Post on 02-Nov-2014
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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
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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
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
Digital Bit Rate Equivalent CarrierSignal Level (Digital) Voice DS0 System
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
Digital Bit Rate Equivalent CarrierSignal Level (Digital) Voice DS0 System
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
32 BYTEPAYLOADFRAME 2
R R R R R R R RN2
C1 C2 OOOO RR
32 BYTEPAYLOADFRAME 3
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