1. SONET

2. What is SONET? Synchronous Optical Network standard Defines a digital hierarchy of synchronous signals Maps asynchronous signals (DS1, DS3) to synchronous format Defines electrical and optical connections between equipment Allows for interconnection of different vendors’ equipment Provides overhead channels for interoffice OAM&P SONET Network Element SONET Network Element Digital Tributaries Digital Tributaries

3. Asynchronous Vs Synchronous Assume Maximum Clock Rate Bit-Stuff As Required Assume Maximum Clock Rate Bit-Stuff As Required DS-M DS-(M+1) Asynchronous (aka Plesiochronous) oooooo Use Network Clock Rate Use Pointers To Find Payload Use Network Clock Rate Use Pointers To Find Payload SONET VT1.5 Or STS-M STS-N (M < N) oooooo

4. Digital Signal Hierarchies Most Common Rates Asynchronous SONET VT1.5 (1.7 Mb/s) STS-3 (156 Mb/s) STS-12 (622 Mb/s) STS-48 (2500 Mb/s) 28843361344 Capacity (DS-1 Equiv) DS-1 (1.544 Mb/s) STS-1 (52 Mb/s) [Non-Standardized] STM-1 STM-4STM-16 SDH DS-0 (64 Kb/s) VC-11VC-3 DS: Digital Signal SONET: Synchronous Optical NETwork (US) SDH: Synchronous Digital Hierarchy (ITU) STS: Synchronous Transport Signal STM: Synchronous Transfer Mode VC: Virtual Container VT: Virtual Tributary DS-3 (45 Mb/s)

5. SONET Rates STS-1OC-1 51.840 STS-3OC-3155.520 STS-12OC-12622.080 STS-48OC-482,488.320 STS-192 OC-192 9,953.280 Level Optical Designation Bit Rate (Mb/s) STS=SYNCHRONOUS TRANSPORT SIGNAL OC=OPTICAL CARRIER (“..result of a direct optical conversions of the STS after synchronous scrambling” - ANSI)

6. SONET Network Layers DS3 etc DS3 etc Path Map Services & POH Into SPE Path Protection/Restoration Other Path OA&M Functions Line Combine SPE & LOH Sync & Mux For Path Layer Line Protection/Restoration Other Line OA&M Functions Section Add SOH & Create STS Signal Framing, Scrambling Section OA&M Functions Physical (Photonic ) E/O Conversion Line Code Physical Signal [No additional overhead] MUXLTERegenMUXLTE Regen Services DS3, DS1, etc SONET ADM Path Line Section

7. Case Study: Two Path Layer Processors are Exchanging DS3s SONET Terminal STS-1 OC-1 SONET Terminal STS-1 OC-1 Regen Mux Section Line Path PTE LTE Map services & Path Over- Head into SPE Map SPE & Line Over- Head into STS-N Map STS-N & Section Overhead into “Pulses” Optical Conversion Terminal Regen Path Line Section Photonic

8. Functional Description of SONET Layers OH: Overhead Path Layer Line Layer Section Layer Photonic Layer Information Payload Path OH Line OH Section OH E/O Conversion Transmission over OC-N Function Payload Mapping Error Monitoring Synchronization Multiplexing Error Monitoring Line Maintenance Protection Switch Order Wire Framing Scrambling Error Monitoring Section Maintenance Orderwire E/O Conversion Pulse Shaping Power Level Wavelenght

9. SONET STS-1 Frame Structure Synchronous Payload Envelope (SPE) TOHTOH Ptr 87 Bytes 3 Bytes SPE 87 Columns POHPOH 9 Rows 87 Bytes 3 Bytes t t FIxedStuffFIxedStuff FIxedStuffFIxedStuff Efficiencies Mb/sec% STS1 STS151.84100% SPE (87 col)50.11 96.67% SPE (84 col)48.38 93.33% DS343.23 86.30% 672 DS0’s43.00 82.96% POHPOH

