IPO Working Group E. Dotaro Internet Draft D. Papadimitriou Document: draft-dotaro-ipo-multi-granularity-00.txt L. Noirie Expiration Date: January 2002 M. Vigoureux L. Ciavaglia Alcatel July 2001 Optical Multi-Granularity û Architectural Framework draft-dotaro-ipo-multi-granularity-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1]. 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. 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 [2]. Abstract In this memo we aim at demonstrating the benefits from the introduction in optical networks of the optical multi-granularity concept. Optical system technologies are able to handle different switching granularities from wavelength to fiber and especially wavebands. Taking benefits from these technologies, switching larger granularities reduce at the same time the complexity of control operations, the amount of hardware in the optical layer, and in addition relax some physical constraints. Gains expected from the IPO Working Group 1 draft-dotaro-ipo-multi-granularity-00.txt July 2001 approach are partly function of the efficiency of the grooming of wavelengths into larger granularities. In particular, intelligent intermediate grooming makes the multi-granularity concept even more attractive since reducing the required size of optical switching matrix typically by a factor of two or more. The proposed concept has to be seen as a new set of optical network features that are compliant and/or implying limited extensions to the Generalized MPLS (GMPLS) protocol suite. Table of Content 1. Terminology 2. Introduction 3. Concept Definition 3.1 Multi-Granularity Concept 3.2 Multi-Granularity-OXC (MG-OXC) Architecture 3.3 Grooming Strategies 3.4 Benefits of the approach 4. Concept Integration in GMPLS 4.1 Multi-Granularity Hierarchy 4.2 LSP Hierarchy 4.3 Impact on GMPLS Protocol Suite 4.3.1 GMPLS Signaling 4.3.2 GMPLS Traffic Engineering Routing Extension 4.3.3 Requirements Statements 5. Security Considerations 6. References 7. Author's Addresses 1. Terminology Conventions, acronyms and abbreviations used in this document. Terminology is based on the definitions in [GMPLS-ARCH] and [GMPLS- SIG] plus specific addition for Multi-Granularity. 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 2. Introduction Optical technology allows the transmission capacity of point to point links to scale up to the predicted traffic requirements of IPO Working Group 2 draft-dotaro-ipo-multi-granularity-00.txt July 2001 multiple Terabit/s. Hence the switching capacity of backbone nodes has to scale up to thousands of wavelength ports. To overcome the bottleneck of electronic switching, wavelength cross-connects (WXC) are introduced with Terabit/s throughput. Optical technologies can also be used to switch larger granularities such as bands of wavelengths (also referred to as wavebands) and fibers. Considering that optical networks will not experience a significant evolution of their topology properties (connectivity, number of nodes), these new granularities will easily support the traffic growth with limited impact on efficiency. The main issue is to find the optimum way to arrange the spatial distribution of traffic flows on the topology in order to create connections at the different optical granularities. The intrinsic properties of a typical backbone network give us good perspectives to achieve the goal of provisioning LSPs at these granularities. The relatively limited number of nodes (tens of nodes) and the relative small connectivity (3 to 8 neighbors per node) allow us to assume that there will be a strong correlation between flows of traffic inside the network. In other terms, it means that, assuming an efficient planning, numerous flows (e.g. STM-N/OC-N or IP flows) have to be processed in the same way in the nodes. Thus, this should give the opportunity to establish wavelength, waveband and fiber connections, and process most of the traffic using optical granularities as large as possible. This will alleviate some capacity bottlenecks and above all reduce the network cost. In this memo, we propose to use this concept of multiple optical granularities in association with grooming strategies and GMPLS integration requirements. 