OSPF-TE Extensions for General Network Element Constraints
Author(s): Greg Bernstein, Jianrui Han, Young Lee, Fatai Zhang, Yunbin Xu
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)....
Network work group Fatai Zhang Internet Draft Young Lee Intended status: Standards Track Jianrui Han Huawei G. Bernstein Grotto Networking Yunbin Xu CATR Expires: December 26, 2013 June 26, 2013 OSPF-TE Extensions for General Network Element Constraints draft-ietf-ccamp-gmpls-general-constraints-ospf-te-05.txt 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 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 December 26, 2013. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. <Zhang> Expires December 2013 [Page 1] Internet-Draft Generic Constraint OSPF-TE June 2013 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 [RFC 2119]. 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 Zhang Expires December 2013 [Page 2] Internet-Draft Generic Constraint OSPF-TE June 2013 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 Zhang Expires December 2013 [Page 3] Internet-Draft Generic Constraint OSPF-TE June 2013 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. Zhang Expires December 2013 [Page 4] Internet-Draft Generic Constraint OSPF-TE June 2013 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. Zhang Expires December 2013 [Page 5] Internet-Draft Generic Constraint OSPF-TE June 2013 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. Zhang Expires December 2013 [Page 6] Internet-Draft Generic Constraint OSPF-TE June 2013 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 [RFC3630], [RFC4203]. Zhang Expires December 2013 [Page 7] Internet-Draft Generic Constraint OSPF-TE June 2013 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 [RFC 2119] 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, RFC2328, April 1998. [RFC5250] L. Berger, I. Bryskin, A. Zinin, R. Coltun "The OSPF Opaque LSA Option", RFC5250, July 2008. Zhang Expires December 2013 [Page 8] Internet-Draft Generic Constraint OSPF-TE June 2013 [RFC3630] Katz, D., Kompella, K., and Yeung, D., "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC3630, September 2003. [RFC4202] Kompella, K., Ed., and Y. Rekhter, Ed., "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC4202, October 2005 [RFC4203] Kompella, K., Ed., and Y. Rekhter, Ed., "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC4203, 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. [RFC6205] T. Otani, H. Guo, K. Miyazaki, D. Caviglia, " Generalized Labels for Lambda-Switching Capable Label Switching Routers", RFC6205, 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)", RFC6163, 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. 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 Zhang Expires December 2013 [Page 9] Internet-Draft Generic Constraint OSPF-TE June 2013 Email: firstname.lastname@example.org Young Lee Huawei Technologies 1700 Alma Drive, Suite 100 Plano, TX 75075 USA Phone: (972) 509-5599 (x2240) Email: email@example.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: firstname.lastname@example.org Greg Bernstein Grotto Networking Fremont CA, USA Phone: (510) 573-2237 Email: email@example.com Yunbin Xu China Academy of Telecommunication Research of MII 11 Yue Tan Nan Jie Beijing, P.R.China Phone: +86-10-68094134 Email: firstname.lastname@example.org Guoying Zhang China Academy of Telecommunication Research of MII 11 Yue Tan Nan Jie Beijing, P.R.China Zhang Expires December 2013 [Page 10] Internet-Draft Generic Constraint OSPF-TE June 2013 Phone: +86-10-68094272 Email: email@example.com 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: firstname.lastname@example.org Ming Chen European Research Center Huawei Technologies Riesstr. 25, 80992 Munchen, Germany Phone: 0049-89158834072 Email: email@example.com Yabin Ye European Research Center Huawei Technologies Riesstr. 25, 80992 Munchen, Germany Phone: 0049-89158834074 Email: firstname.lastname@example.org Acknowledgment We thank Ming Chen and Yabin Ye from DICONNET Project who provided valuable information for this document. 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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. Zhang Expires December 2013 [Page 13]