1. 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

2. Basic Elements of 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.
PBX
PSTN
PSTN GW
Internet GW
Phone
User
Users
Audio Equipped PC 3 3

3. Two Stage Dialing Public Interexchange Network
PBX
Next
Generation
IXC
LEC #1
Packet /
Circuit
Gateway
Local
DS0
Transport
Network T1
Local Switch
H.323
Gatekeeper
Packets
Wide
Area
Data
Network
“1-888-NEXTGEN, ID6,
PIN4, ”
PBX
LEC #2
Local
DS0
Transport
Network
Packets
Local Switch T1
Packet /
Circuit
Gateway

4. Voice Coding Standards

5. Voice Quality and Delay
Processing affects perceived quality (MOS Score)
Compression and packetization introduce delay
for processing
to accumulate speech for a packet.

6. Voice Quality and Delay
One way delay (msec) Perceived Quality
Acceptable for most users
Acceptable but perceptible
Typical of satellites; annoying
Unacceptable for general network purposes.

7. 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”)
Network
Gateway
Gateway
(25 msec) ( msec) ( msec)

8. Worst case 292 ms round-trip latency
Latency - T1 WAN Links
1 ms
20 ms
1 ms
11 ms
Coder
6.5 kbps
Compress
Switch
Routing
2048 byte MTU
Queue Delay
Branch Office
T1 WAN
Uplink
WAN Cloud
Worst case 292 ms round-trip latency
40 ms
LA-NY
HQ LAN
WAN Cloud
1 ms
20 ms
40 ms
1 ms
T1 WAN
Uplink
Coder
6.5 kbps
Decompress
Jitter
Buffer
Switch
Routing
2048 byte MTU
Queue Delay
Branch Office
11 ms

9. 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

10. 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

11. H.323 Network Components POTS Phone H.323 Multimedia PC Gateway
PSTN
Multipoint Control
Unit
H.323 Multimedia PC
Gatekeeper
Firewall
Internet/ Intranet
Router
H.323 Phone
H.323 Phone 11 11

12. H.323 Interworking

13. H.323 Protocol Architecture
Data Appl. or
T.126/T.127
AV Appl.
Q.931 Terminal Control and Mgmt
G.7XX
Audio
H.26X
Video
RTCP
RAS
Term.
<-> GW
H.225.0
Call
Signal
H.245
Call
Signal
T.125
MCS
T.124
GCC
Real-Time
Protocol
(RTP)
Reliable Transport (TCP)
T.123
(ISO+TCP)
Unreliable Transport (UDP)
Network Layer (IP)
Link Layer
Physical Layer 12 12

14. H.232 Layered Architecture

15. Early Internet Telephony
Long Distance Bypass, Fueled by International Tariffs, Domestic Access Charges- Arbitrage opportunity
Often proprietary Internet protocols
Audio only
PBX
PSTN
PSTN GW
Internet GW
Phone
User
Users
Audio Equipped PC 3 3

16. 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.

17. PBX to Gateway VoIP Signalling
PBX
PBX
Corporate
Network
Trunk Signaling
Step 1-- the PBX seizes a trunk line to the gateway, and forwards dial digits

18. PBX to Gateway VoIP Signalling
Corporate
Network
H.323 agent
H.323 agent
Q.931
Step 2 -- The Gateway uses a dial plan to map dial digits into the IP address
of the remote gateway. H.323 agent software initiates a call using Q.931
signaling protocol to remote gateway

19. PBX to Gateway VoIP Signalling
Corporate
Network
Trunk Signaling
Step 3 -- The remote H.323 agent seizes a PBX trunk, returns a Q.931
acknowledgement 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.

20. 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

21. Yesterday’s PBX PSTN Proprietary Line Card(s)
terminals
Proprietary interface
Proprietary Line Card(s)
Proprietary Trunk Card(s)
Mainframe cabinet
Standard interface
Voice Path (TDM)
Proprietary Processor Card(s)
Proprietary
interface
Signaling Path
Applications (Voic /IVR)
Proprietary Ckt switch Card(s)
Proprietary
interface
Yesterday’s PBX was designed in the 70’s and is based upon 60’s technologies. The design attempted to solve the fundamental problem of allowing two users within an enterprise to talk through two terminal phone devices. Another fundamental challenge was to allow those same users to communicate with their customers, colleagues and vendors connected to the Public Switched Network.
The state of the art dictated that voice be transported using circuit-switched or Time Division Multiplexed technology. The solution was a mainframe-like system which connected proprietary phone sets to a proprietary card within the mainframe cabinet called a line card. The PSTN was connected to the cabinet using a trunk card. The interface between the trunk card and the PSTN is a standard dictated by public telecom organizations such as Bellcore in the United States.
The line and trunk cards merely provided an interface to their respective connected devices. No voice path between devices or cards could be dynamically established without another component, the circuit switch card. Again, this card was designed by the PBX manufacturer. The interface between the switch and the trunk and line cards was proprietary in that it was designed and implemented by the manufacturer and not published for the benefit of third party designers.
Managing the devices was a processor assembly that signaled all components through a master-slave relationship. Again, a proprietary hardware and software interface separated the processor and its operating system from other devices.
Finally, applications such as voice mail and interactive voice response systems were connected to the system as bolt-ons, normally built by third-party vendors. The applications had to communicate with the processor through a normally closed (and arcane) signaling interface.
The dominant feature of yesterday’s PBX is its relatively closed architecture. The PBX designer built ALL components, including interface cards, switch cards, processor cards, signaling and voice transport busses and, in many cases, the external applications themselves.
PSTN

