Adapting Legacy Phone Systems to VoIP

uptightexampleNetworking and Communications

Oct 24, 2013 (3 years and 9 months ago)

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www.convergencetechnologycenter.org

DUE 402356

Adapting Legacy Phone
Systems to VoIP

Vincente D’Ingianni

Director of Professional Services

Binary Systems, Inc.

vincente@binary
-
systems.com


www.convergencetechnologycenter.org

2

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

3

The Legacy PSTN

Public Switched Telephone Network

Enterprise Network

PSTN

Enterprise Network

Subscribers

Subscribers


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4

What’s Inside the PSTN?

Class 4

Tandem Switch

Class 5

End Office Switch

Enterprise Network

Subscribers

Subscribers

Enterprise Network

Public Switched Telephone Network


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5

Forgetting the Complexity

Public Switched Telephone Network

Enterprise Network

PSTN

Enterprise Network

Subscribers

Subscribers

All Routing Logic is managed by the

Service Provider’s Network


Not yours.


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6

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

7

Enter the IP Network

Enterprise Network

PSTN

Enterprise Network

Subscribers

Subscribers

IP Network

Public Internet or Private WAN


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8

Focusing on VoIP

Enterprise Network

Enterprise Network

Subscribers

Subscribers

IP Network

Public Internet or Private WAN

VoIP gives you the option to take
control of your Communication
Network


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9

What’s Inside an IP Network?

Enterprise Network

Enterprise Network

Subscribers

Subscribers

Public Internet or Private WAN

Firewall

Firewall

Routers

Routers

Routers

In most cases, IP Routing Logic is
still managed by a Service
Provider’s Network




Not yours


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10

Forgetting the Complexity

Enterprise Network

Enterprise Network

Subscribers

Subscribers

IP Network

Public Internet or Private WAN

VoIP Communication Protocols, such
as SIP & H.323, allow control of your
communication routing without
interfering with the Service Providers
Network


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11

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

12

Fax

-
Demodulation

-

Handshaking

Signaling

Interworking

VoIP<
-
> PSTN

IP

Processing

-
IP

-

TCP

-

UDP

-

RTP

PSTN

PBX

Ethernet

PPP

Frame Relay

ATM

IP Voice

Applications/

Management

Processing

Signaling

Interworking

VoIP <
-
> PSTN

Fax



Demodulation



Handshaking

Voice

-
Compression

-

Echo


Cancellation

-
Silence


Suppression

PSTN

Ports

-
Analog

C.O

-
T1/E1


IP Network

VoIP Media Gateways provide the
bridge between Legacy Phone
Systems and VoIP

What are VoIP Media Gateways?


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13

PSTN

PBX

Ethernet

PPP

Frame Relay

ATM

IP Voice

IP Network

Vega 50

Analog VoIP Gateway


Analog Ports for FXS or FXO Signaling


Supports PSTN/PBX or Telephone Lines


Connection to the IP Network Via 100Base
-
T Ethernet Interface


SIP, H.323


Selectable Coders Per Channel: G.711, G.723, G.729


T.38 Fax Relay

Analog VoIP Gateways


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PSTN

PBX

Ethernet

PPP

Frame Relay

ATM

IP Voice

IP Network

Digital Trunking VoIP Gateways

Vega 400

Trunking VoIP Gateway


Supports PSTN/PBX Digital Trunks


T1 / E1 ISDN, North American CAS, R2


Connection to the IP Network Via 100Base
-
T Ethernet Interface


SIP, H.323


Selectable Coders Per Channel: G.711, G.723, G.729


T.38 Fax Relay


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15

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

16

Bridging the Networks

PSTN

IP Network

VegaStream

Trunking VoIP Gateway

VegaStream

Analog VoIP Gateway

Ethernet

Ethernet

Digital

Trunks

FXO

Lines


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Bridging the Networks (cont.)

Firewall

Firewall

Routers

Routers

Routers

IP Network

Ethernet

Ethernet

VegaStream

Trunking VoIP Gateway

VegaStream

Analog VoIP Gateway


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Bridging the Networks (cont.)

PSTN

Class 4

Tandem Switch

Class 5

End Office Switch

FXO

Lines

Digital

Trunks

VegaStream

Trunking VoIP Gateway

VegaStream

Analog VoIP Gateway


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PSTN

IP Network

Ethernet

Ethernet

User Side

Digital

Trunks

Enterprise Network

Private Extensions

FXS

Lines

Network Side

Digital

Trunks

FXO

Lines

VegaStream

Trunking VoIP Gateway

VegaStream

Analog VoIP Gateway

Bridging Public and Private Networks


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20

The “Leaky” PBX

PSTN

IP Network

Ethernet

Ethernet

Enterprise Network

Network Side

Digital

Trunks

FXO

Lines

Enterprise Network


Using Legacy PBX Routing functionality, users may dial a prefix to bypass the PSTN



Calls are routed via VoIP to remote locations/countries


Standard PSTN Toll charges are bypassed


“Enterprising Enterprises” resell the ability to terminate calls on their local PSTN connection so other VoIP users
can benefit
(not necessarily legal)


