DigiPoints
Volume 1
North American Digital Hierarchy
DIGITAL
SIGNAL
NUMBER
NUMBER O F
64 kb/s
CHANNELS
BIT RATE IN
Mb/s
T CARRIER
IMPLEMENTATION
DS0
1
.064
n/a
DS1
24
1.544
T-1
DS1C
48
3.152
DS2
96
6.312
T-2
DS3
672
44.736
T-3
DS4
4032
274.176
T-4
©SCTE
T-1C
VA 5.1
DigiPoints
Volume 1
Bit Stuffing
Low Speed
Inputs
stuffed bits
High Speed Output
Input Line A
Clock Circuit
Input Line B
REGISTER
Output Line
BUFFER
©SCTE
VA 5.2
DigiPoints
Volume 1
Digital Multiplexer Designations
With Multiplexing Ratios
274.176 Mbps
DS4
M34
6:1
44.736 Mbps
DS3
M13
28:1
MX3
7:1 (DS2)
14:1 (DS1C)
or 28:1 (DS1)
6.312 Mbsp.
DS2
M12
4:1
DS1C
3.152 Mbps
M1C
2:1
DS1
1.544 Mbps
©SCTE
VA 5.3
DigiPoints
Volume 1
European Digital Hierarchy
LEVEL
NUMBER
CEPT1
CEPT2
CEPT3
CEPT4
CEPT5
NUMBER OF VOICE
CIRCUITS
30
120
480
1920
7680
©SCTE
MULTIPLEXER
DESIGNATION
M12
M23
M34
M45
BIT RATE
(Mb/s)
2.048
8.448
34.368
139.264
565.148
VA 5.4
DigiPoints
Volume 1
Why SONET
• Break up of Bell System
• Open Standards
• Bellcore
• Telecommunications Act of 1996
©SCTE
VA 5.5
DigiPoints
Volume 1
Open Standards
• 1985, ANSI T1X1 Committee
• Fiber Optic Equipment
• Multi-vendor Environment
• Open Systems and Standards
»
DO NOT GET LOCKED INTO “A”
VENDORS TECHNOLOGY
©SCTE
VA 5.6
DigiPoints
Volume 1
Phase 1 & 2 SONET
Phase 1
•
•
•
•
•
•
Rates and formats
Mapping hierarchical signals
Performance monitoring
Automatic protection switching
Synchronization requirements
Optical parameter specifications.
Phase 2
• Short reach (INTRA-office) specifications for OC-1 to OC-12
rates.
• Electrical intra-office specifications from EC-1 to EC-12
• Intra-office LAN topology
• Data communications channel protocol using a seven layer stack
• Asynchronous Transfer Mode (ATM) and Fiber Distributed Data
Interface (FDDI) signal mapping
• Core OAM&P
• Synchronization specifications
• Payload and interface jitter and wander specifications.
©SCTE
VA 5.7
DigiPoints
Volume 1
SONET Line Rates
OPTICAL
CARRIER LEVEL
OC-1
OC-3
OC-9
OC-12
OC-18
OC-24
OC-36
OC-48
OC-192
ELECTRICAL
CONNECTION
EC-1
EC-3
EC-9
EC-12
EC-18
EC-24
EC-36
EC-48
EC-192
OC-N
EC-N
©SCTE
LINE RATE
Mb/s
51.840
155.520
466.560
622.080
933.120
1244.160
1866.240
2488.320
9953.280
= N * 51.840
VA 5.8
DigiPoints
Volume 1
SONET Frame
9 X 90 Bytes
51,840,000 bits per second
1
2
3
4
5
6
7
8
9
. . . . . . . . . . . . . . . .
89 90
1
Transport Overhead
2
3
4
5
6
7
8
9
STS Synchronous Payload Envelope (SPE)
SECTION OVERHEAD
PATH OVERHEAD
LINE OVERHEAD
PAYLOAD
©SCTE
VA 5.9
DigiPoints
Volume 1
Types of SONET Overhead
Section
9 Bytes
Line
18 Bytes
Path
9 Bytes
72 bits
36 Bytes
288 bits
774 bytes
6,192 bits
Overhead Total
Payload
Frame Total
810 bytes
72 bits
144 bits
6,480 bits
Section and Line Overhead are
called the Transport Overhead
(TOH)
There are 8000 of these frames each
second to give a total bit rate of
51,840,000 b/s
Thus, the fixed overhead for the SONET frame is 36 bytes or 4.4% of the total bits transmitted.
©SCTE
VA 5.10
DigiPoints
Volume 1
End to End SONET Transmission
Path
Terminating
Equipment
Line
Terminating
Equipment
(MUX)
Section
Regenerator
Line
Terminating
Equipment
(MUX)
Regenerator
Section
Path
Terminating
Equipment
Section
Line
Path
©SCTE
VA 5.11
DigiPoints
Volume 1
SONET Overhead Content
SECTION OVERHEAD
Framing
Framing
A1
A2
BIP-8
Orderwire
B1
E1
Data COM Data COM
D1
D2
Pointer
Pointer
H1
H2
BIP-8
APS
B2
K1
Data COM Data COM
D4
D5
Data COM Data COM
D7
D8
Data COM Data COM
D10
D11
Growth
Growth
Z1
Z2
LINE OVERHEAD
STS-1 ID
C1
User
F1
Data COM
D3
Pointer Action
H3
APS
K2
Data COM
D6
Data COM
D9
Data COM
D12
Orderwire
E2
PATH Overhead
Trace
J1
BIP-8
B3
Signal Label
C2
Path Status
G1
User Channel
F2
Multiframe
H4
Growth
Z3
Growth
Z4
Growth
Z5
Line Overhead and Section Overhead together are referred to as Transport Overhead (TOH).
