© 1998-1999 Marvin A. SirbuPage 1 Carnegie Mellon Voice Data Integration To date voice data...
Transcript of © 1998-1999 Marvin A. SirbuPage 1 Carnegie Mellon Voice Data Integration To date voice data...
© 1998-1999 Marvin A. Sirbu Page 1
Carnegie Mellon
Voice Data Integration
• To date voice data integration in the enterprise has been minimal
– separate logical circuits on the mux network for voice and data.
• New technologies emerging to carry voice over
– ATM networks
– Frame relay networks
– Internet Protocol networks
© 1998-1999 Marvin A. Sirbu Page 2
Carnegie Mellon
Basic Elements of Basic Elements of Voice over Networks Voice over Networks
• Gateway translates between 64 kbps PCM encoded telephony circuit and compressed, packetized voice.
• PC converts between packets and sound card with headset or microphone and speakers.
PSTN
Users
Internet PSTNGW GW
PBX
PhoneUser
Audio Equipped PC
Two Stage Dialing Public Interexchange Network
PBX
Local Switch
Packet / Circuit Gateway
PBX
Local Switch
LocalDS0
TransportNetwork
LocalDS0
TransportNetwork
Packet / Circuit Gateway
H.323 Gatekeeper
WideAreaData
Network
LEC #1
LEC #2
NextGenerationIXC
“1-888-NEXTGEN, ID6, PIN4, 1-234-555-1234”
T1
T1
Packets
Packets
© 1998-1999 Marvin A. Sirbu Page 4
Carnegie Mellon
Voice Coding Standards
Compression Type Data Rate
G.711 – PCM 64 kbps
G.726 – ADPCM 32, 24, 16 kbps
G.728 – LD CELP 16 kbps
G.729 – CS ACELP 8 kbps
G.723.1 - MP-MLQ/ACELP 5.3, 6.3 kbps
© 1998-1999 Marvin A. Sirbu Page 5
Carnegie Mellon
• Processing affects perceived quality (MOS Score)• Compression and packetization introduce delay
– for processing
– to accumulate speech for a packet.
Voice Quality and Delay
Compression MOS Score Delay (msec)
PCM (G.711) 4.4 0.75
32K ADPCM (G.726) 4.2 1
16K LD-CELP (G.728 4.2 3-5
8K CS-ACELP (G.729) 4.2 10
6K MP-MLQ/ACELP(G.723.1)
30
© 1998-1999 Marvin A. Sirbu Page 6
Carnegie Mellon
Voice Quality and Delay
One way delay (msec) Perceived Quality
0-150 Acceptable for most users
150-250 Acceptable but perceptible
250 - 400 Typical of satellites; annoying
400+ Unacceptable for general network purposes.
© 1998-1999 Marvin A. Sirbu Page 7
Carnegie Mellon
Sources of Delay
• Packetization at the source• Queuing delay at packet switches• Propagation delay
– 1 msec/100 miles• Dejitter buffer
– buffer packets at receiver to accommodate variable network delay (“jitter”)
NetworkGateway Gateway
(25 msec) (40 - 200 msec) (50-200 msec)
© 1998-1999 Marvin A. Sirbu Page 8
Carnegie Mellon
Latency - T1 WAN Links
PBX
1 ms
Coder6.5 kbps
Compress
20 ms
SwitchRouting
1 ms
2048 byte MTUQueue Delay
11 ms
WAN Cloud
T1 WANUplink
HQ LAN
WAN Cloud
Branch Office
PBX
1 ms
Coder6.5 kbps
Decompress
20 ms
SwitchRouting
1 ms
2048 byte MTUQueue Delay
11 ms
T1 WANUplink
Branch Office
Worst case 292 ms round-trip latency
JitterBuffer
40 ms
40 msLA-NY
© 1998-1999 Marvin A. Sirbu Page 9
Carnegie Mellon
Reducing Network Delay
• Controlling network delay and variability of network delay important.
• Solutions:
– Use ATM with guranteed quality of service. Low jitter because voice packets can’t get stuck behind large data packets
– Frame relay network with CIR. Some FR networks fragment all packets to reduce jitter.
