1. SDH

2. SDH / SONET Introduction to SDH/ SONET
Applications / advantages/ disadvantages
Physical Configuration
SONET/ SDH Layers
Transmission Formats and Speed
Optical Interfaces Specifications
SONET/ SDH Rings
SONET/SDH Networks

3. Introduction to SDH / SONET
ITU-T standards is called the Synchronous Digital Hierarchy (SDH)
ANSI standards is called the Synchronous Optical Network (SONET)
Three Important concerns in designing SONET/ SDH*
It is a Synchronous network.
A single clock is used to handle the timing of transmission and equipment across the entire network.
Network wise synchronization adds a level of predictability to the system.
This predictability , coupled with powerful frame design, enables individual channels to be multiplexed, thereby improving speed and reducing cost.
Standardization.
SDH/SONET contains recommendations for the standardization of fiber optic transmission system equipment sold by different manufacturers.

4. Introduction to SDH / SONET
3. Universal Connectivity.
SDH/SONET physical specification and frame design include mechanism that allow it to carry signals from incompatible tributary systems. This flexibility gives SONET/ SDH a reputation for universal connectivity.
Applications:
Carrier for ISDN and B-ISDN.
Carrier for ATM cells.
Can support bandwidth on demand.
Can be used as the backbone or totally replace other networking protocols such as SMDS or FDDI.
Can replace PDH system,E1, E3 lines.

5. Introduction to SDH / SONET
Advantages of SDH
Flexible
Cost effective
Manageable
Standardized
International
New generation of multiplexers with direct
access to every single low-speed tributary
(e.g. 2 Mbit/s/1.5 Mbit/s), sophisticated signal protection mechanisms
Integration of multiplex, cross-connect andline terminal functions as part of a software-controlled network element
Adequate and standardized signal overhead capacity for remote operation, administration and maintenance (OAM)
Standardized line signal as a uniform interface for all manufacturers (multi-vendor policy)
Uniform multiplexing principle for both existing hierarchies (USA and Europe)

6. Disdvantages of SDH Abundant
Overheads bits
low bandwidth utilization ratio, contradiction between efficiency and reliability
Mechanism of pointer adjustment is complex, it can cause pointer adjustment jitters
Pointer
adjustment
Software based
Large-scale application of software makes SDH system vulnerable to viruses or mistakes.

7. Physical Configuration*
Add/drop
multiplexer
Regenerator
Regenerator
MUX
MUX
Section
Section
Section
Section
Line
Line
Path

8. Multiplexer/ Demultiplexer: Multiplexer marks the beginning and end points of a SDH link. They provide interface between a tributary network and SDH and either multiplex signals from multiple sources into an STM signal or demultiplex as STM signal into different destination Signals.
Regenerator: Regenerator extend the length of the links, it takes optical signal and regenerates. SDH regenerator replaces some of the existing overhead information with new information. These devices function at the data link layer.
Add/ drop multiplexer: It can add signals coming from different sources into a given path or remove a desired signal from a path and redirect it without demultiplexing the entire signal. Instead of relying on timing and bit position add/drop multiplexer use header information such as addresses and pointers to identify the individual steams.

9. Section: It is the optical link connecting two neighbor devices:
Multiplexer to Multiplexer
Multiplexer to Regenerator
Regenerator to Regenerator
Line: It is the portion of the network between two multiplexers:
STM Multiplexer to add/drop multiplexer
Two add/drop multiplexers
Two STM multiplexers
Paths: It is the end to end portion of the network between two STM multiplexers.
In a simple SDH of two multiplexers linked directly to each other, the section, line, and path are the same.

