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Packet Telephony: Call of the Future

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VoicenData Bureau
New Update

Voice

over ATM. Voice over Frame Relay. Voice over IP. Now IP

telephony! These terms are being used to describe a paradigm

shift occurring in the telecom industry–the shift from circuit

switching and Time Division Multiplexing (TDM) to innovative

packet-based networks designed for data but optimized for voice.

These services are the industry’s response to a fast-growing

problem: Circuit-switched networks that were designed to carry

voice are over-stressed trying



to keep pace as data traffic exceeds voice on public networks.
The introduction of these pioneering technologies has given the

industry valuable insights into the challenges and solutions of

real-life deployment of voice-over-packet technologies. These

efforts have also given rise to new voice-over-packet

technologies that have found their way to the world’s premier

packet-switched network, the Internet.

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Yet

none of the above terms succinctly defines this change that is

taking place. A new word called "packet telephony" has

been coined to reflect the convergence of telephony services and

the packet infrastructure–the logical network transformation

for service providers.

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Packet

Telephony Vis-à-vis Voice-over-Packet

Packet

telephony is much more than a voice-over-technology. It is the

integral combination of the following elements:

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Transport and Access

The network infrastructure

enables communications among people regardless of distance and

time. The primary focus is on providing reliable, scalable,

high-speed/low-latency connections that seamlessly span multiple

networks. Today, the network infrastructure employed for

telephony comprises predominantly circuit switches, wiring

plants, and TDM Wide Area Networks (WANs).

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Connection Control

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This is the basic

intelligence in the network required to manage connections

between end points desiring to communicate. This includes

establishing, monitoring, maintaining, and terminating

connections. This is the functionality required to provide

telephony services over a packet infrastructure. Network and Client Services

Network and client

services are designed to enrich the communications experience

and enhance productivity. Network services such as calling card,

single-stage and multi-stage dialling, automatic route

selection, called number screening, called number digit

manipulation, flexible dialing plans, call detail records and

billing, and interactive voice response address the requirement

to provide network-based functionality beyond basic connection

control.

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From an end-user

perspective, client services are manifested in the form of

terminals (for example, phones and multimedia devices) with

intuitive user interfaces and call management capabilities for

flexible and intuitive interpersonal communications.

In a business environment,

this would be extended to include business-critical

applications. These applications enhance personal productivity

within an enterprise and allow the enterprise to build strong

relationships with the external audience (for example, customers

and suppliers) regardless of distance and time. Custom Local

Area Signalling Services (CLASS), call centres, multimedia

conferencing, Interactive Voice Response (IVR) applications,

speech-activated applications, and unified messaging are just a

few of the examples of business-critical telephony applications.

Today, these services are closely coupled with circuit switches

(PBX, key systems, and central office equipment), as they

typically form the heart of the network infrastructure.

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Network Management

Network management is the

ability to configure, monitor, manage, and report on the

network, including all network elements and services. Beyond

configuration, fault, performance, accounting, and security

management, it must address customer-related items like service

provisioning, delivery, and billing. It must also be able to

deal with the complexity and scale of very large service

provider networks with continuous churn of customer service

requirements.

The Basic

Packet Telephony Components

Media Gateway

The media gateway function

implements bi-directional interfaces between a circuit-switched

network and various media-related elements in a packet network.

Typical associated packet elements are either end-user devices

or other media gateways. The key responsibilities of the media

gateway are to allow media of various types–including voice,

fax, video, and modem data–to be transported as packets in the

packet network and analog or digital streams in the

circuit-switched network without loss of integrity or

degradation of quality. These gateways will be available in

several forms to fit various price/performance and deployment

requirement such as the following:

  • Packet-enabled

    voice switching devices consist of gateways that are

    tightly integrated with central office switches, PBXs, or

    key systems. These gateways are closely coupled with the

    call routing, trunk selection, and telephony

    class-of-service capabilities inherent in the parent voice

    switching devices. They also inherit the reliability and

    scalability characteristics of the parent voice switching

    devices. Telephony-enabled

    network devices consist of gateways that are tightly

    integrated with networking devices such as routers, Frame

    Relay Access Devices (FRADs), concentrators, and switches.

    These gateways are closely coupled with the network routing,

    bandwidth management, and traffic-management characteristics

    of the parent network devices. They also inherit the

    reliability and scalability characteristics of the parent

    networking devices.







