SDH Complete

Transport BasicsTransport Basics

Agenda

Transport Network Basics

Elements of a Transport Network

Multiplexing Concepts

Network Evolution

Equipments

Course CoverageCourse CoverageCourse – 55230 [ SDH Basics Overview]Course – 55230 [ SDH Basics Overview]

Course – 55235 [ SDH Technical Overview]Course – 55235 [ SDH Technical Overview]

Course – 55216 [ DWDM]Course – 55216 [ DWDM]

Transport Network

???

Need ???

Convergence

Voice Entertainment

Data

ISP

ASP

TELECOMNETWORK

Transport Network

ROAD

AIR

RAIL

SHARED INFRASTRUCTURE

ACCESS POINTS

COLLECTION/AGGREGATION

High Capacity/Speed Transport

Telecom Network

Access Network

Collection/Aggregation Network

Transport Network

The Transport PlaneOffers transport service between service

plane and access plane elements

Carries traffic (to/from) between the service plane components : Voice/Data switches and the end users

A transport network connects all network points (voice/data switch, radio terminal, exchanges etc.)

Transport Network Components

Collector Function

Bandwidth Management Function

High Speed Backbone

Trunk/IntercityNetwork

Urban/JunctionNetwork

Access Network

Mesh

Ring & Chain

Ring & Chain

NETWORKCONFIGURATION

• POINT TO POINT (2.5Gbps LTM. REG)• LARGE CAPACITY XC (DCC 4/4)

• ADD-DROP (622 Mbps ADM, REG)• HUBBING (622Mbps ADM, REG)

• ADD_DROP (155Mbps ADM)• HUBBING (155Mbps ADM)

APPLICATION

SDH Network : 3 Layered Architecture

Collector Function

Network interface for all access applications–Local Exchanges–PABX–Access Multiplexers–Wireless Base Stations–ATM Terminals

Primary function of collecting traffic

Bandwidth Management Function

Routing

Grooming

Consolidation

Traffic between collector rings & high speed backbone–Well defined nodes–No major changes

High Speed Backbone

Backbone function

Reliable high speed transport between geographical regions and locations

Telecom Network - View

BTS

Transport Core

ACCESS N/W

COLLECTOR/AGGREGATION N/W

Transport Network – Key Issues

Resilience–Protection from failure

Setup Cost

Service Offering

Future Proof–Scalability/Upgradability

OAM Costs–Minimal

Terminologies

Elements + Media = Network

Method of Interconnection = Topology–Bus/Linear/Chain–Star–Ring - RIC

Transport Network - Elements

Multiplexers–Terminal Multiplexers–Add/Drop Multiplexers

Regenerators

Cross Connect

Multiplexers

A

U1

U2

U3

U4

B

U5

U6

U7

U8

POINT-TO-POINT APPLICATION

TERMINAL MULTIPLXERS

U9

U10

U11U12

ADD/ DROP MULTIPLEXERS

RIC Network

AccessN/W

Collector/Aggregation Ring

Core Transport Ring

AccessN/W Access

N/W

AccessN/W

Collector/Aggregation Ring

BTSCROSS CONNECT

Multiplexing

Combination of several input channels onto a single output channel

Types–Frequency Division Multiplexing (FDM)–Time Division Multiplexing (TDM)

•Static Channel Allocation

–Statistical Time Division Multiplexing•Dynamic Channel Allocation

Frequency Division Multiplexing (FDM)

Separate frequencies to establish multiple channels within a broadband media

Carrier signals at different frequencies

Data signals added to carrier signals

Time Division Multiplexing (TDM)

Divide a single channel into short time slots

Data placed in fixed time slots

Used in baseband systems or individual channels of broadband

Time slots of same length and same order

Also referred to as synchronous TDM

Statistical Time Division Multiplexing

Dynamic allocation of time slots to active devices –First come, First Served basis

Control Field to identify Data Source

Optimal bandwidth usage

Functions

TDM

Analog-to-Digital (A/D) conversion

PCM – Pulse Code Modulation

Three Stages–Sampling–Quantization–Encoding/Decoding

Sampling

A

B

C

D

A

B

C

D

Sampling

Nyquist Theorem– fs > 2 fm

Human Voice Frequency Range–30 Hz – 3300 Hz

Telecom N/W Bandwidth–0 Hz – 4 KHz

fs = 2 * 4 KHz = 8 KHz

Quantization

PCM System

SAMPLER QUANTIZERENCODER/DECODER

A

B

C

D

64 Kbps PCM Signal

A/D CONVERTER

PCM FunctioningPCM Functioning

Synchronization

Need ?

