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

Expires: September 5, 2015                                March 6, 2015




        OSPF-TE Extensions for General Network Element Constraints



         draft-ietf-ccamp-gmpls-general-constraints-ospf-te-10.txt


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., SONET/SDH, 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 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.

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other documents




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   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

   This Internet-Draft will expire on September 5, 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.



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...............................................4
      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..7
   6. Security Considerations........................................7


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   7. Manageability..................................................8
   8. IANA Considerations............................................8
      8.1. Node Information..........................................8
      8.2. Link Information..........................................9
   9. References.....................................................9
      9.1. Normative References......................................9
      9.2. Informative References...................................10
   10. Authors' Addresses ..........................................10
   Acknowledgment...................................................12



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 Network (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. The encoding provided in [GEN-Encode] 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 [GEN-Encode] to enhance the Traffic Engineering (TE) properties
   of GMPLS TE which are defined in [RFC3630], [RFC4202], and [RFC4203].
   The enhancements to the TE properties of GMPLS TE links can be
   advertised 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) 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 are not defined in this
   document. [GEN-Encode] provides encoding details.




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2. Node Information

   According to [GEN-Encode], the additional node information
   representing node switching asymmetry constraints includes Node ID
   and connectivity matrix. Except for the Node ID, which should comply
   with Routing Address described in [RFC3630], the other pieces of
   information are defined in this document.

   Per [GEN-Encode], this document defines the Connectivity Matrix Sub-
   TLV of the Node Attribute TLV defined in [RFC5786].  The new Sub-TLV
   has Type TBD1 (to be assigned by IANA).

   In some specific technologies, e.g., WSON networks, the 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 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 is
   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 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
   [RFC7446].

   The Connectivity Matrix is a sub-TLV of the Node Attribute 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 2.1 of
   [GEN-Encode]. 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], [RFC4203]. For example, Link ID,
   Administrative Group, Interface Switching Capability Descriptor
   (ISCD), Link Protection Type, Shared Risk Link Group Information


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   (SRLG), and Traffic Engineering Metric are among the typical link
   sub-TLVs.

   Per [GEN-Encode], this document defines the Port Label Restrictions
   Sub-TLV of the Link TLV defined in [RFC3630]. The new Sub-TLV has
   Type TBD2 (to be assigned by IANA).

   Generally all the sub-TLVs above are optional, which depends on the
   control plane implementations. 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 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 [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
   [GEN-Encode]. 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 the 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,



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   each nested in a separate 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 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 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
   [RFC3630] Section 3 for related details.



5. Scalability and Timeliness

   This document has defined two 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 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 (Node Attribute TLV)
     2. Port Label Restrictions (Link TLV)

   The Connectivity Matrix can be carried in the Node Attribute TLV as
   defined in [RFC5786] while the Port Label Restrictions can be
   carried in an 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.




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   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.

   In 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 Generalized Multiprotocol
   Label Switching (GMPLS)-controlled networks, please refer to
   [RFC5920].








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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 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 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,
   Management, and Administration (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 is requested to allocate 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".  IANA is requested to assign a
   new code point as follows:

         Type   |  Sub-TLV                      |  Reference
         -------+-------------------------------+------------
         TBD1   |  Connectivity Matrix          |  [This.I-D]




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8.2. Link Information

   IANA maintains the "Open Shortest Path First (OSPF) Traffic
   Engineering TLVs" registry with a sub-registry called "Types for
   sub-LVs of TE Link TLV".  IANA is requested to assign a new code
   point as follows:

         Type   |  Sub-TLV                          |  Reference
         -------+-----------------------------------+------------
         TBD2   |  Port Label Restrictions          |  [This.I-D]


9. References

9.1. 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.

   [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.

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

   [RFC5786] R. Aggarwal and K. Kompella,"Advertising a Router's Local
             Addresses in OSPF Traffic Engineering (TE) Extensions",
             RFC 5786, March 2010.

   [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.





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9.2. Informative References

    [RFC6020] M. Bjorklund, Ed., "YANG - A Data Modeling Language for
             the Network Configuration Protocol (NETCONF)", RFC 6020,
             October 2010.

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

   [RFC6241] R. Enns, Ed., M. Bjorklund, Ed., Schoenwaelder, Ed., A.
             Bierman, Ed., "Network Configuration Protocol (NETCONF)",
             RFC 6241, June 2011.

   [RFC6825] M. Miyazawa, T. Otani, K. Kumaki, T. Nadeau, "Traffic
             Engineering Database Management Information Base in
             Support of MPLS-TE/GMPLS", RFC 6825, January 2013.

   [RFC7446] Y. Lee, G. Bernstein, D. Li, W. Imajuku, "Routing and
             Wavelength Assignment Information Model for Wavelength
             Switched Optical Networks", RFC 7446, February 2015.

   [RFC5920] L. Fang, Ed., "Security Framework for MPLS and GMPLS
             Networks", RFC 5920, July 2010.

   [BGP-LS] H. Gredler, J. Medved, S. Previdi, A. Farrel, S. Ray,
             "North-Bound Distribution of Link-State and TE Information
             using BGP", work in progress: draft-ietf-idr-ls-
             distribution.

10. Contributors


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


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   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


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
   Email: zhangfatai@huawei.com


   Young Lee
   Huawei Technologies
   5360 Legacy Drive, Building 3
   Plano, TX 75023
   USA




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   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 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


Acknowledgment

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












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