Internet Telephony: VoIP, SIP & more

1. Internet Telephony: VoIP, SIP & more Shivkumar Kalyanaraman : “shiv rpi” Adapted from slides of Henning Schulzrinne, Doug Moeller

2. Overview • Telephony: history and evolution • IP Telephony: What, Why & Where? • Adding interactive multimedia to the web • Being able to do telephony on IP with a variety of devices • Consumer & business markets • Key element of convergence in carrier infrastructure • Basic IP telephony model • Protocols: SIP, H.323, RTP, Coding schemes, Megaco • Future: Invisible IP telephony and control of appliances

3. What is VoIP? Why VoIP?Where is VoIP Today?

4. VoIP = “Voice over IP” Transmission of telephony services via IP infrastructure => need history/concepts reg. both “telephony” (or “voice”) and “IP” Complements or replaces other Voice-over-data architecture Voice-over-TDM Voice-over-Frame-Relay Voice-over-ATM First proprietary IP Telephony implementations in 1994, VoIP-related standards available 1996 Buzzwords related to VoIP: H.323 v2, SIP, MEGACO/H.248, Sigtrans What is VoIP?

5. What is VoIP? Protocol Soup SDP MGCP SGCP SIP H.323 Megaco IPDC MDCP “The nice thing about standards is that you have so many to choose from; furthermore, if you do not like any of them, you can just wait for next year’s model.” [Tanenbaum] Q.SIG Sigtrans H.GCP VPIM H.245

6. Telephony over IP standards bodies • ITU - International Telecommunication Union • http://www.itu.org • IETF - Internet Engineering Task Force. • http://www.ietf.org • ETSI - European Telecommunications Standards Institute • http://www.etsi.org/tiphon • ANSI - American National Standards Institute • http://www.ansi.org • TIA - Telecommunications Industry Association • http://www.tiaonline.org • IEEE - Institute for Electrical and Electronics Engineers • http://www.ieee.org

7. Why VoIP? Telephony: Mature Industry AT&T Divestiture

8. Why VoIP: Price/call plummeting due to overcapacity AT&T Divestiture 1996 deregulation

9. Relevant Telecom Industry Trends • 1984: AT&T breakup: baby bells vs long distance carriers • 1996: Telecom deregulation, Internet takeoff • Late 1990s: explosion of fiber capacity in long-distance + many new carriers • Long-distance prices plummet • Despite internet, the last-mile capacity did not grow fast enough • 2000s: shakeout & consolidation in developed countries • Wireless substitution in last mile => cell phone instead of land-lines • Developing countries leap frog to cell phones • 3G, WiMax => broadband, VoIP & mobility • Broadband rollouts happening slowly, but picking up steam now. • Cable offering converged & bundled services: • digital cable, VoIP, video • Recent mergers: AT&T (long-distance & data network provider) bought by SBC (baby bell); Verizon/Qwest vs MCI saga…

10. Why VoIP ? Data vs Voice Traffic Note: quantity  quality  value-added Interactive svcs (phone, cell, sms) still dominate on a $$-per-Mbps basis Infrastructure convergence: Since we are building future networks for data, can we slowly junk the voice infrastructure and move over to IP?

11. Trends: Total Phone vs Data Revenues

12. Motivations and drivers Class-4/5 switches bulky, expensive. Incentive to switch to cheaper easily managed IP PSTN Class 4 switch Class 5 switch Voice Class 5 switch Users Users ISDN Switch H.323 gateway Data Initial gateway between PSTN and Internet was H.323. Gateway did signaling, call control, translation in one box. Not scalable. Packet networks

13. Voice Over IP Marketplace Drivers • Rate arbitrage declining but still has importance as cost driver • TDM origination and termination with IP transport in the WAN • International settlement and domestic access cost avoidance • Enterprises seeking to save on intra-company calls and faxes on converged network • Emergence of native IP origination environments • IP PBX, IP Phones, Soft Phones, Multimedia on the LAN • 3G Wireless, Broadband Networks • Companies: web-based call centers/web callback/e-commerce with IP Enablement • New network-based IP features and services • Hosted IP PBX/IP Centrex , Unified Messaging, Multimedia Conferencing • Presence: Mobility, Follow me, Teleworker, Voice Portal Services, WiFi • Technology maturing with open standards for easier, faster innovation • Converging Local, long-distance (LD) and data services