Line Coding TechniquesLine Coding Techniques Automatic Mark Inversion (AMI)• Alternate 1’s are made (+V) and (-V), 0’s are kept as 0.• Only half pulse-width is used to transmit +/-V.• Prevents droop in the line because maximum time spent at +/-V is 1/2 pulse.

1 1 0 0 1 1 1 1 0 0 1 1 : Transmitted data

+V

0

-V

time

0 1 0 0 0 0 1 1 0 0 0 0 1 1 0 0 0 0 : Data

V-pulse B-pulse V-pulse B-pulse V-pulse

+V

0

-V

Time

High Density Bi-polar Three-zero (HDB3)• 1’s & 0’s are transmitted like AMI, until four 0’s are encountered• But set of four 0’s are substituted by 0’s and B (balance) & V (violation) pulses.• If odd number of 1’s precede four 0’s - transmit three 0’s followed by V-pulse (i.e. 000V).• If even number of 1’s precede four 0’s - transmit B-pulse, two 0’s, V-pulse (i.e. B00V)• Polarity of B & V-pulses would be depend on the last pulse.

Line Coding TechniquesLine Coding Techniques

HDB3 Coding

Initialization – 4 consecutive 0’s

Number of pulses after previous Violation bit:–Odd

•Substitution sequence– 0 0 0 V – Polarity of V bit same as preceding ‘1’ bit

–Even •Substitution sequence

– B 0 0 V – Polarity of B bit opposite to that of the preceding ‘1’ bit– Polarity of V bit same as B bit

Synchronization Methods

Synchronous–Master/Central clock – supplies time to all network

elements

Isochronous–Clocking information embedded within transmitted data

Plesiochronous (Line Timing or Line Extraction)–Clocking information derived form the incoming data

stream

Synchronization

Phase Lock LoopPLL

LOCAL OSCILLATOR

REFERENCE

OUTPUT

PDH Network

Plesiochronous Digital Hierarchy

ITU – T standard – International Telecommunication Union – Telephony–G.702 – Multiplexing Hierarchy–G.703 – Electrical Interfaces

