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Generalized MPLS Plan de controle basé sur IP pour les réseaux optiques

Deuxième journée française sur l'IETF Decembre 2002 - Paris, France. Generalized MPLS Plan de controle basé sur IP pour les réseaux optiques. Papadimitriou Dimitri Network Technology and Analysis dimitri.papadimitriou@alcatel.be. Introduction. Today Connection Service Requests. NMS. NMS.

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Generalized MPLS Plan de controle basé sur IP pour les réseaux optiques

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  1. Deuxième journée française sur l'IETF Decembre 2002 - Paris, France Generalized MPLSPlan de controle basé sur IP pour les réseaux optiques Papadimitriou Dimitri Network Technology and Analysis dimitri.papadimitriou@alcatel.be

  2. Introduction

  3. Today Connection Service Requests NMS NMS Network Operation Center Network Operation Center Network Operation Center FAX FAX NMS NMS NMS I/f between vendor A and B’ I/f between vendor B’ and B” I/f between vendor B’’ and C Standard SDH data plane but all complexity in Management Plane Source Router Dest. Router Metro Vendor A CORE Vendor B Metro Vendor C It works… but actually not a long term solution !!!

  4. How are we approaching the problem? • Generalized MPLS (GMPLS): a set of mechanisms and protocols intended to make switching layers of a network more dynamic in their operation (and in particular the SDH/Sonet, G.709 (pre-)OTN and Ethernet) compatible with the parallel evolution in the IP/MPLS domain • Extend the functions & capabilities of MPLS to work with Optical equipment (and more generally any kind of switching equipment) • Define appropriate architectures and frameworks for this to happen with modern equipment • Define mechanisms strategies for the support of legacy TDM and Optical equipment that was not designed to be controlled • Extend the capabilities of MPLS protocols to operate with TDM and Optical equipment (instead of re-inventing new paradigms) • Standardise GMPLS to ensure interoperability and investment protection for Service Providers • Generalized MPLS would become a super-set of MPLS

  5. An «OPEN» GMPLS Philosophy Research - Academic world Manufacturer's world New SDH & OTN products Useful features being implemented Operational world Abstract world OTN ITU-T Standards Potential new services GMPLS for Optics ASTN - ASON Standards Operational large network GMPLS pre-std ’s Routing RFCs and drafts MPLS RFCs and drafts Engineering World

  6. GMPLS Concepts and Technology Evolution from IETF Perspective

  7. Transmission & Control Plane Evolutions 1970 1995 Today 20xx 20xx Analog (copper) Digital Optical (analog, fiber) point-to-point Transmission Switched Optical packet switching Digital Switching (SDH) Optical Switching (pre-)/OTN Transport plane Framing dependent Framing independent Operator-assisted/centrally managed provisioning Automated & Distributed (GMPLS control plane) ?? Control/management plane Transition Framing dependent meaning LOVC/HOVC/MSn/RSn/OSn switching

  8. GMPLS Objectives Dimension Space Automation Level Operator Resource Optimization Parameter (flexibility) mainly cost dependent May depend on other variables Network Resource Optimization Distribution Level Other criteria Other criteria are mainly (control plane): Availability - Robustness - Scalability but also Survivability(transport plane)

  9. Evolution of a Standard • Step 1. MPLS: Multi-Protocol Label Switching • IP packet based • Traffic Engineering for Packet LSPs (MPLS-TE - Step 2) • Step 3. MPlS: Multi-Protocol Lambda Switching • MPLS control applied on optical channels (wavelengths/lambda’s) & first “optical” IGP TE extensions • New Protocol introduction for Link Management (LMP) • Step 4. GMPLS: Generalized MPLS • MPLS control applied on layer2 (ATM/FR/Ethernet), TDM circuits (SDH/Sonet) and Optical channel and • IGP TE extensions including OSPF & IS-IS • GMPLS: “separation” b/w Technology dependent and independent • LMP extended to “passive devices” via LMP-WDM • GMPLS covers G.707 SDH, G.709 OTN… IETF 46-48 IETF48-49 IETF50-51 IETF52-55+

