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Optical Networking (part 2)

Optical Networking (part 2). Mark E. Allen, Ph.D. mark.allen@ieee.org. Review of Transmission (Transport) Technologies, Architectures and Evolution (Adapted from Shikuma (RIT) Notes. Asynchronous Data Rates. Digital Signal Level 0 DS0 64 Kb/s

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Optical Networking (part 2)

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  1. Optical Networking (part 2) Mark E. Allen, Ph.D. mark.allen@ieee.org

  2. Review of Transmission(Transport) Technologies,Architectures and Evolution(Adapted from Shikuma (RIT) Notes

  3. Asynchronous Data Rates • Digital Signal Level 0 DS0 64 Kb/s • internal to equipment • Digital Signal Level 1 DS1 1.544 Mb/s • intra office only (600 ft limit) • Digital Signal Level 3 DS3 45 Mb/s • intra office only (600 ft limit) • T1 Electrical (Copper) Version of DS1 1.544 Mb/s • repeatered version of DS1 sent out of Central Office • T3 Electrical (Copper) Version of DS3 45 Mb/s • repeatered version of DS3 sent out of Central Office

  4. Asynchronous Digital Hierarchy DS0 (a digitized analog POTS circuit @ 64 Kbits/s) DS3 DS1 DS0 24 DS0s = 1 DS1 28 DS1s = 1 DS3 Asynchronous Optical Line Signal N x DS3s Asynchronous Lightwave Systems typically transport traffic in multiples of DS3s i.e.... 1, 3, 12, 24, 36, 72 DS3s

  5. Asynchronous NetworkingManual DS1 Grooming/Add/Drop D S X 1 D S X 1 D S X 3 D S X 3 LW LW M13 M13 DS3 DS3 DS1 • Manually Hardwired Central Office • No Automation of Operations • Labor Intensive • High Operations Cost • Longer Time To Service

  6. Some Review Questions • What does the acronym SONET mean? • What differentiates SONET from Asynchronous technology? • What does the acronym SDH mean?

  7. The Original Goals of SONET/SDH Standardization • Vendor Independence & Interoperability • Elimination of All Manual Operations Activities • Reduction of Cost of Operations • Protection from Cable Cuts and Node Failures • Faster, More Reliable, Less Expensive Service to the Customer

  8. SONET RatesDS3s are STS-1 Mapped DS0 (a digitized analog POTS circuit @ 64 Kbits/s) STS-1 51.84 Mbits/s DS1 DS0 DS3 24 DS0s = 1 DS1 (= 1 VT1.5) 28 DS1s = 1 DS3 = 1 STS-1 SONET Optical Line Signal OC-N = N x STS-1s N is the number of STS-1s (or DS3s) transported

  9. SONET and SDH OC level STM level Line rate (MB/s) OC-1 - 51.84 OC-3 STM-1 155.52 OC-12 STM-4 622.08 OC-48 STM-16 2488.32 OC-192 STM-64 9953.28

  10. PTE PTE STE STE PTE PTE LTE LTE PTE PTE SONET Layering for Cost Effective Operations DS-3 DS-3 DS-3 DS-3 DS-3 DS-3 OC-3 TM OC-3 TM SONET Section SONET Line SONET Path PTE = Path Terminating Element LTE = Line Terminating Element STE = Section Terminating Element TM = Terminal Multiplexor DS = Digital Signal

  11. SONET Point-to-Point Network Repeater Repeater TM TM Section Line Path Section Overhead STS-1 Frame Format STS-1 Synchronous Payload Envelope STS-1 SPE Path Overhead Line Overhead

  12. Protection Schemes: 1 + 1 Network Protection Working Facility Protection Facility (Source) (Destination) 1 + 1 Protection Switching (50% bandwidth utilization)

  13. . . . 1 for N (1:N) Network Protection Working Facility 1 2 3 Protection Facility (Source) (Destination) 1:n Protection Switching (Bandwidth Efficiencies)

  14. Protection and Restoration Path Protection Line Protection (Loopback) D1 D1 D2 D2 S S 1 + 1 1:n

  15. UPSR Rx Tx Rx Work Protect Tx Rx Unidirectional/Path Switched Ring (UPSR)

  16. BLSR 4 fiber supports span switching 2 fiber doesn’t Work Protect Bidirectional/Line Switched Ring (BLSR) 2 fiber, 4 fiber

