Data Communications, Kwangwoon University17-1 Chapter 17. SONET/SDH 17.1 Architecture 17.2 SONET...
-
Upload
angel-terry -
Category
Documents
-
view
237 -
download
0
Transcript of Data Communications, Kwangwoon University17-1 Chapter 17. SONET/SDH 17.1 Architecture 17.2 SONET...
Data Communications, Kwangwoon University
17-1
Chapter 17. SONET/SDH
17.1 Architecture17.2 SONET Layers17.3 SONET Frames17.4 STS Multiplexing17.5 SONET Networks17.6 Virtual Tributaries
Data Communications, Kwangwoon University
17-2
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
• 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
17-3
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
17-4
SONET/SDH Architecture
• SONET devices: STS multiplexer/demultiplexer, regenerator, add/drop multiplexer, terminals
Data Communications, Kwangwoon University
17-5
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
17-6
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
17-7
Device-Layer Relationship in SONET
Data Communications, Kwangwoon University
17-8
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
17-9
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
17-10
SONET Frames: STS-1
• Section overhead () is recalculated for each SONET device
• Line overhead ()
Data Communications, Kwangwoon University
17-11
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
17-12
Overhead Summary
Data Communications, Kwangwoon University
17-13
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
17-14
STS Multiplexing
• STS multiplexing/demultiplexing and byte interleaving
Data Communications, Kwangwoon University
17-15
An STS-3 Frame
• Byte interleaving preserves the corresponding section and line overhead
Data Communications, Kwangwoon University
17-16
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
17-17
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
17-18
SONET Network
• Point-to-point network
• Multipoint network
Data Communications, Kwangwoon University
17-19
Automatic Protection Switching
• To create protection against failure in linear networks
Data Communications, Kwangwoon University
17-20
Ring Network: UPSR
• Unidirectional Path Switching Ring (UPSR)
Data Communications, Kwangwoon University
17-21
Ring Network: BLSR
• Bidirectional Line Switching Ring (BLSR)
Data Communications, Kwangwoon University
17-22
Ring Network: Combination
• Combination of UPSR and BLSR
Data Communications, Kwangwoon University
17-23
Mesh Network
• Ring network has the lack of scalability
• Mesh network has better performance
Data Communications, Kwangwoon University
17-24
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
17-25
VT Types