Public Switched Telephone Network (S-PSTN)
Mar 29, 2015
Public Switched Telephone Network
(S-PSTN)
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.
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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
Overview
Network setup Switching systems Post-Divestiture network Signaling SS7 CCS
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
Network Overview
What Is A Network ?
Switching
Office
CPE CPE
Transmission Facilities
Switching
Office
Public Switched Telephone Network (PSTN)
Major Components of the Public Switched Telephone Network (PSTN): Switching Offices Transmission facilities Customer Premise Equipment (CPE)
Switching Offices
CONTROL
NETWORK
SWITCHING
OFFICE
Transmission Facilities
Switching
Office
Switching
Office
Trunks
Line Line
Special Service Circuit
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)
Switching Systems
Traffic Networks
The Public Switched Telephone Network:
Pre-divestiture
Post-divestiture
Local Network Structure
ExchangeArea 5
ExchangeArea 4
ExchangeArea 3
ExchangeArea 2Exchange
Area 1
WireCenterA
WireCenterB
•
•
Typical Local Network
Tandem Office T
WireCenter
A
WireCenter
B
WireCenter
C
Tandem TrunkGroups (Final)
Direct Trunk Groups
(High Usage)
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
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
The Post-Divestiture Network
The Post-1984 Network
IEC1
IEC2
IEC3
LATA xInterLATACarriers LATA y
Typical LEC Network
Tandem OfficeCentral Office
Central Office
SwitchingSystems
InterofficeFacilities/Trunks
DistributionFacility/Local Loop
DistributionFacility/Local Loop
LEC IC
IC POP
LATA Access Services
Switched Access
Special Access (Nonswitched)
Switched Access Service
Feature Group A Feature Group B Feature Group C Feature Group D Equal Access End Office
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
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
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
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
Signaling
Signaling
Signaling is the generation, transmission, and reception of information needed to direct and control the setup and disconnect of a call.
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
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
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
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
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.
Signaling System 7 (SS7) LINKS
AAAA
AA AA
EEEE
FF
COCO
COCOCOCO
DDDDBBBBBBBB
CC
CC
STPSTPSTPSTP
STSTPPSTSTPP
STSTPPSTSTPP
STPSTPSTPSTP
SCP SCP
SS7Switching Office A
Switching Office B
Customer “A”
STPSTP
Customer “B”
IAM IAM
ACM ACM
ANM ANM
RELREL
RLC RLC
Network Administration, Maintenance and Services
Network Management Traffic Measurements Billing Maintenance Customer Services