PDH HierarchyORDER EUROPEAN NORTH

AMERICAN

1 32*64Kbps

2.048 Mbps

24*64Kbps

1.544 Mbps

2 * 4

8 Mbps

* 4

6 Mbps

3 * 4

34 Mbps

* 7

45 Mbps

4 * 4

140 Mbps

* 6

275 Mbps

5 * 4

572 Mbps

PDH Networks

64K

2M

U1

U30

64K

2M

U31

U60

64K

2M

U61

U90

64K

2MU120

U91

2M

8M

U1

U120

8M

34M34M

140M

Multiplexing - North American

North American Digital HierarchyNorth American Digital Hierarchy

DS4 274.176 Mbps 4,032 Fiber Optics

DS3 44.736 Mbps 672 (7 DS2s or 28 DS1s) Twisted Pair

DS2 6.312 Mbps 96 (4 DS1s) Twisted Pair

DS1C 3.152 Mbps 48 (2 DS1s) Twisted Pair

DS1 1.544 Mbps 24 Twisted Pair

DS0B 64 Kbps 1 Twisted Pair

DS0A 56 Kbps 1 Twisted Pair

Digital Bit Rate Equivalent CarrierSignal Level (Digital) Voice DS0 System

Multiplexing - Europe

2.048 Mbps

Multiplexing Structure - Europe

European HierarchyEuropean HierarchyEuropean HierarchyEuropean Hierarchy

E3 139.264Mbps Fiber

DS3 34.368mpbs 672 Twisted Pair

E2 8.448mbps Twisted Pair

E1 2.048 Mbps 30 + 2 Twisted Pair

DS0 56/64kbps 1 Twisted Pair


Japanese HierarchyJapanese HierarchyJapanese HierarchyJapanese Hierarchy

E2 32.064mbps Twisted Pair

DS2 6.312mpbs 96 Twisted Pair

DS1c 3.152mbps 48 (2 DS1s) Twisted Pair

DS1 1.544mbps 24 Twisted Pair

DS0 56/64kbps 1 Twisted Pair


DS3c 97.728mpbs Fiber

DS4 397.2mpbs Fiber

140M

34

140

8

34

2

8

8

2

34

8

140

34 140M

Customer

E1

E2

E3

E4E4

Plesiochronous Transmission

PDH LimitationsNo Central timing source

– Point-to-Point synchronization– Each level operates independently

Signal can be de-multiplexed only at level multiplexed

“Multiplexer Mountain” – Inflexibility in provisioning– Setup Cost– Spares inventory– No in-built management functionality

No standards for fiber

Learning Objectives - SDHLearning Objectives - SDH

Understand PDH and its limitationsUnderstand PDH and its limitations

Appreciate the advantages of SDHAppreciate the advantages of SDH

Understand :Understand :– SDH Multiplexing StructureSDH Multiplexing Structure– STM Frame StructureSTM Frame Structure– Mapping of PDH signals on to STM-1Mapping of PDH signals on to STM-1– SDH Path and Section overheads and their SDH Path and Section overheads and their

functioningfunctioning– SDH Pointer ProcessingSDH Pointer Processing– SDH Management Levels and functionsSDH Management Levels and functions

SDH Networks

Synchronous Digital Hierarchy– ITU-T standard–G.707 – SDH Bit rates–G.708 – Network Node Interface–G.709 – Synchronous multiplexing structure

SDH Hierarchy

ORDER UNIT CAPACITY EQUIPMENT

1 STM-1 155.520 Mbps TN-1C/1X

2 STM-4 622 Mbps OPTERA METRO 4100

3 STM-16 2.5 Gbps OPTERA METRO 4200

4 STM-64 10 Gbps OPTERA METRO

LH/DX

SDH & SONET

SDH Network - View

STM-1

STM-4/16

Core Transport RingSTM-64

STM-1STM-1

STM-1

STM-4/16

BTS

Core locations

The Core Backbone NetworkThe Core Backbone Network

NMS/OSS/BSS

Delhi

Hyderabad

Mumbai

Ahmedabad

J aipur

ExpressRing

CentralizedNMS

CollectorRing

InterconnectSDH Rings

DWDM EXP RESS LAYER

SDH COLLECTOR LAYER

SWITCH

DoT TAX EXCHANGE

OTHER SERVICE P ROVIDER TAX

The Core-Backbone Network

SDH Advantages

Network Simplification

Highly Flexible

Inband Management

PDH Integration

Future Proof

Standardized

SDH Synchronization

Master – PRC Primary Reference Clock–Atomic Clocks–SRC- Secondary Reference Clock

•GPS Clocks

Time Synchronization

Stratum Clock Hierarchy

EvolutionDevelopment of Atomic Beam Magnetic Resonance

in 1945 by Professor Isidor Rabi of Columbia University

First Atomic Clock using ammonia molecule developed by National Bureau of Standards (National Institute of Standards & Technology – NIST) in 1949

First Atomic Clock using Cesium atoms as the vibration source developed by NIST in 1952 – NBS-1

Clock Types

Primary Reference Clocks (PRC)–Atomic Clocks

GPS Clocks–GPS Satellites

Atomic Clocks

Cesium atomic clocks – Employs a beam of cesium atoms– The clock separates cesium atoms of different energy levels by magnetic

field

Hydrogen atomic clocks– Maintain hydrogen atoms at the required energy level in a container with

walls of a special material so that the atoms don't lose their higher energy state too quickly

