1. CS 4594 Broadband Communications
SONET

2. Synchronous Optical Network
SONET = Synchronous Optical Network
First standardized by ANSI/ECSA, now SDH by ITU-T.
SONET is Time Division Multiplexing (TDM).
SONET encompasses optical and electrical specifications.
SONET uses octet multiplexing.
SONET uses extremely precise timing.
SONET provides support for operation, maintenance, and administration (OAM).

3. SONET is superior to T-3 and T-4
with improved (over T-carrier)
transport performance
ability to identify substreams
international connectivity
enhanced control and administrative functions

4. SONET electrical signal hierarchy
STS-1 = Synchronous transport signal level 1
speed = Mbit/s
designed to carry DS-3 or a combination of DS-1, DS-1C, and DS-2 signals that are equivalent to DS-3
STS-N = Synchronous transport signal level N
speed = N x Mbit/s
designed to carry multiple STS-1
octet multiplexed STS-1

5. SONET optical signal hierarchy
OC-1 = Optical carrier level 1 (caries STS-1)
OC-N = Optical carrier level N (caries STS-N)

6. Sections, Lines, and Paths
Sections are bounded by repeaters or multiplexers that terminate the line.
Lines may carry several tributary signals.Lines are bounded by multiplexers.
A path goes end to end (between terminating multiplexers).

7. SECTION, LINE, and PATH section section section line path M1 M1
MPX
MPX M1 M1
repeater
repeater
section
section
section
line
path

8. STS-1 Frame
Each STS frame lasts 125 microseconds (8000 types a second)
STS-1 frame has 6480 bits = 810 octets
The octets are understood in terms of a table of 9 rows of 90 columns

9. SONET Frame
3 Columns
87 Columns
Sonet
Frame
9 rows

10. STS-1 Frame - Columns
The first three columns contain TOH = Transport Overhead:
TOH has 9 rows by 3 columns (27 octets) which is subdivided into
SOH = Section Overhead: 9 octets (3 rows of 3 columns)
LOH = Line Overhead:18 octets (6 rows of 3 columns)

11. SECTION, LINE, and PATH section section section line path M1 M1
MPX
MPX M1 M1
repeater
repeater
section
section
section
line
path

12. Overhead patterns - Section and Line

13. Overhead Streams
Section Overhead (SOH) defines and identifies frames, and monitors section errors and communication between section terminating equipment
Line Overhead (LOH) locates first octet of SPE and monitors line errors and communication between terminating equipment
Path Overhead (POH) verifies connection, and monitors path errors, receiver status, and communication between path terminating equipment

14. STS-1 Frame - Columns
The last 87 columns hold SPEs = Synchronous Payload Envelope
SPE has 9 rows by 87 columns which are divided into
POH = Path Overhead
payload
The SPE does not necessarily start in column 4.
The SPE does not necessarily stay within one frame.

15. Two SONET Frames
3 Columns
87 Columns
Sonet
Frame
9 rows

16. SPE = Synchronous Payload Envelope
3 Columns
87 Columns
Sonet
Frame
9 rows
SPE
Path overhead