Internet TelephonyVincent DeclercqMSIT 526: Fall 200519 December 2005

Outline

• History• Deployment• Circuit Switching• Packet Switching• Hardware• Software• Advantages & Disadvantages• Pricing• Future of VoIP

History

• 1836: telegraph– 1st breakthrough in human telecommunication

• 1876: telephone• 1962-1968: packet switching networks• 1971: 1st email• 1995: Internet Telephony.

– Work of some hobbyists in Israel– Vocaltec, Inc. introduced 1st internet phone software

VoIP deployment

• 2005: VoIP enters residential telephony market in the USA. Rapidly becoming billion dollar industry.

• Until 2004 Vonage was the main provider now Multiple System Operators (MSOs) taking over

• FCC may start some regulations

• Biggest threat to cellular companies!

Circuit Switching

• Very reliable – Used over 100 years!

• How it works?

• Connection maintained for the duration of the call

• Dedicated lines - Circuit

• Foundation of the Public Switched Telephone Network (PSTN)

Packet Switching

• VoIP takes analog voice signals and converts them into digital data – in the form of IP packets that are transferred over the internet.

• How it works?• Sends and received data when needed• Very efficient: data packets sent through

a network along thousands of possible paths always choosing least congested.

Comparison

Differences

• Circuit Switching– 64 Kbps each direction (total 128Kbps)– 8Kb in a kilobyte (KB)– 16 KB each second / 960 KB per min– 10 min conversation about 10 Megabytes– Counting dead air!

• Packet Switching– We don’t count dead air– Only 3.5 min about 3.5 Megabytes– Plus even more with data compression

Hardware

• Analog Telephone Adapter (ATA)

• IP Phones

• Computer-to-Computer

ATA

• The ATA is an analog-to-digital converter

• Allows you to connect a standard phone to your computer or your Internet connection for use with VoIP.

• Providers like Vonage and AT&T CallVantage are bundling ATAs free with their service.

IP Phones

• These specialized phones look just like normal phones with a handset, cradle and buttons.

• Instead of having the standard RJ-11 phone connectors, IP phones have an RJ-45 Ethernet connector.

• IP phones connect directly to your router and have all the hardware and software necessary right onboard to handle the IP call.

• New Wi-Fi IP phones to make calls from any Wi-Fi hot spot !

• VOIPsupply Website

Computer to Computer

• Easiest way to use VoIP.

• 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

• Both need same software

Software

• Softphones– Client software that loads VoIP service on

the computer

• Codecs

• Soft Switches

• Protocols

Codecs

• Coder-decoder sampling the audio signal 64,000, 32,000, and 8,000 times per second.

• The most commonly used is the G.729A codec (sampling rate of 8,000 times per second).

• The pieces of audio missing between each sample are so small that to the human ear, it sounds like one continuous second of audio signal.

• Uses advanced algorithms that help sample, sort, compress and packetize audio data.

• The CS-ACELP algorithm (CS-ACELP = conjugate-structure algebraic-code-excited linear prediction) is one of the most prevalent algorithms in VoIP.

Soft Switches

• E.164 is the name given to the standard for the North American Numbering Plan (NANP). A phone number is like an address: (313) 555-1212 : 313=State, 555=City, 1212 = Street address.

• Mapping process: The challenge with VoIP is figuring out a way to translate NANP phone numbers to IP addresses and then finding out the current IP address of the requested number.

• This is handled by a central call processor running a soft switch.

• The soft switch 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.

Protocols

• All of the completely different pieces of hardware and software to communicate efficiently.

• The most widely used protocol is H.323, a standard created by the International Telecommunication Union (ITU).

• An alternative to H.323 emerged with the development of Session Initiation Protocol (SIP).

• Media Gateway Control Protocol (MGCP) is a third commonly used VoIP protocol.

• These three protocols are not always compatible.

Advantages

• Cost savings !!!– More features (Caller ID/waiting/transfer…)

• More capacity• Choose your number(s)• Take your number with you.• Advanced call-filtering options.• Use caller ID information to allow you make a choice

about how calls from a particular number are handled.– Forward the call to a particular number, – Send the call directly to voicemail, – Give the caller a busy signal– Play a "not-in-service" message– Send the caller to a funny rejection hotline.

Disadvantages

• Reliability !!!• Dependant on wall power• Integration with other systems• Challenge of 911• Call quality : Latency, Jitter, Packet loss• Security: Worms, Viruses, Hacking• Limitations of Individual PC

– specifications & power

• No overriding standards

Pricing

• Many options available

• Look for what best suits your specific needs

• Internet research

Future

• A key motivator for IP equipment manufacturers is the migration to IP which will hit most large enterprises once their upgrades made prior to year 2000 near the end of their life cycles.

• The Forrester Research Group predicts that nearly 5 million U.S. households will have VoIP phone service by the end of 2006.

Questions ?