When will the telephone network disappear Henning Schulzrinne

When will the telephone network disappear? Henning Schulzrinne Columbia University June 2002

Overview n n n What is Internet telephony? Why Internet telephony? When? How to transition to IP telephony? What remains to be done?

What is Internet telephony? n Using Internet protocols to transmit voice in real-time n n n but multimedia (and Internet radio and TV) is almost the same every telephone can become a "broadcaster" not necessarily public Internet similar to streaming media, but typically human on both ends also known as Vo. IP, IP telephony related voice-over-packet: ATM, FR, MPLS

What is Internet telephony? PSTN phones soft phones Ethernet phones

Vo. IP protocols n n n Mostly reuse existing protocols, from IP to LDAP RTP for transporting audio and video SIP for setting up sessions (calls) n n web-like protocol for negotiation and user location TRIP for finding gateways

Why Internet telephony? n Residential user perspective n cheaper international calls n n n video calls to relatives integration with IM and presence – no phone tag (packaged) programmable services single number, regardless of medium: n n n U. S. to India, China, Mexico mobile phone home phone office phone easy identifier portability multiple lines cheaper via cable modem, DSL video monitoring don't pay for connect time

Why Internet telephony? n Business user perspective n no feature set differences between large and small businesses n n programmable phone services n n n automatic call distribution (Voice. XML) like web programming (sip-cgi, CPL, servlets) every company own web page every company own phone services easy integration of email, web, IM, databases single CAT 5 Ethernet wiring plant PBX maintenance costs PBX growth limits

Why Internet telephony? n Carrier/ISP perspective n n classical switches stagnant but still expensive n n n Ethernet switch: $0. 04/"circuit" PBX: $218/circuit Local telephone switch: $270/circuit avoid separate management infrastructure for voice new PSTN services hard to deploy avoid dog-legged routing for mobile calls n mobile = wireline infrastructure

Why should carriers worry? n Application-specific infrastructure content-neutral bandwidth delivery n n n GPRS: $4 -10/MB SMS: > $62. 50/MB voice (mobile and landline): $1. 70/MB anybody can offer phone service only need to handle signaling, not media traffic no regulatory hurdles

Some differences: Vo. IP vs. PSTN n n n Separate signaling from media data path But, unlike SS 7, same network lower call setup delay Avoid CTI complexity of "remote control" Mobile and wireline very similar Any media as session: n n any media quality (e. g. , TV and radio circuits) interactive games

Differences Vo. IP vs. PSTN n "Switches" (= SIP proxy servers) are service-transparent: n n n dialog transparency media transparency security transparency topology transparency functional transparency May not be true in 3 GPP

When will it happen? n Took much longer than anticipated in 1995: n n standards (signaling) not really ready until this year not just a protocol, but a whole industry and infrastructure – eco system: n n OSS billing testing features: conferences, voicemail

Technology evolution of PSTN SS 7: 1987 -1997

When will it happen? n Not too soon by traditional phone companies: n Billions of €/$ deployed infrastructure n n $41 billion (est. ) for local switches in U. S. debt-laden carriers U. S. CLECs killed by monopolies But others: n n (business) ISPs cable TV companies

Status in 2002 n n 2000: 6 b minutes wholesale, 15 b minutes retail 2001: 10 b worldwide – 6% of traffic (only phone-to-phone) up to 30% of U. S. -China/India/Mexico traffic e. g. , net 2 phone: 341 m min/quarter

Where are we? n Not quite what we had in mind n initially, SIP for initiating multicast conferencing n n in progress since 1992 still small niche even the IAB and IESG meet by POTS conference… then Vo. IP n n n written-off equipment (circuit-switched) vs. new equipment (Vo. IP) bandwidth is (mostly) not the problem “can’t get new services if other end is POTS’’ “why use Vo. IP if I can’t get new services”