  17. Typical Deployment of UPSR and BLSR in RBOC Network Regional Ring (BLSR) BB DACs Intra-Regional Ring (BLSR) Intra-Regional Ring (BLSR) WB DACs Access Rings (UPSR) WB DACS = Wideband DACS - DS1 Grooming BB DACS = Broadband DACS - DS3/STS-1 Grooming Optical Cross Connect = OXC = STS-48 Grooming DACS=DCS=DXC

  18. Emergence of DWDM • Some Review Questions • What does the acronym DWDM mean? • What was the fundamental technology that enabled the DWDM network deployments?

  19. WDM NE First Driver for DWDMLong Distance Networks BLSR Fiber Pairs BLSR Fiber Pairs WDM NE • Limited Rights of Way • Multiple BLSR Rings Homing to a few Rights of Way • Fiber Exhaustion

  20. 40km 40km 40km 40km 40km 40km 40km 40km 40km TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM Conventional Optical Transport - 20 Gb/s OC-48 OC-48 OC-48 OC-48 OC-48 120 km OC-48 120 km 120 km OC-48 OC-48 OLS TERM OLS RPTR OLS TERM OLS RPTR OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 Fiber Amplifier Based Optical Transport - 20 Gb/s Key Development for DWDM Optical Fiber Amplifier Increased Fiber Network Capacity

  21. Transporting Broadbandacross Transmission Networksdesigned for Narrowband

  22. Core Router Core Router RAS RAS Core Router RAS Access Router RAS RAS Access Router Core Router RAS ATM Switch ATM Switch RAS RAS RAS Core Router ATM Switch ATM Switch RAS RAS Access Router RAS Core Router RAS Access Router RAS RAS RAS Access Router ATM Access ATM Access ATM Access ATM Access Data SP Public/Private Internet Peering EtherSwitch EtherSwitch ATM Access ATM Access Backbone SONET/WDM T1/T3 IP Leased-Line Connections RAS Farms ATM Switch T1/T3 FR and ATM IP Leased-Line Connections T1/T3/OC3 FRS and CRS

  23. High Capacity Path Networking IP router • Existing SONET/SDH networks are a BOTTLENECK for Broadband Transport • Most Access Rings are OC-3 and OC-12 UPSRs while most Backbone Rings are OC-48. Transport of rates higher than OC-48 using the existing SONET/SDH network will require significant and costly changes. Clearly upgrading the SONET/SDH network everytime broadband data interfaces are upgraded based increased IP traffic is not an appropriate solution. IP router IP router STS-12c/48c/... STS-3c Existing SDH-SONET Network

  24. SONET NMS SONET XC SONET SONET ADM/LT ADM/LT WDM WDM LT LT IP/SONET/WDM Network Architecture OC-3/12 [STS-3c/12c] OC-3/12 [STS-3c/12c/48c] OC-48 EMS EMS Access OC-12/48 . . Routers/ Core IP Node . Core IP Node SONET Transport Network . Enterprise . Servers . OTN NMS OC-3/12/48 [STS-3c/12c/48c] OC-3/12/48 [STS-3c/12c/48c] l1, l2, ... Pt-to-Pt WDM Transport Network LT = Line Terminal EMS = Element Management System NMS = Network Management System IP = Internet Protocol OTN = Optical Transport Network ADM = Add Drop Multiplexor WDM = Wavelength Division Multiplexing

  25. l1 l1 l2 l2 lN lN Optical Network Evolution mirrorsSONET Network Evolution Point-to-Point WDM Line System Multipoint NetworkWDM Add/Drop WDMADM WDMADM li lk Optical Cross-ConnectWDM Networking OXC

  26. IP/OTN Architecture EMS . Core Data Node . . mc: multi-channel interface (e.g., multi-channel OC-12/OC-48) mc OTN NMS OXC EMS EMS OXC OXC mc . . Access Routers Core Data Node Core Data Node . mc Optical Transport Network . Enterprise Servers mc . . IP = Internet Protocol OTN = Optical Transport Network OXC = Optical Cross Connect WDM = Wavelength Division Multiplexing EMS = Element Management System NMS = Network Management System

