Optical Transport Network & Optical Transport Module

1. Optical Transport Network & Optical Transport Module "Digital Wrapper" Maarten Vissers Consulting Member of Technical Staff Lucent Technologies email: mvissers@lucent.com April 2002

2. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards Contents

3. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards OTN Characteristics Transitional Approaches Final Phase O/E/O processing objectives Digital processing objectives Contents

4. OTN Characteristics • New transport networking layer (carrier grade solution) • Next step (after SDH/SONET) to support ever growing data driven needs for bandwidth and emergence of new broadband services • Terrabit/second per fiber via DWDM lines (transport level) • Gigabit/second paths at 2.5 Gb/s, 10 Gb/s, 40 Gb/s (networking level) • Service transparency for SDH/SONET, ETHERNET, ATM, IP, MPLS • No change of SDH/SONET! • One exception; interpretation of STM-LOF alarm  + STM-AIS due to OTN fail • Enhanced OAM & networking functionality for all services • Shortest physical layer stack for data services (IP  OTN  Fiber)

5. OTN Characteristics • Gigabit level bandwidth granularity required to scale and manage multi-Terabit networks • Wavelength level switching maximizes nodal switching capacity, the gating factor for reconfigurable network capacity • Avoids very large numbers of fine granularity pipes that stress network planning, administration, survivability, and management

6. Transitional Approaches - Assessment • Extended SDH(attempt at creating a new layer using SDH elements) • Bandwidth multiplication by means of TDM  more Gigabit/s on fiber (4x) • Proprietary approaches attempting to carry lower rate STM-N [including all overhead] as a “service” within a higher rate STM-M (M>N) • strongly limited: SDH multiplexing hierarchy not designed to carry the STM-N (i.e. “itself”) as a service • No timing transparency • 90% of STM-N/OC-N overhead bytes not passed through • No STM-N/OC-N independent monitoring • Multiple proprietary implementations created in industry • no interworking

7. Transitional Approaches - Assessment • Pre-OTN WDM(simple transport - vs. networking - solution) • Bandwidth multiplication by means of WDM  Terabit/s on fiber (100x) • Client signal (e.g. STM-N, GbE) direct on wavelength • simple transport, no monitoring • or client specific non-intrusive monitoring • per client type a monitor is needed • additional client type implies additional monitor to be added • alarm suppression signal (e.g. AIS) specific per client type • additional client type implies additional alarm suppression signal to be added • Point-to-point application that can transport STM-N/OC-N as a service

8. Final Phase • OTN (networking solution) • Management enabler of WDM network by means of addition of: • Overhead to "" and "multi-" signals • "non-associated" or "out-of-channel" overhead; e.g. preventing alarm storms • Optical Channel (OCh) layer • STM-N, IP, ATM and Ethernet signals mapped ("wrapped") into OCh frame (OCh Data Unit (ODUk)) • First transmission technology in which each stakeholder gets its own (ODUk) connection monitoring • In addition ODUk supports/provides: • STM-N independent monitoring, becoming a service signal "itself", shortest physical layer stack for data services, TDM muxing, STM-N inverse multiplexing, client independent protection switching, plesiochronous timing (no sync network required)

9. O/E/O Objectives • Minimise O/E/O processing in OTN • O/E/O processing at edges of administrative/vendor (sub)domains • Span engineering • O/E/O processing at edges of protected or switched domain • Span engineering (short/long route effects) • Signal Fail & Signal Degrade condition determination • If more than 1 optical transparent subnetwork is included • O/E/O processing at intermediate points • Span engineering (long line sections) • Losses in optical fabrics • O/E & E/O processing around electrical fabric

10. Digital Processing Objectives • Digital processing at locations where O/E/O is already performed • Fault and degradation detection • Service Level Agreement (SLA) verification • Signal Fail & Signal Degrade condition determination for protection and restoration (e.g. if high accuracy is required)

11. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards Layer Networks Client Signals Optical Channel Structure Containment Relationships Example of Layer Network Trails OTN Interfaces Standardised and "Proprietary" Stacks Contents

12. ETHERNET STM-N IP/MPLS ATM Interworking with pre-OTN STM-N GbE Optical Channel (OCh) layer network OTM Physical Section (OPSn) Optical Transmission Section (OTSn) layer network OTM-0 OTM-nr, n>1 Optical Transport Module of order n (OTM-n, n1) OTN Layer Networks & Client Signals • Three new layer networks: • one "Gbit/s" path layer • OCh • two section layers • OMSn • OTSn • single channel section layer: • OPS0 • Client signals: • IP/MPLS • ATM • Ethernet • STM-N Optical Multiplex Section (OMSn) layer network

