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Versions: (draft-zhang-ccamp-general-constraints-ospf-ext) 00 01 02 03 04 05 06 07 08 09 10 RFC 7580

Network work group                                          Fatai Zhang
Internet Draft                                                Young Lee
Intended status: Standards Track                            Jianrui Han
                                                                 Huawei
                                                           G. Bernstein
                                                      Grotto Networking
                                                              Yunbin Xu
                                                                   CATR

Expires: January 6, 2013                                   July 6, 2012




        OSPF-TE Extensions for General Network Element Constraints



         draft-ietf-ccamp-gmpls-general-constraints-ospf-te-04.txt


Status of this Memo

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   This Internet-Draft will expire on January 6, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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.



Abstract

   Generalized Multiprotocol Label Switching can be used to control a
   wide variety of technologies including packet switching (e.g., MPLS),
   time-division (e.g., SONET/SDH, 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 OSPF routing protocol
   extensions to support these kinds of constraints under the control
   of Generalized MPLS (GMPLS).

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].

Table of Contents


   1. Introduction...................................................3
   2. Node Information...............................................3
      2.1. Connectivity Matrix.......................................4
   3. Link Information...............................................5
      3.1. Port Label Restrictions...................................5
   4. Routing Procedures.............................................6
   5. Scalability and Timeliness.....................................6
      5.1. Different Sub-TLVs into Multiple LSAs.....................7
      5.2. Decomposing a Connectivity Matrix into Multiple Matrices..7
   6. Security Considerations........................................7
   7. IANA Considerations............................................8
      7.1. Node Information..........................................8
      7.2. Link Information..........................................8


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   8. References.....................................................8
      8.1. Normative References......................................8
      8.2. Informative References....................................9
   9. Authors' Addresses .............................................9
   Acknowledgment...................................................11



1. Introduction

   Some data plane technologies that wish to make use of a GMPLS
   control plane contain 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
   WSON [RFC6163]. Such constraints can lead to the requirement for
   link by link label availability in path computation and label
   assignment.

   [GEN-Encode] provides efficient encodings of information needed by
   the routing and label assignment process in technologies such as
   WSON and are potentially applicable to a wider range of
   technologies.

   This document defines extensions to the OSPF routing protocol based
   on [GEN-Encode] to enhance the Traffic Engineering (TE) properties
   of GMPLS TE which are defined in [RFC3630], [RFC4202], and [RFC4203].
   The enhancements to the Traffic Engineering (TE) properties of GMPLS
   TE links can be announced in OSPF TE 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 (1) Router Address [RFC3630], (2) Link [RFC3630], (3) Generic
   Node Attribute defined in Section 2. In this document, we enhance
   the sub-TLVs for the Link TLV and define a new top-level TLV
   (Generic Node Attribute TLV) in support of the general network
   element constraints under the control of GMPLS.

   The detailed encoding of OSPF extensions are not defined in this
   document. [GEN-Encode] provides encoding detail.

2. Node Information

   According to [GEN-Encode], the additional node information
   representing node switching asymmetry constraints includes Node ID,
   connectivity matrix. Except for the Node ID which should comply with



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   Routing Address described in [RFC3630], the other pieces of
   information are defined in this document.

   This document defines a new top TLV named the Generic Node Attribute
   TLV which carries attributes related to a general network element.
   This Generic Node Attribute TLV contains one or more sub-TLVs

   Per [GEN-Encode], we have identified the following new Sub-TLVs to
   the Generic Node Attribute TLV. Detail description for each newly
   defined Sub-TLV is provided in subsequent sections:

      Sub-TLV Type    Length         Name

         TBD          variable    Connectivity Matrix

   In some specific technologies, e.g., WSON networks, Connectivity
   Matrix sub-TLV may be optional, which depends on the control plane
   implementations. Usually, for example, in WSON networks,
   Connectivity Matrix sub-TLV may appear in the LSAs because WSON
   switches are asymmetric at present. It is assumed that the switches
   are symmetric switching, if there is no Connectivity Matrix sub-TLV
   in the LSAs.