Where are we? n Vo. IP: avoiding the installed base issue n n n cable modems – lifeline service 3 GPP – vaporware? Finally, IM/presence and events n n n probably, first major application offers real advantage: interoperable IM also, new service

How to transition? n Several directions at once: n inside out: n n inter-PBX trunks PSTN backbones signaling links outside in: n n PBX and IP phones PC-based soft phones

How to transition? n 3 GPP and 3 GPP 2 have chosen SIP and packet audio/video as the technology for 3 G Internet multimedia subsystem (IMS) n n mostly "real" SIP, with extensions walled garden mentality – trying to prevent users from choosing other SIP carriers

What remains to be done? n n n n n NAT and firewall traversal cheaper end systems naming and addressing quality of service reliability security emergency (112) features full IM/presence architecture conferencing

Challenges: NATs and firewalls n NATs and firewalls reduce Internet to web and email service n n n firewall, NAT: no inbound connections NAT: no externally usable address NAT: many different versions binding duration lack of permanent address (e. g. , DHCP) not a problem SIP address binding misperception: NAT = security

Challenges: NAT and firewalls n Solutions: n n longer term: IPv 6 longer term: MIDCOM for firewall control? n n control by border proxy? short term: n n NAT: STUN and SHIPWORM send packet to external server returns external address, port use that address for inbound UDP packets

Naming and addressing n Users will have three types of identifiers, several of each: n phone numbers – random # within city random # within country for mobile n n easy to transcribe & key in on 12 -button phones hard to remember portability across carriers iffy email addresses = SIP URIs n n user@domain, sip: user@domain portable if own domain ($20/year) or separate from carrier a pain for existing devices but need better alpha input in any event

Naming and addressing n Web URLs – http: //www. cs. columbia. edu/~hgs n n personal domains? mostly easy to find (Google), but hard to type

Naming and addressing n Have any one of three, need others phone email/SIP web -- ENUM -- LDAP? SIP -- email/SIP LDAP? SIP web tel: sip:

Naming and addressing n n n ENUM: translate +358 8 883 9111 to 1. 1. 1. 9. 3. 8. 8. 5. 3. e 164. arpa and look up SIP-to-x: Return on OPTIONS or 302 Web-to-x: defined business card rather than text search

Vo. IP applications n Trunk replacements between PBXs n n n IP centrex – outsourcing the gateway n n Cisco Avvid, 3 Com, Mitel, . . . Consumer calling cards (phone-to-phone) n n Denwa, Worldcom Enterprise telephony n n Ethernet trunk cards for PBXs T 1/E 1 gateways net 2 phone, i. Connect. Here (deltathree), . . . PC-to-phone, PC-to-PC n net 2 phone, dialpad, i. Connect. Here, mediaring, . . .

Challenges: Qo. S n n Bottlenecks: access and interchanges Backbones: e. g. , Worldcom Jan. 2002 n n n 50 ms US, 79 ms transatlantic RTT 0. 067% US, 0. 042% transatlantic packet loss Keynote 2/2002: “almost all had error rates less then 0. 25%” (but some up to 1%) LANs: generally, less than 0. 1% loss, but beware of hubs voice can tolerate ~10% random loss averages are misleading – impairments are bursty really reliability problem

Challenges: Qo. S n n Not lack of protocols – RSVP, diff-serv Lack of policy mechanisms and complexity n n n which traffic is more important? how to authenticate users? cross-domain authentication may need for access only – bidirectional traffic Diff. Serv: need agreed-upon code points NSIS WG in IETF – currently, requirements only

Challenges: Security n n n PSTN model of restricted access systems cryptographic security Dumb end systems PCs with a handset Objectives: n n identification for access control & billing phone/IM spam control (black/white lists) call routing privacy

SIP security n n Bar is higher than for email – telephone expectations (albeit wrong) Potential for nuisance – phone spam at 2 am Safety – attacker can prevent emergency calls Denial of service attacks – a billion more sources of traffic

