Re-inventing the Telephone System: The Third Generation Henning Schulzrinne Dept. of Computer Science Columbia University CAT Forum -- October 12, 2004

Overview 1 st generation: analog 2 nd generation: digital circuit switched 3 rd generation: packet-switched What is VoIP? Why now? A short history Wireless VoIP Context-aware communications VoIP  IM, presence Challenges ahead

Lifecycle of technologies militarycorporateconsumer traditional technology propagation: opex/capex doesn’t matter; expert support capex/opex sensitive, but amortized; expert support capex sensitive; amateur Can it be done? Can I afford it? Can my mother use it?

Internet and networks timeline theory university prototypes production use in research commercial early residential broadband home ftp DNS RIP UDP TCP SMTP SNMP finger ATM BGP, OSPF Mbone IPsec HTTP HTML RTP 100 kb/s1 Mb/s10 Mb/s XML OWL SIP Jabber 100 Mb/s1 Gb/s port speeds Internet protocols queuing architecture routing cong. control DQDB, ATM QoS VoD p2p ad-hoc sensor

Earlier PSTN changes starting in 1980s: analog  digital transmission in-band  out-of-band (SS7) signaling end systems relatively unaffected few additional services 800# CLASS services (caller ID, call waiting) customer relationship largely unaffected except CLECs and reselling

Technology evolution of the PSTN SS7:

What is VoIP? Voice-over-IP = Internet telephony “Internet telephony refers to communications services—voice, facsimile, and/or voice-messaging applications—that are transported via the Internet, rather than the public switched telephone network (PSTN). The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet; the process is reversed at the receiving end.” (IEC) Not a single technology, but combination of Internet technologies Now typically voice only, but easily extended to video

Brief history of packetized voice 1969: ARPAnet, predecessor of modern Internet 1974: real-time packetized voice (early Internet) 1990: primitive version used for transatlantic calls (G.764) 1991: DARTnet (test network) audio experiments using Sun workstations 1992: first IETF multicast audiocast 1992: RTP (transport) draft 1995: first commercial PC-to-PC voice software (Vocaltec) 1995/1996: first PC-to-PC and PC-to-phone services (Net2Phone, DialPad, Vocaltec, …) 1996: first version of SIP and H.323 standards ~2000: first service providers ~2002: first large-scale consumer services 2002: 3G wireless specifies Internet multimedia subsystem

How has the industry progressed TIA, 2003 Telecommunications Market Review and Forecast Gartner Dataquest, , United States: Fixed Public Network Services Gartner Dataquest, 2002 Premises Based Equipment Sales Softswitch networks carry approximately 2 billion minutes/day vs. 2.3 million in 1999 Services, such as IP-Centrex, are quickly being adopted by enterprises 10% of all international voice traffic to/from U.S. carried on IP primarily prepaid calling cards IP-enabled handset sales over 4.5 million units in % of all total premise sales are IP – enabled IP handset costs drop from $600 in 2001 to $99 today Jack Waters Fall VON 2003

VoIP penetration Glen Campbell Telecom & Cable Analyst Merrill Lynch Canada May 2004 (CITI VoIP workshop) residential & small business

Vonage Subscriber Growth *Cable Datacom News Round Up, September 1, 2003 subscribers in thousands

Why has it taken so long? VoIP technology development since 1995 Web: worked on dial-up, motivated broadband deployment from 1992 to 2000 VoIP: not usable on dial-up, spurred by residential broadband More than just protocols needed: eco-system (management, configuration, OSS, …) interoperability spectrum of products – low to high end interoperation with legacy equipment

Technology introductions Source: OECD, 2003

Conditions for VoIP Multimedia PC with low-latency OS earlier Windows versions not suitable Broadband access for residence modem adds significant delay High-speed switched LANs for businesses  only feasible since mid-1990’s

Total high-speed lines FCC, 2004

DSL usage DSL Forum, Sept. 2004

DSL penetration DSL Forum, Sept. 2004

Who provides VoIP service? voice service provider (Vonage, Lingo, Packet8) cable providers DSL (ILEC) long-distance carrier (e.g., AT&T, MCI) service + gateways + IP network service + gateways service + gateways + IP network + access

Motivations for VoIP access fee taxes monopoly rents local-loop access separate wiring plant cheaper services (caller ID, etc.) higher network efficiency better voice quality possible user-defined services video and app. sharing integration of presence abundance of identifiers mobility media encryption signaling encryption user authentication financial servicessecurity

VoIP models: PBX LAN IP enterprise VoIP gateway call server proxy server “softswitch” analog telephone adapter

VoIP models: IP Centrex LAN IP enterprise or residence service provider

Some differences: VoIP vs. PSTN Separate signaling from media data path But, unlike SS7, same network  lower call setup delay Avoid CTI complexity of "remote control" Mobile and wireline very similar Any media as session: any media quality (e.g., TV and radio circuits) interactive games No need for telephone company voice service provider (RTP, SIP) ISP (IP, DHCP, DNS) dark fiber provider Yahoo MCI NYSERNET

VoIP components Re-uses whole Internet protocol architecture and transmission infrastructure IP, UDP for transport TLS and S/MIME for security HTTP for configuration SIP/SDP H.248 MGCP H.323 signaling ENUM H.350 directories RTP transport provide URI provide destination address codecs (G.7xx, H.26x) 

SIP trapezoid outbound proxy registrar 1 st request 2 nd, 3 rd, … request voice traffic RTP destination proxy (identified by SIP URI domain)

