PSTN Network Hierarchy

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PSTN Network Hierarchy

• Class-5 (lowest level toll center)
• Class-4 (Lower level toll center)
• Class-3 (High level toll center)
• Class-2 (Next higher level toll center)
• Class-1 (Highest level toll center)
• Higher levels in the network hierarchy implies
  greater switching and transmission capacity as
  well as greater expenses.

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PSTN Network Hierarchy

• Class-5 is the local central office (CO) that
  contains a switch and calls come there.
• Then, the CO processes the incoming calls.
• Determines the best path to its destination.
• When calls cannot be handled directly, then the
  Class-5 turns to Class-4, which then turns to
  Class-3, which then turns to Class-2 ,
• Which then turns to Class-1.

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Figure 2-4 Representative Voice Network Heirarchy
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System Signaling

• The information that the the telephone system
  must carry about the call itselfin addition to
  carrying the actual voice signals---is known as
  the System Signaling.

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System Signaling

• SS deals with 3-things
• Call setup
• Call termination
• Many advanced functions
• Call waiting Call blocking
• Call forwarding Caller-ID blocking
• 3-way calling Number redialing
• Automatic redialing of missed calls

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Figure 2-6 Signaling System 7 Protocols and the
OSI Model
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PBX-Concepts

• PBX private branch exchange
• PBX is a switching device that
• Works as a voice-server or switch.
• Deals with a so-called PBX-switching matrix.
• Links the users phones with their destinations.
• Ensures flexible voice commun-capability.
• Mini-PBXs find application in the SOHOs.
• SOHO Small Office Home Office

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Figure 2-11 PBX Physical Architecture
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Call Accounting System

• CAS runs on standalone PCs.
• Execute directly with the PBX.
• Execute specially written software.
• Can track the incoming and outgoing calls.
• Can spot possible call usages and abuses.

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Figure 2-14 Call Accounting Systems Installation
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PBX Trends--in tune with market demands--

• Better connectivity between phones and PCs.
• Better connectivity between PBXs and LANs.
• Better integration of PBX management programs
  with enterprise network management packages.
• Open PBX-architectures for easier access to PBX
  features and services from a variety of computing
  platforms.

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Open PBX Architecture

• PBX is becoming nothing more than a specialized
  communications or voice server.
• It is now integrating all other servers as part
  of an enterprise network.
• Enterprise network is an organizations complete
  network.
• Enterprise network is a kind of corporate network
  that connects various LANs, MANs and WANs
  belonging to the same organization, thereby
  ensuring the benefit of communication with the
  users or applications amongst these networks.

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Figure 2-17 Open PBX Architecture
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C T I Computer Telephony Integration

• Integrates the 2 important productivity network
  devices
• Desktop computer and telephone.
• Optimizes the use of telephone and the desktop
  computer by being able to share the information
  and functionality offered by each.

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CTI Architectures

• Has 3-Architectures
• PBX-to-Host Interface
• Desktop-CTI
• Client-server CTI
• Has 3-important Applications
• API Application Program Interfaces
• TAPI Telephone API
• TAPI has been developed jointly by
  Intel/Microsoft.

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Figure 2-19 CTI Architectures
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CTI-Appln-Development Tool

• Developed based on computing platforms and
  operating systems.
• Based on programming codes.
• These codes are written in JAVA and C.
• Graphical code generators allow easy application
  development with a minimum programming background.

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Figure 2-20 Technology Required to Develop and
Implement CTI Applications
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Voice Transmission Architectures--in addition to
PSTN--

• VOIP Voice over IP
• VOFR Voice over Frame Relay
• FRADFrame Relay Access Device
• VOATM Voice over ATM
• VDMU Voice/Data Multiplexers
• VDMO Voice/Data Modems
• VOISDN Voice over ISDN
• --------------------------------------------------
  ---
• ATM, FR, ISDN are 3 MAN/WAN technologiesservices
  provided by the CCNs.

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VOIP Voice Over IP

• VOIP means
• Voice over any network using the IP-protocol.
• Also represents the IP-based voice transmission
  over the Internet.
• Provides an alternative to the traditional voice
  transmission taking place over the Internet.

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Figure 2-22 VOIP Transmission Technology and
Topologies
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Topology!

• Describes the way a network is set up.
• Provides a geometric configuration of NW.
• Gives an impression of the physical layout of the
  network.
• Common topologies
• Bus, star, ring---------topologies.
• Mesh (full-, partial-, cloud-based mesh)
• Switch, Linear, Tree----topologies.

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Voice Transmission --over Frame Relay Network--

• Frame Relay is an MAN/WAN transmission service.
• Also known as FRAD
• FRAD Frame Relay Access Device
• Uses variable length frames.
• Can accommodate audio/video/data service.
• Ensures audio prioritization over data traffic.
• To ensure efficiency, does packetizingbreaking
  bigger packets into smaller packets.
• Provides point-to-point connection, known as PVC.
• PVC Permanent Virtual Connection

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Figure 2-26 Voice Transmission over a Frame
Relay Network
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Voice Transmission over ATM

• ATM is an MAN/WAN transmission service.
• ATM Asynchronous Transfer Mode.
• Can accommodate audio/video/data service.
• It is a packet switched services network.
• Uses fixed-length (53 bytes) packetscalled
  cells.
• Provides extensive QoS quality of service.
• Provides same data transmission as SONET
• OC-1 51.84 Mbps
• OC-3 155.52. Mbps
• OC-9 466.56 Mbps
• OC-12 622.08 Mbps

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Figure 2-27 Voice Transmission over an ATM
Network
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Integrated Services Digital NW

• ISDN Integrated Services Digital Network
• Is a circuit switched digital service.
• Is used to build MAN/WAN networks.
• Transmits audio/video/data simultaneously.
• Uses ISDN-audio/video/data Modems.
• 2-Types N-ISDN and B-ISDN

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Narrowband-ISDN

• N-ISDN offers 2-Types of Services
• BRI Basic rate interface (2BD)
• 2 B-channels at a rate of 64 Kbps.
• 1 D channel at 16 Kbps.
• --------------------------------------------------
  --------------------------------------------------
  --------------------------------------------------
  --------------
• PRI Primary rate interface (23BD)in USA.
• PRI Primary rate interface (30BD)in Europe.
• 2 B-channels at a rate of 64 Kbps.
• 1 D channel at 64 Kbps.

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Broadband-ISDN

• B-ISDN is an enhancement of N-ISDN
• Supports both BRI and PRI
• Offers 2-symmetric full-duplex services
• 155.52 Mbps (both ways)
• 622.08 Mbps (both ways)
• --------------------------------------------------
  --------------------------------------------------
  --------------------------------------------------
  ---------
• Offers 1-asymmetric full-duplex services
• 155.52 Mbps (one way--upstream)
• 622.08 Mbps (other waydown-stream)

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Figure 2-28 Simultaneous Voice/Data Transmission
with DSVD and ISDN