22. Tomorrow’s PBX - the IP PBX
Intel
Processor
Standard OR Proprietary Interface
Windows NT Server PC
Call Control Application
Voice Path (TDM)
Signaling Path
PSTN
Standard interface
Applications Server (Voic /IVR)
Tomorrow’s IP PBX must solve the same problem. Connect enterprise phones together and to the PSTN.
The IP PBX departs from circuit switched architecture by first using low cost data network components in place of the line interface. Voice is transported in IP packets over standard 10BaseT Ethernet in the simplest, low cost example. Terminals therefore have a 10BaseT Ethernet interface and an IP address. Signals to and from these terminals are transported by TCP/IP. Until very recently, these voice terminal devices were all PCs in which sound cards are installed and voice communications applications were configured. Microsoft’s NetMeeting is the best example.
In 1997, Selsius Systems designed and brought to market the world’s first commercially available Ethernet PBX phone. Vendors such as NBX Corp are expected to bring similar products to market in early To the user, the Ethernet PBX phone looks and operates like a PBX phone. Internally, however, it adds a few 1990’s low cost technologies like a DSP, a CPU, RAM, flash ROM and a 10BaseT Ethernet interface. The phone plugs into an Ethernet repeater or switch.
The nature of the design allows either a standard OR a proprietary signaling interface to be supported, allowing phone makers the flexibility of building a more capable phone than the analog phone’s of today. Supplementary services such as transfer can be extended to these terminals. Phone makers can either confirm with standards and deliver basic services or depart from the standard to build what they consider a better phone.
The TCP/IP network itself serves as both the line interface and the switch. Because TCP/IP is physical transport independent, the core network can be composed of any combination of packet, cell or circuit-switched. The products on which these technologies are founded are more standardized than the internal components of a yesterday’s or today’s PBX. A 3COM Ethernet switch is more likely to be able to interoperate with a Cisco Ethernet switch than an NMS line card will interoperate with a Dialogic switch card.
Serving as a bridge between the TCP/IP network and the circuit-switched PSTN is an IP to PSTN gateway.
Call control is afforded through a call management application on a Windows NT server. No voice processing hardware need be contained in this server.
Finally, applications are delivered as software processes, with a signaling interface to the call control application. The application server will normally make use of a DSP resource card to perform voice processing services. But there is no need for a direct physical TDM connection between the DSP device and a circuit-switch card. As a result, the application process may reside in a server PC that is completely separate from the call control server. System designers who wish to separate applications from call control for reasons of fault-tolerance, will be able to do so.
The fundamental point of an IP PBX is its distributed architecture.
TCP/IP
Network
Standard
OR Proprietary
interface
Ethernet phones
and
PC applications
IP to PSTN
Gateway
Standard
interface

23. 3 Core Components of an IP PBX
Call
Manager
IP Phone
PSTN 3 2 1
IP PBX
IP/PSTN Gateways
PSTN trunk interface
Analog fax/phone/modem
User Instrument
Ethernet IP telephone
Wireless H.323 handset
PC with H.323 softphone
Call Processing
NT server
PBX functionality
PSTN/IP Gateway
Source: Selsius, Corp

24. PBX services
EtherPhone
EtherPhone
Server
EtherPhone
Branch

25. PhoNetwork Topology EtherPhone Branch PhoNetwork Server Gateway
PacketPhone
Area code
“8”

26. 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

27. 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

28. Call Coverage Flexibility
PBX Phones
EXT 8560
PSTN
Multi-line Appearances
Voice
Mail
PBX
Analog or
Digital
Line (s)
Shared/Switched
/10/100/1000
Ethernet
Ethernet
Switch
Gateway
Ethernet
Ethernet Hub PC
Traveler
in other
city
Call Manager
EXT 8565
EXT 8660
EXT 8565
An outside caller or ext 8560 calls ext is traveling and 8660 is supposed to answer the call 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.