  27. Restoration on the backbone • SONET rings • Simple and do the job today • Inefficient and inflexible • Diversely routed working and protect • Next generation options • “Virtual rings” • Mesh with shared protect • Optical rings • Optical mesh

  28. What are the restoration requirements? • Recovery from failures • Equipment failures • Cable cuts • Four 9’s? • Down 52 minutes per year. • Five 9’s? • Down 5 minutes per year. • Need to satisfy the users requirements: Service Level Agreement (SLA) • Service degradation varies by application • 911 calls, voice, video, ATM, Frame, IP • Do customers want to pay for 50ms recovery from a cut? • Wide area rings vs. Local area

  29. Protection & Restoration of Optical Networks

  30. Terminology • Protection • Uses pre-assigned capacity to ensure survivability • Restoration • Reroutes the affected traffic after failure occurrence by using available capacity • Survivability • Property of a network to be resilient to failures

  31. Classification of Schemes

  32. Reactive / Proactive • Reactive • When an existing lightpath fails, a search is initiated to find a new lightpath which does not use the failed components. (After the failure happens) • It cannot guarantee successful recovery, • Longer restoration time • Proactive • Backup lightpaths are identified and resources are reserved along the backup lightpaths at the time of establishing the primary lightpath itself. • 100% restoration guarantee • Faster recovery

  33. Link Based vs. Path Based • Link-based • Shorter restoration time • Less efficient. • Can only fix link failures • Path-based • longer restoration time • More efficient.

  34. Dedicated vs. Multiplexed Backup • Dedicated backup • More robust • Less efficient. • Backup multiplexing • Less robust • More efficient.

  35. Primary Backup MUX • Wavelength channel to be shared by a primary and one or more backup paths

  36. Resilience in Optical Networks • Linear Systems • 1+1 protection • 1:1 protection • 1:N protection • Ring-based • UPSR: Uni-directional Path Switched Rings • BLSR: Bi-directional Line Switched Rings • Mesh-based • Optical mesh networks connected by optical cross-connects (OXCs) or optical add/drop multiplexers (OADMs) • Link-based/path-based protection/restoration • Hybrid Mesh Rings • Physical: mesh • Logical: ring

  37. Unidirectional WDM Path Protected Rings • 1+1 wavelength path selection • Signal bridged on both protection and working fiber. • Receiver chooses the better signal. • Failure: • Destination switches to the operational link. • Revertive /Non revertive switching • No signaling required.

  38. Bidirectional Line switched Ring • Shares protection capacity among all the spans on the ring • Link failure • Working traffic from 1 fiber looped back onto opposite direction. • Signaling protocol required • Node failure • Line switching performed at both sides of the failed node.

  39. 2-Fiber WDM Ring

  40. BLSR - 4 Fiber • Fibers • 2 working • 2 protection • Protection fiber: no traffic unless failure. • Link Failure. • APS channel required to coordinate the switching at both ends of a failure.

  41. 4-Fiber WDM Ring.

  42. 4-Fiber WDM Ring After a Link Failure

  43. 4-Fiber WDM Ring After a Node Failure

  44. Path Layer Mesh Protection • Protect Mesh as a single unit • Pre-computed routes • 1+1 path protection • Protection route per light path • Protection route per failure. • On the fly route computation. • Centralized route computation and coordination • Route computation and coordination at end nodes. • Distributed route computation at path ends. • Decompose into protection domains. • Pure rings • P cycles

  45. Mesh Topologies • Fibers organized in protection cycles. • Computed offline • 4 fibers of each link is terminated by 4 2X2 protection switches • Before link failure, switches in normal position. • After failure, switches moved to protection state and traffic looped back into the protection cycles.

  46. 2X2 Switch

  47. Protection Cycles (cont’d) • Criterion for protection cycles. • Recovery from a single link failure in any optical network with arbitrary topology and bi-directional fiber links • All protection fibers are used exactly once. • In any directed cycle both protection fibers in a pair are not used unless they are in a bridge

  48. Protection Cycles

  49. Protection Cycles (cont’d)

  50. Network With Default Protection Switching

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