Transcript Internet Telephony

VoIP
Presented by:
Adnan Sheikh
Chris Howard
Moises Uribe
Cheri Kishida
Overview
 The History of this new technology.
 What is Internet Telephony?
 How does it work?
 What are the Pros/Cons?
 What are some of the companies that
provide VoIP?
Objectives
 To provide the class with an understanding
of VoIP for personal/home use
 To inform the class of the VoIP service
providers available
 To be able to leave this presentation
knowing how to obtain and implement your
own VoIP services
History
 February 1995, first internet phone released by
VocalTec, then other companies like Cisco &
lucent entered the market
 1996, Internet Telephone Consortium created
(ITC) used as a means of discussing the
technology, regulation policies, and market
structure for the industry
 Over time, Advancements in technology have
made internet phone easy to use and an
affordable service to use
What is Internet Telephony?
 Technology using an Internet connection
to pass voice data using IP instead of the
standard public switched telephone
network
 Current: PSTN & POTS
 Very flexible: supports PC to PC, PC to
Phone, and Phone to Phone
How it Works
 Voice over internet protocol (VOIP) turns
analog voice signals to digital data.
 Lower costs – Domestic & International
 Three types of internet telephony
 ATA
 IP Phones
 PC to PC
ATA
ATA
 Most common method
 Analog Telephone Adaptor (ATA) is an
analog to digital converter
 Enables you to connect a standard phone
to a computer or Internet connection
IP Phones
IP Phones
 Similar to normal phones but have an RJ45 (Ethernet) connection instead of the
standard RJ-11 connection
 Contains all hardware and software
 Connect directly to router
 Offices configured with all IP phones are
said to have an IP Private Branch
Exchange (PBX) set up
Computer to Computer
 Obtain free or very low-cost software from
companies.
 Sender & receiver need equipment.
 Need the software, Internet connection
(preferably high speed), microphone,
speakers, and a sound card..
 Lower cost once equipment is purchased
Standard Phone
 Dial tone means you have connection to local
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office of telephone carrier
Dial the number and call is routed through the
switch
Connection is made using several
interconnected switches along the way
Receiving party answers the call and the
connection opens the circuit
Once you hang up, the circuit is closed and all
lines that were in use are free
VoIP: How it Works
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VOIP involves packet switching, therefore a constant
connection is not required
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The sending computer splits the data up into packets, each
packet containing an address on it so that network devices
know where to send them
Within each packet is a payload. The payload is whatever is
being transmitted.
The packets are then sent to a router which sends the packets
to another router, and so on and so forth until they reach their
destination.
The receiving computer then puts all of the packets back
together again in the proper order using instructions contained
within the packets. These instructions are necessary because
the packets may take different paths and arrive in the wrong
order.
VoIP: How it Works
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VOIP uses the internets packet switching network
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When you pick up the receiver it sends a signal to the ATA
The ATA receives the signal and sends back a dial tone
When you dial a number the tones are converted into a digital format and
then momentarily stored.
The phone number you dialed is then sent in the form of a request to the
VOIP companies call processor
The call processor then checks to see if the request is in a valid format.
The call processor then determines how best to map the call
The phone number is then translated into an IP address.
A device called a soft switch then connects the two devices, whatever
they may be.
A signal is then sent to the now connected phone telling it to ring.
Once the phone is picked up a session is established.
As your conversation is going on packets are sent back and forth
whenever there is data to be sent.
When the phone is hung up the circuit is closed and the ATA sends a
signal to the soft switch terminating the session.
VoIP – Behind the Scenes
 Protocols
 Encoding
 Achieving the quality
The Protocols
 Various protocols include H.323, SIP, Skinny
Client Control Protocol, Megaco (MGCP),
MiNET, IAX, and others
 Source and destination of telephone call must
be equipped with compatible versions of the
same protocol
 Gatekeeper assists the VoIP phones in placing
the call through such functions as Address
Translation, Admission control and Bandwidth
control
 The higher the call quality, the greater the
bandwidth requirement
The Encoding
 Source and destination phones must agree on the
encoder/decoder to use
 Some ITU standards include:
 G.711 – bandwidth requirement around 64kbps
 G723.1 – bandwidth requirement around 5.3kbps
 Source speaks into phone and voice is chopped into 30
millisecond slices, each slice representing a packet of
data
 Packet is given a number and time stamp, placed in a
UDP packet, and sent to destination’s phone via Internet
 When there is silence, packets are even smaller and are
sent only one out of every 180 milliseconds
Achieving the Quality
 Factors of consideration
 Lost Packets
 Latency - amount of time it takes for a
data packet to move across a network
connection
 Jitter – variation in timing or time of
arrival of data packets
Achieving the Quality: Lost
Packets
 Packet loss cannot totally be prevented
due to internet congestion
 Packet loss is acceptable if the lost
packets are distributed evenly and whole
words are not omitted
Achieving the Quality: Latency
 Direct effect on speech quality
 Delays less than 150 milliseconds can go
undetected
 Delays greater than 500 milliseconds are
highly annoying
 Indirect effect on speech quality
 Echo – although this can be minimized
through use of a headset
Achieving the Quality: Jitter
 Sound packets do not arrive at
destination’s phone at the exact timing
they left the source’s phone.