Rubidium atomic clocks– Simplest and most compact– Uses a glass cell of rubidium gas that changes its absorption of light at

the optical rubidium frequency

Working

Measurement of oscillations between the nucleus of an atom and the surrounding electrons

The oscillation frequencies within the atom are determined by the mass of the nucleus and the gravity and electrostatic "spring" between the positive charge on the nucleus and the electron cloud surrounding it

Atomic Second

The interval of time taken to complete 9,192,631,770 oscillations of the cesium 133 atom exposed to a suitable excitation

Accuracy

Long term accuracy of a Cesium Clock is better than 1 sec/million years

Short term accuracy (1 week) of Hydrogen clock ten times better than the long term accuracy of the Cesium clock

GPS Clocks

Makes use of GPS satellites transmitting in the microwave range (1.5GHz)

Satellites synchronized with Atomic sources

Maximum drift of 250 nanoseconds

RIC Time Synchronization

3 PRC–PRC 1 – Master–PRC 2 – Hot Standby–PRC 3 – Backup–GPS 1 & 2 – Backup

Location–Hyderabad–Bangalore–Delhi–Mumbai & Kolkatta

Nortel Synchronization

SSH – Synchronization Source Hierarchy–Table listing four timing sources

SSM – Synchronization Status Messaging–Exchange messages regarding clock source quality

among NE

Operational Modes–Normal–Holdover Mode–Free running Mode

SDH Management

Information Transfer– Inband–Out-of-Management

Operational Mode–Centralized–Distributed

ITU-T Standard–TNM – Telecom Network Management

Telecommunication Management Network (TMN)

Addresses interoperability of multi-vendor equipment used by service providers to define standard interfaces

Management extended to service function of service providers

OAM&P for telecommunication network and services

Provides best customer service, quality and cost

SDH Management NetworkSubset of TMN responsible for managing SDH NE

SDH Management Subnetworks– Set of separate SDH ECCs and associated intra-site data

communication links– Specific local communications network (LCN) of network

operators overall operations data network or TMN

Embedded Control Channel (ECC)– Accesses NE’s by employing communications channel built into

STM SOH– Provides two Network Management Channels

SDH Management Manager communicates to a conveniently located NE –

Gateway NE– LAN/WAN connection employed– Gateway NE effectively provides connection to/from ECC– Management messages sent via ECC to relevant NEs– Message includes address of relevant NE– Each NE has a routing table containing routes to other NEs– Routing table updates by two methods:

• Intelligence within NEs facilitating automatic table buildup– Changes communicated through updates

• Separate system to calculate routing tables and manual update of NEs– Slower option

– Cost Saving

Built-in communications channel faster

Robust & Reliable

Management LevelsLocal Level

– Required for local configuration using local craft devices– Carry out installation & commissioning functions– Not integrated into an NMS

Element Level– Manages each piece of equipment– Lowest granularity level– Manage all features of equipment

Network Level Management– Manages connections between NEs– Other functions:

• Path Provisioning• Path Scheduling• Surveillance• Alarm Management

Specialized Management Functions

Differentiated Services– Higher QOS– Multi Supplier Network

Organizational Process Integration

Operations Systems

Integration with other existing management and operational Systems

Operational Efficiency– Process improvement– Reduction in errors– Resilience

Management Levels

Local Level

Element Level

Network Level Remote

Requirements - 1

Physical Connectivity–CAT – Craft Interface Terminal

•RS-232 interface•25-pin D interface

–LAN port•Remote connectivity

Requirements - 2

User Interface–CLUI

•Command Line User Interface

–GUI•Graphical User Interface

Management

Element Level–Element Controller–Preside EC-1–Unix based–Manages 128 NE

Network Level–Network Management System (NMS)–Preside

SDH Management

LAN

STM-1

LAN Port

Gateway Network Element (GNE)

SDH Network Management

Integrated Management

TN-1P TN-1C TN-1X OM 4100 OM 4200

Preside AP

EC-1

TN-64X TN-16XOptical layer

EC-1:

Span of Control:

