pstn public switched telephone network
TRANSCRIPT
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Public Switched Telephone Network
(S-PSTN)
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S-PSTN
Partial support for this curriculum material was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement Program under grant DUE-9972380 and Advanced Technological Education Program under grant DUE‑9950039.
GWEC EDUCATION PARTNERS: This material is subject to the legal License Agreement signed by your institution. Please refer to this License Agreement for restrictions of use.
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Table of Contents
Overview 5
Learning Objectives 6
Network Overview 7
Switching Systems 13
Post-Divestiture Network 19
Signaling 28
Contributors 38
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Overview
Network setup Switching systems Post-Divestiture network Signaling SS7 CCS
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Learning Objectives
After completing this module you will be able to: Discuss the basic operations of the Public Switched
Telephone Network (PSTN) Define the telephony switching hierarchy Describe the signaling required to complete a typical
telephone call through the PSTN Describe how the SS7 network is overlayed onto the PSTN
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Network Overview
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What Is A Network ?
Switching
Office
CPE CPE
Transmission Facilities
Switching
Office
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Public Switched Telephone Network (PSTN)
Major Components of the Public Switched Telephone Network (PSTN): Switching Offices Transmission facilities Customer Premise Equipment (CPE)
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Switching Offices
CONTROL
NETWORK
SWITCHING
OFFICE
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Transmission Facilities
Switching
Office
Switching
Office
Trunks
Line Line
Special Service Circuit
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Customer Premise Equipment (CPE)
Customer Premise Equipment (CPE) is the term used to identify any piece of equipment supplied by the customer to interface with the PSTN. Examples include: Single Line Telephone Set Modems or Data Sets Private Branch Exchange (PBX)
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Switching Systems
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Traffic Networks
The Public Switched Telephone Network:
Pre-divestiture
Post-divestiture
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Local Network Structure
ExchangeArea 5
ExchangeArea 4
ExchangeArea 3
ExchangeArea 2Exchange
Area 1
WireCenterA
WireCenterB
•
•
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Typical Local Network
Tandem Office T
WireCenter
A
WireCenter
B
WireCenter
C
Tandem TrunkGroups (Final)
Direct Trunk Groups
(High Usage)
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Toll Network StructurePre-Divestiture
Telephone 1 Telephone 2
Regional Center DClass 1
Regional Center CClass 2
Regional Center BClass 3
Toll Center AClass 4
FINALRegional Center E
Sectional Center F
PrimaryCenter
G
HU6
HU5
HU4HU3 HU2
HU1
FIN
AL
FIN
AL
FIN
AL
FIN
AL
FIN
AL
FIN
AL
Toll Center H
Toll Connecting
Local Office
Local Office(End Office)
Class 5Local
TandemOffice
HU7
Toll Connec
ting
Toll Connecting
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Toll Network StructurePre-Divestiture
Regional Center DClass 1
Regional Center CClass 2
Regional Center BClass 3
Toll Center AClass 4
FINALRegional Center E
Sectional Center F
PrimaryCenter
G
HU6
HU5
HU4HU3 HU2
HU1
FIN
AL
FIN
AL
FIN
AL
FIN
AL
FIN
AL
FIN
AL
Toll Center H
Toll Connecting
Local Office
Local Office(End Office)
Class 5Local
TandemOffice
Telephone 1 Telephone 2
HU7
Toll Connec
ting
Toll Connecting
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The Post-Divestiture Network
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The Post-1984 Network
IEC1
IEC2
IEC3
LATA xInterLATACarriers LATA y
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Typical LEC Network
Tandem OfficeCentral Office
Central Office
SwitchingSystems
InterofficeFacilities/Trunks
DistributionFacility/Local Loop
DistributionFacility/Local Loop
LEC IC
IC POP
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LATA Access Services
Switched Access
Special Access (Nonswitched)
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Switched Access Service
Feature Group A Feature Group B Feature Group C Feature Group D Equal Access End Office
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North American Numbering Plan
Numbering Plan Area Central Office Station
N X X N X X X X X X
2-9 0-9 0-9 2-9 0-9 0-9 0-9 0-9 0-9 0-9
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Number Plan Area (NPA)
These special purposes codes include:
NXX Reserved Codes: N11 Reserved Codes:
600 Used in Canada for TWX (teletype service)700 Assigned to ICs800, 888, 877, and 866 Service (INWATS)900 Service (DIAL-IT Service)
311 Non-Emergency Police and Fire411 Local Directory Assistance611 Repair Service*811 Business Office*911 Emergency Number
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Number Plan Area (NPA)
Interchangeable area (or NPA) codes are NPA codes of the format NXX.
By changing from the former N-0/1-X format to the NXX format, the maximum number of assignable NPA codes increased by 640 codes as shown:
Old Format
New format
N 0/1 X8 x 2 x 10 = 160
N X X8 x 10 x 10 = 800
160-8* = 152*Excluding codes of N11 format
800-8* = 792**Excluding codes of N11 format
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International Numbering
If you have made international calls, you know that the familiar NANP is a subset of the ITU international plan.
Until recently, international numbers were limited to 12 digits.
1, 2 or 3 digits
Varies by location
Country CodesTrunk CodeLocal CodeSubscriber Number
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Signaling
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Signaling
Signaling is the generation, transmission, and reception of information needed to direct and control the setup and disconnect of a call.
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SignalingOriginating
CPE
Terminating Switching
OfficeTerminating
CPE
Originating Switching
Office
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Audible Ring Ringing
Answer Off-hook
Disconnect
Idle1
2
3
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SignalingTerminating Switching
Office
Originating CPE
Terminating Switching
OfficeTerminating
CPE
Originating Switching
Office
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Audible Ring Ringing
Answer Off-hook
Disconnect
Idle1
2
4
3
5
6
6
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SignalingTerminating Switching
Office
Originating CPE
Terminating Switching
OfficeTerminating
CPE
Originating Switching
Office
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Audible Ring Ringing
Answer Off-hook
Disconnect
Idle1
2
4
3
5
7
6
6
8
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SignalingOriginating
CPE
Terminating Switching
OfficeTerminating
CPE
Originating Switching
Office
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Audible Ring Ringing
Answer Off-hook
Disconnect
Idle1
2
4
3
5
7
6
6
8
9
10 10
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Common Channel Signaling (CCS)Common Channel Signaling (CCS) is a signaling method that uses a separate dedicated channel to send and receive signaling information for a group of trunks or facilities by means of labeled messages.
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Signaling System 7 (SS7) LINKS
AAAA
AA AA
EEEE
FF
COCO
COCOCOCO
DDDDBBBBBBBB
CC
CC
STPSTPSTPSTP
STSTPPSTSTPP
STSTPPSTSTPP
STPSTPSTPSTP
SCP SCP
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SS7Switching Office A
Switching Office B
Customer “A”
STPSTP
Customer “B”
IAM IAM
ACM ACM
ANM ANM
RELREL
RLC RLC
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Network Administration, Maintenance and Services
Network Management Traffic Measurements Billing Maintenance Customer Services