Voice Over IP (VoIP) &

STREAMING Realised by:

- Ragheb Gmira- Faten barkati

4C_Info2 University year 2015/2016

Outline

VOIP Definition How does it work? VoIP architecture Advantages & limits Protocols

STREAMING Definition How does it work? Protocols Avantages Desavantages

Conclusion

VOIP

Definition

Voice over Internet Protocol (VoIP), is a technology that allows to make voice calls using a broadband Internet connection instead of a regular (or analog) phone line (PSTN).

The use of IP networks, namely the LAN and WAN, to carry voice,

Voice conversations are turned into digitized data and packetized for transmission across a network.

How does it work?

VoIP services convert your voice into a digital signal that travels over the Internet. If you are calling a regular phone number, the signal is converted to a regular telephone signal before it reaches the destination. VoIP can allow to make a call directly from a computer, a special VoIP phone, or a traditional phone connected to a special adapter.

Analog Telephone Adaptor : sometimes called a ‘gateway’, is a device for connecting traditional analog telephones, fax machines, and similar customer-premises devices to a digital telephone system or a voice over IP telephony network.

select whether outgoing calls use VoIP or the standard telephone connection

switch between VoIP and standard phone connection for incoming calls.

VoIP phone : A dedicated VOIP handset looks just like a standard phone, but it is connected directly to router or PC, typically through an Ethernet or USB port. The handset already includes all software necessary to send and receive VoIP calls

Computer to computer using a Software VoIP Phone : As the term suggests, this involves using software on PC and an internet connection to contact someone else with compatible software at their computer. Apart from the software, the computer needs a microphone, speakers, a suitable sound card and a fast internet connection.

VoIP phone calls can be made in one of three ways.

VoIP architecture

PSTN : Public switched telephone network PABX : Private Automatic Branch eXchange

Advantages & limits

Advantages: You don’t need to pay the additional cost for a land-line. Many services allow you to talk for as long as you want. It is easily portable and can be used in any destination. A triple play network: it includes voice, video and data. Many conversations at the same time. Exchange data with people are you talking with, sending images, graphs and

videos.

Limits: The needed is that other person is also connected to Internet at the same time. Voice data communication must be a real time stream

Protocols The protocol H.323 : (Packet-based multimedia communications systems)

a multimedia standard that provides a foundation to transport voice, video and data with a concern for real-time data.

H.323 defines several network elements:o Terminals (LAN Endpoints) :IP phone and PCo Gateways (Optional but really useful) : Device that connects H.323 voice network to

non-H.323 voice network (SIP or PSTN) o Gatekeepers (Also optional)

• Provides address translation (phone number to IP address)

• Admission control for H.323 terminals and gateways

• Manage bandwidth allocation

• Other optional services (LAN traffic management)

o MCUs (multipoint control units) : is a device that is used for multiparty conferencing

The protocol SIP :

o It is an application layer control protocol for creating, modifying and terminating sessions with one or more participants. The architecture of SIP is similar to that of HTTP (client-server protocol). Requests are generated by the client and sent to the serverSIP ,

The SIP System consists ot two components : User Agents and Network Servers

SIP defines a lot of messages :

• INVITE: for inviting a user to a call

• BYE: for terminating a connection between the two end points

• ACK: for reliable exchange of invitation messages

• OPTIONS: for getting information about the capabilities of a call

• REGISTER: gives information about the location of a user to the SIP registration server.

• CANCEL: for terminating the search for a user

The protocol RTP : Real-time Transport Protocol

o Reconstructing the time base flows.

o Sequencing packages.

o Identify the data content for their associate a secure transport.

o Identify the data source.

o Transport of audio and video applications in frame.

The protocol RTCP: Real-time Control Protocol

o Periodic spontaneous trasmission of control packets to all participant.

o Feed back on the quality of data distribution

o useful to sender (e.g to adapt encoding)

o useful to receivers (e.g to evaluate whether problems are local)

o Evaluate the participants and adjust report rate

The protocol SIP

STREAMING

A technique for transferring data such that it can be processed as a steady and continuous stream, client does not have to download the entire file to view it.

Data

SourceNetwork

The portion client is viewingThe portion in the buffer

How does it work?

When audio or video is streamed, a small buffer space is created on the user's computer, and data starts downloading into it. As soon as the buffer is full (usually just a matter of seconds), the file starts to play. As the file plays, it uses up information in the buffer, but while it is playing, more data is being downloaded. As long as the data can be downloaded as fast as it is used up in playback, the file will play smoothly.

How does it work?

Types of streaming

Streaming Stored Audio and Video : The multimedia content has been prerecorded and stored on a server

• User may pause, rewind, forward, etc…

• Constraint: after display start, the playout must be continuous

Streaming Live Audio and Video :• Similar to traditional broadcast TV/radio, but

delivery on the Internet

• Non-interactive just view/listen

• Can not pause or rewind

• Often combined with multicast

Real-Time Interactive Audio and Video :Phone conversation/Video conferencing

• Constraint: delay between initial request and display start must be small

• Constraint: after display start, the playout must be continuous

Protocols

RTP : Real-time transfer Protocol

RTCP : Real-time transport Control Protocol

RTSP: Real-time Streaming Protocol

Real Time Streaming Protocol (RTSP)

RTSP is the control protocol for the delivery of multimedia content across IP networks. It is based typically on TCP for reliable delivery and has a very similar operation and syntax to HTTP. RTSP is used by the client application to communicate to the server information such as the media file being requested

Avantages

It reduces download time

It provides steady service

Slower systems can take advantage of streaming technology

Provide service on demand

Disadvantages

It is difficult to keep the service steady if the bandwidth is low

The maintenance of streaming server is relatively expensive

Packet loss may occur during the transmission

Conclusion

VOIP & Streaming are being developped day by day. We can probably assume that IP will become one day a single standard allowing interoperability of networks globalized. That is why the integration of voice over IP is just one step towards EoIP:

Everything over IP