Page 1 The Essential Developer’s Toolkit for Designing Enterprise IP Telephony Debbie Greenstreet...
-
Upload
harvey-james -
Category
Documents
-
view
216 -
download
0
Transcript of Page 1 The Essential Developer’s Toolkit for Designing Enterprise IP Telephony Debbie Greenstreet...
Page 1
The Essential Developer’s Toolkit for Designing Enterprise IP Telephony
Debbie GreenstreetDirector, Product Management
Texas Instruments
Internet Telephony ExpoFebruary 2003
Page 2
Agenda
Enterprise IP Telephony IP Telephony Architecture Key Functional Attributes Solution Components
Page 3
Enterprise Network Telephony Evolution
PacketNetwork
IP enabled PBX
IP PBX
LAN
Server
SME Gateway
PBX
Page 4
Enterprise Gateway Block Diagram
ENETPHY
RISC
FLASH SDRAM
T1/E1FRAMER T1/E1 TrunkDSPSRAM
VoIP Functionality
Network/PBX Functionality
NetworkSwitch/Router
WAN ENETPHY
ENETPHY
LAN
PBXCall Services
T1/E1 Trunk
Page 5
Enterprise IP Phone Block Diagram
LAN RJ45 PC RJ45DEVICE HOST
User Interface
Memory Interface
Color Graphics
Keypad
Speaker
Microphone
HandsetRJ11
HeadsetRJ11
Ethernet InterfaceUSB Interface
FLASH
SDRAMLCD I/F
Audio I/F
Keypad I/F
USB I/FOR
Memory Intf IP PhoneChipset
Voice Interface
Network Interface
Processor and Associated Logic
Page 6
Voice
VAD
GSM
PacketInterface
Signaling
EchoCanceller
Fax Relay
TxGain
Caller ID
ToneDetection
Signaling Support
VoiceCodec
VoicePlayout
PacketVoice
Protocol
RxGain
Fax Data Pump
Fax ProtocolRelay InterfaceT.30 Fax
NetworkDriver
PCMInterface
ToneGener-ation
CODEC
SLIC
CONF
VoIP Signal Processing Functional Components
Page 7
VoIP RISC Software Functional Components
Hardware Abstraction Layer
DSP Interface
Application Services Layer
Ethernet Drivers
IP
TCP/UDP
Telephony
Hardware
Abstraction Layer
H.323
Protocol
CAS/CCS Signaling
User
Interface Unit
SIP
Protocol
Call Control
RTOS
Supplementary Services
Page 8
Real-Time Fax Relay
FAX signal detection Demodulation of the fax transmission and extracts the fax
data Remodulation of the fax data for transmission to the
receiving fax machine FAX protocol processing
eg, T.30 protocol
Network Protocol Processing Packetizing/depacketizing T.38 UDP (TCP) Jitter control Error recovery
PacketNetwork
64K bps
14.4 Kbps
64K bps
Page 9
Echo Canceller
Functions Removal of echo from frame of PCM samples Doubletalk detection Acoustic Echo cancellation
Important Attributes Convergence time (initial/updates) - time to train on the
echo Convergence on narrowband signals (e.g., MF/DTMF
tones) Suppress echo on DTMF digits Doubletalk detection Performance with high background noise - can cause
instability and loss of echo cancellation
Page 10
Network
Interface
PacketNetwork
Gateway Product
DigitalT1/E1
T3
OC1/OC3
PhysicalInterfaces
Analogulaw
alaw
linear
pulse dialing
2W/4W
loop start
ground start
gain control
ToneInterfaces
Tone GenerationDTMF
Call Progress Tone
Tone DetectionDTMF
V.21
Call Progress
MF (R1, R2)
Modem Tone
DTMF ToneRelay
SignalingInterfaces
CASFXSFXO
E & MTransparent
CCSQ.931QSIG
Transparent
Voice/FaxProcessing
EchoCancellation
VAD
VoiceCoding
Voice Playout
Fax ModemV.21
V.27terV.29V.17V.33
Interoperability - Telephony & Fax Challenges
phone
PBX
CentralOffice
KeySystems
modem
fax
Page 11
Telephony
Interface
Protocol
Stacks
ATM Networks
Frame Relay Networks
IP Networks
H.323Gateway
PC w/H.323 Node
Frame RelayGateway
ATMGateway
Interoperability - Packet Network
Network ManagementInterface Functions
Gateway Product
H.323NetworkProtocolInterface
FRF.11NetworkProtocolInterface
ATMStandard In WorkProprietary Today
Address Translationand Parsing
Fax Relay/Advanced Local
Processing
Signaling TranslationCAS H.323/FRF.11/ATMCCS H.323/FRF.11/ATM
Page 12
Jitter (Variable Delay) Voice/Fax
Key Features for Robust Playout Buffer:•Adaptable playout buffer including:
•Programmable buffer size•Dynamic buffer sizing•Jitter buffer real-time statistics•Fax - large jitter buffer to reduce the chance of lost packets
PlayoutBuffer
GatewayProduct
GatewayProduct
Packet Network
Variations in Packet Inter-arrival Rate•Changes in network load•Variations in routing paths•Variable queuing delays
Page 13
Packet Loss Voice/Fax
Lost Packets Due to:• Network congestion/performance• Network architecture• Improper jitter buffer size• Software not designed for peak load
65 4
3
2 1
PlayoutBufferPacket Network
Lost Lost
Potential Causes of Packet Reordering:• Network congestion/performance• Network architecture
Voice Software Must Provide:• Lost packet compensation for all codecs• Lost packet statistics• Peak MIPS design philosophy
Fax Software Must Provide:• Control packet redundancy to correct for lost packets• Advanced local processing to negate the effects of network problems• Very high call completion rates (100% at 5%; 97% at 10)
Page 14
VoIP Quality Monitoring
What happens if it doesn’t sound good…. Telephony tools
Support production lab testing
LAN, packet network tools Don’t capture voice QOS problems
Need passive monitoring tools Accurately estimate user perceived quality Measure live VoIP calls, not sample test calls Isolate and diagnose packet network quality problems
Separate from signal processing quality problems.
