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When will the telephone network disappear? PowerPoint PPT Presentation

When will the telephone network disappear? Henning Schulzrinne Columbia University June 2002 Overview What is Internet telephony? Why Internet telephony? When? How to transition to IP telephony? What remains to be done? What is Internet telephony?

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When will the telephone network disappear l.jpg

When will the telephone network disappear?

Henning Schulzrinne

Columbia University

June 2002


Overview l.jpg

Overview

  • What is Internet telephony?

  • Why Internet telephony?

  • When?

  • How to transition to IP telephony?

  • What remains to be done?


What is internet telephony l.jpg

What is Internet telephony?

  • Using Internet protocols to transmit voice in real-time

    • 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 VoIP, IP telephony

  • related voice-over-packet: ATM, FR, MPLS


What is internet telephony4 l.jpg

What is Internet telephony?

PSTN phones

soft phones

Ethernet phones


Voip protocols l.jpg

VoIP protocols

  • Mostly reuse existing protocols, from IP to LDAP

  • RTP for transporting audio and video

  • SIP for setting up sessions (calls)

    • web-like protocol for negotiation and user location

  • TRIP for finding gateways


Why internet telephony l.jpg

Why Internet telephony?

  • Residential user perspective

    • cheaper international calls

      • U.S. to India, China, Mexico

    • video calls to relatives

    • integration with IM and presence – no phone tag

    • (packaged) programmable services

    • single number, regardless of medium:

      • 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 telephony7 l.jpg

Why Internet telephony?

  • Business user perspective

    • no feature set differences between large and small businesses

      • automatic call distribution (VoiceXML)

    • programmable phone services

      • 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 CAT5 Ethernet wiring plant

    • PBX maintenance costs

    • PBX growth limits


Why internet telephony8 l.jpg

Why Internet telephony?

  • Carrier/ISP perspective

    • classical switches stagnant

    • but still expensive

      • 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

      • mobile = wireline infrastructure


Why should carriers worry l.jpg

Why should carriers worry?

  • Application-specific infrastructure  content-neutral bandwidth delivery

    • 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 voip vs pstn l.jpg

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


Differences voip vs pstn l.jpg

Differences VoIP vs. PSTN

  • "Switches" (= SIP proxy servers) are service-transparent:

    • dialog transparency

    • media transparency

    • security transparency

    • topology transparency

    • functional transparency

  • May not be true in 3GPP


When will it happen l.jpg

When will it happen?

  • Took much longer than anticipated in 1995:

    • standards (signaling) not really ready until this year

    • not just a protocol, but a whole industry and infrastructure – eco system:

      • OSS

      • billing

      • testing

      • features: conferences, voicemail


Technology evolution of pstn l.jpg

Technology evolution of PSTN

SS7: 1987-1997


When will it happen14 l.jpg

When will it happen?

  • Not too soon by traditional phone companies:

    • Billions of €/$ deployed infrastructure

      • $41 billion (est.) for local switches in U.S.

    • debt-laden carriers

    • U.S. CLECs killed by monopolies

  • But others:

    • (business) ISPs

    • cable TV companies


Status in 2002 l.jpg

Status in 2002

  • 2000: 6b minutes wholesale, 15b minutes retail

  • 2001: 10b worldwide – 6% of traffic (only phone-to-phone)

  • up to 30% of U.S.-China/India/Mexico traffic

  • e.g., net2phone: 341m min/quarter


Where are we l.jpg

Where are we?

  • Not quite what we had in mind

    • initially, SIP 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

      • “can’t get new services if other end is POTS’’  “why use VoIP if I can’t get new services”


Where are we17 l.jpg

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


How to transition l.jpg

How to transition?

  • Several directions at once:

    • inside out:

      • inter-PBX trunks

      • PSTN backbones

      • signaling links

    • outside in:

      • PBX and IP phones

      • PC-based soft phones


How to transition19 l.jpg

How to transition?

  • 3GPP and 3GPP2 have chosen SIP and packet audio/video as the technology for 3G Internet multimedia subsystem (IMS)

    • mostly "real" SIP, with extensions

    • walled garden mentality – trying to prevent users from choosing other SIP carriers


What remains to be done l.jpg

What remains to be done?

  • 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 l.jpg

Challenges: NATs and firewalls

  • NATs and firewalls reduce Internet to web and email service

    • 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 l.jpg

Challenges: NAT and firewalls

  • Solutions:

    • longer term: IPv6

    • longer term: MIDCOM for firewall control?

      • control by border proxy?

    • short term:

      • NAT: STUN and SHIPWORM

      • send packet to external server

      • server returns external address, port

      • use that address for inbound UDP packets


Naming and addressing l.jpg

Naming and addressing

  • Users will have three types of identifiers, several of each:

    • phone numbers – random # within city  random # within country for mobile

      • easy to transcribe & key in on 12-button phones

      • hard to remember

      • portability across carriers iffy

    • email addresses = SIP URIs

      • [email protected], sip:[email protected]

      • 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 addressing24 l.jpg

Naming and addressing

  • Web URLs – http://www.cs.columbia.edu/~hgs

    • personal domains?