10. STS-1 Payloads 1 VT1.5 (1.7 Mb/sec) DS-1 (1.544 Mb/sec) 27 3 Columns 4 columns VT Group (12 Columns) x 4 VT2 (2.3 Mb/sec) 6 columns VT3 (3.5 Mb/sec) 12 columns VT4 (6.9 Mb/sec) VT Group (12 Columns) VT Group (12 Columns) VT Group (12 Columns) x 3 x 2 SPE (84 Usable Columns) Sub STS-1 Mappings 90 Total Columns POHPOH Ctl & Stuff Information StuffStuff Ctl & Stuff Information StuffStuff Ctl & Stuff Information 325 28 Columns 325 28 Columns 325 28 Columns DS-3

11. STS-1 Overhead Structure

12. STS-N And STS-Nc (N = 3, 12, 48) STS-N Formed By Byte-Interleaving N STS-N Signals 3N Columns of Transport Overhead Frame Aligned Redundant Fields Not Used - eg APS, Datacomm N Distinct Payloads (87N Bytes) NOT Frame Aligned N Columns Of Path Overhead - All Used 2N Columns Of Fixed Stuff Bytes 84N Columns Of Information STS-Nc 3N Columns of Transport Overhead Frame Aligned Redundant Fields Not Used - eg APS, Datacomm Single Payload 1 Column Of Path Overhead 3/N - 1 Columns Of Fixed Stuff Bytes 87N - 3/N Columns Of Information

13. STS-1, STS-3, & STS-3c TOH POHPOH 125  sec TOH POHPOH 125  sec TOH POHPOH 125  sec POHPOH POHPOH POHPOH TOH 125  sec POHPOH TOH 125  sec STS-1 STS-3c STS-3

14. Layering Application Bellcore Approach A B C D E Trunks (DS1 = 24 Trunks) 4E A B C D DS3 or OC3 A D E OC-48 A B C D E Switched Cross- Connect Multiplex Photonic LAYER B C DCS ADM DS1 DS3/OC3 OC48 Customer Service Requests Pt-Pt Traffic (Erlangs) DS1 Private Line DS3/OC3/OC12 Private Line [OC48 Private Line]

15. Generic SONET Network Elements oooooo oooooo STS-N Ports STS-N Ports STS-M Fabric (M<N) oooooo STS-M Ports M:N Digital Cross-Connect System (DCS) STS-M Fabric (M<N) oooooo STS-M Ports M:N Add/Drop Multiplexer (ADM) STS-N oooooo STS-M Ports W E STS-N M:N Multiplexer (aka “End Terminal”)

16. SONET Configurations

17. Key SONET Configurations 48 S 48 P Point To Point Compatible With OLS 2 Nodes Per System All T3’s Use DACS III 1x1 Protection Switching Compatible With OLS 2 To 16 Nodes Add/Drop Multiplexing (“Tributary Add/Drop”) - Only DS3’s Changing Routes Or Terminating Use DACS III 1x1 Protection Switching 48 S 48 P DACS III DCS III ADM 48 S 48 P All DS3’s 48 S 48 P ET: End Terminal ADM: Add/Drop Multiplexer ET

18. Key SONET Configurations Linear Office Sequences ET III Point To Point Linear Add/Drop (“Open Ring”) o o o III ET III ET III ET III ET III N Offices 2 End Offices N-2 Interior Offices ET III ETADM ETADM o o o

19. Key SONET Configurations

20. SONET Network Management

21. SONET Ring APS ( Automatic Protection Switching ) Uni-directional Vs. Bi-directional Rings Two-Fiber Vs. Four Fiber Rings Ring Switching Vs. Span Switching Applications of: Bi-directional Line Switched Ring (BLSR) Uni-directional Path Switched Ring (UPSR)

22. Definition of a Ring A Ring is a collection of nodes (NE1, NE2, ….) forming a closed loop. Each node is connected to two adjacent nodes via a duplex communications facility. A SONET Ring will provide: Redundant Bandwidth Redundant Network Equipment or both.