Up to 128 NEs

Up to 30 NEs if co- resident with Preside AP

Warm and Hot Standby

Preside AP Option

• Craft Access Terminal (CAT) is also available for local access

Preside - NMS Connectivity on DCN

OPC

CORE DCN LAYER

Backup NOCNOC

MUMBAI

OPC

OPCEC1 EC1EC1

Thick line = IP, Thin line = OSI

Low CAP OSI ring (ext router and NEs)

Low CAP OSI ring (ext router and NEs)

HYDERABAD

Preside Server Preside Server

DELHI BANGALORE

DX and LH OSI domain

SDH MULTIPLEXING

SDH Multiplexing Elements

Container (Cn , n = 1 to 4)– Basic Element (1.544 Mbps/2.048 Mbps)

Virtual Container (VCn , n = 1 to 4)– Basic Container + POH (path performance monitoring +

signals for maintenance purposes + alarm status)

Tributary Unit (TUn , n = 1 to 3)– VC + TU Pointer

Tributary Unit Group (TUGn , n = 2 or 3)– TU or TUG

SDH Multiplexing Elements

Administrative Unit (AUn , n = 3 or 4)– VCn + AU Pointer

Administrative Unit Group (AUG)– Group of byte interleaved AU

Synchronous Transport Module Level 1 (STM-1)– Basic element of SDH– AUG + SOH ( 270 col * 9 rows – 8 bytes)

PDH MappingC-12

–Defined size of 34 bytes–125 µs time slot–32 bytes payload–2 bytes for “bit stuffing”

VC-12–= C-12 + Path Overhead (1 byte)–POH byte identified as V5 byte (one per multiframe)–4 frame multi-frame to accommodate variations–Justification opportunity once every 4 STM frames

(140 bytes)

125 s

500 s

V5R R R R R R R R

32 BYTEPAYLOADFRAME 1

R R R R R R R RJ2

C1 C2 OOOO RR


R R R R R R R RN2

C1 C2 OOOO RR


R R R R R R R RK2

C1 C2 OOOO RS1

31 7/8 BYTEPAYLOADFRAME 4

R R R R R R R R

S2

VC-12 MULTIFRAMEVC-12 MULTIFRAME

V5

R R R R R R R R

32 BytesPayload

(256 bits)

R R R R R R R R

VC-12 Path Overhead

Stuffing Bits

Justification Bits

Provision for Justification

bits is kept to take care of 2

Mbps + 50PPM frames

JustificationTributary data read into a 3 byte buffer

Monitoring of fill level

Positive or Negative justification

Frame 1 of multiframe contains :– Payload(32 bytes) + 2 bytes fixed stuffing + V5 byte

Frame 2 of multiframe contains :– Payload(32 bytes) + 1 byte fixed stuffing + 1 POH (J2)byte +

Additional byte (2 justification control bits + fixed stuff (R) + reserved undefined bits

Frame 3 similar to Frame 2 except POH byte N2

Justification Process

Frame 4 contains:–POH byte (K4) + 2 justification opportunity bits

(S1&S2) –S2 contains stuff in case of positive justification–S1 contains payload in case of negative justification

Justification Control BitsContent of justification opportunity bits

controlled by justification control bits

C1 controls S1 content

C2 controls S2 content

If justification control bit = 0, corresponding opportunity bit = Stuff

If justification control bit = 1, corresponding opportunity bit = Payload

VC

VC

VC

VC

VC

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

TU

VC

VC

125 s

Hyderabad Mumbai Ahmedabad

VIRTUAL CONTAINER & TRIBUTARY UNITVIRTUAL CONTAINER & TRIBUTARY UNIT

Aligning VC-12 to a TU-12Bit rate adaptation required between lower

order VCs (VC1 or VC2) and higher order VCs (VC3 & VC 4)

TU-12 = VC-12 + TU-12 pointer

TU-12 position fixed w.r.t higher order VC

VC-12 allowed to vary within TU-12

Pointer value corresponds to the starting position of VC-12 (location of V5 byte)

Justification ProcessRequires 4 frame multiframe

Justification opportunity = 1 byte (144 byte multiframe)

