Transcript SONET/SDH

SONET
Y(J)S SONET Slide 1
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 2
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
timeslots
t
Y(J)S SONET Slide 3
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 4
SONET/SDH
motivation and history
Y(J)S SONET Slide 5
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 6
Layers
SONET defines four layers:
1.
Path
2.
Line
3.
Section and
4.
Photonic
Y(J)S SONET Slide 7
SONET architecture
Path
Termination
ADM
regenerator
ADM
Line
Termination
Section
Termination
Line
Termination
Path
Termination
path
line
section
line
section
line
section
section
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

section – physical link between adjacent elements
multiplex section
regenerator section
Each layer has its own overhead to support needed functionality
SONET System consists of Signal, devices and
connections.
SDH terminology
Y(J)S SONET Slide 8
Device–layer relationship in
SONET
Y(J)S SONET Slide 9
rates
and
frame structure
Y(J)S SONET Slide 10
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 51.840 Mbps
Y(J)S SONET Slide 11
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 155.520 Mbps
3 times the STS-1 rate!
Y(J)S SONET Slide 12
SONET/SDH rates
SONET
SDH
STS-1
columns
rate
90
51.84M
STS-3
STM-1
270
155.52M
STS-12
STM-4
1080
622.080M
STS-48
STM-16
4320
2488.32M
STS-192
STM-64
17280
9953.28M
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
Y(J)S SONET Slide 13
STS-1 frame structure
Transport
Overhead
TOH
Y(J)S SONET Slide 14
Y(J)S SONET Slide 15
Y(J)S SONET Slide 16
Y(J)S SONET Slide 17
Y(J)S SONET Slide 18
Y(J)S SONET Slide 19
THANK YOU.
Y(J)S SONET Slide 20