VoIP Voice Over Internet Protocol

Topics

PSTN
VoIP
VoIP Architecture
Codec
VoIP Gateway
Signalling Protocols
VoIP Terminals
Advantages and Disadvantages

PSTN Public Switched Telephone Network

It is known as landline telephone system.
It was designed for purely analog voice communication by using wire network. It meant higher cost for long distance.
Number of switches are involved to establish a connection.
PSTN uses circuit switching. Dedicated path.

VoIP Voice Over IP

Voice over Internet Protocol (VoIP) is a technology that allows users to make phone calls using internet.
It is also known as IP telephony, Internet telephony or internet calling.
The voice (and data) messages are split into packets by using digital signal processors (DSPs).
VoIP uses packet switching. No dedicated path.
Its is very cheap or Free. It uses the existing infrastructure of internet.

VoIP Gateway

A VoIP gateway (or PSTN Gateway) is a device which converts telephony traffic into IP for transmission over a data network.
Perform DSP.
Call Control.
Bandwidth Management.

Codecs

Data Compression.
Data Encoding.

Codec are of different types for data, voice, and Video. The quality and efficiency of the compression software has a big impact on the voice quality of VoIP traffic. There are good compression technologies and there are less good ones. Each compression technology is designed for a specific use under specific circumstances.

Signalling Protocols

The signaling protocols govern the set-up and to many other related call management functions.

H.323.

It is ITU-T standard protocol.It is actually a set of protocols .H.323 was designed for multimedia communication services such as real-time audio,video, and data communications over Ip Network.

SIP (Session Initiation Protocol).

It is IETF standard protocol and younger than H.323,it is lighter (requires less bandwidth). It is text-based. It is specially design for VoIP services.