Download Overview of VoIP - ITU

Introduction to Voice Over IP Technology
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© Internation Institute of Telecommunications inc., 2000-2004
Why integrate voice over IP?
To reduce the costs?

To maximize bandwidth usage
To use a single network?

Telephony on Intranet and Internet
To create new commercial applications?

To integrate voice mail, email and fax

Call Centers
–
CTI (Computer Telephony Integration)
–
Telephony on Internet
Integration of voice-data-images?
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VoIP traffic on the network
Traffic: voice, video…



Isochronous traffic
– Fixed intervals
Throughput
– Constant (voice)
– Variable (video)
Short delays
The IP network:

Asynchronous mode of transfer
–
Process by which the data can be
transmitted at unspecified intervals.
–
Generate variable and unforeseeable
delays
–
T T T T T
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Designed for non isochronous traffic
The traffic adaptation to the network
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3 performance factors
Name three factors which will influence the ambulance delay :


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3 performance factors
Transpose these 3 factors in a network environment and relate them
to packet latencies at a LAN exit point



LAN
LAN
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Router
Router
Constraints / Solutions
Sampling
Delays
Delay variation/jitter
Echo
Compatibility/interworking

Inter local area networks (QoS)

With the PSTN
– Signaling and supervision
– Added value services
Information security
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
Define packets

Signal compression
RTP/UDP
QoS

Priority
– RSVP
– ToS/Diffserv Field
– IPv6

Dimensioning/capacity
Equipment

Gateway, gatekeeper
What are the challenges?







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The signal must be transported via various network types
– A great number of technologies and standards are used
– Interworking and interconnections between various
technologies and equipment
The applications, the services, the technologies and the
standards evolve quickly
– Proprietary solutions versus standards
Maintain the quality of the voice signal
– Toll Quality or equivalent
To preserve the current telephone services
– Call transfer, call on hold, caller ID, etc.
Interworking between the traditional voice network and the IP
network
– Seamless services
– Addressing, classification
– Quality of service, MTBF, MTTR
– Security and confidentiality
Billing
Operations and management
Who are the stakeholders?
Users
(residential, commercial)
Internet service providers
Carriers
Equipment vendors
Technology
(platform, chip, software)
Industry standards
(ANSI, ITU, IEEE, IETF)
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Market trends (U.S.)
Million lines
14000
12000
10000
Overall market
8000
6000
4000
Traditional market
2000
2001 2002
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IP Telephony
2003
2004
2005
Source:
Phillips InfoTech 2002
2006
In the year 2000, some figures…
VoIP will account for 75 % of the world voice services in 2007. *

The number of IP Centrex lines should grow from 13,000 in 2001 to 10
million in 2008. The number of standard Centrex lines in 2001 was
estimated at 16,5 million. *

The market for IP PBX should reach 3,9 billion dollars in 2005, which
represents 20 % of the traditional PBX market. **

The companies will migrate their voice service from traditional networks
towards IP networks at a rate which will generate a world market for IP
PBX of 16,5 billion dollars from here to 2006. ***

90 % of the companies operating in multiple sites will migrate towards
IP systems for the transport of the voice in the next 5 years. ****

25 % of Internet users will adopt IP Telephony PC-TO-TELEPHONE
in 2006. ****
*
**
***
****
*****
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Frost & Sullivan
Synergy research
Allied Business Intelligence
Phillips Group
Ovum
In the year 2000, some figures… (cont’d)

*
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Unified messaging applications will bloom in 2004 and 2005. The
expenditure related to these applications should reach 3.5 billion
dollars in 2005 with an annual growth rate of 32.1 % *
TIA (Telecommunication Industry Association)
Questions?
?
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The protocol suite
Analog to digital sampling
Ethernet Checksum (FCS) 4 bytes
Voice sample N O 1
compression
Voice sample N O 2
n bytes
Voice sample N O 3
packetization
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RTP Header
12 bytes
UDP Header
8 bytes
IP Header
20 bytes
Ethernet/LLC header
18 bytes
Packets construction
Packetization