23. Ring Classification A Unidirectional Line Switched Ring (ULSR) A Bidirectional Line Switched Ring (BLSR) A Unidirectional Path Switched Ring (UPSR) A Bidirectional Path Switched Ring (BPSR) Any of the above type can be a two-fiber or a four fiber ring. Therefore, for all practical applications, SONET/SDH standards provide eight types of ring for network node interconnections.

24. Unidirectional Vs. Bidirectional Rings C B A D A  B : 1 B  A : 2  3  4 1 2 3 4 5 6 7 8 A - Unidirectional Ring C B A D A  B : 1 B  A : 5 1 2 3 4 5 6 7 8 B - Bidirectional Ring

25. Two-Fiber Vs. Four-Fiber Rings C B A D A B Working 1 Protection 2 Working 2 Protection 1 A - Two-Fiber Ring/Span C B A D A B Working 1 Protection 1 Working 2 Protection 2 B - Four-Fiber Ring/Span

26. Ring Switching 2-Fiber Ring C B A D Failure Route before PS (Protection Switching) A: Ring Switching: Two-fiber ring 50% 50% - original + 50% - additional 50% - original + 50% - additional

27. Ring Switching 4-Fiber Ring B: Ring Switching: Four-fiber ring C B A D Route before PS

28. Span Switching - 4-fiber Rings only C B A D Route before PS B: Ring Switching: Four-fiber ring AB Route before PS Route after PS

29. Bi-directional Line Switched Ring No Failures CB A F S S S S S P P P P P D E S P Original Circuit A B CC B A Bidirectional Traffic Unidirectional Traffic

30. SONET Add-Drop Multiplexer (ADM) Lucent FT-2000 LCT Example ) OC-48 STS-3 Fabric STS-3 Terminations (<= 4x16 = 64) STS-3 STS-1/DS3 OC-48 Terminating Equipment OC-48 Terminating Equipment OC-48 Terminating Equipment OC-48 Terminating Equipment SERVICE WEST PROTECTION WEST SERVICE EAST PROTECTION EAST

31. Bi-directional Line Switched Ring Span Switch S F CB S S S S P P P P P D E S P X A Original Circuit Protection Switch

32. SONET ADM Automatic Protection Switching Lucent FT-2000 LCT Example ) OC-48 STS-3 Fabric (60 ms switch time) STS-3 Terminations (<= 4x16 = 64) STS-3 STS-1/DS3 OC-48 Terminating Equipment OC-48 Terminating Equipment OC-48 Terminating Equipment OC-48 Terminating Equipment SERVICE WEST PROTECTION WEST SERVICE EAST PROTECTION EAST

33. Bi-directional Line Switched Ring Ring Switch S E CB A F S S S S P P P P P D S P Original Circuit Ring Switch X

34. SONET ADM Ring Protection Switching Lucent FT-2000 LCT Example ) OC-48 STS-3 Fabric (60 ms switch time) STS-3 Terminations (<= 4x16 = 64) STS-3 STS-1/DS3 OC-48 Terminating Equipment OC-48 Terminating Equipment OC-48 Terminating Equipment OC-48 Terminating Equipment SERVICE WEST PROTECTION WEST SERVICE EAST PROTECTION EAST

35. Ring Restoration Protocol Reference: GR-1230-CORE Issue 1, 12/93 1-45-8 Bridge Request Priority Destination Node ID K1 K2 Sourcing Node ID 1-45 S / L Completed Action 1111 LP-S Protection Lockout (span) or Signal Fail Of Protection(span) 1110 FS-S Forced Switch (Span) 1101 FS-R FS (Ring) 1100 SF-S Signal Failure (Span) 1011 SF-R Signal Failure (Ring) 1010 SD-P Signal Degrade (Protection) 1001 SD-S Signal Degrade (Span) 1000 SD-R Signal Degrade (Ring) 0111 MS-S Manual Switch (Span) 0110 MS-R Manual Switch (Ring) 0101 WTR Wait To Restore 0100 EX-S Exerciser (Span) 0011 EX-R Exerciser (Ring) 0010 RR-S Reverse Request (Span) 0001 RR-R Reverse Request (Ring) 0000 NR No Request 0 Short Path 1 Long Path 111 Line AIS 110 Line RDI : 010 Bridged and Switched) 001 Bridged 000 Idle AIS = Alarm Indication Signal FS = Forced Switch RDI = Remote Defect Indication SF = Signal Failure SD = Signal Degrade FS = Forced Switch 4 bits