 Jitter is minimized when source and
destination are on the same LAN
 Digital buffer is used to ensure packets are
received in the intended order
ATA Implementation
ATA Implementation
ATA Implementation
ATA Implementation
ATA Implementation
ATA Implementation
VoIP Phone Example
VoIP Phone Example
VoIP Phone Example
VoIP Phone Example
VoIP Phone Example
PC to PC
 Very easy to start
 A number of companies offer this service
at little or no cost
 PC to PC communication is usually offered
free of cost to attract customers
 Local, long distance, and international
rates offered are much lower than
traditional telecommunication company
rates
Minimum Requirements
 A Pentium processor based PC
 Microsoft Windows 95 or newer operating
system
 A properly configured sound card
 A pair of speakers and a microphone
 A stable internet connection (at least 28.8
kbps)
Net2Phone.com
 One of the first
companies to start
internet telephony
 Very easy to use:
 Download software
 Create user account
 Select amount of money to
add to your account
 Login to the software
 You are ready to make PC
to PC, PC to Phone, PC to
FAX calls
Net2Phone.com
 Offers free PC to PC
communication
service
 Competitive rates for
international PC to
Phone dialing
Hotfoon.com
 A good service if calls are
mainly made through Asia /
Far East
 Offers PC to Phone service
only
 Rates:
 Whole USA and Canada:
10c/min
 India (All mobiles), some
cities: 10c/min
 Pakistan - some cities at
10c/min
 Bangladesh - Dhaka: 10c/min
 Saudi - Damman, Riyadh,
Jeddah: 12c/min
 U.A.E.: 12c/min
Advantages of VoIP
 A fairly new technology, useful for long distance
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voice communication
A much cheaper, often free, method of
communication
Relatively easy to use and install
Far superior to that of a regular phone,
especially for international calls
You can choose your area code & can take
your phone number wherever you go
Advantages of VoIP
 Low infrastructure costs – once IP is installed,
minimal telephony infrastructure maintenance
is required
 Extra features that ordinary phone companies
don’t offer like having your voicemail being sent
to your email, and dialing numbers from outlook
Disadvantages of VoIP
 The quality of VoIP is variable and degrades
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when there is internet congestion
Possible latency and data integrity problems
Need constant High-speed internet (DSL, Cable)
Dependent on Power and Internet
Inconsistent handling of outgoing calls from fax
machines, satellite television receivers,
conventional modems, or other devices
dependent on voice-grade telephone lines
Disadvantages of VoIP
 911 less effective. Need to register phone or
may not be routed to nearest emergency
dispatch center
Summary
 Cheaper alternative to the conventional
phone services
 Easy to implement and maintain
 VoIP will likely grow in terms of popularity
but may not replace the standard phone
services
 Companies will come out with new
communication services with extensive
features at competitive prices
A look into the future
 Companies will continue to come out
offering new communications services
 Services such as Teleconferencing,
videoconferencing, and collaboration
applications may soon be available as part
of your integrated IP-based voice
communications package
Glossary
 Address translation: The process of converting external
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addresses into standardized network addresses and vice
versa
Admission control: A QoS policy used to control the
admission of network traffic from outside a given
administrative domain
Bandwidth control: Setting the maximum capacity of data
transfer capacity of a digital communications system that
a service is allowed to use
Gatekeeper: a service which provides zone management
in the VoIP environment
Internet Telephony: Technology using an Internet
connection to pass voice data using IP instead of the
standard public switched telephone network
Glossary
 Jitter: - Variation in timing, or time of arrival, of
received signals; an unwanted lack of perfection
which can lead to bit areas
 Latency: Latency is the amount of time it takes
for a data packet (i.e., a unit of data) to move
across a network connection
 Payload: In a set of data, such as a data field,
block, or stream, being processed or
transported, the part that represents user
information and user overhead information, and
may include user-requested additional
information, such as network management and
accounting information
Glossary
 PBX: Private Branch Exchange. A privatelyowned telephone switch, often used in large
corporations to provide inside telephone
connectivity and access to the PSTN
 Protocols: An agreed-upon format for
transmitting data between two devices
 UDP: A connection-less, unreliable, transport
protocol which provides multiplexing and error
detection for applications which require a lowcost protocol for one-shot transactions
Web References
http://en.wikipedia.org/wiki/Voice_over_IP
http://www.cse.ohio-state.edu/~jain/cis78899/ftp/voip_protocols/index.html
http://en.wikipedia.org/wiki/Voice_over_IP
http://www.tldp.org/HOWTO/VoIPHOWTO.html
http://www.wilco-telephony.co.uk/voip.html
http://www.jiwire.com/voip-guide-intro.htm
Web References
http://networking.ittoolbox.com/browse.asp?
c=NetworkingPeerPublishing&r=http%3A
%2F%2Fwww%2Eerlang%2Ecom%2Fprot
ocols%2Ehtml
http://www.protocols.com/papers/pdf/voip_pr
actical_guide.pdf
http://www.net2phone.com/
Web References
http://www.dti.gov.uk/bestpractice/asset
s/voip.pdf
http://vonage.com/
http://hotfoon.com/