IPO Working Group E.Dotaro D. Papadimitriou L. Ciavaglia M. Vigoureux R. Douville L. Noirie Internet Draft Alcatel Document: draft-dotaro-ipo-multi-granularity-01.txt November 2001 Category: Informational Optical Multi-Granularity û Architectural Framework draft-dotaro-ipo-multi-granularity-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. 1. Abstract The multi-granularity concept in optical networks is the ability to simultaneously switch different levels of granularity inside a given optical network. Optical multi-granularity and particularly waveband switching raises some issues for GMPLS. These have been partially addressed in [GMPLS-ARCH] and [GMPLS-SIG] from the CCAMP Working Group. However, enabling multi-granularity in optical networks demands the definition of a more complete set of requirements considering the management, control, routing and signaling issues and their impacts in the GMPLS protocols suite. In this framework document we propose to extend GMPLS previous set of switching capabilities in the optical domain. This by identifying uncovered characteristics of the optical transport, taking into account interest for optical components working at the band level and its impact on the control of the optical networks. E.Dotaro et al. 1 Optical Multi-Granularity û Architectural Framework November 2001 2. Introduction Starting from MPLS labeled packet switching and MPLS-TE concepts, Generalized MPLS (GMPLS) introduces a new architecture and new building blocks to support additional switching layers, i.e. TDM, wavelength, waveband and fiber switching. In the framework of optical networking, the switching types of interest are mainly wavelength, waveband and fiber. Multi-granularity consists in combining and operating these switching layers in optical networks. Optical multi-granularity is quite a new concept, however feasibility and benefits of the approach have already been demonstrated [ONDM00-MGOXC], [OFC01-MGOXC]. Available optical multi-granularity technologies spanning components and systems (de/multiplexer, switch ,MG-OXC,...) indicate the growing interest to multi-granularity concepts and applications, while also answering demands and requirements from carriers for the support and control of multiple switching layers in optical networks. All this aspects concur to position multi-granularity as a relevant item in today optical networking framework. Optical multi-granularity and particularly waveband switching raises some issues for GMPLS. These have been partially addressed in [GMPLS-ARCH] and [GMPLS-SIG] from the CCAMP Working Group. However, enabling multi-granularity in optical networks demands the definition of a more complete set of requirements considering the management, control, routing and signaling issues and their impacts in the GMPLS protocols suite. In this memo, we propose to use this concept of multiple optical granularities in the GMPLS context in association with grooming strategies. Among possible optical switching granularities, waveband is an attractive trade-off for foreseen traffic volumes in next few years and will be particularly considered in the following. For this purpose, a new type of interface û WaveBand Switch Capable(WBSC) - is introduced completing the existing set of interfaces. Consequently a new type of Label Switched Path, the WaveBand-LSP (WB-LSP), is considered along with a new class of Forwarding Adjacencies (FA) as described in Section 4.3. 3. Rationale The sub-IP area and IPO Working Group are the most suitable locations for the proposed document as they addresse issues and considerations related and specific to optical networking. On basis of charter items, this memo fits into the IPO Working Group since it documents issues and requirements of an optical specific concept and technology. The document proposes and describes a framework for optical multi-granularity and its impact on the GMPLS protocols suite, notably routing and signaling aspects. E.Dotaro et al. 2 Optical Multi-Granularity û Architectural Framework November 2001 A complementary work is being initiated in the CCAMP Working Group based on the present document used as architectural framework. It addresses GMPLS building blocks enhancement and protocol suite extension to cover optical multi-granularity and particularly waveband switching. 