2.1. Connectivity Matrix

   It is necessary to identify which ingress ports and labels can be
   switched to some specific labels on a specific egress port, if the
   switching devices in some technology are highly asymmetric.

   The Connectivity Matrix is used to identify these restrictions,
   which can represent either the potential connectivity matrix for
   asymmetric switches (e.g. ROADMs and such) or fixed connectivity for
   an asymmetric device such as a multiplexer as defined in [WSON-
   Info].

   The Connectivity Matrix is a sub-TLV (the type is TBD by IANA) of
   the Generic Node Attribute TLV. The length is the length of value
   field in octets. The meaning and format of this sub-TLV are defined
   in Section 5.3 of [GEN-Encode]. One sub-TLV contains one matrix. The
   Connectivity Matrix sub-TLV may occur more than once to contain
   multi-matrices within the Generic Node Attribute TLV. In addition a
   large connectivity matrix can be decomposed into smaller separate
   matrices for transmission in multiple LSAs as described in Section 5.






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3. Link Information

   The most common link sub-TLVs nested to link top-level TLV are
   already defined in [RFC3630], [RFC4203]. For example, Link ID,
   Administrative Group, Interface Switching Capability Descriptor
   (ISCD), Link Protection Type, Shared Risk Link Group Information
   (SRLG), and Traffic Engineering Metric are among the typical link
   sub-TLVs.

   Per [GEN-Encode], we add the following additional link sub-TLVs to
   the link-TLV in this document.

      Sub-TLV Type    Length         Name

         TBD          variable    Port Label Restrictions

   Generally all the sub-TLVs above are optional, which depends on the
   control plane implementations. If it is default no restrictions on
   labels, Port Label Restrictions sub-TLV may not appear in the LSAs.

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. More dynamic information
   is contained in the information on available labels. Port label
   restrictions are specified relative to the port in general or to a
   specific connectivity matrix for increased modeling flexibility.

   For example, Port Label Restrictions describes the wavelength
   restrictions that the link and various optical devices such as OXCs,
   ROADMs, and waveband multiplexers may impose on a port in WSON.
   These restrictions represent what wavelength may or may not be used
   on a link and are relatively static. The detailed information about
   Port label restrictions is described in [WSON-Info].

   The Port Label Restrictions is a sub-TLV (the type is TBD by IANA)
   of the Link TLV. The length is the length of value field in octets.
   The meaning and format of this sub-TLV are defined in Section 5.4 of
   [GEN-Encode]. The Port Label Restrictions sub-TLV may occur more
   than once to specify a complex port constraint within the link TLV.







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4. Routing Procedures

   All the sub-TLVs are nested to top-level TLV(s) and contained in
   Opaque LSAs. The flooding of Opaque LSAs must follow the rules
   specified in [RFC2328], [RFC5250], [RFC3630], [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 standard-compliant approach is to separate the dynamic
   information sub-TLVs from the static information sub-TLVs, each
   nested to top-level TLV ([RFC3630 and RFC5876]), and advertise them
   in the separate OSPF TE LSAs.

   For node information, since the Connectivity Matrix information is
   static, the LSA containing the Generic Node Attribute TLV can be
   updated with a lower frequency to avoid unnecessary updates.

   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
   information sub-TLV could be nested to the top level link TLVs and
   advertised in the separate LSAs.

   Note that as with other TE information, an implementation SHOULD
   take measures to avoid rapid and frequent updates of routing
   information that could cause the routing network to become swamped.
   A threshold mechanism MAY be applied such that updates are only
   flooded when a number of changes have been made to the label
   availability  information (e.g., wavelength availability) within a
   specific time. Such mechanisms MUST be configurable if they are
   implemented.