– IP network route voice packets with higher priority (Differential service) reserve resources as with ATM (RSVP) run over lightly loaded or controlled load network, not public
Internet
© 1998-1999 Marvin A. Sirbu Page 10
Carnegie Mellon
H.323
• A standard for multimedia communications over networks which do not provide a guaranteed Quality of Service
– (e.g. the Internet, or LAN)• Support for audio and video• Key elements
– H.323 terminals: capture/present audio or video
– H.323 Gatekeeper: provides call setup and control functions
– H.323 Gateway: converts between IP and PSTN style networks
– H.323 Multipoint Control Unit (MCU): Bridging functions
© 1998-1999 Marvin A. Sirbu Page 11
Carnegie Mellon
H.323 Network ComponentsH.323 Network Components
H.323 Multimedia PC
PSTN
POTS Phone
Router
Gateway
H.323 Multimedia PC
GatekeeperFirewall
Multipoint ControlUnit
Internet/ Intranet
H.323 Multimedia
PC
H.323 Phone
H.323 Phone
© 1998-1999 Marvin A. Sirbu Page 13
Carnegie Mellon
H.323 Protocol ArchitectureH.323 Protocol Architecture
Physical Layer
Link Layer
Network Layer (IP)
Unreliable Transport (UDP)Reliable Transport (TCP)
T.123(ISO+TCP)
T.124GCC
T.125MCS
Real-Time Protocol(RTP)
RTCP
G.7XXAudio
H.26XVideo RAS
Term. <->GW
H.225.0Call
Signal
H.245Call
Signal
AV Appl. Q.931 Terminal Control and Mgmt
Data Appl. orT.126/T.127
© 1998-1999 Marvin A. Sirbu Page 15
Carnegie Mellon
Early Internet TelephonyEarly Internet Telephony
• Long Distance Bypass, Fueled by International Tariffs, Domestic Access Charges- Arbitrage opportunity
• Often proprietary Internet protocols• Audio only
PSTN
Users
Internet PSTNGW GW
PBX
PhoneUser
Audio Equipped PC
© 1998-1999 Marvin A. Sirbu Page 16
Carnegie Mellon
Enterprise VoN Bypass
• Company has existing Data network between locations.• Put voice traffic on existing data network and save phone
charges• Network can be any of
– IP
– Frame Relay
– ATM• Private ATM, FR nets mostly have PVCs• Treat PVC between two PBXs same as a leased line.
© 1998-1999 Marvin A. Sirbu Page 17
Carnegie Mellon
PBX to Gateway VoIP Signalling
PBX
CorporateNetwork PBX
Trunk Signaling
Step 1-- the PBX seizes a trunk line to the gateway, and forwards dial digits
527-3845
© 1998-1999 Marvin A. Sirbu Page 18
Carnegie Mellon
PBX to Gateway VoIP Signalling
PBX
CorporateNetwork PBX
Q.931
H.323 agent H.323 agent
Step 2 -- The Gateway uses a dial plan to map dial digits into the IP addressof the remote gateway. H.323 agent software initiates a call using Q.931signaling protocol to remote gateway
© 1998-1999 Marvin A. Sirbu Page 19
Carnegie Mellon
PBX to Gateway VoIP Signalling
PBX
CorporateNetwork PBX
Trunk Signaling
Step 3 -- The remote H.323 agent seizes a PBX trunk, returns a Q.931acknowledgement to the origin, and forwards dial digits to the PBX
Step 4 -- Voice traffic flows between PBXs over the H.323 session established between the two gateways.