  10. From MPLS to GMPLS - Evolution 1996-1998 Transport Plane Evolution IETF - MPLS WG LDP - CR-LDP Not within Optical Networking Priorities MPLS-TE RSVP-TE IGP-TE (Area) “Optical” 1998-2001 Framework MPlS ISP - CLEC impact LMP & LMP-WDM Break-out was the introduction of legacy ITU-T technologies SDH/Sonet 2000 IETF - CCAMP WG GMPLS CR-LDP GMPLS GMPLS IGP-TE (Area) G.709 OTN Slowdown (perceived from mid’01) low impact on Standards but resulted in consolidation & affecting “photonic” evolution GMPLS RSVP-TE Consolidation GMPLS P&R (Recovery) ILEC impact HPN - MRN Re-Charter GMPLS IGP-TE (Multi) 2002-2004 OIF UNI/NNI ASON Model Synchronisation after 2002 OIF ITU-T SG 15

  11. The Early Stage: MPlS • Each OXC includes the equivalent of MPLS-capable Label-Switching Router (LSR) • MPLS control plane is implemented in each OXC • Lambda LSPs (control plane entities) are considered similarly to MPLS Label-Switched Paths (LSPs) • Selection of wavelengths (or lambdas) and OXC ports is considered as similar to the label selection using MPLS • MPLS signaling protocols (such as RSVP-TE, CR-LDP) are adapted for Lambda LSP setup/delete/etc. • IGPs (such as OSPF, ISIS) with “optical” traffic-engineering extensions used for topology/resource discovery using IP address space (no “reachability extensions”)

  12. Label & Lambda Switching equivalence Generalized Label Space  Wavelength Identifier Space - Label Processing at control plane level only Label Space  FEC - Label processing at control and transport level CommonControl Plane MPlS Controller MPLS Controller IF in Label in IF out Label out IF in Label in IF out Label out 2 2 5 5 6 6 4 4 8 4 7 9 9 2 4 7 3 6 8 9 3 4 7 9 mapping mapping Optical Channel Matrix l1, l2 l1, l2 1 1 1 O/E/O O/E/O 1 l1 Packet Switching Matrix 3 x 3 l1, l2 l1, l2 2 2 2 2 O/E/O O/E/O 3 x 3 l2 l1, l2 l1, l2 3 O/E/O O/E/O 3 3 3 DeMux Mux Label Read Label Write Label Switched Router Optical Cross-Connect

  13. Towards Distributed (Common) Control Plane Centralized Distributed Evolution of the NMS includes SNMPv2/3, COPS, LDAP and other Traffic Engineering/ Optimization Tools and QoS Policing SLS/SLA Mgt Management Plane Network Management System NMS Management Channels EMS IP Distributed Control Channels Network Controller Control Plane Network controllers (or GMPLS controllers) can STILL be either co-located or non-co-located within the network device (SDH XC, OADM, OXC, PXC, etc.) Control Plane Network Device Transport Planes Network Device Transport Channels Transport Planes IP Control Channels implemented using IF/IB - IF/OB or OF/OB (signalling transport mechanisms) enabling the transport of “control IP packets” exchanged throughout IP distributed control plane

  14. IP Distributed Control Plane Management Plane Network Management System • IP Control Channels enabling the transport of “control IP packets” exchanged throughout IP distributed control plane Management Channels • IP Control Channels implemented using IF/IB - IF/OB or OF/OB (signalling transport mechanisms) IP Control Channels IP Distributed Control Plane • (G)MPLS Controllers can be either co-located or non-co-located within the network device (ATM/MPLS LSR, SDH XC, OADM, OXC, PXC, etc.) Network Controller • IP Distributed Control Plane topology MAPS the Transport Plane topology - without precluding “virtual topologies” Network Device Transport Channels Transport Plane(s)

  15. Pre-OTN Approaches • Fully transparent: Non-intrusive monitoring of optical signal (LOS) • FEC frame termination • transparent bit stream signal • non-intrusive monitoring STM-N signal (RSn and MSn overhead) • pre-OTN case: 4 x STM-16 multiplex • FEC frame terminated • transparent STM-N MSn signal (repeater functionality) • non-intrusive monitoring of MSn signal • FEC frame terminated • transparent AUG-N signal (back-to-back LTE) • non-intrusive monitoring of HOVC signals • Pre-OTN digital wrapper frame terminated • transparent bit stream signal • non-intrusive monitoring STM-N signal (RSn and MSn overhead) • … Thus interoperability at the transport plane level was not that obvious!