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21

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

22

PSTN

IP Network

Ethernet

Ethernet

Enterprise Network

Network Side

Digital

Trunks

FXO

Lines

Enterprise Network


Calculate the number of calls that you will be making simultaneously over your IP
connection


Estimate approximately 80
-
90 kbps uncompressed per call


A T3 (28 T1s) of voice will fill a 100 Mb Ethernet link

Bandwidth Requirements


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Most cable modems provide asymmetrical
bandwidth


3 Mb downstream is popular


256K upstream is typical


Don’t expect to force an entire trunk worth of voice
through a cable modem or DSL


Vega 400 Trunking

VoIP Gateway

Cable

Modem

256K

Upstream

Bandwidth Requirements


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24

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?




www.convergencetechnologycenter.org

25

PBX/CO


The Switch provides the “Talk Battery” to power
a phone


The switch provides the dial tone


The phone generates the digits

POTS Line

POTS Line connected to a PBX/CO


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Foreign Exchange Office (FXO)

Emulates a telephone set connects to a standard line side interface


of the PBX or central office



Private

Network

PBX/CO

FXO

Foreign Exchange Office (FXO)


This is the way that Interexchange carriers were forced to connect with AT&T
before equal access


Carriers would purchase simple lines in each city to create a POP


These lines were directly connected into their switching networks


Subscribers dialed 7
-
digit access numbers to receive dial tone from the carrier





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27








Foreign Exchange Station (FXS)


Emulates a switch port connects to a standard telephone line

Signaling can be loop start or ground start

Private

Network

FXS

Foreign Exchange Station (FXS)

POTS Line


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Foreign Exchange Office (FXO)

Emulates a telephone set connects to a standard line side interface


of the PBX/CO






Foreign Exchange Station (FXS)


Emulates a switch port connects to a standard telephone line

Signaling can be loop start or ground start

Private

Network

PBX/CO

FXO

FXS

Combination of FXO/FXS allows a remote station to appear as a standard line:

POTS Line

Extensions use a combination of
FXO and FXS


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29

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

30

Public Switched Telephone Network

Enterprise Network

PSTN

Enterprise Network

Subscribers

Subscribers

Remote VoIP Users


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PSTN

Subscribers

Enterprise Network

Remote Lines


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PSTN

Subscribers

Enterprise Network

IP Network

Public Internet or Private WAN

Cable Modems or DSL can be used for low numbers of remote users.

Adding a VoIP Network


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Public Internet or Private WAN

Vega 50

Analog FXO

VoIP Gateway

Vega 50

Analog FXS

VoIP Gateway

PSTN

Subscribers

Enterprise Network

IP Network

Adding VoIP Gateways


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Public Internet or Private WAN

PSTN

IP Network

Subscribers

Enterprise Network

Vega 50

Analog FXO

VoIP Gateway

Vega 50

Analog FXS

VoIP Gateway

Bypassing the PSTN


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35

Public Internet or Private WAN

IP Network

Subscribers

Enterprise Network

Call routing between VoIP
Gateways is configured locally.

Vega 50

Analog FXO

VoIP Gateway

Vega 50

Analog FXS

VoIP Gateway

Remote User Connected via VoIP


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Analog FXO

VoIP Gateway

192.168.1.123

Enterprise Network

Configuring Local FXO Extensions


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Analog FXO

VoIP Gateway

192.168.1.123

Enterprise Network

Configuring Local FXO Routing


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Analog FXS

VoIP Gateway

192.168.1.202

Subscribers

Configuring Remote FXS Extensions


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Analog FXS

VoIP Gateway

192.168.1.202

Subscribers

Configuring Remote FXS Routing


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Public Internet or Private WAN

IP Network

Subscribers

Enterprise Network

Subscribers maintain all feature
functionality as local users on the
PBX.

Vega 50

Analog FXO

VoIP Gateway

Vega 50

Analog FXS

VoIP Gateway

Remote Users connected via VoIP


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IP Network

Subscribers

Enterprise Network

IP Phones


An IP phone is simply a single
-
port VoIP media gateway

Vega 50

Analog FXO

VoIP Gateway

Vega 50

Analog FXS

VoIP Gateway

Adding IP
-
Only Users


www.convergencetechnologycenter.org

42

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

43


In
-
Band Signaling


CAS


Channel Associated Signaling


R2


E&M Wink Start


FGD


D
-
Channel

Trunk Signaling Methods


Out
-
of
-
Band
Signaling


ISDN / Q.931


SS7

Bearer Channel

Combined Voice and
Signaling Channel


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44

D
-
Channel

Network vs. User Side ISDN


Network side ISDN


Network side ISDN provides a standard PRI interface to a
PBX and mimics the behavior of legacy phone switches


User Side ISDN


User side ISDN provides a standard ISDN PRI interface to
the Public Switched Telephone Network (PSTN)


Bearer Channel

PSTN

Network Side

User Side

Clock Timing


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45

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?



