introduction to voip
DESCRIPTION
Introduction to VoIP. Lecture 1 Paul Flynn. VoIP Part 1 – Sept - Dec. Introduction Transporting Voice over IP Network Speech Coding Techniques Signalling 1 – H323 Signalling 2 – SIP Media Gateway Control VoIP and SS7 ATM QOS and Traffic management Designing a VoIP Network. SF. RTP. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/1.jpg)
Introduction to VoIPIntroduction to VoIP
Lecture 1
Paul Flynn
![Page 2: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/2.jpg)
VoIP Part 1 – Sept - DecVoIP Part 1 – Sept - Dec
1. Introduction2. Transporting Voice over IP Network3. Speech Coding Techniques4. Signalling 1 – H3235. Signalling 2 – SIP6. Media Gateway Control7. VoIP and SS78. ATM9. QOS and Traffic management10.Designing a VoIP Network
![Page 3: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/3.jpg)
3
Network ComponentsNetwork Components
CO - Central OfficeTrunk - Switch-switch connectionLoop - Line from switch to phoneTandem switch - provides switch-switch interconnectionIXC - interexchange carrierPBX - Private branch exchange
PBX Switch
Switch
Switch
Switch
Switch
CO
IXCSJ
SF
RTP
![Page 4: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/4.jpg)
4
SSP
SSP
SSPSTP
STP
SCP
•SSP: Service Switching Point (Telephone Switch)
•STP: Signaling Transfer Point (Router)
•SCP: Service Control Point (Database, Logic)
Trunk
Signaling(Packet)
Trunk
Trunk
SS7Voice
The PSTN: Separate Voice The PSTN: Separate Voice and Signaling Networksand Signaling Networks
(TDM)
![Page 5: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/5.jpg)
Local LoopLocal Loop
• 2 wire from phone to switch
• Tip and Ring - derived from old switchboard plugs
• 4 wire used at switch
• Conversion performed by hybrid
2 wire
2 wire
2 wire 2 wire
Switch
switch
Speaker Listener
Talker Echo
![Page 6: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/6.jpg)
Local Loop (cont.)Local Loop (cont.)Problems with Analog TransmissionProblems with Analog Transmission
• Several problems with analog
• Attenuation - loss of signal power
• Distortion - unequal loss at different frequencies
• Noise - induced into line which is amplified along with signal by network components
• Echo - due to 2/4 wire conversion
• Physical impairments - bad lines, bridge taps, load coils
2 wire
2 wire
2 wire 2 wire
Hybrid
Hybrid
Speaker Listener
Talker Echo
![Page 7: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/7.jpg)
7
Digitizing VoiceDigitizing Voice
• Assumption is that human speech information is contained in the range of 300-3400 Hz
Filter & use signal below 4 kHz to prevent aliasing
Sample and quantize signal at 8kHz
encoder produces 64 kbit/sec stream of data
![Page 8: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/8.jpg)
Voice ENCODER
Low Pass FilterBW = Fmax
Low Pass FilterBW = Fmax
BinaryEncoderBinary
EncoderClockClock
Pulse Detector
Pulse Detector
Binary to Decimal Decoder
Binary to Decimal Decoder
FilterBW = Fmax
FilterBW = Fmax
Voice DeCODER
Sampler2 * Fmax Samples/Sec
Sampler2 * Fmax Samples/Sec
Quantizern Bits/Sample2n Levels
Quantizern Bits/Sample2n Levels
Waveform Coders (codec)Waveform Coders (codec)
![Page 9: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/9.jpg)
Non- Linear Encoding
Closely Follows Human Voice Characteristics
High Amplitude Signals Have More Quantization Distortion
(Both a- & - Law)
Input
Output
Linear Encoding
Relatively Easy to Analyze, Synthesize, and Regenerate
All Amplitudes Have Roughly Equal Quantization Distortion
Input
Output
Non-Linear vs. Linear EncodingNon-Linear vs. Linear EncodingCompanding (a-law vs Companding (a-law vs -law)-law)
![Page 10: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/10.jpg)
10
00010010001101000101011110001001101010111100110111101111
00010010001101000101011110001001101010111100110111101111
Linear Predictive CodingLinear Predictive CodingSource CodingSource Coding
00010010001101000101011110001001101010111100110111101111
00010010001101000101011110001001101010111100110111101111
Actual Code Predicted Code
1001 1011
10
20 ms
![Page 11: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/11.jpg)
Bandwidth RequirementsBandwidth Requirements
Voice Band Traffic
Encoding/Encoding/CompressionCompression
ResultResultBit RateBit Rate
G.711 PCMG.711 PCMA-Law/A-Law/uu-Law-Law
64 kbps (DS0)64 kbps (DS0)
G.726 ADPCMG.726 ADPCM 16, 24, 32, 40 kbps16, 24, 32, 40 kbps
G.729 CS-ACELPG.729 CS-ACELP 8 kbps8 kbps
G.728 LD-CELPG.728 LD-CELP 16 kbps16 kbps
G.723.1 CELPG.723.1 CELP 6.3/5.3 kbps6.3/5.3 kbpsVariableVariable
![Page 12: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/12.jpg)
Voice QualityVoice Quality
Compression MethodCompression Method MOS ScoreMOS Score DelayDelay(msec)(msec)
64K PCM (G.711)64K PCM (G.711) 4.44.4 0.750.75
32K ADPCM (G.726)32K ADPCM (G.726) 4.24.2 11
16K LD-CELP (G.728)16K LD-CELP (G.728)
8K CS-ACELP (G.729)8K CS-ACELP (G.729) 4.24.2 1515
8K CS-ACELP (G.729a)8K CS-ACELP (G.729a) 1515
3–53–54.24.2
3.63.6
Anything Above an MOS of 4.0 Is “Toll” Quality
![Page 13: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/13.jpg)
Voice Activity DetectionVoice Activity Detection
