Transcript Voice Over Internet Protocol

Voice Over Internet
Protocol
By Eric Rice
History
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First telephone was
patented in 1870
Rotary dialing first
done in 1891
1905-Party Line
1910-5.1 million
customers
1941-Attacks on Pearl
Harbor cause a 100400 percent spike in
long distance nation
wide
History cont.
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1949-the average calls placed in a day
reach 180 million.
1975-there are 140 million telephone lines
in the US and AT&T controls 85% of them
1993-AT&T offers Caller ID
1995-Vocal Tec release first VOIP software
1996-First cable modem service offered by
Roger Communications
2001-Vonage founded
March 2002-Vonage initiates service
The Issues
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Reliability
911 service
availability
Voice Quality
• Delay
• Jitter
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Features
Signaling Protocol
Reliability
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The current standard
• Five-nines (5 min of downtime a year)
“Networks go down all the time”
 High Internet Traffic
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911 Availability
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Currently address information is linked to
a number
Due to VoIP portability, locations are not
defined
In order to receive 911 service it must
first be set up
Mobile phones have this same problem
Alternate solutions include developing new
port mapping technologies
Using GPS to locate callers
Voice Quality
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Goals
• Make it comparable to wire line
• Minimize bandwidth
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Wire line Voice codec is G.711
• 64kbps
• MOS 4.3 (mean opinion score)
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VoIP Voice codec G.729
• 8kbps
• MOS 4.0
What?
Other Codecs
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These codecs use
a number of
different
compression
algorithms to
minimize required
bandwidth
Delay
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Delay is measured
using Round Trip
Time
Keep delay less
then 300ms
• If greater then
300ms may seem
like making an
international call:
take this situation
Person A
Person B
A Speaks
B interrupts and
starts talking
A hears B’s
interruption and
stops talking
B stops talking
because they
think A ignored
the interruption
B hears A and
stops talking
Uncomfortable
silence
Uncomfortable
silence
A starts talking
B starts talking
A hears B and
stops
B hears A and
stops
Jitter
Occurs when delay changes
 If the delay increases and decreases
sporadically it makes conversations
sound choppy
 RTP (Real Time Transport Protocol)
 Adds a sequence number and a time
stamp to UDP packets
 This allows for delay and jitter to be
calculated accurately
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Solutions to Jitter and Delay
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Add bandwidth to the entire Internet
• We find ways to use up all the bandwidth we
are given
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Reserve bandwidth on the routers it uses
• This would not be fair to the rest of the
packets
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Temporary solution is to simply route the
calls through the current switch network.
SIP (Session Initiation Protocol)
Very simple protocol to use
 Allows for advanced features to be
applied by the user without a
subscription
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Features
Cheaper Service
 No long distance charges
 Caller ID
 Call Forwarding
 Call Screening
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• Users can do other things than just
block a call
• If Kitrek were to call, I would be able to
forward his call to an insult hotline
Features
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Voicemail
• Check it online with fast-forward, rewind, and
pause
• Check it through email
• Check it over the phone
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Require unknown callers to provide an
intent for calling
• If a telemarketer calls they would have to tell
what they wanted
• It would then be displayed on the caller ID
Conclusion
VoIP is a technology which will
eventually replace the current Switch
network.
 With new and fully customizable
features, along with cheaper service
and no long distance charges. We
can expect to see VoIP much more in
the future.
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Resources
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[1] Danial Collins. (2001). Carrier Grade Voice Over IP.
New York. McGraw-Hill.
[2] John Shepler. (2005). The Holy Grail of five-nines
reliability.
Retrieved April 1, 2005 from
http://searchnetworking.techtarget.com/generic/0,295582,
sid7_gci1064318,00.html
[3] Tim Lorello, Rich Tehrani (2005). E-9-1-1. Internet
Telephony, 8, (3), 40-41.
[4] FCC. (2004) VoIP: FCC Consumer Facts. Retrieved April
1, 2005 from
http://www.fcc.gov/cgb/consumerfacts/voip.pdf
[5] Vonage. (2005) Features. Retrieved April 1, 2005 from
http://www.vonage.com/features.php