sdh presentation
DESCRIPTION
The output of a brief study on Synchronous Digital Hierarchy (SDH) at Alcatel-Lucent.TRANSCRIPT
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 1BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 1
SYNCHRONOUS DIGITAL
HIERARCHY (SDH)
…At the Speed of Ideas
By Ayodeji Morakinyo
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 2
Agenda
Introduction
Comparisons between STM-1 and STM-4 & PDH and SDH
The SDH Frame
The Virtual Container and Tributary Units
Faults, Errors & Alarms
Principles of Partitioning & Layering and Network Sync
Equipment Protection
The Cons of SDH Technology
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 3
First approved in 1988, SDH is a high speed and high
capacity optical transport system capable of creating simple,
flexible and economic infrastructures in telecommunication
networks. It is primarily used to carry telephony traffic.
In North America (Canada, USA, etc), SONET is the
equivalent of SDH. The differences are found only in the
terminologies used & the lowest signal level.
The SDH channel range or frequency is between
4GHz to 13GHz frequency bands for LH transmission.
Introduction
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 4
vPDH Equipment
PDH Equipment
ATM Equipment
PDH Equipment
PDH Equipment
ATM Equipment
ATM VP
ATM VP140Mbit/s
2Mbit/s
45Mbit/s
34Mbit/sSTM-4
STM-4
STM-1
STM-16
STM-1
6
STM-1
6
STM-16
STM-1
STM-4
STM
-4
STM-4
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 5
Lowest level SDH signal is called Synchronous Transport
Module level 1 (STM-1) operating at basic rate 155.52Mbps. STM-
1 can be seen as an SDH frame.
STM-N Frame
MUX
Signal A
Signal B
Signal C
Signal D
STM-1 frame
STM-4STM-4
* STM-1 frames multiplexed must have the same:
frame, bit rate and synchronisation.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 6
9 r
ow
s
270 columns
Comparison between STM-1 and STM-4
4 X 270 columns = 1080
In STM-1, 9 columns are used for section overhead.
In STM-4, 36 columns are used for section overhead.
9 r
ow
s
1080 columns
STM-1 STM-4
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 7
N rows X M columns X 8 bits/byte X 2frequency
Therefore,
9X 270 X 8 X 2(4000)frames/sec = 15552000bit/s
Because, the human voice frequency is between 300 & 3400Hz
And with the consideration of band guard, we obtain: 4KHz
Therefore, the frequency utilized is 4000Hz
So, approximately, we have:
155.52Mbit/s
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 8
Higher SDH rates are obtained by multiplexing the base
rate. From STM-1 to higher data rates.
So, there we can have:
STM-N Bit rate
STM-1 155.52Mbps
STM-4 622.08Mbps
STM-16 2488.32Mbps
STM-64 9953.28Mbps
STM-N X 4
STM-4NWhere: N=1, 4,16
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 9
Comparison between PDH & SDH
Unlike PDH, SDH has the advantage of allowing both
system monitoring and management in terms of tributary
access, cost effectiveness, and equipment vendor variability.
It allows for upgrades from the basic rate of 155.52Mbps to
622.08Mbps and so on.
STM-1
STM-4
STM-16
STM-64
155.52Mbit/
s …
...
9953.28M
bit/s
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 10
Plesiochronous Digital
Hierarchy
(PDH)
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 11
PDH SDH
Provision is made for system
monitoring only i.e. no spare
signal capacity.
Allows both system monitoring and
management functions e.g.
maintenance can be performed
remotely from the network
management station. Hence, response
to customers request is swifter.
Only same vendor equipment
are used throughout the
network
Multi-vendor interoperability.
Different vendor-supplied equipment
can be utilized on the network. Hence,
upgrading is easier to perform.
Structure is comparatively rigid. Flexible Architecture.
It is capable of accommodating future
applications with a variety of
transmission rate.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 12
Synchronous Digital
Hierarchy
(SDH)
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 13
The SDH Frame
A frame is a variable-length data packet that can be
transported in a network.
An SDH frame is one of a particular signal capacity (or
STM level) that can be transmitted along an optical link in a
synchronous transport network.
RSOH
Virtual container
PO
H
payload or customer traffic
MSOH
155.52Mbit/s
is the signal
capacity for
STM-1 data
frame
SOH
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 14
SOH
9 columns
POH
1 column
Actual capacity of VC
Finding the actual capacity of the container (VC):
270 columns – (9 + 1) columns = 260 columns
Hence, 9rows X 260columns X 8bits/byte X 2(4000)
Actual capacity of VC payload = 149.76Mbit/s
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 15
SDH
Terminal
Mux
SDH
DXC
SDH
Terminal
Demux
Transport Nodes
Regenerators
Regenerators: examples are optical amplifiers like LOFA
Transport Nodes: examples are DXCs, Muxes and Demuxes.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 16
The SDH frame comprises the section overhead (SOH)
which is responsible for the transmission of the payload and the
payload (or customer traffic) itself.
SOH is the signal capacity contained in each SDH frame to
transport virtual containers between adjacent nodes.
