Data Communications, Kwangwoon University 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

Data Communications, Kwangwoon University 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 Synchronous network 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

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

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

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

Data Communications, Kwangwoon University 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

Device-Layer Relationship in SONET Data Communications, Kwangwoon University

Data Communications, Kwangwoon University 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

Data Communications, Kwangwoon University 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

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

Data Communications, Kwangwoon University 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

Data Communications, Kwangwoon University Overhead Summary Data Communications, Kwangwoon University

Data Communications, Kwangwoon University 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

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

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

Data Communications, Kwangwoon University 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

Data Communications, Kwangwoon University 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

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

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

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

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

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

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

Data Communications, Kwangwoon University 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

Data Communications, Kwangwoon University VT Types Data Communications, Kwangwoon University