10. SONET/SDH Layers Path layer Line layer Section layer Data link
Photonic layer
Physical

11. SONET/SDH Layers
Photonic Layer: Corresponds to the physical layer of the OSI model. It includes physical specifications for the optical fiber channel, the sensitivity of the receiver, multiplexing functions, and so on. It uses NRZ encoding.
Section Layer: It is responsible for the movement of a signal across a physical section. It handles framing, scrambling and error control. Section layer overhead is added to the frame at this layer.
Line Layer: It is responsible for the movement of a signal across a physical line. Line overhead (Pointers, protection bytes, parity bytes etc) is added to the frame at this layers. STM multiplexer and add/drop multiplexers provide line layer functions.
Path Layer: It is responsible for the movement of a signal from its optical source to its optical destination. At the optical source, the signal is changed from an electronic form into an optical form, multiplexed with other signals, and encapsulated in a frame. Path layer overhead is added at this layer. STM multiplexer provide path layer functions.

12. Device Layer Relationship
Path
Path
Line
Line
Line
Section
Section
Section
Section
Section
Photonic
Photonic
Photonic
Photonic
Photonic
Regenerator
Regenerator
MUX
MUX
Add/drop
multiplexer

13. No of E1s in STM-1,STM-4,STM-16 and STM-64 ?
Transmission Formats and speeds
Commonly Used SONET and SDH Transmission Rates
QUIZ:
No of E1s in STM-1,STM-4,STM-16 and STM-64 ?

14. Transmission Formats and speeds
Line rate calculation 9
270
Total Frame Capacity: 270 X 9 = 2430 Bytes
Total Number of Bits = 2430 X 8 = Bits
Time Period of One Frame = 125 microseconds
Bits/Second = 19440/125 X = Mbits/Sec
= STM-1
4X STM-1 = STM-4
4XSTM-4 = STM-16

15. Transmission Formats and seeds
SDH components
SDH Frame is made of the following
SDH payload
Pointer
Path Over head
Section Overhead
Multiplex section overhead
Regenerator section overhead
Overhead is fixed and is like a Header. It contains all information including Monitoring,O&M functions etc.

16. Transmission Formats and speeds
SDH Frame 2 34
140
SDH
270 x N Columns
1 Byte
RSOH
261 Bytes
Pointer
9 Rows
POH
Payload
MSOH
Actual Traffic
STM-1, STM-4, STM-16, STM-64, STM-256

17. SONET/ SDH Rings
SONET and SDH are configured as either ring or mesh architecture.
So Loop diversity is achieved in case of link or equipment failure.
SONET/SDH rings are commonly called self-healing rings. Means automatic switching to standby link on failure or degradation of the link.
Three main features of SONET/SDH rings:
There can be either two or four fibers running between the nodes on a ring.
Operating signal signals can travel either clockwise only (unidirectional ring) or in both directions around the ring (which is called bidirectional ring).
Protection switching can be performed either via line-switching or a path switching scheme.
Line switching moves all signal channels of an entire STM-N channel to a protection fiber.
Path switching can move individual payload channels within a STM-N channel to another path.

18. Two fibers, unidirectional, path-switched ring (two-fiber UPSR)
SONET/ SDH Rings
Following two architectures have become popular for SONET and SDH Networks:
Two fibers, unidirectional, path-switched ring (two-fiber UPSR)
Two fiber or four fiber, bidirectional, line switched ring( two fiber or four fiber BLSR)\
(They are also referred to as unidirectional or
bidirectional self healing ring , USHRs or BSHRs)

19. SONET/ SDH Rings
Generic two fiber unidirectional path-switched ring (UPSR) with counter rotating protection path.
Flow of primary and protection traffic from node 1 to node 3

20. Architecture of a four-fiber bidirectional line-switched ring (BLSR).
SONET/ SDH Rings
Architecture of a four-fiber bidirectional line-switched ring (BLSR).