4 byte pointer value V1, V2, V3 & V4

V1 & V2 combined to provide a pointer value in the range of 0 – 139 depending upon the position of the V5 byte

V3 pointer performs the requisite action (justification)

V4 pointer byte reserved

VC12 V3

TU12

125 s

Offset

Pointer

TU12

125 s

VC12 V2

TU12

125 s

N N N N X X I D I D I D I D I D

10 bit Pointer

VC Size

V1 V2

PACKING VC-12 IN TU12PACKING VC-12 IN TU12

VC12

Plesiochronous Frame Synchronous Frame

V1

Pointer ProcessingV1 & V2 bytes contain :

– TU pointers ( I & D) – I(Increment), D(Decrement)• Negative Justification – Invert 5 D bits

• Positive Justification – Invert 5 I bits

– TU type bits ( S ) – 1 0 for TU-12– New Data flag bits ( N )– Pointer value provides a binary value – Indicates the offset from V2 to the first byte of the VC-12 (V5

byte)– VC-12 pointer values ranges from 0-139– NDF bits facilitates arbitrary change in the value of the pointer or

the size of the TU– Normal Value = ‘0110’– Arbitrary change value = ‘1001’

AU Pointers

|H1|Y |Y |H2 |1 |1 |H3 |H3| H3| –Y = 1001SS11 (S S UNSPECIFIED)–1 = All 1s byte–H3 = Negative justification opportunity–H1 = | N | N | N | N | S | S | I | D |–H2 = | I | D | I | D | I | D | I | D |

•N = New Data Flag•SS – AU/TU Type (’10’ for AU-4)•I = Increment Bit•D= Decrement Bit

Justification Process (TU-12)Mux requires to read value of V1 & V2 for location of

the V5 byte

Pointer ‘0’ value position directly after the V2 byte

Cannot indicate an offset between the position directly after V1 and directly after V2 in the same multiframe

V3 byte provides negative justification opportunity

Following byte provides positive justification

Justification - Summary

Buffer states–Normal–Decrementing (Lower threshold)– Incrementing (Upper threshold)

Buffer Level falling – Action Add stuffing

Buffer Level increasing – Action Add payload

V1K4

34 BYTE

V2V5

34 BYTE

V3J2

34 BYTE

V4N2

34 BYTE

125 s

500 s

V2V5

34 BYTES

V3J2

34 BYTES

V4N2

34 BYTE

V1K5

34 BYTE

VC12’s TU12’s

Position of a VC12’s within

TU12’s is known only after

receiving both V1 & V2

Plesiochronous Frames

Synchronous Frames

POSITIONING VC-12’s IN TU12’sPOSITIONING VC-12’s IN TU12’s

TUTU

VC

TU

TU

TU

TU

VC

VC

125 s

VC

1xVC-3 1xVC-3 21xVC-12

STM-1STM-1

Multiplexing TU-12 TUG 2Each TU-12 frame arranged into a structure which is

9 rows * 4 columns– Consistency with STM Frame structure

3 TU-12 structures byte interleaved into TUG-2 structure

TU-12 pointers form the first three bytes of the structure– Aids in locating the floating VC-12

TUG-2 defined size of 108 bytes (9 * 12 )

7 TUG-2 multiplexed into a TUG-3

TRIBUTARY UNIT GROUPINGTRIBUTARY UNIT GROUPING

Multiplexing TUG-2 into TUG-37 TUG-2 multiplexed into TUG-3

Byte interleaving

TU-12 pointers located adjacent to each other

Positions fixed in relation to TUG-3

TUG-3 has two columns of fixed stuff

1st 3 bytes of 1st column contains a Null Pointer Indicator (NPI)– Indicates whether TUG-3 contains TUG-2 or TU-3

TUG-3 size of 774 bytes (9 * 86)

Multiplexing TUG-3 VC-4

3 TUG-3 byte interleaved into C-4 with 2 columns of fixed stuff

1 column (9 bytes) of POH added to form a VC-4

TU-12 pointers in fixed position adjacent to each other

VC-4 defined size = 2349 bytes (9 * 261)