  16. From MPlS to GMPLS • MPlS assumed only 2 transport layers • Assumption: SDH/Sonet used as framing for p2p links (payload: IP/MPLS or Ethernet) • Therefore core/backbone networks including • “IP/MPLS” packet or Ethernet MAC layer • Optical (pre-OTN based) layer • However, current transmission technologies also include: • SDH (ITU-T G.707) - Sonet (ANSI T1.105) • OTN (ITU-T G.709) • Ethernet (LAN and WAN) • ATM and Frame Relay • Why to consider them ? • Same “drivers” and needs as IP/MPLS and optical layer • Enable fully integrated model • Eliminate the need for UNI specific protocol • Provide complete of MPLS-TE protocol extensions

  17. MPLS - GMPLS Convergence Initial Situation at the IETF Not “classical” IP or IETF topics Packet Network using MPLS Optical Network using GMPLS Traffic Engineering Optical/TDM LSP Provisioning Explicit routed LSP’s Network Resilience Legacy Transmission Protection and Restoration Recovery LSP’s Virtual Private Networks MPLS - BGP/VPN GMPLS - (XXX or BGP ?)/GVPN Class Of Service LSP’s as TE tunnels (FA Concept) Optical CoS (LSP Multiplexing) Competing w/ IP QoS Approach The challenge is how to extend the MPLS-TE Protocol suite to achieve these functions in the optical domain (estimation in ‘00: 2 years - today a minimum of 1 additional year is expected to consolidate 2 first steps) But the problem is related to BGP

  18. GMPLS Key Concepts • Re-use of MPLS-TE concepts for the definition of distributed control plane protocols applicable to non-packet or “optical” oriented networks: • Optical channels/TDM Circuits/etc. define Lambda/TDM/etc. switched path Generalization of label spaces: wavelengths, sub-channels, etc.) • Generalization of IP Address Prefix to “non-packet” terminating interfaces further extended to unnumbered interfaces => allows for separation between transport and control plane • Generalization of TE Link concepts and attributes to “non-packet” resources (in particular: OPTICAL) • Virtual TE Links => Forwarding Adjacencies (FA) => Mapping of several transport plane layers in the control plane (LSP Regions) which delivers the same scalability as control plane associated to layered transport plane technologies • Link Bundling => TE Link recursion • Further generalization to accommodate unnumbered FA and FA bundling • Development of graceful/hitless restart mechanisms (signalling & routing) for increasing reliability taking advantage of transport/control separation

  19. Transport Layers and G.709 TE Links • Hierarchical (Overlaid) Transport Layers • Tributary Slots (sub-channel) • ODU1 (2.5 Gbps) • ODU2 (10 Gbps) • ODU3 (40 Gbps) • or combination • Wavelength (channel) • Fiber (interface) • Discrete Bandwidth Signals • OMS and OCh TE Links Switching Granularity l3 l2 l3 l4 l1 l5 Sub-Channel 1 Sub-Channel 1 Sub-Channel 2 Sub-Channel 2 Control Plane View ODU TE Link ... ... Sub-Channel N Sub-Channel N Channel 1 OCh TE Link Channel N OMS TE Link

  20. Generalized MPLS - Switching Layers GMPLS Signalling uniformly address the issues of LSP establishment (setup) /teardown (delete) through different switching (i.e. networking) layers => GMPLS  “optical” and “optical”  GMPLS ( common control plane) • Classical Packet LSPs in the MPLS switching layer terminating at PSC interfaces (LSR I/f) Packet (IP/MPLS) Switching Layer • TDM LSPs corresponding to STS SPE/ HOVC switching layer terminating at OXC (Label=Sub-Channel, OXC=E-O with TDM I/f and DWDM system) Packet LSP TDM Switching GMP L S Framing • SDH/Sonet or Ethernet used as FRAMING (Adaptation only)  no TDM LSP defined TDM LSP • Lambda LSP (L-LSP) corresponding to optical channel switching layer terminating at OXC/PXC (Label=Wavelength, OXC=E-O-E Matrix or PXC= O-O Matrix with LSC I/f * Wavelength Switching Layer Lambda LSP • Fiber LSP corresponding to fiber switching layer terminating at fiber cross-connects interconnected by fiber bundles (Label=Fiber, Fiber Cross-Connect with FSC interfaces) Fiber (Spatial) Switching Layer Fiber LSP * The wavelength-switching layer can also include waveband switching AAMS, LB, JMS - 10