Continuous signal conversion into individual packets
Packetization
Size of a packet payload
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
Which will be the payload size (in bytes) of a 20ms voice signal
packet when using a 64 Kb/s PCM?
–

The packet size has a significant effect on the quality of service
– Delay
– Echo
– Delay variation
Packet size versus tolerable delay
Did you see the
storm yesterday?
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He cuts me
all the time

200 - 250 ms is tolerable

Overlaps if higher > 250ms
How is your
sister?
Delay Sources

Serialization time

Propagation time

Processing time
“Processing delay”

Time to sit in memory
“Queuing delay”
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Serialization time



Time necessary for the transmission of the first to the last bit of a
given packet.
Called transmission delay
Delay = L/C
C [ bps ]
10 10 01 10 11 00 01 0
L [ bits ]
Time (ms)
Packet
Length
Circuit speed (kbps)
(Bytes)
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56
128
256
1 536
60
8,6
3,8
1,9
0,3
500
71,4
31,3
15,6
2,6
1 500
214
93,8
46,9
7,8
4 000
571
250
125
20,8
Propagation time
T1
T
2
Delay = T 1 + T 2 [ms]
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Processing time

Synchronization

Sampling, compression

Packetization/depacketization

Decision of route choice (routing)

Multiplexing

…
Processor
Header
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Payload
Header
Payload
Queuing / Time to sit in memory
Header
Payload
Header
Header
Payload
Payload
Header
Memory
Queuing delay
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Payload
End-to-end Delays
Gateway
Gateway
IP
network
PBX
Propagation Delay
Queuing, Processing
and Serialization Delays
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PBX
Queuing, Processing
and Serialization Delays
What is echo?
Do I hear
echo ?
Hello!
Hybrid junction
Hybrid junction
PSTN
Hello!

One way delay;
if higher than 20 - 30 ms,
a person distinguishes the echo.
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How can we cancel echo?
What causes echo?
Residential sector
Telephone exchange
Reception
Local loop
Hybrid
Junction
Telephone
Transmission
2 wire to 4 wire conversion
Bad impedance matching
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Echo is always present

Echo varies according to the delay and the power of the return
signal.
Return
signal ,
reduction
of power
Echo is undetectable
(dB)
Echo poses a problem
Delay (ms)
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How to eliminate/minimize echo?
 Decrease the return signal
–
–
Advantage:
• An easy solution
Disadvantages:
• Human intervention
• Reduction of the signal power for the person who speaks
 Installation of echo cancellers
–
–
Advantage:
• Eliminate the return signal (echo)
Disadvantage:
• Costs
 Reduction of the delays
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Voice compression
 Objectives:
– To reduce bandwidth usage.
– To reduce packet size
 Compression algorithms are used for video and voice.
 Disadvantages:
– Reduction in voice quality
– Introduction of delay (echo)
Bandwidth
(kbit/s)
Not
acceptable
Toll
Quality
Quality
commercial
64
PCM (G.711)
Cellular
32
ADPCM 32 (G.726)
24
ADPCM 24 (G.726)
16
ADPCM 16 (G.726)
8
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LD-CELP 16 (G.728)
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0
CS-ACELP 8 (G.729)
MPC-MLQ 5,3 (G.723.1)
Quality
Mean Opinion Score (MOS)
 Evaluation of the sound quality with various compression methods on a
scale of 1 (bad) to 5 (excellent)
 A result of 4,0 is considered “Toll Quality”
 Test conditions:
–
–
–
With background noise, several people discussing at the same time;
Individuals speaking various languages, men and women;
Etc.
4.1
4
3.9
3.8
3.7
MOS
3.6
3.5
3.4
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G.723.1
MPC-MLQ
5,3 kbit/s
G.729a
CS-ACELP
8 kbit/s
G.728
LD-CELP
16 kbit/s
G.729
CS-ACELP
8 kbit/s
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G.726
ADPCM
32 kbit/s
G.711
PCM
64 kbit/s
3.3
Silence suppression