© 1998-1999 Marvin A. Sirbu Page 20
Carnegie Mellon
Future Directions
• Phase 1: wide area bypass
– corporate intranet
– interexchange carriers access charges key
• Phase 2: IP PBX
– easier integration of voice and data
– integration with data for ACD applications• Phase 3: IP based Local Exchange Carriers
Yesterday’s PBX
Proprietary Ckt switch
Card(s)Proprietary
interface
Applications (Voicemail/IVR)
Voice Path (TDM)
Signaling Path
PSTN
Proprietaryterminals
Proprietary interface
Proprietary Line
Card(s)
Proprietary Trunk Card(s)
Mainframe cabinet
Standard interface
Proprietary Processor
Card(s)Proprietary
interface
IntelProcessor Standard
OR Proprietary Interface
Windows NT Server PC
Call Control Application
Tomorrow’s PBX - the IP PBX
Voice Path (TDM)
Signaling Path
PSTN
Standard interface
TCP/IPNetwork
StandardOR Proprietary
interface
Ethernet phonesand
PC applications
IP to PSTNGateway
Standardinterface
Applications Server
(Voicemail/IVR)
© 1998-1999 Marvin A. Sirbu Page 23
Carnegie Mellon
Call ManagerIP Phone
PSTN
IP/PSTN GatewaysIP/PSTN Gateways• PSTN trunk interface• Analog fax/phone/modemUser InstrumentUser Instrument
• Ethernet IP telephone• Wireless H.323 handset• PC with H.323 softphone
Call ProcessingCall Processing• NT server• PBX functionality
PSTN/IP Gateway
3 Core Components of an IP PBX
Source: Selsius, Corp
© 1998-1999 Marvin A. Sirbu Page 24
Carnegie Mellon
PBX servicesPBX services
EtherPhoneServer
EtherPhoneEtherPhone
EtherPhoneBranch
© 1998-1999 Marvin A. Sirbu Page 25
Carnegie Mellon
PhoNetwork TopologyPhoNetwork Topology
EtherPhone
EtherPhoneBranch
PhoNetwork Server
Gateway
PacketPhone
Area code“8”
© 1998-1999 Marvin A. Sirbu Page 26
Carnegie Mellon
IP Phones Product Characteristics
• Ethernet connectivity• IP Address and signaling(TCP/IP)• Audio via RTP/IP (Conforms to H.323 RTP format)• Built-in Compression: G.711, G.723
Managed on a call-by-call basis• Configuration
DHCP or static Config via browser I/F
• Built-in encryption for privacy protection• 3rd-pair powered for wired devices
Call-Manager / gatekeeper Product Characteristics
• Provides intelligent call processing and PBX functionality• H.323 standard-based• Standard PC hardware with only a Ethernet NIC• Signalling support for gateways (Q.931, H.245, H.225, RAS)• Call processing engine
Features: hold, transfer, forward, display messaging, speed dial, call waiting, park, pickup, multi-cast conferencing etc.
Multiple line appearances/single number distribution Bandwidth (Compression) Manager Interface to voice mail
– Manageable using web interface Real-time/historical performance monitor CDR reporting
– Architected for fault-tolerant and redundant operations for scalable/reliable operations
Source: Selsius
An outside caller or ext 8560 calls ext 8565. 8565 is traveling and 8660 is supposed to answer the call. 8660 is at lunch. However, since 8565 is now logged into the network running her virtual phone, she can answer the call herself, by selecting the ringing and blinking line appearance.
PSTN
PBX Phones
PBX
EthernetGateway
Analog orDigitalLine (s)
Call Manager
Ethernet Switch
Ethernet Hub
PC
VoiceMail
Travelerin other
city EXT 8565EXT 8565
EXT 8560
Shared/Switched/10/100/1000
Ethernet
EXT 8660
Multi-line Appearances
Call Coverage Flexibility
© 1998-1999 Marvin A. Sirbu Page 29
Carnegie Mellon
IP Network
PSTN
PSTN
Call ManagementServers
IP Phone
IP Phone
IP Phone
IP Phone IP Phone
IP Phone
IP Phone
PSTN
Remote IPSites
Remote IPSites
Consolidated Phase
Source: Selsius
© 1998-1999 Marvin A. Sirbu Page 30
Carnegie Mellon
The Death of Distance
• Any phone connected to the Internet can be part of the “domain” of a paticular Gatekeeper (“call server”)
• Can create a citywide “PBX” by linking all remote offices to a common Gatekeeper over the Internet
– even worldwide
© 1998-1999 Marvin A. Sirbu Page 31
Carnegie Mellon
Economics of Premises IP Telephony• An IP-PBX enables the use of Internet telephony over a LAN -
allowing a complete integration of voice and data networks.• What does it Cost?
– Develop a cost model to estimate the impact of installing an IP-PBX on the cost of premises, local, and long distance calling.
– Compare with Centrex.