SOH = RSOH + MSOH
SDH Frame = SOH + POH + Payload
SOH bytes occupy the first 9 columns of an STM-1 frame.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 17
RSOH is the regenerator section overhead. It is
responsible for the transmission of the frame between
regenerators (e.g. from amplifier to amplifier, from amplifier to
demux or from DXC to amplifier).
The RSOH bytes and their functions include:
�parity BIP-8 check (B1 byte)
�frame alignment pattern (A1, A2 bytes)
�STM-1 identification (J0 byte)
�user channel (F1 byte)
�datacom channel (D1, D2, D3 bytes)
�voice channel (E1 byte)
RSOH
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 18
MSOH is the multiplexer section overhead and it
manages the transmission between transport nodes (e.g. from
mux to DXC and from DXC to demux).
Some MSOH bytes and their functions are:
�parity check (B2 byte)
�alarm information (S1 byte)
�automatic protection switching (K1,K2 bytes)
�payload pointers (H1,H2,H3 bytes)
�datacom channel (D4 – D12 bytes)
�voice channel (E2 byte)
MSOH
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 19
POH is the path overhead and it manages the transmission
of the virtual container between the mux (where the frame is
assembled) and the demux (where it is disassembled).
POH bytes and functions:
�path trace message (J1 byte)
�parity check (B3 byte)
�user channel (F2,F3 bytes)
�alarm & performance information (G1,N1 bytes)
�virtual container structure (C2 byte)
�automatic protection switching (K3 byte)
�multi-frame indication for TUs (H4 byte)
POH
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 20
The Virtual Container and Tributary Units
The virtual container (VC) is the part of the STM-N
frame that contains the customer traffic. It is designed to
carry 139Mbps actual payload and possesses the ability to
float relative to the STM frame.
The VC can be
divided into tributary
units (TUs)
TU-2 TU-3 TU-12
Tributary Units
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 21
A tributary unit is a low order signal that can be
multiplexed through the tributary channel. It represents
a mini-frame and fixed numbers of TUs can be mapped
into a VC.
Mapping here refers to the process of inserting
signals into the virtual container.
Payload capacity provided for each TU is always
slightly greater than that required by it. For example, a
49.54Mbps TU-3 may be mapped with a 44.736Mbps
capacity.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 22
TU frame is similar to the SDH frame on the basis that
it comprises the TU-SOH, TU-POH and low rate tributary
signal.
TU-SOH
TU-POH
Low rate tributary signal
Tri
bu
tary
Un
it
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 23
Tributary Unit Data Rate Number of Columns
TU-3 49.54Mbps 86
TU-2 6.912Mbps 12
TU-12 2.304Mbps 4
TU-11 1.728Mbps 3
Tributary Unit Group (TUGs) are intermediate
multiplexing levels derived from the smaller tributary units.
TUG-2 = TU-2 + TU-12 + TU-11
TUG-3 = TU-3 + TU-2
AUG = TUG-2 + TUG-3
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 24
TUs have two operating modes:
1.Locked Mode: where the TUs are locked in the VC and they
do not require payload pointers . Also in this mode, the TU
structure does not have a POH. Hence, it is suitable where no
sync problems exist.
2.Floating Mode: is the most utilized mode. Here, the TU’s
virtual container is allowed to float w.r.t the TU frame. This
mode also has two types: the async mode and the byte sync
mode.
No POH
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 25
Why should use TUs?
�Designed to fit neatly into the virtual container
�Allows direct access to lower level tributaries
�Provides efficient transport, add-drop & cross-connection
capabilities with minimum delay
�Cross-connects & add-drop elements do NOT have to
demux to gain access to smaller tributaries.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 26
When transmission errors occur in SDH, they are
detected by the BIP bytes and communicated back
upstream via the REI signal.
REI means Rate Error Indication. It is a signal that is
sent upstream when an error occurs at the far of the frame
block.
In the event of a serious fault, an alarm is generated
[e.g. loss of signal (LOS), frame (LOF) or pointer (LOP)]. A
Remote Detection Indication (RDI) message is sent back to
the transmitting end. NEs downstream are also alerted via
an AIS (Alarm Indication Signal)
Pry
Sec
Faults, Errors & Alarms
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 27
Again, when such major failures occur, the NE will
switch transmission from the line where the fault occurs to the
back-up line. This is initiated by the Multiplexer Section
Protection (MSP).
SDH networks are designed to recover from failure
conditions using protection switching (K1,K2) bytes. To create
the back-up line, the transmission lines are duplicated between
NEs.
Other kinds of errors:
Interruption of line Server signal failure (SSF)
No input signal
Failure of an NE
LOP
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 28
Partitioning Concept: entails representing the physical
implementation as links and sub-networks, starting from the
smallest (indivisible) sub-network or matrix .
Any sub-network may also be partitioned into a number
of smaller sub-networks interconnected by links.
Layering Concept: entails the provision of transport layer by
layer such that each network layer provides transport and uses
transport from the layer below.