13. ATM IP ETHERNET STM-N Optical Channel Payload Unit (OPUk) Optical Channel Data Unit (ODUk) ODUk CF OPUm (m>k) TDM ODUm (m>k) STM-N Optical Channel Transport Unit (OTUk, OTUkV) GbE • Multiplexing (TDM) • ODUk multiplexing • ODUk virtual concatenation Optical Channel (OCh) OCh CF CF: Connection Function Optical Channel Structure • Optical Channel layer network consists of 3+1 structures: • Digital: • OCh Data Unit (ODUk) • OCh Payload Unit (OPUk, k=1,2,3) • OCh Transport Unit (OTUk, OTUkV) • Analogue: OCh

14. Client OCh Payload Unit (OPUk) OH Client Associated overhead Wrapper OCh Data Unit (ODUk) OH OPUk OCh Transport Unit (OTUk) OH ODUk FEC OMSn Optical Channel (OCh) OTUk OH OPSn OTSn Optical Channel Carrier (OCC) OCC OCC OCC OPS0 Optical Multiplex Section OH Non-associated overhead Optical Transmission Section OH OTM Overhead Signal Optical Supervisory Channel OOS Optical Transport Module OSC OSC Optical Physical Section OTN Containment Relationships

15. STM-N ODU k OCh, OTUk OCh, OTU k OCh, OTU k OMSn OMSn OMSn OPS0 OTSn OTSn OTSn OTSn OTSn OSn OTN Layer Network Trails • Example of OTSn, OMSn, OCh, OTUk, ODUk, OPS0 trails • Transport of STM-N signal via OTM-0, OTM-n and STM-N lines DXC 3R 3R LT R OCADM R LT 3R DXC 3R OTM-0 Client OTM-n STM-N Client ODXC LT Line Terminal w/ optical channel multiplexing OCADM Optical Channel Add/Drop Multiplexer ODXC ODU Cross-Connect 3R O/E/O w/ Reamplification, Reshaping & Retiming and monitoring R Repeater

16. OTM NNI OTM IaDI-IrVI NNI OTM IrDI UNI OTM NNI OTM NNI IaDI-IaVI IaDI-IaVI OTN Interfaces • User to Network Interface (UNI) • Network Node Interface (NNI) • Inter Domain Interface (IrDI) • Intra Domain Interface (IaDI) • between equipment of different vendors (IrVI) • within subnetwork of one vendor (IaVI) Network Operator B Network USER Operator A C Vendor X Vendor Y

17. Proprietary elements: OTM-n.m optical parameters number of wavelengths bit rates of wavelengths supervisory channel OTUkV FEC frame format ODUk mapping Clients (e.g. STM-N, ATM, IP, Ethernet) OPUk ODUkP ODUk ODUkT OCh substructure OTUk OTUk OTUkV OTUkV OChr OCh OMSn OPSn OTSn used between (and within) OTN transparent subnetworks OTM-0.m OTM-nr.m OTM-n.m Full functionality Reduced functionality used within OTN transparent subnetworks; implementations are very much technology dependent Standardised & "Proprietary" stacks

18. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards Application Nesting Overlapping Contents

19. Path CM Verify QoS CM UNI-UNI CM ODUk NNI-NNI CM Working W/P CM Protection ODUk Multi-level Connection Monitoring:Applications Status of working [protection] connection is monitored for SF and SD switch conditions ODUk switched circuit: UNI-UNI CM to initiate "connection re-establishment" QoS of client signal transport is monitored by User QoS provided by leased circuit is monitored by User QoS of provided leased circuit is monitored by Service Provider QoS of provided leased circuit is monitored by Network Operator Client Signal USR2 NO A NO B NO C USR1 Client Signal

20. Multi-level Connection Monitoring:Nesting

21. Multi-level Connection Monitoring:Nesting and Overlapping

22. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards OTM Interface Signals OTM-16r.m OTM-0.m OTM-n.m OTM Signals versus OTN I/F OTM Overhead Signal Frame Formats OTUk, ODUk Overhead OTUk, ODUk OTUkV Overhead versus OTN I/F Contents

23. OTM-16r.m Signal (m=1,2,3,12,23,123) • Up to 16 wavelengths carrying traffic, with fixed 200 GHz grid independent of bit rate (2G5, 10G, 40G) • Optical parameters according to ITU-T Recommendation G.959.1 • Bit rate and format of the associated overhead according to ITU-T Recommendation G.709 • No Optical Supervisory Channel (OSC) • non-associated overhead not required; i.e. 3R points at each end, no repeaters

24. OTM-0.m Signal (m=1,2,3) • Single channel signal ("colourless": 1310 or 1550 nm) • Optical parameters according to ITU-T Recommendation G.959.1 • Bit rate and format of the associated overhead according to ITU-T Recommendation G.709 • No Optical Supervisory Channel (OSC) • non-associated overhead not required; i.e. 3R points at each end, no repeaters