Voice “Spurt” Silence
Pink Noise
Time
Voice Activity(PowerLevel) SID Buffer SID
Hang Timer No Voice Traffic Sent
B/W Saved
- 54 dbm
- 31 dbm
Voice “Spurt”
![Page 14: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/14.jpg)
Rensselaer Polytechnic Institute
14
Applications of Speech Coding
Telephony, PBX Wireless/Cellular Telephony Internet Telephony Speech Storage (Automated call-centers) High-Fidelity recordings/voice Speech Analysis/Synthesis Text-to-speech (machine generated speech)
![Page 15: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/15.jpg)
Different Types of SignalingDifferent Types of Signaling(when you place a call)(when you place a call)
• Supervisory - Determines state of line/trunk whether on/off-hook
EM signal leads, loop open/closed
• Addressing - passes digit information for call routingDTMF, MF, DNIS
• Informational - indicates call progressBusy signal, dial tone, ring back
![Page 16: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/16.jpg)
16
Summary PageSummary Page
PBX Switch
Switch
Switch
Switch
Switch
CO
IXCSJ
SF
RTP
T1/ E1DTMF/ MFCAS/ CCS
Local LoopFXS/ FXOLoopstart/Gndstart
![Page 17: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/17.jpg)
17
Voice Transport ProtocolsVoice Transport Protocols
![Page 18: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/18.jpg)
18
Voice Transport ProtocolVoice Transport ProtocolOverviewOverview
PSTN
PBX
ATM, FR, HDLC
IP
CiscoGateway
CiscoGateway
T1/E1CAS/CCS
Encoder/Decoder
![Page 19: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/19.jpg)
QueuingQueuing
• Voice always given priority over data
• Real-time queue for voice and videoData queue serviced only if nothing in Real Time queue - (Exhaustive like priority queuing)
• Non-real time queue (Data)WFQ by default
WFQ Disabled if Frame Relay Traffic Shaping Enabled
Fancy queuing disabled if voice-encap set on interface
![Page 20: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/20.jpg)
20
Voice Over IPVoice Over IP
![Page 21: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/21.jpg)
21
Protocols Used
• H.225.0 for Connection and Status
– Q.931 ‘derived’ messages
– ‘RAS’ for Endpoint-GK signaling.
• H.245 for negotiating channel usage and capabilities
• Media transport– RTP/RTCP -- standard payloads
(RFC1889/1890)
– ‘native’ uni/multicast support
![Page 22: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/22.jpg)
Rensselaer Polytechnic Institute
22
VoIP Camps
ISDN LAN conferencin
g
IP
H.323
I-multimediaWWW
IP
SIP
Call AgentSIP & H.323
IP
“Softswitch” BISDN, AIN
H.xxx, SIP
“any packet”
BICC
Conferencing Industry
Netheads“IP over
Everything”
Circuit switch
engineers “We over
IP”
“Convergence” ITU
standards
Our focus
![Page 23: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/23.jpg)
Rensselaer Polytechnic Institute
23
Are true Internet hosts
• Choice of application
• Choice of server
• IP appliances
Implementations
• 3Com (3)
• Columbia University
• MIC WorldCom (1)
• Mediatrix (1)
• Nortel (4)
• Siemens (5)
4
IP SIP Phones and Adaptors
1
3
Analog phone adaptor
Palmcontrol
2
54
![Page 24: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/24.jpg)
Rensselaer Polytechnic Institute
24
PSTN to IP Call
PBXPSTN
External T1/CAS
Regular phone(internal)
Call 93971341
SIP server
sipd
Ethernet
3
SQLdatabase
4 7134 => bob
sipc
5
Bob’s phone
GatewayInternal T1/CAS(Ext:7130-7139)
Call 71342
![Page 25: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/25.jpg)
Rensselaer Polytechnic Institute
25
IP to PSTN Call
Gateway(10.0.2.3)
3
SQLdatabase
2Use sip:[email protected]
Ethernet
SIP server
sipdsipc
1Bob calls 5551212
PSTN
External T1/CAS
Call 55512125
5551212
PBX
Internal T1/CASCall 85551212 4
Regular phone(internal, 7054)
![Page 26: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/26.jpg)
26
End-to-End Delay
Sender Receiver
NetworkTransit Delay
t
AA AA
Network
Last BitReceived
First BitTransmitted
ProcessingDelay
ProcessingDelay
End-to-End Delay
![Page 27: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/27.jpg)
Fixed Delay ComponentsFixed Delay Components
• Propagation—six microseconds per kilometer
• Serialization
• Processing
Coding/compression/decompression/decoding
Packetization
Processing Delay
Propagation Delay
Serialization Delay—Buffer to Serial Link
![Page 28: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/28.jpg)
Variable Delay Components Variable Delay Components
• Queuing delay
• Dejitter buffers
• Variable packet sizes
DejitterBuffer
Queuing Delay
Queuing Delay
Queuing Delay
![Page 29: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/29.jpg)
29
Delay Variation—“Jitter”Delay Variation—“Jitter”
t
t
Sender Transmits
Sink Receives
AA BB CC
AA BB CC
D1 D2 = D1
Sender Receiver
D3 = D2D3 = D2
Network
85
![Page 30: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/30.jpg)
30
Network QoS ToolkitNetwork QoS Toolkit
![Page 31: Introduction to VoIP](https://reader030.vdocuments.us/reader030/viewer/2022012922/568137d7550346895d9f7830/html5/thumbnails/31.jpg)
31
Logical ConnectionsLogical Connections
Call Leg 3
Call Leg 1
IP Cloud
Call Leg 2
Call Leg 4