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, waveband switching is introduced as an additional sub-layer between the Lambda and the Fiber layer i.e. between corresponding Lambda-LSP (wavelength switching) and Fiber-LSP (spatial switching). However, this sub- layer does not introduce either a new type of interface or a new class of Forwarding Adjacencies (FA) class since we consider a Lambda LSP (L-LSP) as a particular case of a more generic Waveband LSP (WB-LSP) as described in Section 4. In terms of grooming strategies, we also propose to have both end- to-end and intermediate grooming at waveband and fiber levels to make the concept more attractive. Intermediate grouping is referred to as the aggregation of traffic with different source nodes and/or different destination nodes but with a common sub-path in the optical layer. End to end grooming is a particular case of intermediate grooming where the sub-path in the optical layer is the entire optical path between source and destination. IPO Working Group 3 draft-dotaro-ipo-multi-granularity-00.txt July 2001 3. Concept Definition 3.1 Multi-Granularity definition The multi-granularity concept in optical networks is the ability to simultaneously switch different levels of granularity inside a given optical network. The granularities we considered inside optical networks are single wavelengths (L-LSP), bundles of wavelengths which we call wavebands (WB-LSP), and whole fibers (F-LSP). There may be different levels of waveband in the multi-granularity optical networks. The main idea behind multi-granularity inside optical networks is that the number of nodes inside a given network is limited, and if a lot of wavelengths are required to carry all the traffic, some of them will start from the same source node to go to the same destination nodes, and even more wavelengths will follow the same sub-paths inside the network. Thus it is useless to switch them separately through some optical nodes, they can be switched by groups (wavebands, or even fibers if there are a lot of wavelengths). 3.2 Multi-Granularity-OXC Architecture A Multi-Granularity Optical Cross-Connect (MG-OXC) extends classic WXC (wavelength switching only) to support switching of other kind of optical granularities or LSPs. Therefore a MG-OXC can either switch wavelengths, wavebands or fiber LSPs, or a combination of any. By these means, such a Cross-Connect is capable of terminating L- LSPs through a Lambda Switching Capable interface (LSC), WB-LSPs through Waveband Switching Capable interface (WBSC) and F-LSPs through Fiber Switching Capable (FSC) interface. The following figure shows a possible architecture of a MG-OXC. The MG-OXC considered has the ability to switch the three types of LSPs but this is not mandatory. IPO Working Group 4 draft-dotaro-ipo-multi-granularity-00.txt July 2001 F-LSP WB-LSP L-LSP L-LSP WB-LSP F-LSP | | | | | | | | | | | | | | | | | | | +-->---+ +--->--+ | | | | | +--->--+ | | +-->---+ | | | | | | | | | | | | +---------------+ | | | | +-->--| Switch Matrix |->---+ | | | | | +->-| WXC |->-+ | | | | | | | +---------------+ | | | | | | | | | | | | | | | | | | _|_|_ _|_|_ _|_|_ _|_|_ | | | | \ D / \ D / \ M / \ M / | | | | \ / \ / \ / \ / | | | | | | | | | | | | | +-<-+ +-<-+ | | | | | / | | \ | | | | | +---------------+ | | | | +--..|..->-| Switch Matrix |->-..|..--+ | | | +->-| WB-XC |->-+ | | | | | +---------------+ | | | | _|_|_ _|_|_ _|_|_ _|_|_ | | \ D / \ D / \ M / \ M / | | \ / \ / \ / \ / | | | | | | | | | +-<-+ +-<-+ | | | | | | | | +---->---..|..--->--+ | | +-->---..|..--->----+ | | | | | | | +---------------+ | Fibers -->-----+ | Switch Matrix | +----->-- Fibers In -->----------| FXC |---------->-- Out +---------------+ Moreover different architectures can be envisaged, depending on the degree of flexibility one wants to have. The architecture shown in the above figure is the most generic one. It combines the functionality of both the static and flexible architectures. The static architecture presents the lowest degree of flexibility. Indeed if one wants to terminate an L-LSP (resp. WB-LSP) at this node he has to make sure to switch the LSP in the right waveband and fiber (resp. fiber). On the contrary the flexible architecture gives the possibility to dynamically redirect higher order LSPs (F-LSPs, WB-LSPs) to lower order ones (L-LSPs, WB-LSPs) through the switching fabric and demultiplexers, and vice-versa. Note that the possible architectures have different impact on LSPs switching but also on the physical performance. Wavelength (resp. WaveBand) conversion may be required at the WXC IPO Working Group 