Example SIP phones about $85

PSTN vs. Internet Telephony Signaling & Media Signaling Media PSTN: Internet telephony: China Belgian customer, currently visiting US Australia

SIP as service enabler Rendezvous protocol lets users find each other by only knowing a permanent identifier Mobility enabler: personal mobility one person, multiple terminals terminal mobility one terminal, multiple IP addresses session mobility one user, multiple terminals in sequence or in parallel service mobility services move with user

Changes caused by VoIP Access independence: single-function network to voice-over-any-network separation of transport and services Transition from “polling” service (try until user happens to be available) to “presence” service Voice special  voice just one media among many

(Early) Adulthood “fully developed and mature” Not quite yet, but no longer a teenager probably need another 6 years to be grown up… Responsibilities: Dealing with elderly relatives  POTS Financial issues  payments, RADIUS Family emergencies  911

Emerging technologies Core VoIP technology largely finished deployment largely due to cost savings, not new services toll and fee bypass integrated infrastructure (LAN & WAN) extend “PBX” reach to home and branch offices Presence  from “polling” to “status report” special case of event notification events as common infrastructure for services location-based services Integration of IM and VoIP often used in same conference (side channel) IM as initiator of real-time voice/video

Near future: Location-based services Finding services based on location physical services (stores, restaurants, ATMs, …) electronic services (media I/O, printer, display, …) not covered here Using location to improve (network) services communication incoming communications changes based on where I am configuration devices in room adapt to their current users awareness others are (selectively) made aware of my location security proximity grants temporary access to local resources

Location-based IM & presence

User service creation Tailor a shared infrastructure to individual users traditionally, only vendors (and sometimes carriers) learn from web models not one “killer application” grass-roots applications not foreseen by carriers programmer, carrier end user network servers SIP servlets, sip-cgi CPL end systemVoiceXMLVoiceXML (voice), LESS

Near future: Multimedia Wideband audio “better than phone quality”  lectures, discussions, speaker phone better codecs  same bandwidth as existing NB codecs Video phone itself remains niche application given low incremental cost, may be viable useful for sign language Video for group meetings capture whiteboard Shared applications (WebEx, etc.) still requires standardization Instant messaging side channel Better means of coordination (floor control) wideband audio

Near future: VoIP over WiFi Not fundamentally different from landline VoIP combination cellular + WiFi = wide-area + “cordless” phone Small packet sizes make VoIP over WiFi far less efficient than nominal data rate Hand-off delay between different base stations  interruptions  CU modified hand-off algorithm Delay jitter with high loads  new scheduling algorithms L3 hand-off across different network types

Challenge: Global interconnect Currently, each VoIP “network” largely isolated interconnect via PSTN even if both endpoints are on IP interconnect via few peering points even if neighbors Long-term solution: ENUM DNS listing administration appears difficult Short-term for pure-IP (FWD, etc.): special number prefixes GW VSP A Enterprise B

Challenge: CALEA (lawful intercept) Existing models assume congruence of signaling and voice flows Challenges: voice service providers outside the US signaling-only providers or no voice providers end-to-end media and signaling encryption (Skype, SRTP)  Intercept IP traffic, not application Assume that long-term, all application traffic (except browsing of public web pages) will have strong encryption

Challenge: User-programmable and context-aware services Universal reachability  control reachability in time and space by context allow callee to decide reachability (defer and decline communication) choose appropriate media (text, automated data response) timeCall Processing Language (CPL), sip-cgi, … capabilitiescaller preferences locationlocation-based call routing location events activity/availabilitypresence sensor data (mood, bio)not yet, but similar to location data

Challenge: Spam prevention Currently, telemarketing restricted to in-country calling With VoIP, few economical constraints on automated calls from anywhere Also, SPIM (instant message spam) Cannot use content-based filtering Public key infrastructure (PKI) for individual verification has never scaled provide domain-level verification (~ TLS) in signaling blacklists and whitelists may depend on local domain policies for user verification reputation-based systems

Challenge: Service reliability “ QoS”  service availability loss of network connection loss of infrastructure components DNS, SIP servers, DHCP, … bursts of packet loss  cannot be repaired at end system sustained high packet loss (> 10-15%) Current service availability probably around 99.5% realistic goal: 99.9% (10h/year) to 99.99% (1h/year)

Challenge: Emergency calling 911 calling system largely unchanged since 1980s call routing to appropriate destination deliver caller location information Fundamental differences for VoIP: may not have phone number may be no “phone company” identifier does not describe location location determination more difficult Also use solution for “311” and other location-based call routing systems

Three stages to VoIP 911 spec. available? use 10- digit admin. number? mobilitycallback number to PSAP? caller location to PSAP? PSAP modification ALI (DB) modification new services I1 nowallowedstationaryno none I2 Dec. 2004nostationary nomadic yes no (8 or 10 digit) updatenone I3 late 2004nostationary nomadic mobile yes IP-enabledALI not needed MSAG replaced by DNS location in- band GNP multimedia international calls

* gray features in progress. Prototype

SIPc client receives callsGeoLynx software displays caller location Call taker setup

Conclusion VoIP on cusp of widespread deployment: commercial-grade VoIP products mature standards for key components widespread broadband availability better Internet QoS Focus may shift from “bare-bones” VoIP to context-aware communications Operational and technical challenges 911, CALEA, network reliability, user-defined services, multimedia Thus, roughly where PSTN was in 1980