36. Route Failure In Ring FADE P Ring Bridge & Switch X X X S P X Ring Bridge & Switch SF-R/E F/L/Br&Sw X SF-R/F E/L/Br&Sw Detect Failure on Working & Protection Detect Failure on Working & Protection SF-R/E F/L/Idle SF-R/F E/L/Idle SF-R/E F/L/Idle SF-R/F E/L/Idle 1 1 2 2

37. Bi-directional Line Switched Ring Ring Switch - Node Failure F CB A S S S S S P P P P P D S P E x Original Circuit Ring Switch

38. Bi-directional Line Switched Ring No Failures CB A F S S S S S P P P P P D E S P Original Circuits (Both Slot 2)

39. Bi-directional Line Switched Ring Need For Squelching CB A F S S S S P P P P P D E S P Original Circuits (Both Slot 2) x Requires Sharing of State Information Significant Software Complexity

40. Bi-directional Line Switched Ring Double Ring Failure (No Recovery) Original Circuit Ring Switch CB A F S S S S S P P P P P D E S P X X

41. SONET Rings will fail -- The question is “When?” Initial estimates of DWDM hardware show that it is 8 times more reliable than WDM equipment. –POEs not included Ring reliability is dependent upon ring mileage. –Ring sizes vary from 200 miles to 2800 miles. Ring Failures: –Given 100, 1000-mile perimeter rings: Current optimistic estimation is 1 network ring failure every 5 yrs. PCIs not included –Most probable cause of a complete ring failure is an equipment failure and a fiber cut. Physical diversity violations in some rings ( single-pt-of-failure).

42. Restoration Alternatives Target Failure Modes Route (Ring) 1 Fiber (Ring or Pt-Pt) Span Protection Switch Ring Protection Switch Nominal Response Time Yes No Yes 50 ms 100 ms No Total Ring Interconnect Node Access/Egress Node or ADM Multiple Rings No Ring Node No Yes Route (Pt-Pt) No

43. Ring Interworking Interconnect Problem (No Recovery) A C B D Z E D S S S S S P P P P P Office X S S S S S P P P P P Ring 1 Ring 2 X Original Circuit Failure

44. Dual Ring Interworking (Unidirectional A => Z Circuit) No Failure A C B Z E D S S S S S P P P P P Office X Office Y S S S S S P P P P P SS Ring 1 Ring 2 v v v v v v v Original Circuit Secondary (Inactive) v v

45. Dual Ring Interworking (Unidirectional A => Z Circuit) ADM Failure A C B Z E D S S S S S P P P P P Office X Office Y S S S S S P P P P P SS Ring 1 Ring 2 v v v v X Original Circuit Secondary Circuit Ring Switch

46. Dual Ring Interworking (Unidirectional A => Z Circuit) Office Or Double ADM Failure E v A C B Z D S S S S S P P P P P Office X Office Y S S S S S P P P P P Ring 1 Ring 2 SS X X Original Circuit Secondary Circuit Ring Switch

47. DRI Capacity Impact All Transit Traffic Example X Y 24 DS-3s Z X YZ 48 DS3s 48 DS3s 48 DS3s (a) No DRI(b) With DRI (Secondary Channel On Service Capacity) 24 DS3s 24 DS3s

48. Restoration Alternatives * If restoration capacity is available ** Can help in a limited number of specific failure situations Target Failure Modes Route (Ring) 1 Fiber (Ring or Pt-Pt) Span Protection Switch Ring Protection Switch DRI Nominal Response Time Yes No Yes No 50 ms 100 ms No Yes** No Yes Total Ring Interconnect Node Access/Egress Node or ADM Multiple Rings No Ring Node No Yes No Route (Pt-Pt) No