• Joint work with Kanchana Wanichkorn
© 1998-1999 Marvin A. Sirbu Page 32
Carnegie Mellon
Network Architecture
Backbone Fast EthernetSwitch
Router CSU/DSU
Gateway
Gatekeeper
Leased Linesto ISP’s POP
Trunk Linesto PSTN’s CO
Corporate Office
10 Mbps Switched Ethernet
100 Mbps Fast Ethernet
DesktopEthernet Switch
To eachemployee’sPC andTelephoneHandset
DesktopEthernet Switch
DesktopEthernet Switch
© 1998-1999 Marvin A. Sirbu Page 33
Carnegie Mellon
End User Configuration
Voice over IPAdapter
DesktopEthernet Switch
Type 1: Traditional Telephone with Voice over IP Adapter DesktopEthernet Switch
Each PC equipped withVoice over IP Interface card
Type 2: Computer Telephone
DesktopEthernet Switch
Micro HubIP Telephone HandsetType 3: IP Telephone
© 1998-1999 Marvin A. Sirbu Page 34
Carnegie Mellon
Centrex Scenario• Two choices of long distance call routing via
1. a traditional Interexchange Carrier (IXC)
2. an Internet Telephony Interexchange Carrier (ITXC)
IXC
LEC LEC
ITXC
1
2
Dial-in Gateway
Circuit Switched
IP
© 1998-1999 Marvin A. Sirbu Page 35
Carnegie Mellon
IP-PBX Scenario • Three choices of long distance call routing via
1. a traditional Interexchange Carrier (IXC)
2. an Internet Telephony Interexchange Carrier (ITXC)
3. an Internet Service Provider (ISP) - intra-corporate calls
Circuit Switched
IP
IXC
LEC LEC
ITXC
1
3
2 Remote Gateway
ISP
© 1998-1999 Marvin A. Sirbu Page 36
Carnegie Mellon
Key Assumptions
• 15 kbps per voice channel.• Where the infrastructure exists, corporations always
choose to route toll calls over an Internet Telephony Interexchange Carrier (ITXC).
• The ITXC provides an additional discount for net to phone service, which saves the ITXC the costs of an originating gateway.
© 1998-1999 Marvin A. Sirbu Page 37
Carnegie Mellon
Results
Centrex IP-PBX IP-PBX IP-PBX (200 lines) (100 lines) (20 lines)
Equipment $5 $21 $24 $40LEC service $52 $21 $24 $34Long distance calling $27 $19 $21 $34Maint., move, and change $4 $10 $11 $16Total monthly cost per line $89 $71 $80 $124
© 1998-1999 Marvin A. Sirbu Page 38
Carnegie Mellon
IP-PBX Cost Breakdown
$0
$20
$40
$60
$80
$100
$120
$140
Large(200 lines)
Medium(100 lines)
Small(20 lines)
IP-P
BX
Mo
nth
ly C
ost
pe
r L
ine IXC and ITXC
Maintenance,move, and change
LAN upgrade
ISP access andservice
PSTN trunk linesand local usage
Gateway andgatekeeper
Handset(computertelephone)
© 1998-1999 Marvin A. Sirbu Page 39
Carnegie Mellon
Optimal Choices
LEC Cost Small Medium Large(20 lines) (100 lines) (200 lines)
Low Centrex Centrex IP-PBX
Base Centrex IP-PBX IP-PBX
High Centrex IP-PBX IP-PBX
© 1998-1999 Marvin A. Sirbu Page 40
Carnegie Mellon
Cost Comparison among Different Scenarios
$0
$20
$40
$60
$80
$100
$120
$140
$160
Large Medium Small
(20 lines)
To
tal
Mo
nth
ly C
ost
per
Lin
e Centrex with IXC
IP-PBX with IXC(no IP intra-corporate)
Centrex with ITXC
IP-PBX with ITXC (IP intra-corporate)
IP-PBX withdiscount ITXC
(IP intra-corporate)(100 lines)(200 lines)
© 1998-1999 Marvin A. Sirbu Page 41
Carnegie Mellon
Economic Implications
• The major saving of an IP-PBX over Centrex comes from the saving in intra-corporate long distance calls.