4. Terminology Conventions, acronyms and abbreviations used in this document. Terminology is based on the definitions from [GMPLS-ARCH] and [GMPLS-SIG] plus specific addition for Multi-Granularity vocabulary. L-LSP = Lambda-LSP WB-LSP = WaveBand-LSP F-LSP = Fiber-LSP WXC = Wavelength Cross-Connect WBXC = WaveBand Cross-Connect FXC = Fiber Cross-Connect LSC = Lambda Switch Capabale WBSC = WaveBand Switch Capable FSC = Fiber Switch Capable MG-OXC = Multi-Granularity Cross-Connect 5. Multi-Granularity Considerations 5.1 Context and definition Considering that traffic increases faster than connectivity, widening switching granularity scope becomes valuable. Optical multi-granularity concept, including particularly waveband switching, allows to match those new requirements of granularity diversity. The use and exploitation of multiple granularities in optical networks relies on availability of proper hardware (components and systems), on methods to nest LSPs and especially on protocols integrating the specific features of optical multi-granularity. The multi-granularity concept in optical networks refers to the ability to simultaneously switch different levels of granularity inside a given optical network. The granularities considered at the optical layer are single wavelengths (L-LSP), band of wavelengths, i.e. wavebands (WB-LSP), and fibers (F-LSP). In order to take benefits from these switching granularities, it is necessary to be able to provision and handle LSPs at such granularities. The operation to assemble and combine LSPs into coarser LSPs is called grooming, also known as LSPs nesting. The process of grooming lower granularity LSPs into larger ones is analog to the LSP stacking scheme used in MPLS. Typical case of E.Dotaro et al. 3 Optical Multi-Granularity û Architectural Framework November 2001 grooming consists in aggregating L-LSPs into WB-LSPs and WB-LSPs into F-LSPs. Section 6.1 addresses the various aspects of grooming strategies. Therefore, extensions to GMPLS previous set of switching capabilities in the optical domain are proposed in this framework document. This is achieved by identifying uncovered characteristics of the optical transport, taking into account interest for optical components working at the band level and its impact on the control of the optical networks. In the efforts of describing the requirements and set of capabilities for optical multi-granularity, three approaches to waveband switching have been identified: - Inverse Multiplexing - Wavelength Concatenation - Waveband The availability of optical and/or photonic switching equipment capable to work at the band level û i.e. build out of band components and hardware - motivates the redefinition of waveband switching as defined in the GMPLS architecture. Current definition of waveband switching (see [GMPLS-ARCH] and [GMPLS-SIG]) refers to inverse multiplexing mechanism or wavelength concatenation (ôcontiguousö lambdas) were one can request a 10 Gbps L-LSP (logical waveband) while the underlying (physical) wavelength operates at 2.5 Gbps. While this definition is still valid and applicable, it does not consider the approach where band has a physical signification, i.e. where the interface is waveband switch capable (WBSC). The following paragraph shows the location of optical multi-granularity and highlight the new definition of waveband switching. 5.2 Hierarchy Overview The integration of optical multi-granularity in the GMPLS architecture requires modifications and extensions to current definitions. For this purpose, a new type of switch capable interface is first introduced: the Waveband Switch Capable Interface (WBSC). The WBSC interface materializes the physical reality of optical waveband as an atomic entity or granularity. As with the introduction of the waveband switch capable interface, a new class of LSP is defined: the WaveBand LSP (WB-LSP). LSP Hierarchy Interfaces Network Element P-LSP <---> PSC <----> Router L2-LSP <---> L2SC <----> Bridge,Switch TDM-LSP <---> TDM <----> DXC L-LSP <---> LSC <----> WXC -\ | E.Dotaro et al. 4 Optical Multi-Granularity û Architectural Framework November 2001 WB-LSP <---> WBSC <----> WBXC > Optical | MG F-LSP <---> FSC <----> FXC -/ WXC, WBXC and FXC can be part of the same entity referred to as MG- OXC or MG-PXC. The above figure illustrates the hierarchy of the switching layers and highlights the optical multi-granularity part. The network element column shows typical real-life boxes that support such interfaces. Note that this representation does not aim at restricting interfaces that network elements can support. Section 7 further details the extensions required to support the new definition of waveband switching in GMPLS. 5.3 Optical networking with Multi-Granularity Enabling multi-granularity into optical networks implies the use of specific optical components and systems, which are band-specific (filtering and switching functions). The use of multi-granularity results in reduction of the number of connections through each optical node. This means from the hardware point of view a reduction of the number of ports both for the switches and for the optical multiplexers and demultiplexers. Hence the optical switches have to be seen as a combination of Fiber Cross-Connects (FXC), WaveBand Cross-Connects (WBXC) and Wavelengths Cross-Connects (WXC) with a significant size reduction. Other benefits of multi-granularity systems, especially with waveband-based components have to be considered in terms of physical impairments since constraints are relaxed by decreasing the optical losses. The proposed multi-granularity scheme adds a relation between the Wavelength layer and the Waveband layer which is similar to the relation between IP and the optical