49. Ring/Mesh Example - 1 40 T3 40 T3 40 T3 Balanced Demands 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) ADM/DWDM $2.0M $2.0M $2.0M Protection Access 0 0.8 0.4 TOTAL $2.0 $2.8 $2.4 Ring/Mesh Ratio 0.72 0.83 RING Restn Restn 100% PMO MESH Ring Mesh ADM DACS III ADM DACS III Svce Prot Note: DWDM Costs Prorated Per OC-48. No OA’s.

50. Ring/Mesh Example - 1 40 T3 40 T3 40 T3 60 T3 40 T3 40 T3 40 T3 Balanced Demands Unbalanced Demands 1 OC48 (1x1) 2 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 2 OC48 (1x1) 2 OC48 (1x1) 2 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) 1 OC48 (1x1) ADM/DWDM $2.0M $2.0M $2.0M Protection Access 0 0.8 0.4 TOTAL $2.0 $2.8 $2.4 Ring/Mesh Ratio 0.72 0.83 ADM/DWDM$4.0M $2.9M $2.9M Protection Access 0 0.9 0.6 TOTAL $4.0 $3.8 $3.5 Ring/Mesh Ratio 1.06 1.15 RING Restn Restn 100% PMO MESH RING Restn Restn 100% PMO MESH Ring Mesh Note: DWDM Costs Prorated Per OC-48. No OA’s.

51. Ring/Mesh Example - 2 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 RingMesh One Extra 1x1 OC-48 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3 40 T3

52. Ring/Mesh Example - 3 RingMesh New Route

53. Hybrid Network Concept Both Ring & Mesh Restoration Architectures Would Be Used Each OC-48 Would Be Either Ring Or Mesh Protected, But Not Both DWDMU Network Would Be Shared An Office Would Have A Mix Of Ring & Mesh OC-48’s, Depending On Service Mix & Economics

54. Sample SONET Architecture Light Terminating equipment

55. Restoration of DS-3 Services u DS-3s services can be routed on all rings, all mesh, or hybrid ring/mesh. u Ring portion of DS-3: –Restored by self-healing ring for multiple electrical or single optical/fiber failures, including fiber cuts. –Backed up using DCS for multiple failure scenarios. Restoral is semi-manual and expected to take at least 20 min. u Mesh portion of DS-3: –Restored via some “restoration platform”. –Future restoration via the SONET DCS.

56. Sample T3 Architecture DCS: Digital Cross Connect System

57. Sample SONET Architecture P Circuit DCS 48 S 48 P 48 S ADM DCS P S Circuit DCS S P S Light Terminating Equipment ADM DCS P Circuit DCS 48 S 48 P 48 S ADM DCS P S Circuit DCS S P S Light Terminating ADM DCS P Circuit DCS 48 S 48 P 48 S ADM DCS P S Circuit DCS S P S ADM DCS

58. Other Types Of SONET Self-Healing Rings (2-Fiber Unidirectional Line-Switched Ring) ADM A ADM A ADM Z ADM Z ADM Notes: Each Link Is Just 1 (1-Way) Fiber Transmission Directions Routed Differently Service Protection A=>Z Z=>A A=>Z Z=>A

59. Other Types Of SONET Self-Healing Rings (2-Fiber Unidirectional Line-Switched Ring) ADM A ADM A ADM Z ADM Z ADM Service Protection Z=>A A=>Z Z=>A A=>Z Z=>A A=>Z

60. Other Types Of SONET Self-Healing Rings (2-Fiber Bi-directional Line-Switched Ring) ADM A ADM A ADM Z ADM Z ADM Note: Each Link Uses 1 (1-way) Fiber Capacity On Each Fiber Divided Equally Between Service & Protection (2 “Logical Fibers”) Service/Protection