  21. LSP Hierarchy (Nesting) and FA-LSP

  22. Key Enablers - Advantages • Lambda/TDM/etc. LSP’s w/ label space: wavelengths/timeslot/etc. • Provide flexibility in (link) resource selection (for bi-directional LSP setup) • Generalization of IP Address Prefix to “non-packet” terminating interfaces • Avoid definition of dedicated (new) address space per technology - further extended to unnumbered interfaces • Control/Transport plane separation (resilience) and avoid waste of packet terminating address space values • Generalization of TE Link concepts and attributes to “non-packet” resources (in particular OPTICAL) • Virtual TE Links (Forwarding adjacencies): Mapping of several transport plane layers in control plane (a.k.a. LSP Regions) which delivers the same scalability as the one provided by layered transport plane technologies => SCALABILITY (routing) • Link Bundling => SCALABILITY (routing) allowing TE Aggregation => Specific (component) Resource Selection (local policy) provides robustness and contention avoidance

  23. IETF GMPLS Work per Plane Not done at the IETF, specific task of the ITU-T (SG15) for SDH/OTH, IEEE for Ethernet, etc. Already widely developed but we need now to manage the control plane, IETF developments for SNMP MIBs. Right in the IETF scope since application of MPLS generalization (GMPLS is a super-set of MPLS) Management Plane Forwarding Plane Control Plane E.g.TMN or SNMP or TL-1 Signaling Plane Adapted from IP such as RSVP-TE or CR-LDP Routing Plane Adapted from IP such as OSPF-TE, ISIS-TE E.g. SDH/SONET, G.709, Ethernet GMPLS

  24. Global Picture (IETF View) User Admin Domain User Admin Domain User Admin Domain Internet Provider C Admin Domain Inter-domain Inter-domain Administrative Domain A Administrative Domain B Inter-domain Intra-domain Intra-domain Inter-domain Inter-domain GMPLS Protocol suite applies at intra- and inter-domain interfaces I-NNI Administrative Domain C Intra-domain Actually, GMPLS is “model independent” it just follows the well known “internet” engineering principles from the node to the area then from the area to the Autonomous System (intra-carrier) and last between AS’s (inter-carrier)

  25. GMPLS Building Blocks Technology Indpt Technology Dept Meta Extensions Starting Point - MPLS Architecture and MPLS-TE Framework and requirements GMPLS Architecture Others Core signaling (TE-)Link Management Technology extensions(*) Generalized VPN Protection & Restoration Core TE - Routing Transmission Background (*) Includes SDH/Sonet and G.709 OTN

  26. GMPLS Building Blocks draft-ietf-ccamp-gmpls-architecture-03.txt Last Call Framework and requirements GMPLS Architecture draft-ietf-mpls-generalized-signaling-09.txt draft-ietf-mpls-generalized-rsvp-te-09.txt draft-ietf-mpls-generalized-cr-ldp-07.txt Others Proposed Standard Core signaling (TE-)Link Management draft-ietf-ccamp-gmpls-g709-03.txt draft-ietf-ccamp-gmpls-sonet-sdh-07.txt Technology extensions Under AD Review Protection & Restoration Core TE - Routing draft-ietf-ccamp-gmpls-routing-05.txt draft-ietf-ccamp-ospf-gmpls-extensions-09.txt draft-ietf-isis-gmpls-extensions-14.txt draft-ietf-ccamp-lmp-07.txt Under Review Under AD Review MPLS Related draft-ietf-mpls-bundle-04.txt draft-ietf-mpls-lsp-hierarchy-07.txt draft-ietf-mpls-rsvp-unnum-08.txt draft-ietf-mpls-crldp-unnum-10.txt Note: several other more specialized I-d ’s under discussion

  27. CCAMP WG Protection and Restoration Design Team Start Dec’01 Draft-ietf-ccamp-gmpls-recovery-terminology-00.txt To be finalized with the other drafts (cycle) Terminology Mar’02 - IETF 53 Draft-papadimitriou-ccamp-gmpls-recovery-analysis-03.txt To provide an analysis grid to be used to evaluate, compare and contrast the GMPLS based recovery mechanism WG document requested, to be taken on the list Analysis Aug’02 - IETF 54 Draft-bala-gmpls-recovery-functional-01.txt To determine and discuss recovery scenarios to be covered (what’s in what’s out) by the protocol dependent specification Functional Specification Nov’02 - IETF 55 Ongoing effort, first version to be issued after consensus on previous step (expectation ~1Q’03) GMPLS Signalling

