comp514 – advanced communications lecture 2: sdh matthew luckie [email protected]
TRANSCRIPT
Lecture Outline
• SDH : Synchronous digital hierarchy
• Self-healing rings
• OAM
• Fault location
Synchronous Digital Hierarchy (SDH)
• Dominant standard for digital telecommunications networks
SONET SDH Data Rate (Mbps)
STS-1 / OC-1 51.84
STS-3 / OC-3 STM-1 155.52
STS-12 / OC-12 STM-4 622.08
STS-48 / OC-48 STM-16 2488.32
STS-192 / OC-192 STM-64 9953.28
STS-768 / OC-768 STM-256 39813.12
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
STM-1 Frame
SectionOverhead(9 bytes)
9 R
ows
Payload(261 bytes)
AU Pointer
RegeneratorSection
Overhead(RSOH)
MultiplexerSection
Overhead(MSOH)
InformationPayload
PathOverhead
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
SDH NetworksDXC
DXCDXC
DXC
ADM
ADM
ADM
ADM
ADM
ADM
DXC
ADM
ADM
DXC
DXC
ADM
DXCADM
ADM
C
ADM
C
DXC
ADM
ADMADM
C C
RegionalNetworks
Backbone
Local MetroNetworks
Customers
SDH Multiplexers
• Add-drop multiplexers allow individual streams to be added or removed from the STM-1
ADMSTM-n STM-n
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
DXCSTM-n STM-n
STM-n
SDH Repeater
• A repeater regenerates the optical signal
Self Healing Rings
Bidirectional links between nodes
Self Healing Rings
Bidirectional links between nodes
Self Healing Rings
Bidirectional links between nodes
Operations and Maintenance (OAM)
• Goals of OAM are– Performance monitoring– Fault detection– Fault notification– System protection– Point-of-fault identification
OAM
• Hierarchical structure– F1: Repeater section– F2: Digital section– F3: Transmission path– F4: Virtual Path (VP)– F5: Virtual Channel (VC)
OAM for ATM
• If the first twobits of payloadtype field are1 and 0– OAM cell
– 100 : segment– 101 : end-to-end
8 567 4 123
CRC
Virtual Channel Identifier (VCI)
CLPPayload Type
Virtual Path Identifier (VPI)