Adapting Legacy Phone Systems to VoIP [ppt]

www.convergencetechnologycenter.org DUE 402356

Adapting Legacy Phone Systems to VoIP

Vincente D’IngianniDirector of Professional ServicesBinary Systems, [email protected]

2 www.convergencetechnologycenter.org

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?


The Legacy PSTN

Public Switched Telephone Network

Enterprise Network

PSTN

Enterprise Network Subscribers

Subscribers


What’s Inside the PSTN?

Class 4 Tandem Switch

Class 5 End Office Switch

Enterprise Network

Subscribers

Subscribers

Enterprise Network



Forgetting the Complexity


Enterprise Network

PSTN


Subscribers

All Routing Logic is managed by theService Provider’s Network – Not yours.




Enter the IP Network

Enterprise Network

PSTN


Subscribers

IP Network

Public Internet or Private WAN


Focusing on VoIP

Enterprise Network


Subscribers

IP Network


VoIP gives you the option to take control of your Communication

Network


What’s Inside an IP Network?

Enterprise Network


Subscribers


Firewall

Firewall

Routers

Routers

Routers

In most cases, IP Routing Logic is still managed by a Service

Provider’s Network – Not yours


Forgetting the Complexity

Enterprise Network


Subscribers

IP Network


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

Network




Fax-Demodulation- Handshaking

SignalingInterworking

VoIP<-> PSTN

IPProcessing

-IP- TCP- UDP- RTP

PSTN

PBX

EthernetPPP

Frame RelayATM

IP Voice

Applications/ManagementProcessing

SignalingInterworking

VoIP <-> PSTN

Fax– Demodulation– Handshaking

Voice-Compression- Echo Cancellation-Silence Suppression

PSTNPorts

-AnalogC.O

-T1/E1IP Network

VoIP Media Gateways provide the bridge between Legacy Phone

Systems and VoIP

What are VoIP Media Gateways?


PSTN

PBX

EthernetPPP

Frame RelayATM

IP Voice

IP Network

Vega 50Analog 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


PSTN

PBX

EthernetPPP

Frame RelayATM

IP Voice

IP Network

Digital Trunking VoIP Gateways

Vega 400Trunking 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




Bridging the Networks

PSTN

IP Network

VegaStreamTrunking VoIP Gateway

VegaStreamAnalog VoIP Gateway

EthernetEthernet

DigitalTrunks

FXOLines


Bridging the Networks (cont.)

Firewall

Firewall

Routers

Routers

Routers

IP Network

EthernetEthernet




Bridging the Networks (cont.)

PSTN

Class 4 Tandem Switch

Class 5 End Office Switch

FXOLinesDigital

TrunksVegaStreamTrunking VoIP Gateway



PSTN

IP NetworkEthernet

Ethernet

User SideDigitalTrunks

Enterprise Network

Private Extensions

FXSLines

Network SideDigitalTrunks

FXOLines



Bridging Public and Private Networks


The “Leaky” PBX

PSTN

IP NetworkEthernetEthernet

Enterprise Network


FXOLines

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)




PSTN


Enterprise Network


FXOLines

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


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 TrunkingVoIP Gateway

E1 PRI

CableModem

256KUpstream

Bandwidth Requirements




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


Foreign Exchange Office (FXO) Emulates a telephone set connects to a standard line side interface of the PBX or central office

PrivateNetwork

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


Foreign Exchange Station (FXS) Emulates a switch port connects to a standard telephone line Signaling can be loop start or ground start

PrivateNetwork

FXS

Foreign Exchange Station (FXS)

POTS Line


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

PrivateNetwork

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





Enterprise Network

PSTN


Subscribers

Remote VoIP Users


PSTN

SubscribersEnterprise Network

Remote Lines


PSTN


IP Network


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

Adding a VoIP Network



Vega 50Analog FXO

VoIP Gateway

Vega 50Analog FXS

VoIP Gateway

PSTN


IP Network

Adding VoIP Gateways



PSTN

IP Network


Vega 50Analog FXO

VoIP Gateway

Vega 50Analog FXS

VoIP Gateway

Bypassing the PSTN



IP Network


Call routing between VoIP Gateways is configured locally.

Vega 50Analog FXO

VoIP Gateway

Vega 50Analog FXS

VoIP Gateway

Remote User Connected via VoIP


Analog FXOVoIP Gateway192.168.1.123

Enterprise Network

Configuring Local FXO Extensions


Analog FXOVoIP Gateway192.168.1.123

Enterprise Network

Configuring Local FXO Routing


Analog FXSVoIP Gateway192.168.1.202

Subscribers

Configuring Remote FXS Extensions


Analog FXSVoIP Gateway192.168.1.202

Subscribers

Configuring Remote FXS Routing



IP Network


Subscribers maintain all feature functionality as local users on the

PBX.

Vega 50Analog FXO

VoIP Gateway

Vega 50Analog FXS

VoIP Gateway

Remote Users connected via VoIP


IP Network

SubscribersEnterprise NetworkIP Phones

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

Vega 50Analog FXO

VoIP Gateway

Vega 50Analog FXS

VoIP Gateway

Adding IP-Only Users




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


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





Enterprise Network

PSTN


Subscribers

Remote VoIP Locations – PSTN Connectivity


PSTN

Enterprise Network

Enterprise Network

Network Side

User Side

User Side

ISDN PRI

ISDN PRI

Remote VoIP Locations – Connecting Locations via PSTN


IP Network

PSTN

Enterprise Network

Enterprise Network

Remote VoIP Locations - Adding VoIP


PSTN

Enterprise Network

Enterprise Network

IP Network

Remote VoIP Locations – Adding VoIP


PSTN

IP Network

Enterprise Network

Enterprise Network

Network Side

Network Side

User Side

User Side

ISDN PRI

ISDN PRI

Vega 400PRI VoIP Gateway


Remote VoIP Locations – Adding VoIP Gateways


IP Network

Enterprise Network

Enterprise Network

Network Side

Network Side

User Side

User Side

ISDN PRI

ISDN PRI



Remote VoIP Locations – PSTN Bypass


IP Network

Enterprise Network

Enterprise Network

IP Phones



Remote VoIP Locations – Adding IP-Only Users




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?


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?


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?


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

IP Network

Enterprise Network

Enterprise Network

IP PhoneIP Phone

SoftswitchFeature Server



How Many VoIP Endpoints Do You Have?




PSTN


Enterprise Network


FXOLines

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’sSoftswitch / Feature Server

Do I Need a VoIP Carrier?




Can I Cut the Cord to the PSTN?

IP NetworkEthernet

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’sSoftswitch / Feature Server

Ethernet





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!

Documents

Adapting Legacy Phone Systems to VoIP [ppt]