  28. Future Developments • Short term: • Keeping track of G.709 OTN evolutions • Shared meshed (multi-layer) recovery and Routing diversity • … we are nearly done ! • Longer term: Tackle “All-Optical” challenges • optical physical routing impairments • transparency issues • optical performance measurement and monitoring • Refine GMPLS management model including • performance management • security and policy • scheduling services • billing/accounting

  29. Global Picture (ITU & OIF View) User Admin Domain User Admin Domain User Admin Domain Single Carrier 1 - Single Administrative Domain Provider C Admin Domain UNI UNI Control Domain B (e.g., vendor 2, core) E-NNI Control Domain A (e.g., vendor 1, metro) I-NNI I-NNI E-NNI E-NNI Control Domain C Multi-vendor Agreement E-NNI E-NNI I-NNI Single Carrier 3 - Single Administrative Domain Single Carrier 2 - Single Administrative Domain GMPLS Protocol suite with interface specific extensions applied at UNI and E-NNI (intra-/inter- carrier) interfaces E-NNI

  30. From the Meta model to the Protocol(s) GMPLS Protocol Suite remains in the very long term (no model) OIF UNI 1.0 GMPLS profile and extensions (shorter term models) OIF NNI 1.0 OIF NNI 1.0 Domain Service & Overlay Control Plane Interconnection Model GMPLS + Extensions G.ASTN (G.807) G.ASON (G.8080) G.dcm, G.rtg and others PNNI + extensions from scratch + new protocols Std body Meta model Abstract model Abstract protocol Real protocol(s) Re-use of well known Internet (existing) principles IETF Track Unified Service Model - Peer & Overlay Control Plane Inter - Connection Model OIF Track ITU-T Track Engineering world: implementation Abstract and Formal world

  31. GMPLS Implementation Survey

  32. Company Type Signaling Protocol SDH/SONET Extensions Software Genealogy Switching Capability Label Type Status Availability Accelight Equip. R Yes External P T L M G S Beta - Agilent Tester R Yes Internal P T L F M G W S Product On sale Alcatel Equip R Yes External T L F G W S Beta On sale Calient Equip. R Ext + TE L F G Beta On sale Ciena Code R Yes External T S Alpha Internal Data Connection Code R Yes Ext + GMPLS P T L F M G W S Product On sale Equipe Equip. R Yes Internal P T G S Alpha internal First Wave Code R + L Internal L F G W Alpha Internal HCL Techno. Code R Yes ISI+TE,GMPLS T G S Develop - Intel Equip. R Yes Internal P T M G S Develop - Japan Telecom Code R Internal - G Develop Internal Juniper Equip. R Yes Internal P M G S Beta Field trial Lumentis Equip. R Ext+GMPLS L G Develop Internal Marconi Equip. R Yes Internal T L F G W S - On sale Movaz Equip. R Yes LabN+GMPLS L G S Product On sale NEC Equip R Yes External T S Product On sale NetPlane Code R Yes Internal P T L F M G W S Product On sale NTT Equip. R External P L M G W Develop Internal Nortel Code L Yes - - M G W S - - Polaris Equip R Yes External T S Develop Internal Tellium Equip. R Yes External T L F G S Alpha Internal Tropic Equip. R External P L F M G W Develop Internal Wipro Code R + L Yes Internal P T M G S - On sale Anonymous 2 - R External L G Develop Internal 24 Equip: 14 Code: 8 R:23 L:3 17 Internal: 9 External: 14 P: 10, T: 14, L: 14, F: 9 M: 10, G:21, W: 9, S: 17 P: 4, A: 4, B: 3, D: 7 On sale: 8 P=PSC, T=TDM, L=LSC, F=FSC M=MPLS label, G=generalized label, W=waveband label, S=SDH/SONET label