5 draft-dotaro-ipo-multi-granularity-00.txt July 2001 (resp. WB-XC) outputs, and regeneration may also be required at the input and/or output fibers like in classical OXC architectures, but they are not represented here. 3.3. Grooming strategies One of the interests of multi-granularity is to simplify switching procedures of numerous Lambda-LSPs. This is achieved by forming groups of Lambda-LSPs and switching them as a single entity. The groups formed are waveband LSPs or fiber LSPs. The grooming strategy consists in forming Waveband-LSPs and/or Fiber-LSPs (resp. Fiber-LSPs) with Lambda-LSPs (resp. Waveband-LSPs) which do not have the same source or/nor destination in the optical network but, which share a common sub-path across this network. This grooming method is called intermediate grooming with regards to end- to-end grooming. End-to-end grooming can be seen as a peculiar case of intermediate grooming. End-to-end grooming consists in forming higher order LSPs with lower order ones, which have the same source and the same destination in the optical network. End-to-end grooming is the simplest strategy, but it is the combination of both end-to-end and intermediate grooming strategies, which is clearly the most efficient (see Section 3.4). Note that one could decide to form and then establish a waveband or fiber LSP even if this LSP cannot be fully filled with Lambda-LSPs. The following example illustrates these grooming strategies. --- --- | A | | G | ---\ /--- \ / \ / \ / \ / \--- --- --- ---/ | C |-------| D |-------| E |-------| F | /--- --- --- ---\ / \ / \ / \ / \ ---/ \--- | B | | H | --- --- Let us consider in this example that wavebands are composed of 4 wavelengths and that fibers are composed of 4 wavebands. Let us also consider 9 L-LSPs from A to G and 7 L-LSPs from B to H. IPO Working Group 6 draft-dotaro-ipo-multi-granularity-00.txt July 2001 With end-to-end grooming 8 out of the 9 L-LSPs from A to G could be nested in two WB-LSPs, leaving one L-LSP. In the same manner 4 of the 7 L-LSPs from B to H could be nested in one WB-LSP leaving 3 L-LSPs. This would result in having 3 WB-LSPs and 4 L-LSPs between C and F which, could in turn be nested in a F-LSP between these nodes using intermediate grooming strategy. 3.4 Benefits of the approach In optical networks, the main benefits of the multi-granularity approach with waveband switching are the reduction of the number of connections inside each optical cross-connect. 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. With waveband switching, the cost of switching and (de)multiplexing is shared between a group of N (typically N=4 or 8) wavelengths. With fiber switching, when one can switch a whole fiber in the node, the cost of switching is shared by more wavelengths (typically 40, 80, etc.) and there is no demultiplexing. The multi-granularity approach will thus decrease the total cost of each optical node inside the network. To illustrate this point, for an optical node which switches 1000 wavelengths without the multi-granularity approach, the number of ports can be decreased up to more than 75% (see [OFC01-MGOXC]) with the introduction of multi-granularity and waveband switching inside the optical network, using the grooming strategy defined in part 3.3 (end-to-end grouping and intermediate grouping) and the node architecture given in Section 3.2. This reduction is even more important for higher node capacity. The other benefits of multi-granularity and waveband switching is also to make the design of optical nodes easier by decreasing optical losses (and thus relaxing the constraints on optical amplification) and by reducing the issue of optical filter cascade (no filtering with fiber switching, easier filtering with waveband switching compared to wavelength switching). Of course this easier design of optical nodes will decrease the total cost of the whole optical network. 