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Mobile Multimedia and VoIP
Prof. Henning SchulzrinneAndrea Forte · Matthew Mintz-Habib · Takehiro Kawata · Jonathan Lennox ·
Anshuman Rawat · Ron Shacham · Kundan Singh · Sangho Shin · Xiaotao WuDepartment of Computer Science
Columbia Universityhttp://www.cs.columbia.edu/IRT
CATT Research Review, December 3, 2004CATT Research Review, December 3, 2004
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December 3, 2004 CATT Research Review 2
Research projects
• Research issues in VoIP and multimedia moving from core protocols to services and mobility support
• PSTN emulation new services
• Large-scale deployments security, spam, management
911 for VoIPVoIP spam prevention
location-based services
session mobilityprofile mobility
SIP terminal mobility
TCP for streaming media
rapid DHCPpredictive handover
L2 handoff accelerationL2 VoIP capacity enhancement
applications
session
transport
network
link
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December 3, 2004 CATT Research Review 3
Making 802.11 work for VoIP
• IEEE 802.11 not designed for VoIP• Long layer-2 hand-off delays cannot
replace cordless phones in building• Lots of related work on MAC layer
– but most requires dramatic changes in APs and mobile hosts
– we aim for backward-compatible changes• Designed and implemented algorithms for
– rapid L2 hand-off– increase capacity for VoIP calls by 25%,
while reducing delay in mixed voice/data networks
– decrease L3 hand-off• DHCP optimizations in protocol and
implementation• predictive address acquisition
Packet Delay in Sender
0
50
100
150
200
250
Normal Handoff Selective Scanning Caching
Ave
rage
Del
ay (
ms)
25.323.122.320.1
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 1 2 3
Number of FTP Sessions
Th
rou
gh
pu
t (k
bp
s)
0
50
100
150
200
250
300
350
400
450
500
En
d-t
o-E
nd
De
lay
(ms)
FTP Throughput (download)
VoIP Throughput
VoIP Delay (90%)
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December 3, 2004 CATT Research Review 4
Re-architecting “9-1-1” for a VoIP world
• U.S. 9-1-1 emergency calling system is 1970’s technology – reaching end of extensibility
• VoIP imposes new constraints and offers new opportunities
• We are designing protocols and prototyping systems in cooperation with NENA (National Emergency Number Association) and MapInfo
911112
sip:sos@domainw/location or w/out location
geo location
POTS/Wireless Network
IP Network
911
IP Gateway
sip:sos@domainwithout location
Envinsa Server
sip:psap@domainwith location
location
GeoLynx Display
ALI ServerDHCP Server
DNS Server**
DHCP InformMAC Address
Location Info
TCP Socket Telephone Number
PSAP Info
HTTP SOAPLatitude/Longitude
Location Info
VerifiedLocation
Info
civil location**
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December 3, 2004 CATT Research Review 5
Session and profile mobility
• Beyond terminal mobility• Mobile devices limited I/O capabilities
– small screen– lo-res camera not suited for conferencing
• Utilize ubiquitous resources– video projectors– networked cameras– speaker phones
• Move session transparently from mobile to local (fixed) resources – and back
• Profile mobility: make “borrowed” devices behave as if they were the user’s
– Internet pay phone– outbound call personalization– call authorization
SA
DA
ResourceControl(3pcc)
Service LocationQuery
SA
sendaudioto SIPUA2
NetworkAppliance
Control
SIP UA1
turn onprojector
SIPUA2call
ResourceDiscovery(SLP UA)
audioand
videostreams
Scriptengine
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December 3, 2004 CATT Research Review 6
Spam prevention in VoIP
• Spam & phishing likely to be a problem for VoIP– cheap– anonymous– easily automated
• Content-based spam filtering unlikely to work
• Designing spam prevention based on– user management policies– social networks
Alice Bob
CarolDavid
Emily Frank
has sentemail to
has sentIM to
is this a spammer?