29. Consolidated Phase Remote IP Sites IP Network PSTN IP Phone
Call Management
Servers
IP Phone
Remote IP
Sites
Source: Selsius

30. 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

31. 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

32. Network Architecture Router CSU/DSU Gateway Gatekeeper Leased Lines
Backbone Fast Ethernet
Switch
Router
CSU/DSU
Gateway
Gatekeeper
Leased Lines
to ISP’s POP
Trunk Lines
to PSTN’s CO
Corporate Office
10 Mbps Switched Ethernet
100 Mbps Fast Ethernet
Desktop
Ethernet Switch
To each
employee’s
PC and
Telephone
Handset

33. End User Configuration
Desktop
Ethernet Switch
Voice over IP
Adapter
Type 1: Traditional Telephone with Voice over IP Adapter
Desktop
Ethernet Switch
Each PC equipped with
Voice over IP Interface card
Type 2: Computer Telephone
Desktop
Ethernet Switch
IP Telephone Handset
Micro Hub
Type 3: IP Telephone

34. 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
ITXC 1 2
Dial-in Gateway
Circuit Switched IP

35. 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 1
IXC
LEC
LEC
ITXC 2
Remote Gateway
ISP 3
Circuit Switched IP

36. 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.

37. Results Centrex IP-PBX Equipment $5 $21 $24 $40 LEC service $52 $34
(200 lines)
(100 lines)
(20 lines)
Equipment $5
$21
$24
$40
LEC service
$52
$34
Long distance calling
$27
$19
Maint., move, and change $4
$10
$11
$16
Total monthly cost per line
$89
$71
$80
$124

38. IP-PBX Cost Breakdown Large (200 lines) Medium (100 lines) Small$0
$20
$40
$60
$80
$100
$120
$140
Large
(200 lines)
Medium
(100 lines)
Small
(20 lines)
IP-PBX Monthly Cost per Line
IXC and ITXC
Maintenance,
move, and change
LAN upgrade
ISP access and
service
PSTN trunk lines
and local usage
Gateway and
gatekeeper
Handset(computer
telephone)

39. Optimal Choices LEC Cost Small Medium Large (20 lines) (100 lines)
Low
Centrex
IP-PBX
Base
High

40. Cost Comparison among Different Scenarios
$160
Centrex with IXC
$140
$120
IP-PBX with IXC
(no IP intra-corporate)
$100
Total Monthly Cost per Line
$80
Centrex with ITXC
$60
$40
IP-PBX with ITXC
(IP intra-corporate)
$20 $0
IP-PBX with
Large
Medium
Small
discount ITXC
(IP intra-corporate)
(200 lines)
(100 lines)
(20 lines)

41. 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.

42. 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.

43. IP PBX Application Scenarios
CMU Central Receiving
located about two miles from main campus
connected by 10 Mbps ethernet over TCG fiber
Office is not served by same Bell Atlantic CO
CMU pays $17 month for a marginal analog Centrex line on campus
CMU pays additional $47 per month per line for FX service to CMU Centrex switch for this location
By putting Selsius IP phones at warehouse with a gateway on campus, can use IP as an FX substitute.
Lack of analog DID implied one Centrex line and gateway port for each Selsius phone

44. Central Receiving Scenario
Preliminary cost/benefit analysis showed ~26 month payback
did not account for increased operational support costs for a non-standard system
high availability not fully costed
emergency backup power
redundant servers
increased network operations support
Most promising scenario we explored.

45. 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

46. 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

47. 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?

48. 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.

49. 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.

50. Cost of an IP-Based Residential Network
In-home network providing high speed data, voice and video
Residential gateway mediating between in-home and external networks
Digital Subscriber Line (xDSL), Hybrid Fiber Coax (HFC) and Fiber to the Curb (FTTC) providing a multiservice data link to a Central Office/Headend
Voice service provided over the data network by packets between user terminals
Call management services provided by shared servers

51. Local Premise After xDSL
POTS
Backup Lifeline Service PC
Other IP
Appliance
From Telco
xDSL
Ethernet
Ethernet Hub
IP Phone
Set Top
Box
RJ11
Converter
Box
Legacy Phones
Source: J. Rinde, MCI

52. Models for the Local Exchange Network of the Future
Assume that dominant architecture is based on H.323 telephony
Central Office becomes a router and Gatekeeper
gateways for interconnection to legacy PSTN
Subscriber loop becomes an ADSL link
Residential gateway is an ADSL-R with Ethernet interface or microhub
Hybrid Fiber Coax and Cable Modem as an alternative
Telephone handset is an H.323 terminal with a 10BaseT RJ45 cord instead of an RJ11
alternatively, residential gateway acts as H.323 gateway to convert signals from analog handsets