  33. Conclusions

  34. Conclusion • GMPLS is not the future, … it is the present • It constitutes an integral part of the coming generation of packet, frame and optical integrated networks providing unified services • NMS proprietary solutions might be pragmatic as a short term solution, they don’t address the current carrier/service provider needs • GMPLS provides common mechanisms applicable to IP and optical layers, allowing interoperable, scalable, parallel, reliable and cohesive evolution of networks in the IP and optical dimensions • Both GMPLS@UNI (at OIF) and GMPLS (at IETF) are standards-based and have their specific domain of use: the debate peer versus overlay is off (if used in their applicability scope then co-existence) • The LSP hierarchy, bundling and hitless restart creates sufficient scalability, flexibility and resiliency for common network operations • The enhanced signaling capabilities GMPLS allow service provider to quickly and efficiently build high capacity agile infrastructures supporting fast connection provisioning • Therefore, GMPLS is critical in any carrier/service provider solution that aims to enable large volumes of traffic in a cost-efficient manner

  35. Thanks for your attention... … Questions ?

  36. References • E.Mannie (Editor) et al., ‘Generalized MPLS Architecture’, Informational Draft, draft-ietf-ccamp-gmpls-architecture-03.txt, February 2002. • Lou Berger (Editor), et al., ‘Generalized MPLS Signaling – Signaling Functional Requirements,’ Internet Draft, Work in progress, draft-ietf-mpls-generalized-signalling-09.txt, August 2002. • Lou Berger (Editor) et al., ‘Generalized MPLS Signaling – RSVP-TE Extensions,’ Internet Draft, Work in progress, draft-ietf-mpls-generalized-rsvp-te-09.txt, October 2002. • Lou Berger (Editor) et al., ‘Generalized MPLS Signaling – CR-LDP Extensions,’ Internet Draft, Work in progress, draft-ietf-mpls-generalized-cr-ldp-07.txt, August 2002. • E.Mannie and D.Papadimitriou (Editors) et al., ‘Generalized MPLS Extensions for SONET and SDH Control’, Internet Draft, Work in progress, draft-ietf-ccamp-gmpls-sonet-sdh-06.txt, August 2002. • D.Papadimitriou (Editor) et al., ‘Generalized MPLS Extensions for G.079 Optical Transport Networks Control’, Internet Draft, Work in progress, draft-ietf-ccamp-gmpls-g709-03.txt, November 2002. • K. Kompella et al., “Routing Extensions in Support of Generalized MPLS”, Internet Draft, Work in progress, draft-ietf-ccamp-gmpls-routing-05.txt, August 2002. • K. Kompella et al., “IS-IS Extensions in Support of Generalized MPLS”, Internet Draft, Work in progress, draft-ietf-isis-gmpls-extensions-14.txt, August 2002. • K. Kompella et al. “OSPF Extensions in Support of Generalized MPLS”, Internet Draft, Work in progress, draft-ietf-ccamp-ospf-gmpls-extensions-08.txt, August 2002.

  37. References • E.Mannie, D.Papadimitriou et al., ‘Extensions to OSPF and IS-IS in support of GMPLS for SDH/SONET Control,’ Internet Draft, Work in progress, draft-mannie-ccamp-gmpls-sonet-sdh-ospf-isis-01.txt, June 2002. • G.Gasparini, D.Papadimitriou et al., ‘TE-Routing Extensions to OSPF and ISIS for GMPLS Control of G.709 Optical Transport Networks’, Internet Draft, Work in progress, draft-gasparini-ccamp-gmpls-g709-ospf-isis-03.txt, June 2002. • K.Kompella, Y.Rekhter, “Signalling Unnumbered Links in RSVP-TE”, Internet Draft, Work in progress, draft-ietf-mpls-rsvp-unnum-07.txt, August 2002. • K.Kompella, Y.Rekhter, “Signalling Unnumbered Links in CR-LDP”, Internet Draft, Work in progress, draft-ietf-mpls-crldp-unnum-07.txt, August 2002. • K.Kompella and Y.Rekhter, LSP Hierarchy with MPLS TE, Internet Draft, Work in progress, draft-ietf-mpls-lsp-hierarchy-07.txt, August 2002. • K.Kompella, Y.Rekhter and L. Berger, “Link Bundling in MPLS Traffic Engineering”, Internet Draft, Work in progress, draft-ietf-mpls-bundle-04.txt, June 2002. • D. Awduche et al., ‘Multi-Protocol Lambda Switching: Combining MPLS Traffic Engineering Control With Optical Cross-Connects,’ Internet Draft, Work in progress, draft-awduche-mpls-te-optical-03.txt, April 2001.

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