©SCTE
VA 5.12
DigiPoints
Volume 1
Virtual Tributary (VT) Data Rates
VT Type
VT1.5
VT2
VT3
VT6
VT Rate
Mb/s
1.728
2.304
3.456
6.912
Example Payload
Mb/s
DS-1
@ 1.544
CEPT-1 @ 2.048
DS-1C @ 3.152
DS-2
@ 6.312
©SCTE
STS-1 Columns
Needed
3
4
6
12
Total Payloads
Carried in a STS-1
28
21
14
7
VA 5.13
DigiPoints
Volume 1
Size Comparison of VT Frames Carried in the SPE
1 2 3
1 2 3 4
VT1.5
1.728 Mb/s
VT2
2.304 Mb/s
1 2 3 4
5 6
1 2 3 4
5 6
7 8 9 10 11 12
1
2
3
4
5
6
7
8
9
VT3
3.456 Mb/s
VT4
6.912 Mb/s
VT Overhead
©SCTE
VA 5.14
DigiPoints
Volume 1
VT Combinations Examples
Asynchronous
Signal
EXAMPLE 1
DS-1
DS-1C
DS-2
CEPT-1
EXAMPLE 2
DS-1
DS-1C
DS-2
CEPT-1
EXAMPLE 3
DS-1
DS-1C
DS-2
CEPT-1
Quantity
VT Frames
Required
VT Groups
Used for this
Signal Level
Total
VT Groups
Spare Space in VT Group
at this Rate
3
1
4
1
3 - VT1.5
1 - VT3
4 - VT4
1 - VT2
1
1
4
1
1
2
6
7
1 - DS-1
1 - DS-1C
2 - CEPT-1
5
0
4
3
5 - VT1.5
0
4 - VT4
3 - VT2
2
0
4
1
2
2
6
7
3 - DS-1
-
0
0
6
2
0
0
6 - VT4
2 - VT2
0
0
6
1
0
0
6
7
1 - CEPT-1
©SCTE
VA 5.15
DigiPoints
Volume 1
SONET Frame
A11 A12 A13 A21 A22 A23
1
1
2
3 4
5
6
7
8
9
. . . . . . . . . . . . . . . .
89 90
A13 A23
2
1
1
1
2
3
2
A11 A21
2
3
1
A12 A224
2
5
3 4
3
4
5
5
6
3 4
7
8
5
6
7
8
9
. . . . . . . . . . . . . . . .
9
. . . . . . . . . . . . . . . .
89 90
89 90
6
7
8
6
9
4
5
7
STS Synchronous Payload Envelope (SPE)
8
6
9
7
STS Synchronous Payload Envelope (SPE)
8
9
STS Synchronous Payload Envelope (SPE)
©SCTE
VA 5.16
DigiPoints
Volume 1
SONET STS-9 Multiplexing
1
STS-1
STS-1
2
3 2 1
STS-3
1st Frame’s byte
in 1st Position
3:1
STS-1
3
4th Frame’s Byte
in 2nd Position
4
STS-1
6 5 4
STS-1
5
STS-3
3:1
3:1
9 6 3 8 5 2 7 4 1
STS-9
STS-1
6
7
7th Frame’s Byte
in 3rd Position
STS-1
STS-1
8
9 8 7
STS-3
3:1
STS-1
9
©SCTE
VA 5.17
DigiPoints
Volume 1
SONET Standards
US
ANSI T1.106
ANSI T1.105
ANSI T1.117
ANSI T1.119
ANSI T1-101
ANSI T1-204
ANSI T1-208
ANSI T1-210
ITU-T
(formerly CCITT)
Bellcore
Generic Requirements
G.707 ~ G.709
G.957
G.958
G.803
G.774
G.831
Blue Books
TR NWT 253
TA NWT 253
TA NWT 1042
TA NWT 1042 issue 3
TA NWT 1250
TA TSY 000378
TR TSY 000064
TR TSY 000482
TR TSY 000499
©SCTE
VA 5.18
DigiPoints
Volume 1
NORTH AMERICAN, CEPT, AND SONET
HIERARCHY
T1
Span
Analog
Optics
or RF
T3
Span
90 Mb/s
Optics
T2
Span
2
1
SONET STS-1E or EC-1 51.840 Mb/s
OC-3
SONET
1
OC-N
SONET
3
N
672 Channels
1
DS3
44.736 Mb/s
672 Channels
7
14
1
DS2 6.312 Mb/s 96 Chan
28
DS1C 3.152 Mb/s 48 Chan
4
CEPT 2.048 Mb/s 30 Bearer Chan
DS1
1.544 Mb/s
©SCTE
2
24 DS0 Channels
VA 5.19