1. IP telephony overview and demonstration
Prof. Henning Schulzrinne
(presented by Andrea Forte, Ron Shacham,
Sangho Shin, Kundan Singh and Xiaotao Wu)

2. Research topics in IRT lab
Internet telephony
Internet radio/TV
Peer-to-peer systems
Quality of service
Security
Internet Real Time
Internet service discovery
Content distribution
VoIP and wireless
Resource reservation
Wireless ad hoc networks

3. What is IP telephony? Phone call + Internet User identifier
Session Initiation Protocol – SIP
office.com
Bob
(2)
(1)
pc4.columbia.edu
(3)
home.com
columbia.edu

4. Personal mobility tel:12129397000 alice_95@yahoo.com Home
tel:
Mobile
cs.columbia.edu
host.cs.columbia.edu
Office

5. Call setup Office Forking Mobile Visiting university Redirect Home
Media path
Control path
Office
Forking
Mobile
Visiting university
Redirect
Bob
columbia.edu
Home

6. Programmability Common gateway interface (CGI)
Double ringing sound when boss calls…
Enter your authentication PIN for billing…
Use finger for locating user…
B2BUA
Endpoint
Make call when boss is online …
Proxy/registrar
Endpoint
Forward to office phone during day, and home phone during evening…
Common gateway interface (CGI)
Call processing language (CPL)
SIP servlet
Language for End System Services (LESS)

7. Clients and servers IP phones Server Proxy, register, redirect.
Conferencing.
Voic , IVR.
Hardware phones
Urgent
SIP server
Phone
script
Low-priority
Voic
Software phones

8. Interworking with PSTN
x7040
(212)
Telephone
network
(PSTN)
Telephone
subscriber
PBX
SIP/PSTN
gateway
SIP server
IP endpoint
Translating:
Audio – better codecs on IP
Signaling – some features are lost
Identifiers – phone numbers
Determining transition points

9. Enterprise VoIP PSTN CINEMA servers Telephone switch
Local/long distance
e.g.,
sipconf:
conference server
rtspd: media server
PSTN
RTSP
RTSP clients
e.g., Quicktime
Department
PBX
sipum:
unified
messaging
Internal
Telephone
e.g., 7040
sipd:
proxy,
redirect,
registrar
713x
SQL
database
cgi
Web server
Web based
configuration
SIP/PSTN Gateway
e.g., Cisco 2600
vxml
SIP
VXML
7134
7136
siph323:
SIP-H.323
translator
H.323
(software phone)
H.323 clients
e.g., NetMeeting

10. VoIP and wireless Which wireless network? What is handoff? 802.11a/b/g
Infrastructure mode (security)
Ad-hoc mode
What is handoff?
Handoff happens when a mobile node moves beyond the radio range of one access point and enters another.
Internet

11. VoIP and wireless What is the problem?
L2 Handoff time is too big (~500 ms) for seamless VoIP sessions (90 ms).

12. VoIP and wireless
Improvement in our solution

13. Session Mobility
Focus on communication media: audio, video, instant messaging
Location sensors and presence, along with service discovery yields a list of local devices
Seamlessly transfer an active session between devices
Transfer all media to a single device or split over multiple devices
Privacy: keep audio on handset, watch video on large screen
Take advantage of benefits of different devices

14. Session Mobility Internet Transcoder Local Devices SLP DA
Correspondent
Node (CN)
SIP UA
SLP UA
SIP SM
Local Devices
SLP SA
SLP DA
Mobile Node (MN)
SLP
SIP
RTP
Transcoder

15. Serverless (P2P) VoIP Server-based Peer-to-peer P2P-SIP
Cost: maintenance, configuration
Central points of failures
Controlled infrastructure (e.g., DNS)
Peer-to-peer
Robust: no central dependency
Self organizing, no configuration
Scalability
P2P-SIP
Efficient, interoperable, hybrid
Prototype implementation C S P

16. Summary SIP-based architecture Heterogeneous endpoints
Telephone, SIP phone, H.323
Devices like lamp, video encoder
Multimedia collaboration
Conference, IM, discussion board, voic , file sharing
Advanced services
Programmable call routing, voice mail, interactive voice response
Fast handoff for WirelessLAN
P2P-SIP for serverless VoIP

17. Conferencing sipconf e*phone Web configuration Audio mixing
Video replication
SIP, PSTN or H.323
sipc
sipconf
e*phone
SIP/PSTN

18. Voicemail and IVR Multi-platform (phone, PC) access
Standard based (SIP, RTSP)
Programmable dialogues

19. Location-based Services in our lab
Room conf
Location agent
Device GW
SLinke
Bob is in conf
Turn on light
Bob
Proxy LS
Trigger
an action
X10
You are
In conf
sip:conf_pingtel
for audio
Turn on
conf’s light
What’s available
iButton
reader
RFID reader
SLP DA
sip:conf
SLP SA
Resource
discovery
Location
NOTIFY
Tracking
Location-based Services in our lab

20. Location-based Services in our lab
Room conf
Location agent
Device GW
SLinke
Bob is in conf
Turn on light
Bob
Proxy LS
X10
You are
In conf
sip:conf_pingtel
for audio
What’s available
INVITE sip:anyone_roomconf
Turn on
conf’s light
iButton
reader
RFID reader
SLP DA
sip:conf
SLP SA
Guard communication behavior
Location
‘Talk’ to a location
NOTIFY
Location-based Services in our lab