SIP in wireless applications

1
SIP in wireless applications

• Henning Schulzrinne
• Dept. of Computer Science
• Columbia University

2
Overview

• New developments
• presence and IM ? location-based services
• identity management
• Standardization status
• Issues
• complexity
• integration
• spam
• Resources

3
New developments presence, location-based
services, IM

• Old ring-and-hope (or ring-and-annoy) model is
  obsolete
• Presence and event notification model
• human availability
• environmental events (alarms)
• business events (e.g., machine malfunction)
• Mobile devices as prime sources of presence
  information
• recent device use
• outbound calls
• answered calls
• unanswered calls
• location information (from Phase II 911)
• including motion (driving)
• longer term activity information

4
GEOPRIV and SIMPLE architectures
rule maker
DHCP
XCAP (rules)
target
location server
location recipient
notification interface
publication interface
GEOPRIV
SUBSCRIBE
presentity
presence agent
watcher
SIP presence
PUBLISH
NOTIFY
caller
callee
SIP call
INVITE
INVITE
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The role of presence for call routing
PUBLISH

• Two modes
• watcher uses presence information to select
  suitable contacts
• advisory caller may not adhere to suggestions
  and still call when youre in a meeting
• user call routing policy informed by presence
• likely less flexible machine intelligence
• if activities indicate meeting, route to tuple
  indicating assistant
• try most-recently-active contact first (seq.
  forking)

PA
NOTIFY
translate RPID
LESS
CPL
INVITE
6
RPID rich presence
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New developments location-based services

• My lab working on language for end-system
  services (LESS), including location-based
  services
• User (or administrator) creates services
• Designed to be portable across devices
• Java APIs ? alternatives with different trade-offs

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Service creation
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SIP is PBX/Centrex ready
boss/admin features
centrex-style features
attendant features
from Rohan Mahys VON Fall 2003 talk
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A constellation of SIP RFCs
Non-adjacent (3327) Symmetric resp.
(3581) Service route (3608) User agent caps
(3840) Caller prefs (3841)
Request routing
Resource mgt. (3312) Reliable prov. (3262) INFO
(2976) UPDATE (3311) Reason (3326)
SIP (3261) DNS for SIP (3263) Events (3265) REFER
(3515)
ISUP (3204) sipfrag (3240)
Mostly PSTN
Core
Content types
Digest AKA (3310) Privacy (3323) P-Asserted
(3325) Agreement (3329) Media auth. (3313) AES
(3853)
DHCP (3361) DHCPv6 (3319)
Configuration
Security privacy
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An eco system, not just a protocol
configures
XCAP (config)
SIMPLE policy RPID .
XCON (conferencing)
initiates
carries
SIP
RTSP
SDP
carries
controls
provide addresses
STUN TURN
RTP
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SIP, SIPPING SIMPLE 00 drafts
includes draft-ietf--00 and draft-personal--00
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RFC publication
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When are we going to get there?

• Currently, 14 SIP 33 SIPPING 17 SIMPLE WG
  Internet Drafts 64 total
• does not count individual drafts likely to be
  promoted to WG status
• The .com consultant linear extrapolation
  technique
• pessimist ? 4 more years if no new work is added
  to the queue and we can keep up productivity
• optimist ? 3 more years (lots of drafts are in
  almost-done stage)

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SIP a bi-cultural protocol

• multimedia
• IM and presence
• location-based service
• user-created services
• decentralized operation
• everyone equally suspect

• overlap dialing
• DTMF carriage
• key systems
• notion of lines
• per-minute billing
• early media
• ISUP BICC interoperation
• trusted service providers

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Does it have to be that complicated?

• highly technical parameters, with differing names
• inconsistent conventions for user and realm
• made worse by limited end systems (configure by
  multi-tap)
• usually fails with some cryptic error message and
  no indication which parameter
• out-of-box experience not good

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Issues for SIP in 3GPP/3GPP2

• Complexity
• 14 messages
• PSTN-based worldview
• somewhat peculiar notions of scaling
• may be able to combine multiple logical elements
• Cross-carrier roaming
• Integration with non-3G systems
• e.g., seamless integration with enterprise SIP
  systems or landline service providers
• separation of bearer and identity
• possibly share same mobile device
• Service creation by non-carriers
• e.g., vertical applications

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3G Architecture (Registration)
mobility management
signaling
serving
interrogating
interrogating
CSCF
proxy
home IM domain
registration signaling (SIP)_
visited IM domain
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SIP network architectureScalability requirement
depends on role
Cybercafe
ISP
IP network
IP phones
GW
ISP
MG
MG
SIP/MGC
GW
SIP/PSTN
SIP/MGC
Carrier network
MG
GW
PBX
T1 PRI/BRI
PSTN phones
PSTN
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Reliability and scalabilityAnalysis, simulation
and measurement proposal
Rp Mp
a1
Rs Ms
P11
s1
a2
S3
? ?R ?P REGISTER INVITE, etc
B2
s2
?/B
?r, ?p
s3
b1
?s
b2
ex

• When is stateless proxy stage needed
• What are the optimal values for S,B,P
• for required scalability (1-10 million BHCA) and
  reliability (99.999)
• using commodity hardware

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Scaling example
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Scaling and reliability

• No single point of failure
• Geographical redundancy
• Can use commodity servers to build 6-nines
  system
• Each cluster with 3 servers with 99 uptime (3
  days/year outage) ? 99.9999 availability
• Scalable to roughly 10 million BHCA
• 5ESS 4 m BHCA

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Software Resources

• Lots of commercial and open-source components,
  e.g.,
• proxies
• iptel.org (OSS), sipd,
• application servers
• Ubiquity, Broadsoft
• SIP stacks
• reSIProcate (OSS), Hughes, RADvision, various
  Java stacks
• SIP test tools
• sipsak, SIP Forum test suite (SFTF)

http//www.cs.columbia.edu/sip/implementations.htm
l
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Why is Skype successful?

• All the advantages of a proprietary protocol
• Peer-to-peer coincidental
• Good out-of-box experience
• Software vendor service provider
• Didnt know that you couldnt do voice quality
  beyond PSTN
• others too focused on PSTN interoperability why
  do better voice than PSTN?
• Simpler solutions for NAT traversal
• use TCP if necessary
• use port 80
• Did encryption from the very beginning
• Kazaa marketing vehicle