06-E3-E4 CFA-Overview of SDH.pdf

7/25/2019 06-E3-E4 CFA-Overview of SDH.pdf

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For internal circulation of BSNL only

E3E3--E4 (CFA)E4 (CFA)

Overview of SDHOverview of SDH


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AGENDA

SDH & PDH Hierarchy

SDH Network Survivability


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SynchronousAll elements are synchronized with one master

clock. DIGITALInformation is in binary.

HIERARCHYSet of bit rates in a hierarchical order.

SDH is an ITU-T Standard Technology

SDH OVERVIEW


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Synchronous: The digital transitions in the signalsoccur exactly at the same rate. In Synchronous

network, all the clock are traceable to one PRC,derived from a cesium atomic clock.

Plesiochronous: The digital signal transitionsoccur at almost same rate and variation remainswithin limit as per ITUT recommendation G-811. Iftwo n/w need to inter-work, their clock may bederived from two different PRC, there is a smallfrequency difference between one clock and theother.

CONCEPT OF SYNCHRONOUS,PLESIOCHRONOUS, ASYNCHRONOUS


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CONCEPT OF SYNCHRONOUS,PLESIOCHRONOUS, ASYNCHRONOUS

Asynchronous: Transitions of the signal doesntnecessarily occur at same nominal rate. Two

clock are derived from free-running quartzoscillators. (difference between two clock is muchgreater than a Plesiochronous difference).


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SDH- ADVANTAGES

1. Network simplification .

2. Reduction in the amount of equipment.

3.Multi-vender interoperability

4. Accommodating future application

5. Protection

6. NMS Functionality


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9 261

PAYLOAD

SO

H

270

(MATRIX REPRESENTATION)

SDH FRAME REPRESENTATION


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BIT RATE : STM-N

Number of Rows = 9Number of Columns = 9+261=270

Number of Bytes = 9x270Number of Bits = 9x270x8Number of Bits/Second = 9x270x8x8000

=155520000=155.520 Mbps (STM-1)

Bit Rate of STM-N = (Nx155.520) Mbps


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SDH NETWORK ELEMENTS

SDH Repeater

STM-n STM-n Applications:Line Signal Regenerationin Point-to-Point and RingNetworks

Terminal Multiplexer

STM-nPDH &STM-m

Tributariesm


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STM-1/4STM-1/4

Tributary Ports : n x 2 Mbit/s ( 34 Mbit/s)

ADM

......

WEST EAST

ADD DROP MULTIPLEXER


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NETWORK TOPOLOGY

TM TM

TM TMADM

* Point-To-Multipoint:

* Point-To-Point:


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* Ring-Topology:

NETWORK TOPOLOGY

ADM

ADM

ADM

ADM

Best Advantage of This Topology is Strong Survivability.


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MESH TOPOLOGY

Multiple optional rout between two nodes,complex structure ,high cost and high reliability

DXC/ADM

DXC/ADM DXC/ADM

DXC/ADM


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A self healing network means that a network can

automatically recover the services from a failurefault in a very short period of time without makingusers be aware of any network fault.

A Self-healing network involves no repairing andreplacement of a specific faulty component orpart but the reestablishment of communication.

SURVIVABILITY OF SDH NETWORK


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1. Linear ProtectionThere are three different protection scheme inLinear Protection

a. 1+1 Protection scheme (1+1 configuration)Each working line is protected by oneprotection line. The same signal is transmitted

on both lines. If a failure or degradation occur,the network elements switch the connectionover to the Protection line at the receive end.

W

P

SURVIVABILITY OF SDH N/W (Contd.)


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b. 1:1 Protection scheme (1:1 configuration)A protection line is used to directly replace the

working line when it fails. The protection pathcan only be used if a switchover takes place atboth the transmitting end and the receiving end.

W

P



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c. 1:N Protection schemeA 1:N configuration represents a more cost-effective

solution than the other two mechanisms. N workingchannels are protected by one protection channel. Ifthere are no defects in the network, this protection

channel can be used to transport low priority traffic.W

W

P



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Sub Network Connection (SNC) Protection:

Sub network connection protection is a pathprotection Mechanism that It is required to createtwo path for each circuit, one working and one

protection. It can be used to protect a portion of apath (e.g. that where two Separate pathsegments are available), It need not be used onall VCs within all multiplex section.



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SDH is normally configured in a ring architecture. It is done to create loop diversity for uninterrupted

service protection in case of link failures. The SDH rings are commonly called self healing

rings, because traffic flowing in a certain path can

be automatically switch to an alternate path. Self healing rings works in two different type of way:

A- Unidirectional Self healing rings.

B- Bi-directional Self healing rings.

The concept of traffic in both type ring is different.



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Features of SDH Rings There can be either two or four fibers running

between the nodes on a ring. The operating signals can travel either clockwise

only (USHR). The operating signals can travel in both directions

around the ring (BSHR). Protection switching can be performed either via a

line switched or a path switched scheme.

In BSNL only two fiber ring mechanism is beingadopted.



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Concept Of Line Switched Protection

Uni-Directional Self Healing Ring

RX TX

TX RX

TX RX

RX TX

RX TX

TX RX

TX RX

RX TX

ADM A

ADM B

ADM C

ADM D



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Features of USHR This scheme offers less information regarding

operating System. In normal condition the traffic flows in clockwise

directions In one fiber.

In failure condition the traffic flows in counterclockwise direction path and is used as alternatepath for protection against ring or node failure.

The USHR mechanism itself does not remain awarewhich fiber is carrying traffic.



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Features of USHR (contd.)

In case traffic is switched over to alternate

path the traffic is not returned on normalpath after restoration.

USHR is less informative but it protect

traffic positively. It offers cost effective solution for low level

of capacity network.



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Concept of Speech in SDH Ring

Bi-Directional Self Healing Ring

RX TX

TX RX

TX RX

RX TX

Node 1

Node 2

Node 3

Node 4

RX TX

TX RX

TX RX

RX TX

1p

2p

3p

4p

5p

6p7p

8p



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Feature of BSHRBSHR is more informative.

The scheme requires a APS protocol to make itoperative. The traffic flows from node 1 to node 3 in clockwise

direction along links 1p and 2 p. But in return path the traffic flows in counterclockwise from node 3 to node1 along links 7p and 8p. Thus the information exchange between nodes 1 and3 does not tie up any of the primary channel bandwidthin the other half of the ring.



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Ms Shared Protection Rings MS shared protection rings scheme is supported by

BSHR only. The ring protocol is essential for both two fiber ringas well as four Fiber ring.

In BSNL only two fiber rings are deployed. MS shared protection rings are characterized by

dividing the total payload per multiplex sectionequally into working and protection capacity.

For a two fiber STM-N ring, N/2 administrative unitgroups (AUGs) available for working and N/2

(AUGs) for protection.



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Ms Shared Protection Rings (Contd.) The protection capacity is shared between multiple

multiplex sections.

The sharing of protection capacity may allow amultiplex section shared protection ring to carry moretraffic under normal conditions than other ring type.

The sum of the tributaries that transverse a spancannot exceed the maximum capacity of the particularspan.

In MS shared protection the service can be routed ineither one of the two directions, the long way aroundthe ring or the short way.



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Ms Shared Protection Rings (Contd.)

For normal working shortest path is preferable. For failure condition ,the alternate path in used.

Maximum station may not be more than 16excluding regenerator.



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Thanks

06-E3-E4 CFA-Overview of SDH.pdf

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