layer from the connectivity point of view. Hence, all the analysis made in order to justify the sub-IP layers may be reuse. For instance the provisioning of cut- trough WaveBand-LSP below wavelength layer will allow to save a large amount of resource for this last layer. It is analog to lightpaths, acting as tunnels for the IP layer. Finally, most of existing routing and signaling protocols building blocks are applicable, including dissemination of topology information with Forwarding Adjacencies (FA) based on WB-LSP. 6. Multi-granularity Concept Applicability 6.1 Grooming strategies E.Dotaro et al. 5 Optical Multi-Granularity û Architectural Framework November 2001 The relative limited number of nodes and the relative small connectivity in an optical network allows assuming that there is potentially a strong correlation between flows of traffic inside such network. Hence, a grooming strategy can be envisaged to nest low order L-LSPs into higher order LSPs (eg. WB-LSPs or F-LSPs) in order to take benefit of the different switching level (i.e. switching granularities). Considering a set of L-LSPs sharing the same ingress and egress nodes, a higher order LSP could be provisioned between theses nodes and the L-LSPs nested into it. This provisioning method is called End-To-End grooming. Furthermore, we can assume that the correlation of traffic flows will be greater in the core of the network than at its periphery. Considering a set of L-LSPs not sharing the same ingress or/nor the same egress nodes, but sharing a common sub-path, a higher order LSP could be provisioned over this sub-path and the L-LSPs nested into it. This grooming strategy is called Intermediate grooming. Note that End-To-End grooming is just a peculiar case of Intermediate grooming, where the sub-path shared by the L-LSPs equals the entire path (i.e. same source-destination pair). 6.2 Grooming applicability scope The current L-LSPs nesting definition under the concept of waveband, as defined in [GMPLS-ARCH] and [GMPLS-SIG], has a restricted applicability scope. We propose to enhance the grooming possibilities of L-LSPs so as to widen this field. From these definitions, two L-LSPs nesting scenarios have been envisaged. (1) Waveband switching refers to inverse multiplexing such that only end-to-end grooming can be achieved and consequently quite restrictive and limited in its applicability scope. (2) Waveband switching refers to a kind of optical wavelength virtual concatenation (wavebands are logically defined û at the control plane level only - as a group of wavelengths). This scenario is quite flexible in terms of L-LSP virtual nesting but is incompatible with the physical constraints of effectively switching a set of wavelengths as a single physical unit. In the context of this memo, these two previous scenarios either do not take advantage of the natural intermediate grooming strategy or do not take advantage of the emerging waveband switching and multiplexing technologies. The principle of grooming optical granularities, taking into account the new WB-LSP, is analog in the optical domain to LSPs stacking in MPLS-TE and to the LSP hierarchy that ensues. The following example illustrates the new grooming strategy combined with the WB-LSP. E.Dotaro et al. 6 Optical Multi-Granularity û Architectural Framework November 2001 +----+ +----+ | | *** WB-LSP | | | | --- L-LSP | | | | | | | |-\ /-| | | | \ / | | | A |-\ \ / /-| C | +----+ \ \ +----+ +----+ +----+ +----+ / / +----+ \ \-| | | | | | | |-/ / \ | |-----| |-----| |-----| | / +----+ \-| | | | | | | |-/ +----+ | |-------| |*****| |*****| |*****| |-------| | | |-------| | | | | | | |-------| | | |-------| E | | F | | G | | H |-------| | | | +----+ +----+ +----+ +----+ | | | | | | | B | | D | +----+ +----+ Let us consider, in this example, that wavebands are composed of four wavelengths. Let us also consider that A has one L-LSP established with C and one with D, that B has one L-LSP established with C and two with D. In a wavelength only switching network, these connections would have been established and routed as L-LSPs and wavelengths switched. But in a wavelength and waveband switching network, where nodes E, F, G and H are wavelength and waveband switch capable, a WB-LSP could be established and routed between nodes E and H. The WB-LSP formed is composed of any four L-LSPs amongst the five ones entering node E. 6.3 Provisioning Strategies The introduction of multi-granularity has proven its potential, however the provisioning of the corresponding LSPs brings a new set of problems such as information flooding, LSPs establishment (dynamicity, triggering process, service disruption ...) and other issues like protection. In order to make efficient use of waveband switching concept, the new WBSC interfaces should be advertised. It is envisaged that IGP such as OSPF or IS-IS could flood the relative information. The introduction of the new WBSC interface is compliant, considering few minor enhancements, with Traffic Engineering extensions to OSPF [OSPF-TE] or