EE33-E4 (CFA) E4 (CFA) Overview of SDH CFA-Overview of SDH.pdf · • SDH & PDH Hierarchy ... path...

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E3E3--E4 (CFA) E4 (CFA)

Overview of SDHOverview of SDH

AGENDA

• SDH & PDH Hierarchy

• SDH Network Survivability

� 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

• Synchronous: The digital transitions in the signalsoccur exactly at the same rate. In Synchronousnetwork, 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 ITU–T 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

CONCEPT OF SYNCHRONOUS,

PLESIOCHRONOUS, ASYNCHRONOUS

• Asynchronous: Transitions of the signal doesn’tnecessarily occur at same nominal rate. Twoclock are derived from free-running quartzoscillators. (difference between two clock is muchgreater than a Plesiochronous difference).

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

(MATRIX REPRESENTATION)

SDH FRAME REPRESENTATION

BIT RATE : STM-N

Number of Rows = 9Number of Columns = 9+261=270Number of Bytes = 9x270Number of Bits = 9x270x8Number of Bits/Second = 9x270x8x8000

=155520000=155.520 Mbps (STM-1)

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

SDH NETWORK ELEMENTS

SDH Repeater

STM-n STM-nApplications:

Line Signal Regeneration

in Point-to-Point and Ring

Networks

Terminal Multiplexer

STM-nPDH &

STM-mTributaries

Applications:

Point-to-Point

Transmission Systems

(STM-1, STM-4, STM-16)

STM-1/4STM-1/4

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

......

WEST EAST

ADD DROP MULTIPLEXER

NETWORK TOPOLOGY

TM TMADM

* Point-To-Multipoint:

* Point-To-Point:

* Ring-Topology:

NETWORK TOPOLOGY

Best Advantage of This Topology is Strong Survivability.

MESH TOPOLOGY

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

DXC/ADM

DXC/ADM DXC/ADM

DXC/ADM

� A self healing network means that a network can automatically recover the services from a failure fault in a very short period of time without making users be aware of any network fault.

• A Self-healing network involves no repairing and replacement of a specific faulty component or part but the reestablishment of communication.

SURVIVABILITY OF SDH NETWORK

1. Linear ProtectionThere are three different protection scheme in Linear Protection

a. 1+1 Protection scheme (1+1 configuration)Each working line is protected by one protection line. The same signal is transmitted on both lines. If a failure or degradation occur, the network elements switch the connection over to the Protection line at the receive end.

SURVIVABILITY OF SDH N/W (Contd.)

b. 1:1 Protection scheme (1:1 configuration)A protection line is used to directly replace the working line when it fails. The protection path can only be used if a switchover takes place at both the transmitting end and the receiving end.

c. 1:N Protection schemeA 1:N configuration represents a more cost-effective solution than the other two mechanisms. N working channels are protected by one protection channel. If there are no defects in the network, this protection channel can be used to transport low priority traffic.

Sub Network Connection (SNC) Protection:

Sub network connection protection is a path protection Mechanism that It is required to create two path for each circuit, one working and one protection. It can be used to protect a portion of a path (e.g. that where two Separate path segments are available), It need not be used on all VCs within all multiplex section.

• 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.

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 being

adopted.

Concept Of Line Switched Protection

Uni-Directional Self Healing Ring

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 counter

clockwise direction path and is used as alternate path for protection against ring or node failure.

• The USHR mechanism itself does not remain aware which fiber is carrying traffic.

Features of USHR (contd.)

• In case traffic is switched over to alternate path the traffic is not returned on normal path after restoration.

• USHR is less informative but it protect traffic positively.

• It offers cost effective solution for low level of capacity network.

Concept of Speech in SDH Ring

Bi-Directional Self Healing Ring

Node 1

Node 2

Node 3

Node 4

Feature of BSHR•BSHR is more informative.• The scheme requires a APS protocol to make it operative.• 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 counter clockwise from node 3 to node1 along links 7p and 8p.• Thus the information exchange between nodes 1 and 3 does not tie up any of the primary channel bandwidth in the other half of the ring.

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

BSHR only.• The ring protocol is essential for both two fiber ring

as 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 section equally into working and protection capacity.

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

(AUGs) for protection.

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

multiplex sections.• The sharing of protection capacity may allow a

multiplex section shared protection ring to carry more traffic under normal conditions than other ring type.

• The sum of the tributaries that transverse a span cannot exceed the maximum capacity of the particular span.

• In MS shared protection the service can be routed in either one of the two directions, the long way around the ring or the short way.

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 16

excluding regenerator.

Thanks

EE33-E4 (CFA) E4 (CFA) Overview of SDH CFA-Overview of SDH.pdf · • SDH & PDH Hierarchy ... path...

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