CSG mini-WorkshopVoice over IP
Jim Jokl – Virginia
Susan DeLellis – Harvard
May, 2001
VoIP Systems: Lots of definitions
PBX VoIP line or trunk card - A Call path between IP phones via PBX Initial releases by Lucent, NEC, others
PBX VoIP line or trunk cards - B Call path between IP phones via LAN Nortel, Siemens, others have systems Most PBX manufacturers working towards this type
of functionality
Major advantage: phone features
More VoIP System Definitions
LAN-based Systems Call setup via LAN call processing server Call path between all peripherals via LAN Cisco Call Manager Siemens HiPath Xpress Nortel Business Communications Manager Others
LAN-based systems generally limited ACD, console, call center applications
Packet Voice: What is different?
Traditional Phone Switch Voice over IP (VoIP)
Phone Switch
Phone
Phone
PhonePhone Phone
Phone
PSTN
Campus Network
Routers, hubs, switches
PSTN
Gateway
Call Manager
Network Capacity for Multimedia Applications
05
10152025303540
Percent
Method
Percent of Standard Ethernet
VoIPNetMeetingMPEG-4VCONWMMPEG2 (a)MPEG2 (b)
Network Capacity for Packet Voice Services
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
G.711 G.726 G.728 G.729 G.723.1 G.723.1
Voice Codec Type
% o
f E
the
rne
t R
eq
uir
ed
0
10
20
30
40
50
60
70
80
90
100
Su
bje
cti
ve
Vo
ice
Qu
ali
ty
(%) % Ethernet
% Quality
Network Infrastructure for Voice over IP Support
Low latency Low loss Predictable packet arrival High availability
Minimal capacity
Network Quality of Service (QoS)
Goal: provide better service for some
Build lots of network capacity Layer 3 QoS Layer 2 QoS
QoS: Useful for?
Have we seen the light?
Solving capacity problems? Protect voice traffic?
Need a way to remap QoS parameters where traffic enters the network
Personal Computer
IP Phone
IP Phones and QoS
IP phone generates 802.1p CoS = 5 and IP precedence = 5
Switch in phone can clear PC’s QoS header settings
Phone and PC can be in different VLANs
Switched Network
Wall Jack
IP Telephones and Power
Powering options Via Ethernet cable Via wall power transformer
Phone power consumption Tested Cisco and Nortel phones Between 4 and 6.5 watts/phone
Large wiring closet 250 phones, 75% efficiency
Closet power: 400 Watts Powering phones – no worse than 72 switch ports
My Other Wireless Phone
Wireless Data VoIP
Symbol NetVision Phone H.323 on 802.11 But no DSSS yet (summer)
Spectralink NetLink Phone System VoIP-based Both FHSS and DSSS available Proprietary adapter integration
Killer App: 802.11b/PCS dual mode phone?
Wireless & QoS
Challenge: protect voice traffic Wireless LANs low bandwidth Easy to overload
SpectraLink Voice Priority (SVP) Retransmission modification Priority queuing in base station
Symbol Similar capabilities
Standards?
Preparations at VirginiaThe Network
New backbone this summer Layer 3 switching IP Precedence
Wiring Closet 802.1p/Q New edge switches will reclassify traffic
Policy management, multicast Closet UPS and cooling work
Are these VoIP costs?
VoIP at Virginia
Initial application: toll bypass AS-5300 Gateway – T1 to PBX 2600/3600/3810 at remote location Analog interface to remote PBX
Added Cisco Call Manager Couple dozen phones Voice mail issues Number portability
VoIP at Virginia
Siemens HiPath 5500 One dozen phones PRI connection to Hicom PBX CorNet features
Nortel Business Communications Manager Planned for summer
Symbol?
Next Steps
Continue to prepare network for converged applications
Select a VoIP system for larger pilots Harvest some low hanging fruit
Safe areas Telecommuters Wireless?
Solve the wired/wireless VoIP question Continue to watch technology
Issues: Financial Model
Converged networks, especially VoIP, break most existing funding models
What to bill for Wall outlet? MAC Address? IP phone or soft phone? A tax based on headcount or NASF?
Central funding?