Automatically deactivated for fax/modem

Background noise generated at the destination
-31 dbm
Voice signal
power
Meter
Bandwidth
Economy
-54 dbm
Time
Voice Signal
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Silence
Voice Signal
Large DATA packets affect voice
Gateway
Gateway
WAN
56 kbit/s
Voice
1 500 bytes data
Voice
Data Packet
Serialization time:
PBX
Voice
Voice
1 500 bytes data
PBX
214 ms
Voice
1 500 bytes data
Voice
Voice packets
60 bytes every 20 ms
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Voice packets
60 bytes every 214 ms
Solution - Fragmentation
Gateway
Gateway
WAN
56 kbit/s
500
Voice
500 Voice
Data packet
Serialization time
PBX
Voice
Voice
1 500 bytes data
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60 bytes every 20 ms
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71,4 ms
PBX
Voice
1 500 bytes data
Voice
Voice packets
31
500
Voice packets
60 bytes every 71,4 ms
Packet construction
The packetization
The sample
The sample
12 bytes
RTP
8 bytes
UDP
20 bytes
IP
LLC/802.3
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22 bytes
Appendix - Acronym list
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Acronym list
3GPP
Third Generation Partnership Project
CIR
Committed Information Rate
ABR
Available Bit Rate
CM
Cable Modem
ACF
Admission Confirm
CMIP
Common Management Information Protocol
ACM
Address Complete Message
CMTS
Cable Modem Termination System
ADPCM
Adaptive Differential Pulses Code Modulation
CO
Central Office
ADSM
Asymmetric Digital Subscriber Line
CoPS
Common open Policy Server
AF
Assured Forwarding
CoS
Class of Service
ALI
Automatic Location Identifier
CPL
Common Programming Language
ANI
Automatic Number Identifier
CPU
Central Processing Unit
ANM
Answer Message
CRTP
Compressed Real-Time Protocol
ANSI
American National Standard Institute
CS-ACELP
Conjugate Structure Adaptive Code Excited Linear Prediction
ARP
Address Resolution Protocol
CSRC
Contributing Source
ARQ
Admission Request
CTD
Click-To-Dial
ASCII
American Standard Code for Information Interchange
CTI
Computer Telephony Integration
ASN
Abstract Symbol Notation
dB
Decibel
ATM
Asynchronous Transfer Mode
dBm
Decibel relative to 1 milliwatt
BGP
Border Gateway Protocol
DHCP
Dynamic Host Configuration Protocol
bps
Bits Per Second
DiffServ
Differentiated Services
CA
Call Agent
DNS
Domain Name Server
CAC
Connection Admission Control
DOCSIS
Data Over Cable Interface Specifications
CAN
Campus Area Network
DS
Differentiated Services
CAR
Committed Access Rate
DSCP
Differentiated Services Code Point
CBWFQ
Class-Based Weighted Fair Queuing
EF
Expedited Forwarding
CGI
Common Gateway Interface
EGP
Exterior Gateway Protocol
CIC
Circuit Identification Code
EIGRP
Enhanced Interior Gateway Routing Protocol
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Acronym list (cont'd)
ERP
Enterprise Resource Planning
ISDN
Integrated Services Digital Network
ETSI
European Telecomm Standards Institute
ISUP
Integrated Services Digital Network User Part
FCS
Frame Check Sequence
ITSP
Internet Telephony Service Provider
FEC
Forward Equivalence Class
ITU
International Telecommunication Union
FRF
Frame Relay Forum
ITU-T
ITU - Telecom
FRTS
Frame Relay Traffic Shaping
JPEG
Joint Photographic Expert Group
FTP
File Transfer Protocol
kbps
Kilobits Per Second
GK
Gatekeeper
LAN
Local Area Network
GTS
Generic Traffic Shaping
LDP
Label Distribution Protocol
HFC
Hybrid Fiber Coax
LD-CELP
Low-Delay Code Excited Linear Prediction