25. 3 OTM-n.m Signal (m=1,2,3,12,23,123) • Up to "n" wavelengths carrying traffic, with a grid dependent on bit rate • 1 "out-of-band" Optical Supervisory Channel (OSC) transporting the OTM Overhead Signal (OOS) • OTM Overhead Signal transports OTS, OMS, OCh (non-associated) overhead and General management communications

26. OTM Signals versus OTN Interfaces

27. FDI-O n FDI-P TTI 3 2 1 BDI-O BDI-O FDI-O Non-Associated overhead BDI-P BDI-P FDI-P Vendor Specific OMSn PMI PMI OCI OTSn OCh General Management Communications BDI: Backward Defect Indication OCI: Open Connection Indication FDI-O: Forward Defect Indication - Overhead PMI: Payload Missing Indication FDI-P: Forward Defect Indication - Payload TTI: Trail Trace Identifier OTM Overhead Signal (OOS)«Non-associated overhead» OCh OH extensions may be expected in future to support e.g. OCh protection (e.g. OCh SPring) • OOS functions subject to standardization • OOS bit rate & format not standardized

28. 14 15 16 17 1 7 8 3824 3825 4080 1 2 3 4 Client Signal OTUk OH OPUk - Optical Channel Payload Unit Client Signal mapped in OPUk Payload Alignm ODUk - Optical Channel Data Unit k indicates the order: 1 2.5G 2 10G 3 40G OTUk FEC OPUk OH OPU k Payload ODUk OTUk - Optical Channel Transport Unit Alignment OTUk and ODUk frame formats (k=1,2,3) ODUk bit rate: 239/(239-k) * "STM-N" OTUk bit rate: 255/(239-k) * "STM-N"

29. RES Mapping & Concat Specific PT 0 1 OPUk OH OPU k Payload Mapping & Concat Specific FAS MFAS SM GCC0 RES PSI 255 ACT: Activation/deactivation control channel APS: Automatic Protection Swiching coordination channel EXP: Experimental FAS: Frame Alignment Signal FTFL: Fault Type & Fault Location reporting channel GCC: General Communication Channel MFAS: MultiFrame Alignment Signal PCC: Protection Communication Control channel PM: Path Monitoring PSI: Payload Structure Identifier RES: Reserved for future international standardisation SM: Section Monitoring TCM: Tandem Connection Monitoring 1 2 3 OTUk OH 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 Alignm TCM PM 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 TCM6 TCM5 TCM4 BDI FTFL TTI BIP-8 STAT BEI ACT TCMi BDI TTI BIP-8 STAT BEI/BIAE EXP TCM3 TCM2 TCM1 PM ODUk GCC1 GCC2 APS/PCC RES OTUk and ODUk Overhead (k=1,2,3)«Associated overhead»

30. OTUkV (k=1,2,3) • Frame format is vendor specific • Forward Error Correction code is vendor specific • Minimum overhead set to support is: • Trail Trace Identifier • Error Detection Code (e.g. BIP) • Backward Defect Indicator • Backward Error Indicator • (Backward) Incoming Alignment Error • Other overhead is vendor specific • ODUk mapping into OTUkV is vendor specific

31. Overhead versus OTN Interfaces • OTM Interface Ports on IP Router, ATM Switch, Ethernet Switch and SDH equipment should support the following minimum set of overhead • OPUk Client Specific • OPUk Payload Structure Identifier (PSI) • ODUk Path Monitoring (PM) • OTUk Section Monitoring (SM) • Frame Alignment (FAS, MFAS)

32. Overhead versus OTN Interfaces • Overhead passed through network • OTM UNI to OTM UNI • OTM NNI IrDI to OTM NNI IrDI

33. Overhead versus OTN Interfaces • Overhead passed through network from OTM UNI to OTM UNI interface • OPUk PSI, Client Specific • ODUk PM, TCM ACT, TCM1..TCMn, TCM ACT, RES • ODUk GCC1, GCC2 according contract • ODUk APS/PCC definition is under study

34. Overhead versus OTN Interfaces • Overhead passed through network from OTM NNI IrDI to OTM NNI IrDI interface • OPUk PSI, Client Specific • ODUk PM, TCM ACT, TCM1..TCMm, TCM ACT, FTFL, RES • "m" in TCMm > "n" in TCMn (UNI-UNI) • ODUk GCC1, GCC2 according contract • ODUk APS/PCC definition is under study

35. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards Forward Defect Indication (FDI, AIS) Backward Defect & Error Indication (BDI, BEI) Open Connection Indication (OCI) Locked (LCK) Fault Type & Fault Location (FTFL) Contents

