1. COMP514 – Advanced Communications Lecture 2: SDH Matthew Luckie mluckie@cs.waikato.ac.nz

2. Lecture Outline SDH : Synchronous digital hierarchy Self-healing rings OAM Fault location

3. Synchronous Digital Hierarchy (SDH) Dominant standard for digital telecommunications networks SONETSDHData Rate (Mbps) STS-1 / OC-151.84 STS-3 / OC-3STM-1155.52 STS-12 / OC-12STM-4622.08 STS-48 / OC-48STM-162488.32 STS-192 / OC-192STM-649953.28 STS-768 / OC-768STM-25639813.12

4. STM-1 STM-1 frame rate 8000/second –125 microseconds STM-1 frame 270 columns by 9 rows –2430 bytes / 19440 bits 19440 * 8000 = 155.52 Mbps

5. STM-1 Frame Section Overhead (9 bytes) 9 Rows Payload (261 bytes) AU Pointer Regenerator Section Overhead (RSOH) Multiplexer Section Overhead (MSOH) Information Payload Path Overhead

6. STM-1 / STM-n STM-1 frames begin with A1/A2 frame alignment bytes. –Receiver can watch for this sequence every 125us to gain synchronisation STM-n is formed by byte-multiplexing STM-1 frames. –STM-4 frame begins with A1 A1 A1 A1 A2 A2 A2 A2

7. SDH Networks DXC ADM DXC ADM DXC ADM DXC ADM C C DXC ADM CC Regional Networks Backbone Local Metro Networks Customers

8. SDH Multiplexers Add-drop multiplexers allow individual streams to be added or removed from the STM-1 ADM STM-n

9. SDH Multiplexers Digital Cross Connects (DXC) demux the entire stream and switch channels to other SDH circuits –Core equipment will break down to STM-n rate –Edge equipment will break down entire stream DXC STM-n

10. SDH Repeater A repeater regenerates the optical signal

11. Self Healing Rings Bidirectional links between nodes

12. Self Healing Rings Bidirectional links between nodes

13. Self Healing Rings Bidirectional links between nodes

14. Operations and Maintenance (OAM) Goals of OAM are –Performance monitoring –Fault detection –Fault notification –System protection –Point-of-fault identification

15. OAM Hierarchical structure –F1: Repeater section –F2: Digital section –F3: Transmission path –F4: Virtual Path (VP) –F5: Virtual Channel (VC)

16. OAM for ATM If the first two bits of payload type field are 1 and 0 –OAM cell –100 : segment –101 : end-to-end 85674123 CRC Virtual Channel Identifier (VCI) CLPPayload Type Virtual Path Identifier (VPI)