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
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
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%)
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**
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
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?