SIP in 2002

1
SIP in 2002

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

2
Overview

• Where are we?
• Uses of SIP new and old
• Challenges
• IM
• 3GPP
• Security
• Emergency calling

3
Where are we?

• SIP as the signaling protocol for future
  applications
• 3GPP
• Cable modems (DOCSIS DCS)
• IM AOL interworking, Windows Messenger
• but H.323 dominates videoconferencing, trunk
  replacement
• Proprietary protocols dominate for Ethernet
  phones
• Slow uptake of VoIP

4
Where are we?

• Not quite what we had in mind
• initially, for initiating multicast conferencing
• in progress since 1992
• still small niche
• even the IAB and IESG meet by POTS conference
• then VoIP
• written-off equipment (circuit-switched) vs. new
  equipment (VoIP)
• bandwidth is (mostly) not the problem
• cant get new services if other end is POTS ??
  why use VoIP if I cant get new services

5
Where are we?

• VoIP avoiding the installed base issue
• cable modems lifeline service
• 3GPP vaporware?
• Finally, IM/presence and events
• probably, first major application
• offers real advantage interoperable IM
• also, new service

6
SIP in the Enterprise

• Greenfield
• save on wiring and admin expenses
• per-seat cost similar (500)
• Existing installations
• small PBX (lt 8 lines) cheap
• cant beat 80 phones
• move towards multi-cordless (Gigaset, etc.)

7
Where are we?

• Number of robust SIP phones
• not yet in Wal-Mart
• SIP carriers terminate LAN VoIP
• number portability?
• 911
• 50 vendors at SIPit
• Building blocks media servers, unified
  messaging, conferencing, VoiceXML,

8
SIP at Home

• Lifeline (power)
• Multiple phones per household
• expensive to do over PNA or 802.11
• BlueTooth range too short
• need wireless SIP base station handsets
• PDAs with 802.11 and GSM? (Treo)
• Incentives
• SMS IM services

9
SIP phones

• Hard to build really basic phones
• need real multitasking OS
• need large set of protocols
• IP, DNS, DHCP, maybe IPsec, SNTP and SNMP
• UDP, TCP, maybe TLS
• HTTP (configuration), RTP, SIP
• user-interface for entering URLs is a pain
• see success of Internet appliances
• PCs with handset cost 500 and still have a
  Palm-size display

10
SIP developments in 2001

• SIP revision (RFC2534bis) almost done
• semantically-oriented rewrite
• layers message, transport, transaction,
  transaction user
• SDP extracted into separate draft
• UA and proxy have the same state machinery
• better Route/Record-Route spec for loose routing
• no more Basic authentication
• few optional headers (In-Reply-To, Call-Info,
  Alert-Info, )
• Integration of reliable provisional responses and
  server features
• DNS SRV modifications

11
SIP developments in 2001

• SIP revision backwards compatible
• new messages work with RFC 2543 implementations
• some odd allowed RFC 2543 behavior no longer
  allowed
• CPL almost finished merger with iCal
• sip-cgi published
• IM presence mostly done, except for IM sessions
  (over TCP) IMTP, BEEP

12
SIP developments in 2001

• Work continues on staples
• early media (announcements)
• resource reservation (COMET)
• SIP security
• SIP events
• User identification
• Call transfer and call control
• Now three SIP working groups
• SIP for protocol definition and extensions
• SIPPING for applications and vetting
• SIMPLE for IM presence

13
SIP security

• Bar is higher than for email telephone
  expectations (albeit wrong)
• SIP carries media encryption keys
• Potential for nuisance phone spam at 2 am
• Safety prevent emergency calls

14
SIP security

• Exposes weak state of general Internet security
  tools
• Attempt to re-use existing mechanisms
• HTTP digest authentication, with additions to
  protect crucial headers (e.g., Contact in
  REGISTER) for e2e and proxy authentication
• TLS and IPsec for hop-by-hop authentication and
  confidentiality
• S/MIME for end-to-end

15
SIP security

• Security with random strangers is hard!
• Identities are cheap cant use for filtering
  bozos
• often only need to verify that same good person
  as before see ssh
• Symmetric (secret) key doesnt scale
• Public key cryptography only modest help
• need certification authorities
• what is being certified?
• CRLs
• hard to move keys to new devices smartcard?
• Kerberos needs extensions for interdomain

16
SIP security longer term

• EAP for authentication (used in 3GPP)
• Third-party signatures
• this caller is an employee of Visa
• REFER authentication
• Alice (verifiable) asked Bob to call Carol

17
Other SIP standardization projects

• Call history where has this request been?
• Emergency calling (911/112)
• universal number sipsos_at_domain
• finding the emergency call center
• PSTN interoperation
• Emergency preparedness
• priority access to PSTN and IP resources

18
Instant message presence

• SIMPLE MESSAGE, SUBSCRIBE, NOTIFY
• Also for various SIP-related events, e.g., in
  REFER and conferences
• Just a special case of event notification tell
  me if something happened something happened!

19
Event notification

• Missing new service in the Internet
• Existing services
• get put data, remote procedure call HTTP/SOAP
  (ftp)
• asynchronous delivery with delayed pick-up SMTP
  ( POP, IMAP)
• Do not address asynchronous (triggered)
  immediate

20
Event notification

• Very common
• operating systems (interrupts, signals, event
  loop)
• SNMP trap
• some research prototypes (e.g., Siena)
• attempted, but ugly
• periodic web-page reload
• reverse HTTP

21
SIP event notification

• Uses beyond SIP and IM/presence
• Alarms (fire on Elm Street)
• Web page has changed
• cooperative web browsing
• state update without Java applets
• Network management
• Distributed games

22
SIP doesnt have to be in a phone
23
SIP longer-term issues

• SDPng?
• XML-based generalization
• better negotiation and grouping
• API standardization
• JAIN servlets
• APIs for IM and presence
• Operational issues
• How to configure 10,000 phones without editing
  config files?

24
Conclusion

• SIP technology vibrant, with large developer
  community
• Deployments and awareness lag
• VoIP as replacement technology conversion from
  analog to digital PSTN took decades
• Not XML, but will soon be on every desktop