21. SONET/ SDH Rings
Reconfiguration of a four-fiber BLSR under transceiver or line failure.

22. SONET /SDH Networks Point-to-point links Linear chains UPSRs BLSRs
SONET/SDH equipment allows the configuration of a variety of network architectures, as shown in next slide. For example
Point-to-point links
Linear chains
UPSRs
BLSRs
Interconnected rings
Each of the individual rings has its own failure recovery mechanisms and SONET/SDH network management procedures.
An important SONET/SDH network element is the add/drop multiplexer
(ADM). This piece of equipment is a fully synchronous, byte-oriented multiplexer that is used to add and drop subchannels within an OC-N signal.
The SONET/SDH architectures also can be implemented with multiple wavelengths. For example, Fig in next slide, will show a dense WDM deployment on an OC-192 trunk ring for n wavelengths

23. SONET /SDH Networks
Where
OC-3 = STM-1
OC-12 = STM-4
OC-48 = STM-16
OC-192= STM-64
Generic configuration of a large SONET network consisting of linear chains and various types of interconnected rings.

24. SONET /SDH Networks
Functional concept of an add/drop multiplexer for SONET/SDH applications.

25. SONET /SDH Networks
Dense WDM deployment of n wavelengths in an OC-192/ STM-64 trunk ring.

26. Mapping
Is the procedure through which signals are packed inside an SDH frame
PDH signal passes through the following steps before emerging as an SDH Signal
Container (C-X)
Virtual Container (VC-X)
Tributary Unit (TU-X)
Tributary Unit Group (TUG-X)
Administrative Unit (AU-4)
STM Signal

27. How 2 Mb signals are mapped into an SDH stream?
Container
C-12
2 Mb/Sec
Path Overhead (POH)
Virtual Container
VC-12

28. How 2 Mb signals are mapped into an SDH stream?
VC-12
Payload
Starting address of Payload in VC.
Pointer TU
(Tributary Unit)
SOH
STM-1/4/16
SOH 9
270

29. Formation of Synchronous Signal
Plesiochronous signal
Container (C)
Path overhead
Additional information for end-to-end monitoring
Virtual
container (VC)
Pointer
Phase relation between
virtual container (payload)
and subordinate frame
Tributary unit (TU)
Synchronous Signal

30. ITU-T recommendation G.707 and its realization
STM-N
× n
× 1
AUG
AU4
VC4 C4
140 Mbit/s
× 1
× 3
TUG3
TU3
VC3
34 Mbit/s
AU3
VC3 C3
(45 Mbit/s)
AU/G Administrative unit/group
C Container
STM Synchronous transport module
TU/G Tributary unit/group
VC Virtual container
Pointer processing
Multiplexing
Aligning
Mapping
Cross-connect level
× 7
× 1
TUG2
TU2
VC2 C2
(6 Mbit/s)
× 3
TU12
VC12
C12
2 Mbit/s
TU11
VC11
C11
(1.5 Mbit/s)
Source: TR BM TP 5

31. Structure of a STM-1 frame
270 bytes 9
261
Payload 3
SOH
1 × AU-4 pointer
3 × TU-3 pointer
SOH 1
PTR
9 rows
VC-4 P
SOH O H
SOH 5 P
VC-3
e.g.
3 × VC-3
in VC-4 O H
Frame length 125 s
POH Path overhead
PTR Pointer
SOH Section overhead
SDH – Basic information

32. SDH Overheads STM-1 SOH SOH POH VC-4
An overhead is like a delivery notice with the parcel which contains information about the contents, Condition, type, address, postal date, weight etc. of the parcel.
In the SDH a distinction is made between Section Overhead (SOH) and Path Overhead (POH)
STM-1
SOH
SOH
POH
VC-4

33. SDH Multiplexing Structure×1
Mapping
AUG-64
STM-64
Aligning ×4
Multiplexing ×1
AUG-16
STM-16
Pointer processing ×4 ×1
AUG-4
STM-4 ×4 ×1 ×1
AU-4
VC-4
C-4
STM-1
AUG-1
kbit/s ×3
此页标题禁止有多级标题，更不要出现所在章节的名称。
此页标题要简练，能直接表达出本页的内容。
内容页可以除标题外的任何版式，如图、表等。
该页在授课和胶片＋注释中都要使用。
TU-3
VC-3
C-3
TUG-3 ×1
34368 kbit/s ×7
TUG-2
TU-12
VC-12
C-12
2048 kbit/s ×3

34. Intentionally Left Blank