4. Concept integration in Generalized MPLS 4.1 Multi-Granularity Hierarchy The following definitions are proposed in order to improve the current LSP hierarchy defined in [MPLS-LSP] used to specify the LSP multiplexing capabilities of TE links: - Waveband . A waveband is a "grouping" of N wavelengths of the same capacity IPO Working Group 7 draft-dotaro-ipo-multi-granularity-00.txt July 2001 (bit-rate). . The number of wavelengths within a given waveband is configurable but hardware dependent - i.e. number of ports in de/multiplexer, de/multiplexer specifications in terms of spectrum width, spacing,... . Each of these wavelengths represents (i.e. transports) one given Lambda-LSP i.e. an L-LSP. - Waveband-LSP (WB-LSP) . A WB-LSP includes one or more (N) L-LSP and is transported across MG-OXC in one (or more than one) waveband(s). Notice that waveband nesting (i.e. wavebands into wavebands) is possible but add unnecessary complexity. Therefore this concept is not studied in this document. - Fiber . A fiber is a grouping of M wavebands. . Wavebands within a fiber can either be contiguous or interleaved depending on the capabilities of the system hardware (multiplexer, demultiplexer). . The number of wavebands within a given fiber is configurable but hardware dependent - i.e. number of ports in de/multiplexer, de/multiplexer specifications in terms of spectrum width, spacing,... - Fiber-LSP (F-LSP) . A F-LSP includes one or more (M) WB-LSP and is transported across MG-OXC in one single fiber. Given the above definition of the Multi-Granularity hierarchy, a Lambda-LSP (L-LSP) can now be considered as a particular case of a Waveband-LSP (WB-LSP) defined when the number of wavelengths within a waveband is N=1. The following figure illustrates the Multi-Granularity hierarchy defined here above: Lambda[1] Lambda[2] ... Lambda[N] | | | | | | WB-LSP[1] WB-LSP[2] WB-LSP[N] (L-LSP, N=1) | | | | | | <----- Waveband[1] ------> <- WB[2]-> <- WB[3]-> <- WB[M]-> | | | | | | | | WB-LSP <-- WB-LSP --> WB-LSP | | | IPO Working Group 8 draft-dotaro-ipo-multi-granularity-00.txt July 2001 | | | <-------------------- Fiber ---------------------> | | F-LSP 4.2 LSP Hierarchy The [GMPLS-ARCH] document considers waveband switching a particular case of lambda switching. As specified, a waveband represents a set of contiguous wavelengths, which can be switched together to a new waveband. However, this waveband switching definition doesnÆt introduce a new LSP Encoding Type. This means that the corresponding generalized label sent back to the upstream node precludes the usage of wavelength label on such links. Moreover, such a definition assumes that the underlying layer (spatial switching layer) is dedicated to support only waveband switching. Since the scope of this document is to introduce multi-granularity at the optical layer, one has to extend this definition and consider a Lambda-LSP (L-LSP) as a particular case of Waveband-LSP (WB-LSP). Taking into account the previous definition of the Multi-Granularity hierarchy, the LSP Hierarchy can be represented as follows if we except the TDM-LSP layer: Packet-LSP <---> PSC Interface | | | v Waveband-LSP <---> WBSC Interface | | | v Fiber-LSP <---> FSC Interface Therefore, we consider here that a WBSC interface behaves by default as an LSC interface when the number of wavelength comprised into a specific waveband is equal to 1. 4.3 Impact on GMPLS Protocol Suite 4.3.1 GMPLS Signalling As described in [GMPLS-SIG], waveband switching definition implicitly refers to an inverse multiplexing mechanism were one can request a 10 Gbps L-LSP while the underlying wavelength have a 2.5 Gbps bit-rate. Therefore, when requesting such L-LSP four labels are IPO Working Group 9 draft-dotaro-ipo-multi-granularity-00.txt July 2001 returned back to the upstream node as waveband label (see Section 3.3 in [GMPLS-SIG]). Here, the definition of a waveband requires defining a Multiplier field as it is already the case in [GMPLS-SSS] and [GMPLS-G709]. This because at the opposite of the inverse multiplexing case the upper layer must preserve the visibility of the L-LSP embedded into the waveband. Since the Multiplier enables to setup N x L-LSP, one can suggest to use this definition in order to define a Waveband-LSP (WB-LSP). When requesting an L-LSP the Multiplier field (MT field) would be equal to 1 and when requesting a Waveband including N wavelengths the Multiplier field will be equal to N. However, in order to preserve backward compatibility with the current Generalized Label Request defined in [GMPLS-SIG] Section 3.1, one could also define an additional dedicated flag in order to determine whether or not the Multiplier field must be considered. Therefore, when this flag is set to zero, the current Lambda-LSP Label Request is left unchanged. 