VOIP TECHNOLOGY- THE NEXT STEP IN GLOBAL COMMUNICATIONS

SUSMITA MITRA

SCS DelhiNUES Presentation on:

Voice Over Internet Protocol

16-17 April 2008

Talk Overview Introduction Using VoIP VoIP- Packet Switching Major concerns of VoIP CODECS VoIP: Soft Switches and Protocols VoIP: Quality of service

What is VOIP?Voice over Internet Protocol (VoIP) is a technology that enables one to make and receive phone calls through the Internet instead of using the traditional analog PSTN (Public Switched Telephone Network) lines.

Call anyone in the world at unbelievably low rates Call anyone in the world at unbelievably low rates

Why VoIP? Can make and receive calls with / without a computer Can surf the net while making calls Can make local / long distance calls Can make and receive call to / from PSTN

Cost effective Digital features not commonly available on PSTN lines such as :

v o i c e m a i l , c a l l e r I D , c o n f e r e n c e a n d s o o n.

Flavors of VoIP ATA

Connects a standard phone to a computer or an Internet connection for use with VoIP.

The ATA is an analog-to-digital converter.

IP Phones connect directly to a router and have all the hardware and

software necessary right onboard to handle the IP call.

Computer-to-computer There are several companies offering free or very low-cost

software that you can use for this type of VoIP. All you need is the software, a microphone, speakers, a sound

card and an Internet connection

How does VoIP work?

VoIP converts the voice signal from your telephone into a digital signal that travels over the Internet. If you are calling a regular phone number, the signal is then converted back at the other end. Internet Voice can allow you to make a call directly from a personal computer. If you make a call using a phone with an adaptor, you’ll be able to dial just as you always have.

The users voice (or fax) is converted into a digital signal, compressed, and broken down into a series of packets.

The packets are then transported over private or public IP networks and reassembled and decoded on the receiving side.

At the receiving end, the re-assembled packets arrive as a normal sounding voice call.

Packet switching is very efficient. It lets the network route the packets along the least congested and cheapest lines. It also frees up the two computers communicating with each other so that they can accept information from other computers, as well.

PACKET SWITCHING

CHALLENGES Some VoIP service providers may have limitations to their 911 service. Some VoIP services don’t work during power outages VoIP is susceptible to worms, viruses and hacking. Because VoIP uses an Internet connection, it's susceptible to all the

hiccups normally associated with home broadband services. All of these factors affect call quality:

Latency Jitter Packet loss

Phone conversations can become distorted, garbled or lost because of transmission errors.

V o I P – C O D E C S A codec, which stands for coder-decoder, converts an audio signal into compressed digital form for transmission and then back into an uncompressed audio signal for replay. It's the essence of VoIP.

Codecs sample the audio signal several thousand times per second.

Summary of available codecs:

VoIP software processes and routes the calls.

8 kbpsG.729

16 kbpsG.728

32 kbpsG.721

64 kbpsG.711

Soft Switches and Protocols Soft Switches- where to send data? It contains a database of users and phone numbers. If it doesn't have the information it

needs, it hands off the request downstream to other soft switches until it finds one that can answer the request.

VoIP-Protocols:-

H.323 - ITU-Standard initially a multimedia conferencing protocol. Defines all aspects of call transmission, from call establishment to capabilities

exchange to network resource availability.

SIP - IETF’s standard for establishing VOIP connections. Defines how sessions are to be set up and torn down.

Q o s - i n V o I P

Quality of Service is essential for the success of VoIP.

The human ear is extremely sensitive to even minor changes in an audio signal.

Loss of quality occurs when the voice packets are transferred over the inherently unreliable packet-based networks.

Some methods to enhance the QoS achieved in VoIP are:

Classification of Service: Using the TOS bits in the IP header to set a priority for the voice packet.

Tagging the packets with labels and using the labels to decide the route. Voice packets can be routed over less congested networks.

Reserving resources to meet requirements for bandwidth, delay, jitter, etc. along a particular path through a series of routers.

Q o s - i n V o I P

CREDITS http://communication.howstuffworks.com/ip-telephony.htm http://www.fcc.gov/voip/ http://www.discover-voip.info/branded-voip/branded-voip.html http://www.packetizer.com/ipmc/papers/understanding_voip/

hype_vs_reality.html