Transcript Voice over IP

I/ OVERVIEW OF VoIP SYSTEM
1.
2.
3.
4.
5.
Definition
The connection types
VoIP network components
Action procedure
Strengths and weaknesses ( compare with
telephone)
I/ 1. Definition of VoIP
1. Voice over Internet Protocol (Voice over IP, VoIP) is a
family of technologies, methodologies, communication protocols,
and transmission techniques for the delivery of voice
communication and multimedia sessions over Internet Protocel
(IP) networks.
2. Other terms frequently encountered and often used
synonymously with VoIP are
1.
2.
3.
4.
IP telephony
Internet telephony
Voice over broadband (VoBB)
Broadband telephony, and broadband phone.
I/ 2. The connection types
1. Computer to computer
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Use Internet
Free service
Caller and receiver using a common VoIP service (Skype, MSN,
Yahoo Messenger, ...), 2 headphone + microphone, sound card.
2. Computer to phone
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Use Internet
Charges service: pay to have an account and software
3. Phone to phone
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Not use Internet, use a VoIP adapter connect to phone -> IP
phone
Charges service
I/ 3. VoIP network components
1. User Agent
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In a VoIP network, any device that can make or receive
telephone calls is called a User Agent (UA). Each User Agent
contains a User Agent Server(UAS) and a User Agent Client
(UAC
2. Gateways
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A gateway is a device which acts as a bridge between VoIP and
the PSTN network
3. Proxy servers
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In a SIP system, a proxy server (used with a registrar and a
location server), can provide the following services:
• Call Routing including URI translation.
• Registration.
• Access (authentication) to a SIP network.
I/ 4. Action procedure
Voice  digital bit  packets  voice
1. Call Setup:
1. Proxy server make a connection between caller’s
and recipient's address.
2. Voice data processing
1. Speech signal (convert to) digital signal
(compressed and encrypted) voice samples
(insert into) RTP packet (transmitted by UDP
protocol) -> recopient
I/ 5. Strengths and weaknesses
1. Strengths:
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Costs
Applications
Easy to enjoy
Change
2. Weaknesses
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Quality of service
Susceptibility to power failure
Security
Caller ID
Fax handling