    • mostly easy to find (Google), but hard to type


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Naming and addressing

  • Have any one of three, need others


Naming and addressing26 l.jpg

Naming and addressing

  • ENUM: translate +358 8 883 9111 to 1.1.1.9.3.8.8.8.8.5.3.e164.arpa and look up

  • SIP-to-x: Return on OPTIONS or 302

  • Web-to-x: defined business card rather than text search


Voip applications l.jpg

VoIP applications

  • Trunk replacements between PBXs

    • Ethernet trunk cards for PBXs

    • T1/E1 gateways

  • IP centrex – outsourcing the gateway

    • Denwa, Worldcom

  • Enterprise telephony

    • Cisco Avvid, 3Com, Mitel, ...

  • Consumer calling cards (phone-to-phone)

    • net2phone, iConnectHere (deltathree), ...

  • PC-to-phone, PC-to-PC

    • net2phone, dialpad, iConnectHere, mediaring, ...


Challenges qos l.jpg

Challenges: QoS

  • Bottlenecks: access and interchanges

  • Backbones: e.g., Worldcom Jan. 2002

    • 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 qos29 l.jpg

Challenges: QoS

  • Not lack of protocols – RSVP, diff-serv

  • Lack of policy mechanisms and complexity

    • which traffic is more important?

    • how to authenticate users?

    • cross-domain authentication

    • may need for access only – bidirectional traffic

    • DiffServ: need agreed-upon code points

  • NSIS WG in IETF – currently, requirements only


Challenges security l.jpg

Challenges: Security

  • PSTN model of restricted access systems  cryptographic security

  • Dumb end systems  PCs with a handset

  • Objectives:

    • identification for access control & billing

    • phone/IM spam control (black/white lists)

    • call routing

    • privacy


Sip security l.jpg

SIP security

  • 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 l.jpg

Challenges: service creation

  • Can’t win by (just) recreating PSTN services

  • Programmable services:

    • equipment vendors, operators: JAIN

    • local sysadmin, vertical markets: sip-cgi

    • proxy-based call routing: CPL

    • voice-based control: VoiceXML


Emergency calls l.jpg

Emergency calls

  • Opportunity for enhanced services:

    • video, biometrics, IM

  • Finding the right emergency call center (PSAP)

    • VoIP admin domain may span multiple 911 calling areas

  • Common emergency address

  • User location

    • GPS doesn’t work indoors

    • phones can move easily – IP address does not help


Emergency calls35 l.jpg

Emergency calls

common emergency identifier: [email protected]

EPAD

REGISTER sip:sos

Location: 07605

302 Moved

Contact: sip:[email protected]

Contact: tel:+1-201-911-1234

SIP proxy

INVITE sip:sos

Location: 07605

INVITE sip:[email protected]

Location: 07605


Scaling and redundancy l.jpg

Scaling and redundancy

  • Single host can handle 10-100 calls + registrations/second  18,000-180,000 users

    • 1 call, 1 registration/hour

  • Conference server: about 50 small conferences or large conference with 100 users

  • Reliability: single expensive 99.999% system  two cheap 99.7% systems

    • typical reliability of good ISP: 99.5%  dual-homing

  • For larger system and redundancy, replicate proxy server


Scaling and redundancy37 l.jpg

Scaling and redundancy

  • DNS SRV records allow static load balancing and fail-over

    • 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

    • can separate REGISTER

    • make rest read-only


Reliability power l.jpg

Reliability: power

  • In US, typically about 1.5-4 hours/year of power outage (SAIDI, 99.95%)

    • plus ~3 short (< 5 min) outages (MAIFIe)

  • Alternatives:

    • cell phone 

    • UPS in Ethernet switches

    • Ethernet power on spare pairs


Large system l.jpg

Large system

stateless proxies

sip1.example.com

a1.example.com

a2.example.com

sip2.example.com

sip:[email protected]

b1.example.com

sip:[email protected]

sip3.example.com

b2.example.com

_sip._udp SRV 0 0 b1.example.com

0 0 b2.example.com

_sip._udp SRV 0 0 sip1.example.com

0 0 sip2.example.com

0 0 sip3.example.com


Migration strategy l.jpg

Migration strategy

  • Add IP phones to existing PBX or Centrex system – PBX as gateway

    • Initial investment: $2k 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 l.jpg

Example: Columbia Dept. of CS

  • About 100 analog phones on small PBX

    • DID

    • no voicemail

  • T1 to local carrier

  • Added small gateway and T1 trunk

  • Call to 7134 becomes sip:[email protected]

  • Ethernet phones, soft phones and conference room

  • CINEMA set of servers, running on 1U rackmount server


Cinema components l.jpg

CINEMA components

Cisco 7960

MySQL

sipconf

rtspd

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

Nortel

Cisco

Meridian

2600

VoiceXML

PBX

server

T1

T1

SIP

sipvxml

PhoneJack interface

sipc

SIP-H.323

converter

sip-h323


Sip doesn t have to be in a phone l.jpg

SIP doesn’t have to be in a phone


Event notification l.jpg

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


Event notification45 l.jpg

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


Sip event notification l.jpg

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


Controlling devices l.jpg

Controlling devices


Conclusion l.jpg

Conclusion

  • Transition to VoIP will take much longer than anticipated  replacement service

    • digital telephone took 20 years...

    • 3G (UMTS R5) as driver?

  • combination with IM, presence, event notification

  • Emphasis protocols operational infrastructure

    • security

    • service creation

    • PSTN interworking


For more information l.jpg

For more information...

  • SIP: http://www.cs.columbia.edu/sip

  • CINEMA: http://www.cs.columbia.edu/IRT/cinema


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