HTTP
Hypertext Transfer Protocol
LER
Label Edge Router
Hz
Hertz
LIB
Label Information Base
IAM
Initial Address Message
LLC
Logical Link Control
ICMP
Internet Control Message Protocol
LLQ
Low Latency Queuing
IDC
International Dated Corporation
LS
Location Server
IEEE
Institute of Electrical and Electronic Engineers
LSR
Label Switch Router
IETF
Internet Engineering Task Force
MAC
Media Access Control
IGP
Interior Gateway Protocol
MAN
Metropolitan Area Network
IHL
Internet Header Length
MAP
Mobile Application Part
INAP
Intelligent Network Application Profile
MCR
Minimum Cell Rate
IntServ
Integrated Services
MCU
Multipoint Control Unit
IP
Internet Protocol
MDCP
Media Device Control Protocol
IPv4
IP version 4
Megaco
Media Gateway Control
IPv6
IP version 6
MG
Media Gateway
IPDC
IP Device Control
MGC
Media Gateway Controller
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Acronym list (cont'd)
MGCP
Media Gateway Control protocol
PCM
Pulse Code Modulation
MIB
Management Information Base
PHB
Per-Hop Behavior
MIME
Multipurpose Internet Mail Extension
POP3
Post Office Protocol version 3
MIPS
Million Instruction Per Second
POTS
Plain Old Telephone Service
MMUSIC
Multiparty Multimedia Session Control
PPP
Point-to-Point Protocol
MOS
Mean Opinion Score
PQ
Priority Queuing
MPLS
Multi Protocol Label Switching
PS
Proxy Server
MP-MLQ
Multipulse Multilevel Quantization
PSTN
Public Switched Telephone Network
ms
Millisecond
QoS
Quality of Service
MTBF
Mean Time Between Failure
RARP
Reverse ARP
MTP
Message Transfer Part
RAS
Registration Admission Status
MTTR
Mean Time To Repair
RFC
Request For Comment
NAT
Network Address Translation
RMON
Remote Monitoring
NCS
Network-based Control Signaling
RPC
Remote Procedure Call
NFS
Network File System
RS
Registration Server
NNTP
Network News Transfer Protocol
RSVP
Resource Reservation Protocol
OLC
Open Logical Channel
RTCP
Real-time Control Protocol
OMAP
Operational, Management and Admin Process
RTP
Real-time Protocol
OPX
Off Premise Extension
SCCP
Signalling Connection Control Part
OSPF
Open Shortest Path First
SCP
Signal Control Point
OSI
Open System Interconnection
SCTP
Stream Control Transmission Protocol
PAN
Personal Area Network
SDH
Synchronous Digital Hierarchy
PBH
Per-Hop Behavior
SDP
Session Description Protocol
PBX
Private Branch Exchange
SGCP
Simple Gateway Control Protocol
PCR
Peak Cell Rate
SIGTRAN
Signalling Transport
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Acronym list (cont'd)
SIP
Session Initiation Protocol
VPN
Virtual Private Network
SLA
Service Level Agreement
WAN
Wide Area Network
SLIP
Serial Line Internet Protocol
WFQ
Weighted Fair Queuing
SMTP
Simple Mail Transfer Protocol
WRED
Weighted Random Early Drop
SNMP
Simple Network Management Protocol
SONET
Synchronous Optical Network
For additional acronyms,
SS7
Signaling System 7
http://www.csrstds.com
SSP
Switching Service Point
SSRC
Synchronisation Source
STHML
Safe Hypertext Transfer Protocol
STP
Signal Transfer Point
SVC
Switched Virtual Circuit
TCAP
Transaction Capabilities Application Part
TCP
Transport Control Protocol
TDM
Time Division Multiplexing
TFTP
Trivial File Transfer Protocol
TIA
Telecommunication Industry Association
ToS
Type of Service
TTL
Time To Live
UA
User Agent
UDP
User Datagram Protocol
URL
Uniform Resource Locator
VAD
Voice Activation Detection
VBR-rt
Variable Bit Rate - Real-time
VoIP
Voice over IP
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