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Chapter 17. SONET/SDH

Chapter 17. SONET/SDH. 17.1 Architecture 17.2 SONET Layers 17.3 SONET Frames 17.4 STS Multiplexing 17.5 SONET Networks 17.6 Virtual Tributaries. SONET/SDH. Digital transmission standards for fiber-optic cable Independently developed in USA & Europe

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Chapter 17. SONET/SDH

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  1. Chapter 17. SONET/SDH 17.1 Architecture 17.2 SONET Layers 17.3 SONET Frames 17.4 STS Multiplexing 17.5 SONET Networks 17.6 Virtual Tributaries Data Communications, Kwangwoon University

  2. SONET/SDH • Digital transmission standards for fiber-optic cable • Independently developed in USA & Europe • SONET(Synchronous Optical Network) by ANSI • SDH(Synchronous Digital Hierarchy) by ITU-T • Synchronousnetwork using synchronous TDM multiplexing • All clocks in the system are locked to a master clock • It contains the standards for fiber-optic equipments • Very flexible to carry other transmission systems (DS-0, DS-1, etc) Data Communications, Kwangwoon University

  3. SONET/SDH Architecture • Architecture of a SONET system: signals, devices, and connections • Signals: SONET(SDH) defines a hierarchy of electrical signaling levels called STSs(Synchronous Transport Signals, (STMs)). Corresponding optical signals are called OCs(Optical Carriers) Data Communications, Kwangwoon University

  4. SONET/SDH Architecture • SONET devices: STS multiplexer/demultiplexer, regenerator, add/drop multiplexer, terminals Data Communications, Kwangwoon University

  5. SONET/SDH Architecture • Connections: SONET devices are connected using sections, lines, and paths • Section: optical link connecting two neighbor devices: mux to mux, mux to regenerator, or regenerator to regenerator • Lines: portion of network between two multiplexers • Paths: end-to-end portion of the network between two STS multiplexers Data Communications, Kwangwoon University

  6. SONET Layers • SONET defines four layers: path, line, section, and photonic • Path layer is responsible for the movement of a signal from its optical source to its optical destination • Line layers is for the movement of a signal across a physical line • Section layer is for the movement of a signal across a physical section, handling framing, scrambling, and error control • Photonic layer corresponds to the physical layer of OSI model Data Communications, Kwangwoon University

  7. Device-Layer Relationship in SONET Data Communications, Kwangwoon University

  8. SONET Frames • Each synchronous transfer signal STS-n is composed of 8000 frames. Each frame is a two-dimensional matrix of bytes with 9 rows by 90 × n columns. • A SONET STS-n signal is transmitted at 8000 frames per second • Each byte in a SONET frame can carry a digitized voice channel Data Communications, Kwangwoon University

  9. SONET Frames • In SONET, the data rate of an STS-n signal is n times the data rate of an STS-1 signal • In SONET, the duration of any frame is 125 μs Data Communications, Kwangwoon University

  10. SONET Frames: STS-1 • Section overhead () is recalculated for each SONET device • Line overhead () Data Communications, Kwangwoon University

  11. SONET Frames: SPE • SPE(Synchronous Payload Envelope) contains the user data and the overhead related to the user data (path overhead) • Path overhead is only calculated for end-to-end at STS multiplexers Data Communications, Kwangwoon University

  12. Overhead Summary Data Communications, Kwangwoon University

  13. SPE Encapsulation • Offsetting of SPE related to frame boundary • Use of H1 and H2 pointers to show the start of an SPE in a frame Data Communications, Kwangwoon University

  14. STS Multiplexing • STS multiplexing/demultiplexing and byte interleaving Data Communications, Kwangwoon University

  15. An STS-3 Frame • Byte interleaving preserves the corresponding section and line overhead Data Communications, Kwangwoon University

  16. Concatenated Signal • The suffix c (for concatenated) means that the STS-n is not considered as n STS-1 signals. So, it cannot be demultiplexed into n STS-1 signals • An STS-3c signal can carry 44 ATM cells as its SPE • SPE of an STS-3c can carry 9 x 260 = 2340 which can accommodate approximately 44 ATM cells, each of 53 bytes Data Communications, Kwangwoon University

  17. Add/Drop Multiplexer • Only remove the corresponding bytes and replace them with the new bytes including the bytes in the section and line overhead Data Communications, Kwangwoon University

  18. SONET Network • Point-to-point network • Multipoint network Data Communications, Kwangwoon University

  19. Automatic Protection Switching • To create protection against failure in linear networks Data Communications, Kwangwoon University

  20. Ring Network: UPSR • Unidirectional Path Switching Ring (UPSR) Data Communications, Kwangwoon University

  21. Ring Network: BLSR • Bidirectional Line Switching Ring (BLSR) Data Communications, Kwangwoon University

  22. Ring Network: Combination • Combination of UPSR and BLSR Data Communications, Kwangwoon University

  23. Mesh Network • Ring network has the lack of scalability • Mesh network has better performance Data Communications, Kwangwoon University

  24. Virtual Tributaries • Partial payload that is inserted into an STS-1 frame • Each component of subdivided SPE • Provides backward compatibility with the current hierarchy • Four types of VTs • VT1.5 : For DS-1(T-1: 1.544Mbps) • VT2: For European CEPT-1(E-1: 2.048Mbps) Data Communications, Kwangwoon University

  25. VT Types Data Communications, Kwangwoon University

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