53. Jetstream CLEC/Small Business Product
Unity Access Network Architecture

54. 2nd Century Product

55. IP-based Central Office
IP-Based Network
Interoffice Transport
POTS Customer Premise
POTS Lines
IP Gateway
Router
Servers
DSLAMs
ATM Switch
ADSL Customer Premise
ATU-C
ADSL Lines RG
IP-based Central Office
Copper Pair

56. CO, ISP Equipment, and Interoffice Transport
Model Results
Costs are categorized into 3 groups
CO, ISP Equipment, and Interoffice Transport
SONET Ring
Local Loop
CPE
The results of the cost model are categorized into three main groups which are 1) CPE, 2) local loop, and 3) central office, ISP equipment and interoffice transport as shown in this picture.
Tandem
Gateway
Router
Servers
IXC/ISP
ATM
Switch
DSLAMs
DSLAM
Central Office
Customer Premises

57. Average Cost per Location
Residence Business
$27
$25
$23
$16
CPE
CO, ISP Equipment, Interoffice Transport
Monthly Cost per Location
Local Loop
This graph shows average monthly cost per location. In the PSTN case, each home has two telephone lines, one for voice and one for dial-in Internet access.
And each business has 4 telephone lines, three for voice, and another one for dial-in Internet access. In the IP/ADSL scenario, each home and business in the serving area has one ADSL line providing both voice and Internet access services.
As shown in the graph, the PSTN-based architecture is cheaper for residences but the IP/ADSL architecture is cheaper for businesses.
If you look at the first two graphs for residences, you can see that the sum of the orange and the blue bars are about the same for both architectures. This means the savings due to lower loop costs in the IP-based architecture balances the higher investment in CO equipment. The total cost for IP/ADSL is higher due to more expensive CPE cost.
As for businesses, the saving in loop cost more than offsets the higher CPE cost, resulting in a lower total cost.
PSTN IP/ADSL PSTN IP/ADSL .

58. Cost Model Summary
The IP/ADSL integrated network is cost effective for small businesses.
Lower loop and transport cost
If costs of RG and DSLAM continue to decline, the IP/ADSL architecture will be cost effective for residences as well.
First IP/ADSL customers targeted by LEC:
small businesses
Centrex users
multiple dwelling units.
Even without the additional revenue that a LEC might be able to earn for provisioning superior Internet service via DSL, an integrated IP/ADSL network is cost effective for small businesses simply on the basis of lower loop and interoffice transport costs.
If the costs of premises gateways and DSLAMs continue to decline, we can expect that an IP/ADSL architecture will eventually be cost effective for residences as well.
The results also suggest that small businesses, Centrex users, and Multiple Dwelling Units might be the first customers targeted by an LEC seeking to migrate to an integrated packet network.

59. Model Limitations Assumed TELRIC loop costs, no stranded loop
But, this is what CLECs pay
Other Important Costs
Network operations
PSTN OSS are mature
In-building networks
Alternatively, IP access could be provisioned over Hybrid Fiber/Coax using cable modems or FTTC.
As Daniel mentioned before, costs included in the model are only network direct expenses which are capital carrying costs of network investment and network maintenance.
The model does not include network management costs such as ordering, provisioning, billing, and marketing costs. If included, they could contribute a high portion to the cost originally estimated by the model.
Another important cost factor is in-building network cost. CPE cost included in the model is only residential gateway cost. Other home area network costs are not included. If the installation of typical Category 5 LAN cabling is required to equip a home for integrated IP service, the costs could be significant. Retrofitting a home for LAN service can easily cost over a thousand dollars.
In addition, we have not examined any potential benefit to consumers of an IP/ADSL service in the form of lower long distance calling costs. The saving could be substantial as we witness in the current voice over IP market.

60. VoIP over Cable Modem VOIP Telephony & Cable Modem Architecture CM
Internet
PSTN
Telephony
Gateway
Router
CMTS
BTI CM
Local
hub
Primary
Hub
Tap
Fiber
Node

61. Full Service Packet Based Network
End-user Applications
Network and Service Management
Network
Management
Resource
Servers
Feature
Servers
Network
Databases
Internet Servers
Broadband Access
Server/MUX
Wired
Large Business
Access
Wireless
Residence/Small
Business Access
Core Network
Fixed
Wireless
Access
Server
STM/Optical IP
xDSL
Cable Access
Access
Server
Wireless Mobility Access
Access
Server
Gateway
Packet
Phone
Adapter
HFC
Plant
Cable
Modem
PSTN
Settop
Box
Public Internet
Source: Lucent

62. 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