Challenges: service creation n n Can’t win by (just) recreating PSTN services Programmable services: n n equipment vendors, operators: JAIN local sysadmin, vertical markets: sip-cgi proxy-based call routing: CPL voice-based control: Voice. XML

Emergency calls n Opportunity for enhanced services: n n Finding the right emergency call center (PSAP) n n n video, biometrics, IM Vo. IP admin domain may span multiple 911 calling areas Common emergency address User location n n GPS doesn’t work indoors phones can move easily – IP address does not help

Emergency calls common emergency identifier: sos@domain EPAD REGISTER sip: sos 302 Moved Contact: sip: sos@psap. leonia. nj. us Contact: tel: +1 -201 -911 -1234 Location: 07605 INVITE sip: sos Location: 07605 SIP proxy INVITE sip: sos@psap. leonia. nj. us Location: 07605

Scaling and redundancy n Single host can handle 10 -100 calls + registrations/second 18, 000 -180, 000 users n n n Conference server: about 50 small conferences or large conference with 100 users Reliability: single expensive 99. 999% system two cheap 99. 7% systems n n 1 call, 1 registration/hour typical reliability of good ISP: 99. 5% dualhoming For larger system and redundancy, replicate proxy server

Scaling and redundancy n DNS SRV records allow static load balancing and fail-over n n n but failed systems increase call setup delay can also use IP address “stealing” to mask failed systems, as long as load < 50% Still need common database n n can separate REGISTER make rest read-only

Reliability: power n In US, typically about 1. 5 -4 hours/year of power outage (SAIDI, 99. 95%) n n plus ~3 short (< 5 min) outages (MAIFIe) Alternatives: n n n cell phone UPS in Ethernet switches Ethernet power on spare pairs

Large system stateless proxies sip 1. example. com a 2. example. com sip: bob@example. com sip: bob@b. example. com b 1. example. com sip 3. example. com b 2. example. com _sip. _udp SRV 0 0 sip 1. example. com 0 0 sip 2. example. com 0 0 sip 3. example. com _sip. _udp SRV 0 0 b 1. example. com 0 0 b 2. example. com

Migration strategy Add IP phones to existing PBX or Centrex system – PBX as gateway 1. n 2. 3. 4. Initial investment: $2 k for gateway Add multimedia capabilities: PCs, dedicated video servers “Reverse” PBX: replace PSTN connection with SIP/IP connection to carrier Retire PSTN phones

Example: Columbia Dept. of CS n About 100 analog phones on small PBX n n n n DID no voicemail T 1 to local carrier Added small gateway and T 1 trunk Call to 7134 becomes sip: 7134@cs Ethernet phones, soft phones and conference room CINEMA set of servers, running on 1 U rackmount server

CINEMA components Cisco 7960 My. SQL sipconf user database LDAP server conferencing server (MCU) sipd proxy/redirect server rtspd RTSP media server RTSP unified messaging server Pingtel Nortel Meridian PBX T 1 sipum Cisco 2600 T 1 Voice. XML server SIP sipvxml Phone. Jack interface sipc SIP-H. 323 converter sip-h 323 plug'n'sip wireless 802. 11 b

SIP doesn’t have to be in a phone

Event notification n n Missing new service in the Internet Existing services: n n n get & put data, remote procedure call: HTTP/SOAP (ftp) asynchronous delivery with delayed pickup: SMTP (+ POP, IMAP) Do not address asynchronous (triggered) + immediate

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

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

Controlling devices

Conclusion n Transition to Vo. IP will take much longer than anticipated replacement service n n digital telephone took 20 years. . . 3 G (UMTS R 5) as driver? combination with IM, presence, event notification Emphasis protocols operational infrastructure n n n security service creation PSTN interworking

For more information. . . n n SIP: http: //www. cs. columbia. edu/sip CINEMA: http: //www. cs. columbia. edu/IRT/cinema