14. North America Rest of the World North America Rest of the World VoIP Volumes Are Accelerating While Adoption of Applications is Growing M of Minutes VoIP VPN Traffic Enterprise Adoption of VoIP / IPT Applications Respondents M ofMinutes Virtual PBX + Managed IP PBX traffic Source: Giga Group, "Next Generation IP Telephony Applications Deliver Strategic Business Value", October 20, 2003 • VoIP VPNs will continue to be driven by increased IPT deployments in larger enterprises, coupled with economic benefits accruing, especially for MNCs • IPT Deployments are the leading edge market driver for the development of converged LANs and WANs Source: Probe Research Inc.: Reaching the Big Guys + Global Enterprise Forecast. September 2002

15. Business Case Justification Based on Investment Protection Percentage IP Phones Performing Functions Other Than POTS Business Case Justification Based on Cost Savings Business Case Justification Based on Business Value V2 Apps V3 Apps V1 Apps 2002 2003 2004 2005 2006 2007 2008 V1 Apps - e.g. IP-PBX, Basic Call Functions, Branch offices, Toll-bypass V2 Apps - e.g. Call Center Functions, Messaging, Administration Tools and Reports V3 Apps - e.g. Unified Communications, Application Integration With Communications Gartner Group, Sept. 16, 2003 Drivers Are Evolving From Cost Savings to Added Business Value… Cost Savings • Toll By-Pass • Effective Use of Bandwidth • Personnel / Staffing Efficiencies • Less Expensive Moves, Adds Changes • Convergence / Consolidation • Decreased Capital • Upgrading to an IP PBX Increased Investment Protection • Contact Center Functions • Future Proofing Infrastructure • Leveraging embedded infrastructure with a phased roll-out • Networking Expertise for Integration From Concept to Deployment Optimized Business Value • Services over IP • Consistent Client / User Experience • Integrated Infrastructure • End-to-End Interoperability

16. Cost reduction: Toll by-pass WAN Cost Reduction Lowered Infrastructure Costs Operational Improvement: Simplification of Routing Administration LAN/Campus Integration Policy and Directory Consolidation Business Tool Integration: Voice mail, email and fax mail integration Mobility enabled by IP networking Web + Overseas Call Centers Collaborative applications New Integrated Applications Summary: Why VoIP? 3Cs: “Convergence” & “Costs” & “Competition”

17. Where is VoIP? Consumer VoIP Markets • Convergence & Competition • Vonage: pure VoIP CLEC (300K subscribers) • Cable companies: • Eg: Time Warner (220K subscribers and signing on 10K per week (end of 2004)): • Bundled with digital cable services • Skype (computer-computer p2p VoIP): tens of millions… • Also has a WiFi service & a product co-developed by Motorola (over 3G networks) • Long-distance providers: AT&T CallVantage • Local (ILECs): Verizon • Future: convergence of VoIP + WiMax (802.16) as a open low-cost competitor to 3G wireless (closed system) • Combines: broadband Internet, mobility and VoIP

18. Consumer VoIP over broadband Broadband Infrastructure Residential Media Gateway Media Gateway Controller Traditional phone Signaling and media gateways To reach PSTN or other networks

19. Consumer VoIP at home with cable PacketCable standard with DOCSIS 1.1 access infrastructure Call Management Server Media Gateway Cable Modem Term. Sys. MGC Signaling Gateway Cable Modem MTA (Media Terminal Adapter) Other access mechanisms will similarly hand over to an MGC

20. Consumer VoIP: AT&T CallVantage • New consumer services: • Personal conferencing: earlier available to businesses only • Prepaid Calling cards offering personal conferencing • Portable TA (terminal adaptor): can plug into any ethernet jack or WiFi (eg: many hotels providing free internet) • Universal messaging: voice messages in email • LocateMe, • Do-Not-Disturb, • Unified Portal

21. Skype: p2p VoIP over Internet • Skype is entirely peer-to-peer and is equivalent to two H.323 terminals or 2 SIP terminals talking to each other • Provides a namespace • Efficient coding of voice packets • Instant messaging with voice • Uses Kazaa-like p2p directory + secure authentication (login server) and e2e encryption

22. VoIP over Wireless • Cellular networks with 2.5G and 3G have packet services • 1xRTT on 2.5 G • EV-DO on 3G • The voice on these networks is circuit switched voice… • However, … • Combined with bluetooth or USB interfaces, a PC-based VoIP software can do VoIP anywhere there is cellular coverage. • Or Cellphone can be a SIP terminal • Near Future: VoIP over WiMax (802.16) and WiFi (802.11) networks