www.convergencetechnologycenter.org

46

Public Switched Telephone Network

Enterprise Network

PSTN

Enterprise Network

Subscribers

Subscribers

Remote VoIP Locations


PSTN
Connectivity


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PSTN

Enterprise Network

Enterprise Network

Network Side

User Side

User Side

ISDN PRI

ISDN PRI

Remote VoIP Locations


Connecting
Locations via PSTN


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IP Network

PSTN

Enterprise Network

Enterprise Network

Remote VoIP Locations
-

Adding
VoIP


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PSTN

Enterprise Network

Enterprise Network

IP Network

Remote VoIP Locations


Adding
VoIP


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PSTN

IP Network

Enterprise Network

Enterprise Network

Network Side

Network Side

User Side

User Side

ISDN PRI

ISDN PRI

Vega 400

PRI VoIP Gateway

Vega 400

PRI VoIP Gateway

Remote VoIP Locations


Adding
VoIP Gateways


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51

IP Network

Enterprise Network

Enterprise Network

Network Side

Network Side

User Side

User Side

ISDN PRI

ISDN PRI

Vega 400

PRI VoIP Gateway

Vega 400

PRI VoIP Gateway

Remote VoIP Locations


PSTN
Bypass


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IP Network

Enterprise Network

Enterprise Network

IP Phones

Vega 400

PRI VoIP Gateway

Vega 400

PRI VoIP Gateway

Remote VoIP Locations


Adding IP
-
Only Users


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53

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?




www.convergencetechnologycenter.org

54

Do I Need a Softswitch?


Ask these questions:


Does your existing PBX have the features that you
need?


What VoIP control protocols do your
gateways/endpoints support?


How many VoIP gateways/endpoints do you need?






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55


Remote VoIP users can transparently utilize
features from the legacy PBX/switch


Virtual Private Networks for Voice can be
created via existing PBX Routing Tables


Features such as T.38 Fax Relay and RFC 2833
digit transport provide reliable communication
over low bandwidth connections


Does Your Existing PBX Have the
Features That You Need?


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56


MGCP and MEGACO are Master
-
Slave protocols


MGCP and MEGACO require a Call Agent/Softswitch to instruct the
Endpoint to perform all functionality


If communication with the Call Agent is lost, the endpoint cannot
function


These protocols require a Softswitch


SIP and H.323 are peer
-
to
-
peer protocols


SIP and H.323 gateways offer internal routing tables and features
that often rival the legacy PBX or Key System itself


If communication with the Proxy/Gatekeeper/Softswitch is lost,
internal routing tables may be used. For example, “911”



SIP is continually evolving to support next generation features

What VoIP Control Protocols do
Gateways Support?


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57


Softswitches, SIP proxies, and H.323 gatekeepers provide a
single point of configuration for advanced network features


IP Network

Enterprise Network

Enterprise Network

IP Phone

IP Phone

Softswitch

Feature Server

Vega 400

Trunking VoIP Gateway

Vega 400

Trunking VoIP Gateway

How Many VoIP Endpoints Do You
Have?


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58

What We’ll Cover…


What’s inside the PSTN?


What’s inside the IP network?


VoIP gateways


Connecting the IP network to the PSTN


Bandwidth


Remote PSTN users


“The Old Way”


Remote VoIP users



The New Way



Remote PSTN locations


“The Old Way”


Remote VoIP locations



The New Way



Do I need a Softswitch?


Do I need a VoIP carrier?


www.convergencetechnologycenter.org

59

PSTN

IP Network

Ethernet

Ethernet

Enterprise Network

Network Side

Digital

Trunks

FXO

Lines

Enterprise Network


VoIP Carriers provide alternate IP
-
based call routing to remote endpoints via the public
Internet


Calls are routed via VoIP to remote locations/countries and standard PSTN Toll charges are
bypassed


VoIP Carrier’s

Softswitch / Feature Server

Do I Need a VoIP Carrier?

Vega 400

Trunking VoIP Gateway

Vega 50

Analog VoIP Gateway


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60

Can I Cut the Cord to the PSTN?

IP Network

Ethernet

Enterprise Network

Enterprise Network


If you are satisfied with the reliability of your high
-
speed internet provider and VoIP
carrier’s feature set and destination choices, you may choose to cut the cord


But first, ensure that your gateways, as well as, your VoIP Carrier’s network support
T.38 faxes and a compatible modem passthrough functionality


VoIP Carrier’s

Softswitch / Feature Server

Ethernet

Network Side

Digital

Trunks

Vega 400

Trunking VoIP Gateway

Vega 50

Analog VoIP Gateway


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61

Key Points to Remember


Don’t underestimate the complexity of the PSTN and IP network


Choose the right VoIP Endpoint for your application


Follow the industry


Use SIP for new installations


Analog FXS or FXO Gateways for lines and key systems


Digital Trunking Gateways for PBXs


IP phones for new user installations


Be sure you can support T.38 for faxes and bypass for modems


Be sure you have a big enough IP pipe to add voice


SIP and H.323 VoIP Gateways can provide stand
-
alone routing and
feature functionality


Use a Softswitch to manage numerous gateways and advanced
features


VoIP carriers can provide connectivity beyond your private network


Yes, you can cut the cord to the PSTN!