Y(J)S SONET Slide 1 SONET

Y(J)S SONET Slide 2 The PSTN circa 1900 pair of copper wires “local loop” manual routing at local exchange office (CO) Analog voltage travels over copper wire end-to-end Voice signal arrives at destination severely attenuated and distorted Routing performed manually at exchanges office(s) Routing is expensive and lengthy operation Route is maintained for duration of call

Y(J)S SONET Slide 3 The Digitalization of the PSTN Shannon (Bell Labs) proved that Digital communications is always better than Analog communications and the PSTN became digital Better means More efficient use of resources (e.g. more channels on trunks) Higher voice quality (less noise, less distortion) Added features After the invention of the transistor, in 1963 T-carrier system (TDM) 1 byte per sample – 8000 samples per second t timeslots

Y(J)S SONET Slide 4 OAM Analog channels and 64 kbps digital channels do not have mechanisms to check signal validity and quality thus major faults could go undetected for long periods of time hard to characterize and localize faults when reported minor defects might be unnoticed indefinitely Solution is to add mechanisms based on overhead as Packet networks evolved, more and more overhead was dedicated to Operations, Administration and Maintenance (OAM) functions including: monitoring for valid signal defect reporting alarm indication/inhibition (AIS)

Y(J)S SONET Slide 5 SONET/SDH motivation and history

Y(J)S SONET Slide 6 First step SONET was developed by ANSI; SDH TSDH was developed by ITU-T. Synchronous Optical NETwork Designed for optical transport (high bitrate) Direct mapping of lower levels into higher ones Carry all Packet types in one universal hierarchy –ITU version = Synchronous Digital Hierarchy –different terminology but interoperable Overhead doesn’t increase with rate OAM designed-in from beginning

Y(J)S SONET Slide 7 Layers SONET defines four layers: 1. Path 2. Line 3. Section and 4. Photonic

Y(J)S SONET Slide 8 SONET architecture SONET (SDH) has at 3 layers: path – end-to-end data connection, muxes tributary signals path section –there are STS paths + Virtual Tributary (VT) paths line – protected multiplexed SONET payload multiplex section section – physical link between adjacent elements regenerator section Each layer has its own overhead to support needed functionality SDH terminology Path Termination Path Termination Line Termination Line Termination Section Termination path line ADM regenerator section SONET System consists of Signal, devices and connections.

Device–layer relationship in SONET Y(J)S SONET Slide 9

Y(J)S SONET Slide 10 rates and frame structure

Y(J)S SONET Slide 11 SONET STS-1 frame Each STS-1 frame is 90 columns * 9 rows = 810 bytes There are 8000 STS-1 frames per second so each byte represents 64 kbps (each column is 576 kbps) Thus the basic STS-1 rate is Mbps

Y(J)S SONET Slide 12 SDH STM-1 frame Synchronous Transport Modules are the bit-signals for SDH Each STM-1 frame is 270 columns * 9 rows = 2430 bytes There are 8000 STM-1 frames per second Thus the basic STM-1 rate is Mbps 3 times the STS-1 rate!

Y(J)S SONET Slide 13 SONET/SDH rates STS-N has 90N columns STM-M corresponds to STS-N with N = 3M SDH rates increase by factors of 4 each time STS/STM signals can carry PDH tributaries, for example: STS-1 can carry 1 T3 or 28 T1s or 1 E3 or 21 E1s STM-1 can carry 3 E3s or 63 E1s or 3 T3s or 84 T1s SONETSDHcolumnsrate STS M STS-3STM M STS-12STM M STS-48STM M STS-192STM M

Y(J)S SONET Slide 14 STS-1 frame structure Transport Overhead TOH

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THANK YOU. Y(J)S SONET Slide 20