020,
            DOI 10.17487/RFC6020, October 2010,
            <http://www.rfc-editor.org/info/rfc6020>.
 [RFC6163]  Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
            "Framework for GMPLS and Path Computation Element (PCE)
            Control of Wavelength Switched Optical Networks (WSONs)",
            RFC 6163, DOI 10.17487/RFC6163, April 2011,
            <http://www.rfc-editor.org/info/rfc6163>.
 [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
            and A. Bierman, Ed., "Network Configuration Protocol
            (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
            <http://www.rfc-editor.org/info/rfc6241>.
 [RFC6825]  Miyazawa, M., Otani, T., Kumaki, K., and T. Nadeau,
            "Traffic Engineering Database Management Information Base
            in Support of MPLS-TE/GMPLS", RFC 6825,
            DOI 10.17487/RFC6825, January 2013,
            <http://www.rfc-editor.org/info/rfc6825>.
 [RFC7446]  Lee, Y., Ed., Bernstein, G., Ed., Li, D., and W. Imajuku,
            "Routing and Wavelength Assignment Information Model for
            Wavelength Switched Optical Networks", RFC 7446,
            DOI 10.17487/RFC7446, February 2015,
            <http://www.rfc-editor.org/info/rfc7446>.
 [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
            Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
            <http://www.rfc-editor.org/info/rfc5920>.

Zhang, et al. Standards Track [Page 10] RFC 7580 Generic Constraint OSPF-TE June 2015

Acknowledgments

 We thank Ming Chen and Yabin Ye from DICONNET Project who provided
 valuable information for this document.

Contributors

 Guoying Zhang
 China Academy of Telecommunication Research of MII
 11 Yue Tan Nan Jie
 Beijing
 China
 Phone: +86-10-68094272
 EMail: zhangguoying@mail.ritt.com.cn
 Dan Li
 Huawei Technologies Co., Ltd.
 F3-5-B R&D Center, Huawei Base
 Bantian, Longgang District
 Shenzhen 518129
 China
 Phone: +86-755-28973237
 EMail: danli@huawei.com
 Ming Chen
 European Research Center
 Huawei Technologies
 Riesstr. 25, 80992
 Munchen
 Germany
 Phone: 0049-89158834072
 EMail: minc@huawei.com
 Yabin Ye
 European Research Center
 Huawei Technologies
 Riesstr. 25, 80992
 Munchen
 Germany
 Phone: 0049-89158834074
 EMail: yabin.ye@huawei.com

Zhang, et al. Standards Track [Page 11] RFC 7580 Generic Constraint OSPF-TE June 2015

Authors' Addresses

 Fatai Zhang
 Huawei Technologies
 F3-5-B R&D Center, Huawei Base
 Bantian, Longgang District
 Shenzhen 518129
 China
 Phone: +86-755-28972912
 EMail: zhangfatai@huawei.com
 Young Lee
 Huawei Technologies
 5360 Legacy Drive, Building 3
 Plano, TX 75023
 United States
 Phone: (469)277-5838
 EMail: leeyoung@huawei.com
 Jianrui Han
 Huawei Technologies Co., Ltd.
 F3-5-B R&D Center, Huawei Base
 Bantian, Longgang District
 Shenzhen 518129
 China
 Phone: +86-755-28977943
 EMail: hanjianrui@huawei.com
 Greg Bernstein
 Grotto Networking
 Fremont, CA
 United States
 Phone: (510) 573-2237
 EMail: gregb@grotto-networking.com
 Yunbin Xu
 China Academy of Telecommunication Research of MII
 11 Yue Tan Nan Jie
 Beijing
 China
 Phone: +86-10-68094134
 EMail: xuyunbin@mail.ritt.com.cn

Zhang, et al. Standards Track [Page 12]

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