IS-IS [ISIS-TE]. Following information dissemination, different scenarii are envisaged for the provisioning of WB-LSPs. E.Dotaro et al. 7 Optical Multi-Granularity û Architectural Framework November 2001 Several provisioning/grooming strategies can be foreseen depending on the various triggering mechanisms with more or less Traffic Engineering implication. From the simple point-and-click case to sophisticated traffic driven one, these approaches will use the information resulting from the flooding of the FAs. The definition of new traffic engineering parameters associated to this new class of FA is beyond the scope of this document. Nevertheless two TE based approaches dealing with two different grooming strategies may illustrate TE implication in provisioning/ grooming process. - On one hand WaveBand-LSPs can be pre-provisioned and then considered as tunnels for L-LSPs to be routed/nested into it. This method is an application of intermediate grooming paradigm (see Section 6.1). Provisioning of such WB-LSPs should be based on large time scale rules. - On the other hand WaveBand-LSPs can be dynamically established in response to a specific triggering mechanism. WB-LSPs can be established from end-to-end in response to a WB-LSP request, or can be established following several L-LSPs requests. Note that re-routing already established L-LSPs into WB-LSPs induces an interruption of service during switching time. 7. GMPLS Protocol suite extensions Enabling optical multi-granularity demands the definition of a complete set of requirements considering the management, control, routing and signaling issues. The details of the enhancement are addressed in the companion document [CCAMP-WB] in the CCAMP WG. It covers particularly the routing and signaling aspects. The major extension is the introduction of a WaveBand Switch Capable Interface (WBSC) with its associated components (WB-LSP, Link Multiplex Capability Value and Descriptor,). Routing aspects also include the definition of new sub-TLV descriptor for OSPF and IS-IS to advertise waveband capable links (FAs). From a signaling point of view, the Generalized Label Request is augmented to support WB-LSP establishment, while the generalized label is kept unchanged. Specific extensions to signaling protocols (RSVP-TE, CR-LDP) are currently under definition. Other open issues such as LMP considerations, definition of waveband specific TE parameters will be further specified. 8. Security Considerations This memo does not introduce new security consideration from the one already detailed in the GMPLS protocol suite. 9. References E.Dotaro et al. 8 Optical Multi-Granularity û Architectural Framework November 2001 1. [GMPLS-ARCH] E.Mannie et al., æGeneralized MPLS ArchitectureÆ, Internet Draft, Work in progress, draft-ietf-ccamp-gmpls- architecture-01.txt, June 2001. 2. [GMPLS-SIG] P.Ashwood-Smith, L.Berger et al., æGeneralized MPLS - Signaling Functional DescriptionÆ, Internet Draft, Work in progress, draft-ietf-mpls-generalized-signalling-06.txt, October 2001. 3. [OSPF-TE] K. Kompella et al., 'OSPF Extensions in Support of Generalized MPLS', Internet Draft, Work in progress, draft-ietf- ccamp-ospf-gmpls-extensions-00.txt, September 2001 4. [CCAMP-WB] R.Douville et al., æExtensions to GMPLS for Waveband SwitchingÆ, Internet Draft, Work in progress, draft-douville- ccamp-waveband-extension-00.txt, November 2001. 5. [OFC01-MGOXC] L.Noirie et al., æImpact of intermediate traffic grouping on the dimensioning of multi-granularity optical networksÆ, Paper presented during OFC 2001. 6. [ISIS-TE] K. Kompella et al., 'IS-IS Extensions in Support of Generalized MPLS', Internet Draft, Work in progress, draft-ietf- isis-gmpls-extensions-04.txt, September 2001 7. [ONDM00-MGOXC] C. Blaizot et al., æMulti-Granularity Optical NetworksÆ, Paper presented during ONDM 2000. 10. Acknowledgments The authors would like to thank Bernard Sales, Emmanuel Desmet and Amaury Jourdan for their constructive support, comments and inputs. 11. Author's Addresses Emmanuel Dotaro Alcatel Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-1307 Email: emmanual.dotaro@alcatel.fr Dimitri Papadimitriou Alcatel Francis Wellesplein 1, B-2018 Antwerpen, Belgium Phone: +32 3 240-8491 Email: dimitri.papadimitriou@alcatel.be Ludovic Noirie Alcatel Route de Nozay E.Dotaro et al. 9 Optical Multi-Granularity û Architectural Framework November 2001 91460 Marcoussis, France Phone: +33 1 6963-1136 Email: ludovic.noirie@alcatel.fr Laurent Ciavaglia Alcatel Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-4429 Email: laurent.ciavaglia@alcatel.fr Martin Vigoureux Alcatel Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-1852 Email: martin.vigoureux@alcatel.fr Richard Douville Alcatel Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-4431 Email: richard.douville@alcatel.fr E.Dotaro et al. 10 Optical Multi-Granularity û Architectural Framework November 2001 Full Copyright Statement "Copyright (C) The Internet Society (date). 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