  • Standalone

    gateways are translation devices whose sole purpose

    is to provide the gateway functions. These are optimized for

    high-density applications typically found in service

    provider networks and very large enterprises.

Signalling Gateway

The signalling gateway

function implements bi-directional interfaces between an SS7

network and various call control-related elements in a packet

network. The associated packet network elements typically

implement either media controller functions or database query

functions. The key responsibilities of the signalling gateway

are to repackage SS7 information into formats understood by

elements in each network and to present a reliable view of the

elements in the packet network to the SS7 network.

Controller

The controller function

issues instructions to various media, signalling, and

service-related elements in a packet network. Typical associated

packet elements are media gateways, signalling gateways, service

modules, or sophisticated end-user devices. The key

responsibilities of the controller are to make decisions based

on flow related information and to provide associated

instructions on the interconnecting of two or more interested

parties wishing to exchange information. This includes call

signal processing, call establishment and related management,

resource management, service delivery, and admissions control in

a packet network environment.

Controllers typically

maintain current status information of all information exchanges

and generate administrative records necessary for activities

including billing. Today vendors like Nortel are offering two

types of controllers that are optimized for different deployment

scenarios and are designed to interwork with each other: Server-based

controllers consist of software implemented on server

platforms and can be replicated for redundancy and

availability.



  • Voice

    switching device-based controllers consist of software that

    is tightly integrated into central office switches, PBXs, or

    key systems, and leverage the call control and service

    delivery functionality inherent in the parent

    voice-switching device.

  • End-User Devices

    End-user devices are

    usually IP-enabled telephony clients that enable personal

    communications, which include:

    • IP-enabled

      phones

    • Adapters to

      adapt and extend the life of analog and digital phones

      intended for use with circuit-switched voice systems

    • Virtual

      phones based on software running on a workstation or

      personal computer, enabling multimedia communications and

      telecommuting

    • Universal

      Serial Bus (USB)-based phones to work with personal

      computers.

    Service Modules

    These provide value-added

    capabilities beyond plain telephone communications. This

    includes network services, including calling card, single stage

    and multi-stage dialing, automatic route selection, called

    number screening, called number digit manipulation, flexible

    dialing plans, call detail records and billing, and IVR.

    • CLASS

      services, including caller ID, calling name ID, repeat

      dialling, call return, selective call

      rejection/forwarding/acceptance, VIP alert, do not disturb

    • Advanced

      business services, including call waiting, call transfer,

      three-way calling, call hold, speed dialling

    • Centrex

      services, including private numbering plans and closed user

      groups

    • Multimedia

      conferencing services

    • Desktop

      services, including unified messaging applications that

      integrate voice mail, e-mail, and fax mail

    • E-commerce

      services, including call centres

    • Remote user

      services, including roaming support and virtual second line

    • Speech-activated

      services

      The Value Matrix

      Value of

      Packet Telephony to Service Providers

      The

      technological innovations associated with the information age

      have brought an unparalleled freedom in the ways people

      communicate. Personal computers, portable phones, and Personal

      Digital Assistants (PDAs) with user-friendly graphical

      interfaces, fibre optics, the growth of Internet, and the

      associated IP applications have all given rise to an evolving

      user that demands:

      • Mobility–any

        service delivered anytime, anywhere

      • Bandwidth–highly

        interactive, bandwidth-hungry graphical interfaces

      • Real-time–support

        for delay-sensitive traffic, such as voice

      • Integration–the

        ability to access all types of messages, such as voice,

        e-mail, and fax, through a common interface

      • Ease of use–an

        easy-to-understand interface that encourages use

      With any disruptive

      technology, the full impact of the paradigm shift cannot be

      totally quantified at first, yet the fear sometimes is, "If

      you stand still you will be trampled!" Though the services

      and the way services are delivered are changing, the way service

      providers make money remains fundamentally the same with local,

      national, international, and wholesale services. Service

      providers are still in the business of satisfying end-user needs

      to communicate and share ideas and information.

      What

      Is Packet Telephony?

      To

      understand the term "packet telephony" one must

      first define it. The word "packet" focuses on

      the transport mechanism. It is an all-encompassing term

      that can be used to describe the gamut of packet-based

      technologies, including IP, ATM, Frame Relay, wireless

      packet, and others. Traditionally, the word

      "telephony" focused on voice-based

      communications. It is much more than voice transport. It

      encompasses the full set of high quality communications

      services provided by today’s Public Switched Telephone

      Network (PSTN).