Page 15
Other Features to Consider
Security Often mentioned, but no common standard yet CableLabs including security for Voice over Cable
IPSEC for signaling
AES for voice packets
Wireless LAN Natural progression from data network popularity Business office applications Consumer opportunities in Asia/Japan
Page 16
Issues in Standards-Based Technologies
New emerging markets and technology Need for interoperability among vendors, providers Standards bodies produce comprehensive specifications
No way to avoid infringement Compliance requires use of third party IP Work-arounds/design-arounds not possible
Infringement is easily identifiable If you are “in” a particular area you are infringing Website searches flag product offerings
Potential liability is uncertain Validity/Invalidity of claimants’ IP Claimants may have IP but no pricing structure
Page 17
Company Profiles Affect Risk and Response
Three categories of companies at risk Technology providers Original equipment manufacturers End users
Location in the “food chain” affects both risk and response
Technology Providers
Service Providers
End
Users
OEMManufacturers
IP Claim #n
IP Claim #1
Example: Sum = $9/port
No Licensing, Indemnification $9/port
Non-Payment can Result in Enjoinment
Page 18
VoIP Product Development Checklist
Time to Market Goal Product schedule Opportunity costs
Internal Resources How many Expertise
Product Differentiation Corporate expertise Market needs
Risk Assessment Technology Intellectual property Scalability Feature growth
Page 19
VoIP Toolkit – Silicon
UniversalSerialBus
ReducedInstruction
SetComputer Processor
DigitalSignal
Processor
AnalogEncoderDecoder
SubscriberLine
InterfaceCircuitry
DSPRAM
EthernetSwitch
SynchronousDynamicRandomAccessMemory
ENET MediaAccessControl
ENETPhysicalInterface
PeripheralComponent
Interconnect
802.11
InternetProtocolSecurity(IPSEC)
ENET MediaAccessControl
ENETPhysicalInterface
Page 20
IP Network
HardwareDSP SoftwareTelephony
Hardware
VoIP Toolkit - Software
Hardware Abstraction Layer
DSP Interface
Application Services Layer
Ethernet Drivers
IP
TCP/UDP
Telephony
Hardware
Abstraction Layer
H.323
Protocol
CAS/CCS Signaling
User
Interface Unit
SIP
Protocol
Call Control
RTOS
Supplementary Services
Applications
Page 21
VoIP Toolkit – Board Level
Options Board level VoIP
functionality with common interface, eg PCI, for insertion in larger system
Basic level of core VoIP software often included
IP phone reference design
Benefits Board level design
(hardware and software) complete
Reduces hardware and software resources requirements
ENETPHY
RISC
FLASH SDRAM
T1/E1
FRAMER
T1/E1 TrunkDSPSRAM
Page 22
Toolkit Questions to Ask
Silicon What hardware interfaces are required What level of functional integration makes sense
Software What RTOS model makes sense Protocol source
VoIP technology provider
Third party expert
Proprietary solution
Call Control, Supp Services, etc How much is needed, uniqueness, expertise
Applications model Feature differentiation
Development/test tools
Page 23
Your VoIP Product - Pulling It All Together
Enterprise IP Telephony Requirements Variety of features, protocols – what is right for your product Market, cost goals Feature differentiation
Evaluate Development Options Internal resources, expertise Off the shelf products
Tools Available Hardware
Chip sets, boards, reference designs Software
RTOS Protocol stacks Call control, supplementary service
Don’t forget test, quality of service, serviceability