Aligning VC-4 AU-4VC-4 allowed to float within within AU-4 structure

9 bytes of AU-4 pointers added to locate the first VC-4 byte

Facilitates dynamic bit rate adaption between VC-4 and STM-n SOH in increments of 3 bytes

Also allows arbitrary changes in pointer values

3 bytes of AU-4 pointers provide negative justification opportunity

3 bytes of payload directly opposite AU-4 pointers provide positive justification opportunity

MULTIPLEXER SECTION

OVERHEAD

AU3 POINTER

REGENERATORSECTION

OVERHEADP

AT

H O

VE

RH

EA

D

774 Bytes

STM -1 FRAME STRUCTURESTM -1 FRAME STRUCTURE

87 BYTES3 BYTES

9 B

YT

ES

STM - 4 Frame Structure4 AUG + SOH

One byte interleaved

Fixed phase relationship with respect to STM-4

SOH occupies :– Col 1 to 36– Rows 1 to 3 & 5 to 9 of the frame

Not all overhead bytes required since STM Frame is transmitted across single multiplexer section

SDH Generalized Multiplexing Structure

KLM NumberingCommon vendor standard for identifying VC12, VC2

and VC3 channels within a VC4

K – VC3 or TUG3 [ Value 1-3]

L – VC2 or TUG2 [ Value 1-7]

M – VC12 [ Value 1-3]

Example:– To identify a VC-3 , ‘K’ identifies the VC-3 and the value of ‘L’ and

‘M’ equal O – VC3 = K200

In case of STM-n letter ‘J’ identifies VC-4 followed by appropriate KLM designation

VC-12 Path Overhead

BIP-2 VC-12 Path Error Monitoring Function

REI Communicate BIP-2 errors to path originator

RFI Not Used

SIGNAL LABELPayload Mapping/Equipped Status

RDI Communicate TU path alarms to originator

VC-3/VC-4 Path Overhead

VC-3/VC-4 Path OverheadPath trace (J1)

– Used to provide a fixed length string transmitted repetitively which is used by the receiving terminal can verify connection to the intended transmitter

Path BIP-8 (B3)– Error monitoring function for the VC-3/VC-4 path

Signal label (C2)– Indicate the composition of the VC-3/VC-4 payloads

Path status (G1)– Convey path terminating status and performance information back to the

VC-3/VC-4 path originator•

VC-3/VC-4 Path OverheadPath user channel (F2)

– Available for user communication purposes between path elements– Not used in present applications

Multiframe indicator (H4)– Provides a generalized multiframe indicator for VC-12 payloads.

Automatic Protection Switching (APS) (K3)– Allocated for APS signaling for high order path protection.

Spare (F3, N1)– Not used in present applications

Section Overhead

RSOH BytesFraming (A1, A2)

– Used for frame alignment purposes.

BIP-8 (B1)– Provide error monitoring function for regenerator section,

also used in the frame alignment process

Order wire (E1)– Provide an order wire channel accessed at regenerators and

multiplexers.

User channel (F1)– Reserved for user purposes. Not used in present systems

RSOH Bytes

DCCR (D1 to D3)– Data Communication Channel (DCC) bytes– Provide a 192 kbit/s regenerator data channel.

Regenerator Section Trace (J0). Not used in present applications.

MSOH BytesBIP-24 (B2)

Used to provide an error monitoring function for the multiplex section

APS channel (K1, K2)

Used for APS signalling– Currently used to communicate REI & Alarm indications over a

multiplexed channel– Signal (AIS) indications to the far multiplexer.

DCCM (D4 to D12)– Provide a 576 kbit/s multiplex data channel

MSOH Bytes

Order wire (E2)– Provide an order wire channel which may be accessed only

at multiplex section terminations

Synchronization Status Messaging Byte (S1)– This byte is used for transmitting synchronization status.

Section REI (M1)– Not used in present applications

STM-N Frame Format

STM – N General Format–Basic STM – 1 Frame composition

•270 * 9 = 2430 Octets•9 * 9 – 81 Octets Section Overhead (SOH)•2349 Octets payload

–Higher rate frames formed as multiples of STM - 1

SDH Complete

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