IP TELEPHONY Voice over IP VoIP

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IP TELEPHONYVoice over IP (VoIP)
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What is IP Telephony?
Compression to less than 32Kbps
Transfers through Routers, LAN Switches etc,
using their Protocols
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VoIP Placement

• Telephone Replacement
• IPHONE, Ethernet Phone
• Transmission Substitution
• Tie Line, Trunk, Loop
• Switching Alternatives
• PBX, CO, CENTREX

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Convergence

• Adding Voice, Video, Fax to Data Network
• Unified Messaging
• Centralized Communication Services
• Email, Telephony, Multi-media
• Common Protocol (IP)

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Voice To/From IP
Voice
Analog
CODEC Analog to Digital
Compress
Create Voice Datagram
Add Header (RTP, UDP, IP, etc)
Digital
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Voice To/From IP
Digital
Process Header
Re-sequence and Buffer Delay
Decompress
CODEC Digital to Analog
Analog
Voice
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Traditional Network Characteristics
Voice
Data

• Dedicated Point-to-point
• Short/Constant Delay
• No Retransmission
• Low Error Tolerance
• Direct Pass Through

• Mainly connectionless
• Variable Delay
• Packet Loss
• Retransmission
• Uses protocols

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Packet Network Technologies
Same Components Different Performance
An Intranet

• Routing (TCP/IP)
• Frame Relay
• ATM
• MPLS

• Routing (TCP/IP)
• Frame Relay
• ATM
• MPLS

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Voice Over IP Networks
VPN
An Intranet

• Subscribed
• Environment
• No Control except SLA
• No Guarantees

• Controlled
• Environment
• Performance Objectives
• Designed to perform

VPN Virtual Private Networks
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Voice Over IP Requirements

• Compression
• Reduced bps vs. Quality
• Silence Suppression
• Assumptions
• Signaling
• Functions
• Speed

• Echo Control
• Local
• Quality of Service (QoS)
• Toll quality
• Voice Enhancements
• Directory services
• Feature CLID, Call waiting

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IP PBX (LAN PBX)
LAN PHONES
GATEKEEPER VIRTUAL PBX (SERVER BASED
PBX) GATEWAY EXTERNAL ACCESS CONNECTOR MCU
MULTIPOINT CONTROL UNIT (Conf. Call, 3 or more
units)
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Technical Issues

• 64 Kbps or Compressed Voice
• Standard or Proprietary
• Network Size
• Cable Distance (100m)
• Operation Through LAN Switches
• VoLAN or VoIP over LAN/WAN
• Desktop Requirements
• Global VoIP Standards

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Voice Over IP Building Blocks
Voice
IP
Protocol
Network
Regulatory
Protocol
Standards
Performance
Stanndards
Standard
Jitter
Speech
Coding
IP
Delay
Access
UDP
Fees
Call Control
TCP
congestion
Separation
SIP
Network
Payments
RTP
packetiza- tion
Interface
RTCP
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H.323 Protocol Stack
Call Control
Audio
Video
A/V Control
Data
G.7xx
H.26x
H.225
SIP
H.245
T.120
RTCP
RAS
Q.931
RTP
TCP
UDP
IP
SIP Session Initiation Protocol is an
alternative to H.323
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