• Even without a discount in the ITXC rate, an IP-PBX costs less than Centrex as long as there are some calls made directly from one IP-PBX to another.
• The incremental cost of allocating more voice traffic to IP is less than the incremental cost of allocating more voice traffic to the PSTN.
• An IP-PBX is not yet economical for small corporations.
© 1998-1999 Marvin A. Sirbu Page 42
Carnegie Mellon
Additional Considerations
• IP-PBX simplifies construction of Call Center applications
– speech is already digitized and compressed
– IVR applications can be constructed entirely in software without need for DSP boards to digitize voice or generate call control signals.
© 1998-1999 Marvin A. Sirbu Page 45
Carnegie Mellon
Features
• Compared Current VoIP PBX product features to CMU’s most recent premises RFP (1989)
• Many capabilities not available• Availability standards not met
– Move entire LAN to telephony availability standards? 99.991% uptime
• Fault logging and notification standards not met
© 1998-1999 Marvin A. Sirbu Page 46
Carnegie Mellon
Moves, Adds and Changes
• In theory, can move phone to new office, plug it in and have all features.
– Limitations works within bridged subnet within routed subnets, must use DHCP to automatically assign
appropriate IP address to phone
© 1998-1999 Marvin A. Sirbu Page 47
Carnegie Mellon
Security Issues
• If you swap handsets with the President, you can highjack all the President’s calls
• Must have voice traffic encryption
– CMU has many hackers• Security of NT Server OS?
© 1998-1999 Marvin A. Sirbu Page 48
Carnegie Mellon
Electric Power
• Must provide uninterruptible 48V DC power via 10BaseT cable to handsets
– CMU is largely wired with IBM Type 3 cable containing two shielded twisted pair for data and 4 pair for voice.
STP doesn’t have power pair
– CMU moving to 100BaseT as standard either ethernet phones would need to support 100BaseT ports, or would
need separate ports in each office for computing and phones.
• Emergency Phone Power– All wiring closets would need UPS.
– Conducted preliminary analysis of cost of acquiring 4 hour UPS for all LAN equipment and uninterruptible 48V DC power for 7,000 phones.
Estimated cost at $500,000 for the entire campus.
© 1998-1999 Marvin A. Sirbu Page 49
Carnegie Mellon
Conclusions• An IP-PBX is more expensive than Centrex when only
premises telephony costs are considered. • When the impact of premises voice system choice on toll
calling costs is included, an IP-PBX is shown to provide a significant cost savings for medium and large firms.
• These savings are largely obtained on intra-corporate calls.• Regulatory policies which reduce access charges for all IXCs
or impose them on phone-to-phone ITXCs will likely slow the growth of ITXCs. However, it is likely that IP-PBX users may continue to benefit from an access charge exemption.
© 1998-1999 Marvin A. Sirbu Page 60
Carnegie Mellon
RouterCMTS
VoIP over Cable Modem
PSTN
TelephonyGateway
BTI CM
Tap Fiber Node
Local hub
PrimaryHub
Internet
VOIP Telephony & Cable Modem Architecture
Full Service Packet Based NetworkEnd-user Applications
Network and Service ManagementNetwork
ManagementInternetServers
NetworkDatabases
FeatureServers
Core Network
STM/Optical
Gateway
PSTN
Broadband AccessServer/MUX
Wired
Large BusinessAccess
Wireless AccessServer
IP
FixedWireless
Residence/Small Business Access
AccessServer
Wireless Mobility Access
ResourceServers
Cable Access
AccessServer
HFCPlant
xDSL
PacketPhone
Adapter
CableModem
SettopBox
Public Internet
Source: Lucent
© 1998-1999 Marvin A. Sirbu Page 62
Carnegie Mellon
Summary• Voice data integration is finally beginning to appear practical• Cost savings realizable today by moving some voice to corporate
data networks.• IP-based IXCs cheaper largely because they don’t pay access
charges• Technology is still fairly new. Features more limited than
traditional telephone switches• Increased pressure for QoS features in data networks.
– New economic models needed to pay for QoS• Data networks and PCs not as reliable as telephone today.
– Will phone still work when the power goes out?• Radical paradigm shift underway throughout the telephone
industry