36. R at 3R point OCh-FDI is converted into ODUk-AIS use of OTN maintenance signal OTS-PMI (and OMS-PMI) at line termination point OMS-FDI is converted into OCH-FDI will prevent OTS [OMS] LOS alarm OCh-FDI l when none of s is present OCh-FDI OMS-FDI OCh-FDI R ODUk-AIS OTS-PMI OTS-PMI l 1000 /fiber x 96 fibers/cable OCh-FDI x 5 cables/duct = 500k lost signals ==> 500k LOS alarms in network OTN Maintenance Signals: Alarm Suppression R use of OTN maintenance signals FDI, AIS and PMI will reduce number of alarms from 500k to 1 per broken fiber R 3R R

37. OTN Maintenance Signals: Alarm Suppression (FDI, AIS) • AIS/FDI at • clients • AIS at • ODUk • AIS at • OTUk • FDI at • OCh • FDI/PMI at • OMSn • PMI at • OTSn

38. OTN Maintenance Signals:Alarm Suppression (FDI, AIS) • Generated at egress of OMSn, OCh and ODUk Link Connections • Inserted on detection of Signal Fail • OMSn-FDI and OCh-FDI • is non-associated overhead • ODUk-AIS • is special ODUk signal pattern (0xFF)

39. insertion detection Generic-AIS [STM-AIS] • New maintenance signal @ STM-N level • a continuous repeating 2047-bit PN-11 (1 + x9 + x11) sequence • Generated in OTN tributary ports • ingress trib: on detection of STM-N LOS • egress trib: on detection of ODUk signal fail type defect • To be detected in SDH line/trib ports in addition to STM-LOF as "STM-AIS" •  In existing equipment detected as STM-LOF 

40. OTN Maintenance Signals: Backward Information (BDI, BEI) • RDI/REI at • Clients • BDI/BEI at • ODUk • OTUk • No BI at • OCh • BDI at • OTSn • OMSn

41. OTN Maintenance Signals:Open Connection Indication (OCI) • Generated in a Fabric • Inserted when output port is not connected to input port • OCh-OCI • is non-associated overhead • ODUk-OCI • special ODUk signal pattern (0x66)

42. OTN Maintenance Signals:Locked (LCK) • Generated in ODUk Tandem Connection endpoint • Inserted when Administrative State is Locked • to block a user to access the connection • to prevent test patterns within the network entering a user domain • ODUk-LCK • special ODUk signal pattern (0x55)

43. Fault Type & Fault Location (FTFL) • Helps Service Provider to automatically locate fault/degradation to specific Network Operator domain • No need to call around any longer • Section and Tandem Connection endpoints insert FTFL in forward direction on detection of SF or SD condition • Specific FTFL function at UNI • extracts forward info and sends it in opposite direction as backward info • filters outgoing and incoming FTFL information (security issue) • Specific FTFL extraction function • reads FTFL forward and backward information at intermediate point along connection

44. OTN Rationale OTN Layer Networks Multi level Connection Monitoring OTM Signals Maintenance Signals Mapping Client Signals Multiplexing Virtual Concatenation OTN Standards CBR (e.g. STM-N) IP, ETHERNET ATM Test Signals Bit stream with/without octet timing Bit Rate Agnostic CBR Contents

45. Mapping STM-N (N=16,64,256) • G.709 provides two mappings for STM-N signals • bit synchronous • asynchronous • G.709 defines interworking between both mappings • common demapper, and • bit synchronous mapping has fixed Justification Control (JC) STM-16 STM-64 STM-256 D: Data, FS: Fixed Stuff, JC: Justification Control, N/PJO: Negative/Positive Justification Opportunity

46. Mapping IP and Ethernet • G.709 provides an encapsulation for packet based client signals • There is no need for SDH or 10G-Ethernet to encapsulate IP • A new protocol is being defined: Generic Framing Procedure • a generic mechanism to carry any packet signal over fixed rate channels (e.g. SDH, SONET and OTN's ODUk) - ITU-T Rec. G.gfp Bandwidth for GFP stream in ODU1: 2 488 320 kbit/s ODU2: 9 995 276 kbit/s ODU3: 40 150 519 kbit/s

47. Generic Framing Procedure G.7041

48. Mapping ATM • G.709 provides a mapping for cell based client signals • Mapping ATM into ODUk is similar to mapping into SDH Bandwidth for ATM stream in ODU1: 2 488 320 kbit/s ODU2: 9 995 276 kbit/s ODU3: 40 150 519 kbit/s

49. Mapping Test Signals • G.709 provides a mapping for test signals • Two test signals are defined • NULL sequence (all-0's)

50. Mapping Test Signals • Two test signals are defined (continued) • 2 147 483 647-bit Pseudo Random Binary Sequence (PRBS) 1 + x28 + x31 • groups of 8 successive PRBS bits are mapped into a data byte