Voice over Internet Protocol(VoIP)

Training and Development

IP Network

Multimedia PC

Multimedia PC

Initially, PC to PC voice calls over the

Internet

PSTN

Gateway

PSTN

Gateway

Public Switched Telephone Network

Gateways allow PCs to also reach phones

…or phones to reach phones

IP Telephony Model

Why VoIP ? Allows voice to be an IP Application

Converged Networks

Voice, Video & Data over an IP network

Monetary Savings

Functional Elements In IP-Telephony networks, following functional elements are mostly found.

• Media Gateway

• Media Gateway Controller

• Signaling Gateway

Media Gateway

Media Gateway performs functions like

• Physical T1/E1 facility termination

• Voice Packetization

• Voice Compression using ITU recommendations

G.711,G.723.1 and G.729 etc

Media Gateway Controller (MGC)

• A media gateway controller is the overall controller of the system.

• Media Gateways receives commands from the media gateway controller which define their operations.

MGC performs core functions like:

• Address Resolution

• Call Routing

• Resource Management

• Call Detail Record (CDR) Generation

A media gateway controller is also known as a Soft Switch

Signaling Gateway (SG)

• Signaling gateway transfers signaling information between PSTN node and Media gateway controller (MGC)

Media GatewayMedia Gateway ControllerSignaling Gateway

May be separate physical devices or

Integrated in any combination

e.g. SG/MG functions

Implemented in one unit

IP Telephony Model

SG

PSTNNode

PSTNNode

SGSS7 SS7

MG MGPSTN

TrunksPSTN

Trunks

MGC

SS7 over IP

SS7 o

ver I

P

RTP / UDP / IP

MGCP /

H.248 MGCP / H.248

IP Network