      Thus, conceptually,

      "packet telephony" means today’s telephony

      services delivered over a packet network. In reality,

      packet telephony is much more than that. It is a means to

      an end–a service-enabling solution that allows the

      creation of integrated services and networks.

      Telephony networks have

      been focused on people–where advancements have been

      directed at improving personal networking and human

      efficiency through new and advanced services.

      Packet networks,

      particularly IP and Internet-based networks, have been

      focused on computers–where advancements have been

      directed at improving speed, automation, and user

      interface.

      Integrating telephony

      services with packet networking, therefore, gives us

      powerful ways of improving the way humans communicate,

      such as allowing users to travel and receive calls and

      other telephony features at their temporary locations.

      Voice and data can be combined in innovative ways for

      improved user interface to access voice mail, e-mail, and

      fax mail.

      Also, the convergence of

      packet and telephony will allow the unification of the

      network infrastructure, including directories, network

      management, and policies.



      Packet

      Telephony Definition

      Packet

      telephony is a packet-based communications solution that

      has the following characteristics:
      • Reliably supports today’s

        complete portfolio of high-quality telephony services

        with no need to change customer behavior
      • Enables the transport of

        both telephony and data on a common packet-based

        infrastructure
      • Transparently

        interoperates with the existing circuit-switched

        networks
      • Provides efficiencies in

        both transport and infrastructure
      • Facilitates the

        decoupling of services from transport
      • Enables the development

        of new services and new ways of communicating and

        doing business that leverage voice/data convergence

      Circuit

      Networks

      Packet

      Networks

      Transport

      TDM

      Packet

      Media

      Dedicated

      Shared



      Topology

      Hierarchical

      Flat, meshed

      Bandwidth

      Narrowband

      Broadband

      Networks

      Multiple, specialized

      Single, multiservice

      Architecture

      Centralized

      Distributed

      Design Point

      Voice

      Data

      Service Location

      Switch-based

      Server-based

      Revenue Growth

      The

      enterprise market is driving the introduction of converged

      telephony and data telecom solutions, which capture the

      efficiencies of multi-service networks and meet the exploding

      demand for data and multimedia communications. Service providers

      must compete aggressively for this business by offering Virtual

      Private Networking (VPN) solutions for voice and data.

      New applications such as

      unified messaging, which links e-mail, fax, and voicemail will

      become standard offerings. In addition, new broadband services,

      such as videoconferencing, will expand rapidly in the enterprise

      market. A multi-service packet network will enable service

      providers to address these opportunities.

      Cost Optimization

      WANs are increasingly

      dominated by data traffic. Therefore, WANs of tomorrow

      (optimized to carry data and telephony) will naturally have to

      be adapted to coexist in a packet-dominated WAN. Using a

      packet-optimized WAN for telephony transport significantly

      reduces costs by sharing expensive WAN bandwidth with data. In

      addition, data and telephony network administration can be

      significantly simplified by collapsing voice onto the data

      network.

      Enterprise LANs are

      dominated by Ethernet at Layers 1 and 2 and IP at Layer 3.

      Connecting end-user telephony clients over such LAN

      infrastructures allows sharing of campus infrastructure

      equipment between telephony and data networks and results in

      reduction of in-building (and campus) equipment and

      administration required for wiring infrastructures. In addition,

      moves, adds, and changes can be simplified by employing the

      plug-and-play advantages of Ethernet and IP.

      Flexibility and Responsiveness

      With the continuous

      acceleration of change in technology, it is difficult to

      maintain a leading-edge position in offering competitive telecom

      services. New packet-based network solutions are built on a

      distributed architecture, with open interfaces that support the

      rapid introduction of new services.

      Packet

      Telephony Solutions for Service Providers

      There

      is no single packet telephony solution that fits all service

      providers. Rather, each service provider must implement a

      network strategy that is aligned with its unique business

      strategy. For the existing service providers, this could involve

      migrating to packet networks to reduce costs and provide new

      revenue opportunities while protecting their current revenue

      stream. For the new service providers, packet telephony provides

      them the opportunity to create a unified network. For many

      incumbent service providers, the need is to rapidly transform

      their existing TDM networks into multi-service packet networks.

      Other incumbent service providers will choose to build entirely

      new overlay networks. Many new service providers will build new

      IP-optimized networks. And that is the reason why the market

      leaders like Lucent Technologies, Nortel Networks, and Cisco

      Systems, amongst others, all have a considerable

      "packet-telephony" strategy, which may be adopted in

      part or in full.

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