Mobile Services Using SIP and 7DS

1
Mobile Services Using SIP and 7DS

• Henning Schulzrinne
• Joint work with Jonathan Lennox, Maria
  Papadopouli, Jonathan Rosenberg, Sankaran
  Narayanan, Kundan Singh, Xiaotao Wu and other
  members of the IRT lab
• Columbia University
• August 2002

2
Outline

• SIP as enabler of mobile services
• quick overview of SIP
• terminal, service and session mobility
• event notification
• machine-to-machine communications
• location-based services
• Multimodal communications
• 7DS

3
SIP

• IETF-standardized application-layer signaling
  protocol
• SIP URIs sipalice_at_example.com, sipsbob_at_foo.net
  (TLS)
• Uses Session Description Protocol (SDP) to
  describe multimedia streams
• Syntax similar to HTTP and SMTP/RFC 2822
• methods, extensible header, opaque body
• built-in mobility model
• registrars track end system location
• proxies to provide known contact point
• "soft handoff" ? one identifier, multiple
  terminals
• mid-call session renegotiation

4
System model
outbound proxy
SIP trapezoid
a_at_foo.com 128.59.16.1
registrar
5
SIP session setup
INVITE
INVITE sipbob_at_biloxi.com SIP/2.0 Via
SIP/2.0/UDP pc33.atlanta.com branchz9 Max-Forw
ards 70 To Bob ltsipbob_at_biloxi.comgt From Alice
ltsipalice_at_atlanta.comgt tag1928301774 Call-ID
a84b4c76e66710_at_pc33.atlanta.com CSeq 314159
INVITE Contact ltsipalice_at_pc33.atlanta.comgt Conte
nt-Type application/sdp Content-Length 142
REGISTER
BYE
6
SIP in 3GPP

• 3GPP (and 3GGP.2) uses SIP as signaling protocol
  for Internet Multimedia Subsystem (IMS)
• but mobile operator mentality
• regular SIP client may not work on 3G network
• limited interworking with clients on wired side
• lack of openness and transparency
• trusted network model ltgt IETF protect user from
  network (and other users)

7
SIP design

• Framework with three applications
• route messages to abstractly specified
  (user_at_domain) destination
• possibly with multiple physical destinations
• applications
• Establishing and controlling IP telephony and
  multimedia sessions
• instant messaging
• presence

8
SIP transparency

• Not Q.931/ISUP split ? signaling messages and
  intent preserved by network
• Transparency (D. Willis)
• dialog (sequence number)
• identity of user
• header ? new services without network knowledge
• body ? new session negotiation
• topology ? discovery, loop prevention
• functional ? new methods

9
Event notification

• Missing service glue
• network management
• alarms "water in level 2"
• email alert
• geographic proximity alert
• "friend Alice is in the area"
• see geopriv work in the IETF ? location object
  with embedded security and privacy policy
• media interaction ? DVR
• "start of show postponed by 30 minutes"
• "semantic SMS"
• can build services one-by-one ? generic platform
  for quick service creation

10
Event notification
video
process control
temperature
IR detector
alarms
audio
100
10
1
0.1
0.01
1000
event interval
email
polling
SIP events
RTP
11
Controlling devices
12
CINEMA

• Integrated communications environment
• multimedia audio, video, shared applications,
  chat,
• call handling and routing
• conferencing
• unified messaging
• control of networked devices
• instant messaging and presence
• Carrier (hosted) or enterprise environment
• Integrated with existing PSTN environment

13
CINEMA components
Cisco 7960
MySQL
rtspd
sipconf
user database
LDAP server
plug'n'sip
RTSP
conferencing
media
server
server
(MCU)
wireless
sipd
802.11b
RTSP
proxy/redirect server
unified
messaging
server
Pingtel
sipum
Cisco
Nortel
2600
Meridian
VoiceXML
PBX
server
T1
T1
SIP
sipvxml
PhoneJack interface
sipc
SIP-H.323
converter
sip-h323
14
sipjohn_at_cs.columbia.edu
INVITE sipjohn_at_cs.columbia.edu
My owners SIP address is sipjohn_at_cs.columbia.edu
Help!!! (invoke sipc to call sipjohn_at_cs.columbia.
edu
15
Device control
Do siplamp_at_cs.columbia.edu SIP/2.0 .. ltControlgt
ltActiongtturn lamp onlt/Actiongt lt/Controlgt
serial port
16
Terminal mobility

• Terminal moves to different network
• usually, via mobile IPv4/6
• but requires home network support
• not likely to work through firewalls
• SIP can support limited terminal mobility
• pre-call redirection
• mid-call re-INVITE (but not simultaneous moves)
• not good for TCP applications except with NATs

17
Session mobility

• Move existing session from one (logical) terminal
  to another
• e.g., from 3G to 802.11 terminal to landline
  terminal
• not IP mobility ? maintain separate interfaces
• use SIP REFER for transferring session