The layer providing transport is called a SERVER while the
one using transport is termed a CLIENT.
Principles of Partitioning & Layering and Network Sync
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 29
Transit part sub-
network in a
national part
sub-network
Local part sub-
network in a
national part
sub-network
National part
sub-networkInternational part
sub-network
PARTITIONING CONCEPT
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 30
LAYERING CONCEPT
PDH or ATM VP Layer Network
VC - 11 VC - 12 VC- 2 VC -3
VC - 4
Multiplexer
section
Regenerator
Section
Pa
th L
ay
er
Se
ctio
n L
ay
er
Low
ord
er
Hig
h o
rde
r
High and low order
path layers handle the
termination and
generation of POH
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 31
The partitioning concept is vital for defining:
•The network structure within a layer network
•Administrative boundaries between network operators
jointly providing connections within a single layer network
The layering concept allows:
•Simple modelling of networks that contain multiple
transport technologies
•Independent design and operation of each network layer
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 32
Network Synchronization
SDH networks are used to transport PDH and ATM signals
hence, they must be able to convey data in both synchronous
and asynchronous modes.
Clock Types
1. Primary Reference Clock (PRC): ensures that NEs are
synchronously clocked or timed. PRC can be doubled or
tripled on different sites for safety purpose with one
acting as the master clock and the others as slave e.g.
Rubidium-clock or GPS: 10-11/day frequency shift.
2. Synchronous Supply Unit (SSU): is used for refreshing sync
signals after 20 NEs. The transit mode is 10-8/day. Local
mode is 10-9 /day.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 33
3. Synchronous Equipment Clock (SEC): is the lowest level of
clocking obtainable in SDH networks. The frequency drift is at
10-8
/day.
PRC
SSU
SEC
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 34
1. Equipment Protection Switching (EPS): the matrix, clock,
control and power parts are protected via EPS (1+1) while
all electrical I/O boards are optically protected via the EPS
(1:N).
In EPS (1+1) protection mechanism, one working
equipment is protected by another redundant one so that
if the working equipment fails, the faulty one can be
exchanged. Its’ mode is non-revertive.
Equipment 1
Equipment 2
Equipment Protection
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 35
In EPS (1:N), N working pieces of equipment are
protected by just one equivalent. During normal operation
without equipment failure, the protecting equipment is
inactive. However, it may also be used to transfer extra
traffic (low priority line).
Equipment 1
Equipment 2
Equipment N
Equipment P
…
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 36
Tx
Rx
Rx
Tx
Rx
Tx
Tx
Rx
High Priority Line
MS
Low Priority Line
EPS (1:N) mode is revertive.
*Traffic is sent back to the working channel when the fault
has been rectified; once the wait-to-restore time(5-12mins)
has elapsed*
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 37
2. Multiplex Section Protection (MSP): provides
equipment protection in the NE, line protection between
adjacent multiplex elements and all optical I/O boards inside
NE are optically protected via MSP(1+1).
Node A Node B
SOH
Normal Traffic Channel
Protection Channel
SOH
Normal Traffic Channel
Protection Channel
STM-16 Fibre
Normal Channel
AU: 1-8
Protection Channel
AU: 9-16
MS-SPRING
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 38
Network Restoration: is an alternative to network protection in
which DXC together with SDH network manager provide support for
path restoration, MSP & SNCP as well as SNCP protection &
restoration combined.
DXC
A
NE
B
NE
C
DXC
D
NE
F
NE
E
DXC
A
NE
B
NE
C
DXC
D
NE
F
NE
E
VC-n
VC-n
VC-n
VC-n
Few seconds later . . .
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 39
1. Fixed Circuits causes data traffic limitation
SDH provisions dedicated P-to-P circuits between ring
nodes hence, each has fixed allocation of BW that limits the
maximum burst traffic data transfer rate. This is the
disadvantage for data traffic because it is inherently bursty.
2.Waste of BW for meshing
Mesh creation results in inefficient BW usage since
meshes in metro networks require ease of deployment,
maintenance and upgrading.
The Cons…
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 40
In conclusion, SDH transport network saves the customer the
hassles of labour-intensive maintenance and provides the
advantage of using different vendor equipment on the same
network.
SDH offers more flexibility and relatively economic solutions.
SDH is therefore customer friendly and
as a result, helps in attaining one the
objectives of Alcatel-Lucent.
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 41
END OF PRESENTATION
MERCI MERCI MERCI MERCI
BEAUCOUP!BEAUCOUP!BEAUCOUP!BEAUCOUP!
BY AYODEJI MORAKINYO BIMONTHLY PRESENTATION 42
Acronyms
ATM = Asynchronous Transfer Mode
BIP-8 = Bit Interleaved Polarity Eight
BW = Bandwidth
Demux = Demultiplexer
DXC = Digital Cross-connect
I/O = Input/output
LOFA = Light Optical Fibre Amplifier
MUX = Multiplexer
NE = Network Element
P-to-P = Point to Point
SNCP = Sub-network Connection Protection
SONET = Synchronous Optical Network
VP = Virtual Path