5. Scalability and Timeliness

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




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   5.1. Different Sub-TLVs into Multiple LSAs

   Two sub-TLVs are defined in this document:

     1. Connectivity Matrix (Generic Node Attribute TLV)
     2. Port Label Restrictions (Link TLV)

   Except for the Connectivity Matrix all these are carried in an Link
   TLV of which there can be at most one in an LSA [RFC3630]. Of these
   sub-TLVs 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 [GEN-Encode] a
   connectivity matrix just consists of pairs of input and output ports
   that can reach each other and hence such this decomposition would be
   straightforward. Each of these sub-matrices would get a unique
   matrix identifier per [GEN-Encode].

   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 then 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.

6. Security Considerations

   This document does not introduce any further security issues other
   than those discussed in [RFC 3630], [RFC 4203].






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7. IANA Considerations

   [RFC3630] says that the top level Types in a TE LSA and Types for
   sub-TLVs for each top level Types must be assigned by Expert Review,
   and must be registered with IANA.

   IANA is requested to allocate new Types for the TLV or sub-TLVs as
   defined in Sections 2 and 3 as follows:

7.1. Node Information

   This document introduces a new Top Level Node TLV (Generic Node
   Attribute TLV) under the OSPF TE LSA defined in [RFC3630].

      Value    TLV Type

      TBA      Generic Node Attribute

   This document also introduces the following sub-TLVs of Generic Node
   Attribute TLV:

      Type     sub-TLV

      TBD      Connectivity Matrix

7.2. Link Information

   This document introduces the following sub-TLV of TE Link TLV (Value
   2):

      Type     sub-TLV

      TBD      Port Label Restrictions

8. References

8.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC5250] L. Berger, I. Bryskin, A. Zinin, R. Coltun "The OSPF
             Opaque LSA Option", RFC 5250, July 2008.




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   [RFC3630] Katz, D., Kompella, K., and Yeung, D., "Traffic
             Engineering (TE) Extensions to OSPF Version 2", RFC 3630,
             September 2003.

   [RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing
             Extensions in Support of Generalized Multi-Protocol Label
             Switching (GMPLS)", RFC 4202, October 2005

   [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions
             in Support of Generalized Multi-Protocol Label Switching
             (GMPLS)", RFC 4203, October 2005.

   [GEN-Encode] G. Bernstein, Y. Lee, D. Li, W. Imajuku, " General
             Network Element Constraint Encoding for GMPLS Controlled
             Networks", work in progress: draft-ietf-ccamp-general-
             constraint-encode, May 2011.

   [RFC6205] T. Otani, H. Guo, K. Miyazaki, D. Caviglia, " Generalized
             Labels for Lambda-Switching Capable Label Switching
             Routers", RFC 6205, January 2011.



8.2. Informative References

   [RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS and
             PCE Control of Wavelength Switched Optical Networks
             (WSON)", RFC 6163, February 2011.

   [WSON-Info] Y. Lee, G. Bernstein, D. Li, W. Imajuku, "Routing and
             Wavelength Assignment Information Model for Wavelength
             Switched Optical Networks", work in progress: draft-ietf-
             ccamp-rwa-info, September 2011.



9. Authors' Addresses

   Fatai Zhang
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28972912



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   Email: zhangfatai@huawei.com


   Young Lee
   Huawei Technologies
   1700 Alma Drive, Suite 100
   Plano, TX 75075
   USA

   Phone: (972) 509-5599 (x2240)
   Email: ylee@huawei.com


   Jianrui Han
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28977943
   Email: hanjianrui@huawei.com


   Greg Bernstein
   Grotto Networking
   Fremont CA, USA

   Phone: (510) 573-2237
   Email: gregb@grotto-networking.com


   Yunbin Xu
   China Academy of Telecommunication Research of MII
   11 Yue Tan Nan Jie Beijing, P.R.China
   Phone: +86-10-68094134
   Email: xuyunbin@mail.ritt.com.cn


   Guoying Zhang
   China Academy of Telecommunication Research of MII
   11 Yue Tan Nan Jie Beijing, P.R.China



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   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 P.R.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


Acknowledgment

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


Intellectual Property






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Full Copyright Statement

   Copyright (c) 2010 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
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   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.




























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