Public Switched Telephone Network (S-PSTN)

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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
7
What Is A Network ?
Switching Office
Switching Office
CPE
CPE
Transmission Facilities
8
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
SWITCHING OFFICE
CONTROL
NETWORK
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Transmission Facilities
Switching Office
Switching Office
Trunks
Line
Line
Special Service Circuit
11
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
13
Traffic Networks

• The Public Switched Telephone Network
• Pre-divestiture
• Post-divestiture

14
Local Network Structure
Exchange Area 2
Exchange Area 5
Exchange Area 1
Wire Center B

Wire Center A

Exchange Area 3
Exchange Area 4
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Typical Local Network
Tandem Office T
Wire Center C
Tandem Trunk Groups (Final)
Wire Center A
Wire Center B
Direct Trunk Groups
(High Usage)
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Toll Network StructurePre-Divestiture
Telephone 1
Telephone 2
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Toll Network StructurePre-Divestiture
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The Post-Divestiture Network
19
The Post-1984 Network
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Typical LEC Network
Tandem Office
Central Office
IC POP
Switching Systems
Distribution Facility/Local Loop
Interoffice Facilities/Trunks
Distribution Facility/Local Loop
Central Office
LEC
IC
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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
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Number Plan Area (NPA)

• These special purposes codes include

NXX Reserved Codes
N11 Reserved Codes
311 Non-Emergency Police and Fire 411 Local
Directory Assistance 611 Repair Service 811
Business Office 911 Emergency Number
600 Used in Canada for TWX (teletype service) 700
Assigned to ICs 800, 888, 877, and 866 Service
(INWATS) 900 Service (DIAL-IT Service)
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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

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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.

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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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Signaling
Terminating Switching Office
Originating Switching Office
Originating CPE
Terminating CPE
Idle
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Ringing
Audible Ring
Answer
Off-hook
Disconnect
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Signaling
Terminating Switching Office
Terminating Switching Office
Originating Switching Office
Originating CPE
Terminating CPE
Idle
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Ringing
Audible Ring
Answer
Off-hook
Disconnect
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Signaling
Terminating Switching Office
Terminating Switching Office
Originating Switching Office
Originating CPE
Terminating CPE
Idle
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Ringing
Audible Ring
Answer
Off-hook
Disconnect
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Signaling
Terminating Switching Office
Originating Switching Office
Originating CPE
Terminating CPE
Idle
Off-hook
Dial Tone
Dialed Digits
Off-hook
Off-hook (wink)
On-hook (wink)
Dialed Digits
Ringing
Audible Ring
Answer
Off-hook
Disconnect
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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
CO
CO
CO
A
A
STP
STP
C
STP
STP
C
A
A
SCP
SCP
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SS7
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Network Administration, Maintenance and Services

• Network Management
• Traffic Measurements
• Billing
• Maintenance
• Customer Services