4.3.2 GMPLS Traffic-Engineering Routing Extensions Clearly, the support of interfaces with multiple switching (i.e. multiplexing) capabilities such as LSC (Lambda Switching Capable), WBSC (Waveband Switching Capable) and FSC (Fiber Switching Capable) must be flooded through the use of an IGP routing protocol such as OSPF and IS-IS. For this purpose extensions of the Link Multiplexing Capability defined in [MPLS-HIER] can be considered. For this purpose, one could propose to enhance the traffic- engineering extensions defined for GMPLS purposes (see [GMPLS-OSPF- TE] and [GMPLS-ISIS-TE]) by extending the Link Multiplexing Capability sub-TLV (type 10) of the Link-TLV as defined for OSPF in [MPLS-HIER]. For IS-IS, the same enhancement can be provided to the Link Multiplex Capability which is defined as a sub-TLV in [MPLS- HIER] of the extended IS reachability TLV (type 22) as specified in [ISIS-TE]. Additionally, it seems also quite reasonable to use a dedicated sub- TLV to indicate the min/max number of wavelength (N) and the min/max number of waveband (M) supported respectively by WBSC interfaces and FSC interfaces. These capabilities could be included in a dedicated sub-TLV similarly to the one defined in [GMPLS-IGP-709]. 4.3.3 Requirement Statements For the first step of multi-granularity approach, very few modifications or extensions are needed, as described in the above sections. A more complete and optimized multi-granularity optical network will require further enhancements to the GMPLS Signaling and TE-Routing IPO Working Group 10 draft-dotaro-ipo-multi-granularity-00.txt July 2001 protocols. Those requirements are for further study since impacting several working groups of the sub-IP area. 5. Security Considerations Security considerations are outside of the scope of this document. 6. Reference 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-CRLDP] P.Ashwood-Smith, L.Berger et al., æGeneralized MPLS û Signaling Functional DescriptionÆ, Internet Draft, Work in progress, draft-ietf-mpls-generalized-cr-ldp-03.txt, May 2001. 3. [GMPLS-RSVP] P.Ashwood-Smith, L.Berger et al., æGeneralized MPLS û Signaling Functional DescriptionÆ, Internet Draft, Work in progress, draft-ietf-mpls-generalized-rsvp-te-03.txt, May 2001. 4. [GMPLS-SIG] P.Ashwood-Smith, L.Berger et al., æGeneralized MPLS - Signaling Functional DescriptionÆ, Internet Draft, Work in progress, draft-ietf-mpls-generalized-signalling-04.txt, March 2001. 5. [GMPLS-SSS] E.Mannie et al., æGeneralized MPLS Signalling û SONET/SDH ExtensionsÆ, Internet Draft, Work in progress, draft- ietf-ccamp-gmpls-sonet-sdh-01.txt, June 2001. 6. [GMPLS-G709] M.Fontana et al., æGeneralized MPLS Signalling û G.709 OTN ExtensionsÆ, Internet Draft, Work in progress, draft- fontana-ccamp-gmpls-g709-00.txt, July 2001. 7. [GMPLS-G709-IGP] G.Gasparini et al., æTraffic Engineering Routing Extensions to OSPF and ISIS for GMPLS Control of G.709 Optical Transport NetworksÆ, Internet Draft, Work in progress, draft- gasparini-ccamp-gmpls-g709-ospf-isis-00.txt, July 2001. 8. [MPLS-HIER] K.Kompella et al., æLSP Hierarchy with MPLS TEÆ, Internet Draft, Work in progress, draft-ietf-mpls-lsp-hierarchy- 02.txt, February 2001. 9. [OFC01-MGOXC] L.Noirie et al., æImpact of intermediate traffic grouping on the dimensioning of multi-granularity optical networksÆ, Paper presented during OFC 2001. 7. Acknowledgments The authors would like to thank Bernard Sales, Emmanuel Desmet and Amaury Jourdan for their constructive comments and inputs. 8. Author's Addresses IPO Working Group 11 draft-dotaro-ipo-multi-granularity-00.txt July 2001 Emmanuel Dotaro Senior Planning Team Leader Alcatel R&I ONA Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-4723 Email: emmanuel.dotaro@alcatel.fr Dimitri Papadimitriou Optical Networking Senior R&S Engineer Alcatel NSG-NA IPO Francis Wellesplein 1, B-2018 Antwerpen, Belgium Phone: +32 3 240-8491 Email: dimitri.papadimitriou@alcatel.be Ludovic Noirie Research Engineer Alcatel R&I OSS Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-1136 Email: ludovic.noirie@alcatel.fr Laurent Ciavaglia Research Engineer Alcatel R&I ONA Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-4429 Email: laurent.ciavaglia@alcatel.fr Martin Vigoureux Research Engineer Alcatel R&I OSS Route de Nozay 91460 Marcoussis, France Phone: +33 1 6963-1852 Email: martin.vigoureux@alcatel.fr IPO Working Group 12 draft-dotaro-ipo-multi-granularity-00.txt July 2001 Full Copyright Statement "Copyright (C) The Internet Society (date). 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