18
Service mobility

• Ability to transparently move services between
  devices ? much more data than in GSM SIM
• end-system call handling descriptions
• address books
• call logs
• Solutions
• SyncML (with SIP event notification?)
• SIP URI binding for configuration information ?
  SIP BIND proposal

19
Current SIP standardization activities

• IM/presence infrastructure
• authorization, buddy lists, presence publication,
  ...
• authentication and anonymity
• emergency calls and ETS
• conferencing support

20
Multimodal networking

• "The term multimodal transport is often used
  loosely and interchangeably with the term
  intermodal transport. Both refer to the transport
  of goods through several modes of transport from
  origin to destination." (UN)
• goods packaged in containers ? packets and
  messages
• Networking ? combine different modes of data
  transport that maximize efficiency

21
Multimodal networking

• Speed, cost and ubiquity are the core variables
• cf. pipelines, ships, planes, trucks
• Traditional assumption of value of immediacy from
  PSTN ? demise of Iridium

22
Access modalities
delay
high low
high 7DS 802.11 hotspots
low satellite SMS? voice (2G, 2.5G)
bandwidth (peak)
23
Cost of networking
Modality mode speed /MB ( 1 minute of 64 kb/s videoconferencing or 1/3 MP3)
OC-3 P 155 Mb/s 0.0013
Australian DSL (512/128 kb/s) P 512/128 kb/s 0.018
GSM voice C 8 kb/s 0.66-1.70
HSCSD C 20 kb/s 2.06
GPRS P 25 kb/s 4-10
Iridium C 10 kb/s 20
SMS (160 chars/message) P ? 62.50
Motient (BlackBerry) P 8 kb/s 133
24
New wireless modes

• High upstream cost ? caching
• cf. early Internet (Australia)
• expand reach by leveraging mobility
• locality of data references
• mobile Internet not for general research
• Zipf distribution for multimedia content
• newspapers
• local information (maps, schedules, traffic,
  weather, tourist information)

25
A family of access points
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Our Approach

• Increase data availability by enabling devices to
  share resources
• Information sharing
• Message relaying
• Bandwidth sharing
• Self-organizing
• No infrastructure
• Exploit host mobility

27
7DS

• Application
• Zero infrastructure
• Relay, search, share disseminate information
• Generalization of infostation
• Sporadically Internet connected
• Coexists with other data access methods
• Communicates with peers via a wireless LAN
• Power/energy constrained mobile nodes

28
Examples of services using 7DS
news
WAN
events in campus, pictures
where is the closest Internet café ?
pictures, measurements
service location queries
schedule info
autonomous cache
29
Information sharing with 7DS
cache miss
Host C
WLAN
cache hit
data
Host B
Host A
30
7DS options
Cooperation Server to client Peer to peer
Querying active (periodic) passive
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7DS cooperation

• Server to client
• only server acquires and shares data
• fixed server
• mobile server (taxi, bus)
• peer-to-peer
• all peers share data
• either data of local interest
• or "memory dump" (iPod 10 GB disk)
• incentives
• recover expensive 3G bandwidth costs ?
  cooperative, currency
• enhanced user environment

32
Simulation environment
pause time 50 s mobile user speed 0 .. 1.5
m/s host density 5 .. 25 hosts/km2 wireless
coverage 230 m (H), 115 m (M), 57.5 m
(L) ns-2 with CMU mobility, wireless
extension randway model
querier
wireless coverage
dataholder
randway model
33
Dataholders () after 25'
high transmission power
P2P
Mobile Info Server
Fixed Info Server
2
34
Average Delay (s) vs dataholders ()peer-to-peer
schemes
high transmission power
medium transmission power
35
Fixed Info Serversimulation and analytical
results
high transmission power
Probability a host will acquire data by time t
follows 1-e-a?t
36
Delay (s) vs. dataholders ()
Fixed info server
one server in 2x2 high transmission power
4 servers in 2x2 medium transmission power
37
Message relaying with 7DS
WAN
Gateway
WLAN
Message relaying
Host B
Host A
38
Messages () relayed after 25 min
avg. of buffered messages 5
2
39
7DS Implementation
"sports"
proxy cache
list of items
7DS peer
HTTP GET

• full-text content index with HTML parser
• type index ("news", "sport", "map")
• select according to age, size, origin
• FAZ gt SZ gt AZ

40
7DS implementation

• Initial Java implementation on laptop
• Compaq Ipaq (Linux or WinCE)
• Inhand Electronics
• ARM RISC board
• Low power
• PCMCIA slot for storage, network or GPS

41
7DS deployment ideas
42
Conclusion

• Mobility is more than mobile IP and RAN...
• SIP as service enabler for mobile services
• not necessarily mobile terminals
• Multimodal networks for cost-efficient mobile
  data access