23. Enterprise: Private Branch Exchange (PBX) Post-divestiture phenomenon... 7040 212-8538080 External line 7041 Telephone switch Corporate/Campus Private Branch Exchange Another switch 7042 7043 Corporate/Campus LAN Internet

24. Enterprise VoIP: Yesterday’s networks Circuit Switched Networks (Voice) CO PBX PBX CO CO Headquarters Branch Offices Router Router Router Router Router Packet Switched Networks (IP)

25. Enterprise VoIP: Today’s networksToll by-pass Circuit Switched Networks (Voice) PBX CO PBX CO Headquarters CO Branch Offices Router Router Router Router Router Packet Switched Networks (IP)

26. Enterprise VoIP:Tomorrow’s networksUnified/Converged Networks CO CO Legacy PSTN Router Router Router Router Router Unified Networks (Voice over IP) Headquarters Branch Offices

27. PSTN H.323 endpoints SIP endpoints MGCP endpoints AT&T’s Integrated Infrastructure Supports Multiple Endpoints, Access Technologies and Application Services Voice Applications: IP Centrex, IP Call Center and Distant Worker • VoIP infrastructure is converged onto a single IP/ MPLS network • Open standards architecture based on SIP protocol • Call Control Element manages all SIP signaling within our core network • Access Agnostic: TDM, ATM, Frame, MIS, IP Enabled Frame and EVPN • Border Elements: “translate” the multiple protocols into SIP, provide compression and security • Provides secure, integrated voice / data / video access • Flexibility to support future applications AT&T Call Control Element Common VoIP Connectivity Layer NG Border Elements SIP Border Elements H.323 Border Elements MGCP Border Elements IP/MPLS Converged Network

28. VoIP Network UtilitiesEnsure Seamless Operations • Outbound Call • IP to Circuit Switched Circuit Switched Network • Inbound Call • Circuit Switched to IP Network Adjunct Customer Records • 800 Call • Circuit Switched to IP Media Server App. Server App. Server Gateway Softswitch • Redirect Call • Circuit Switched to IP IP Network • SDN Call • IP to Circuit Switched

29. IP-enabled circuit switches • PBX with VoIP trunk card • trunk between PBX • Key system or PBX with VoIP line card • for IP phones VoIP Gateway CO Switch

30. Telephony-enabled packet networks • Enterprise Router with telco interfaces • T1/PRI • BRI • Branch office router with telco interfaces • BRI • Analog trunk/line • Analog “dongle” • a few analog lines for fax/phone Central Office Router VoIP Gateway

31. VoFR (Voice over Frame Relay) • FRF.11 standard • Allows for G.711, 729, 728, 726, and 723.1 • Signaling is done by transporting CAS natively or CCS as data • Has support for T.30 Fax, and Dialed Digits natively Router Switch PBX VFRAD VFRAD PBX Switch Switch

32. Voice over Packet: Market Forecast – North America

33. Telephony: History, Review & Trends

34. VoIP: Where Does it Fit in Trends ? • Phase 1: Analog Networks: • Voice carried as analog signal • Phase 2: Digital Networks & the rise of the Internet • Network is digital: analog conversion at end systems • Benefits: [Noise , capacity] • Egs: TDM and T-hierarchy (T1, T3, SONET etc) • Used as the base for the internet & private data networks • Phase 3:Voice-over-X: • Voice over Packets: VoFR, VoIP • Key: Voice moves to a higher layer (from layer 1) • I.e. an app over a frame relay, ATM or IP network • VoIP Sales pitch: Convergence, Choice, Services, Integration with Web applications • [Better chance of convergence compared to earlier attempts: ISDN, B-ISDN]

35. Public Telephony (PSTN) History • 1876 invention of telephone • 1915 first transcontinental telephone (NY–SF) • 1920’s first automatic switches • 1956 TAT-1 transatlantic cable (35 lines) • 1962 digital transmission (T1) • 1965 1ESS analog switch • 1974 Internet packet voice • 1977 4ESS digital switch • 1980s Signaling System #7 (out-of-band) • 1990s Advanced Intelligent Network (AIN)

36. PSTN Evolution Office Switched W/ Hierarchy Full Mesh Office Switched

37. AT&T Telephony Hierarchy Class 1 Class 2 Class 3 Class 4 Class 5 Source: Computer Networks, Andrew S. Tanenbaum

38. PSTN early days 40s-60s • In-band signaling: voice and control channel same • Complex and dedicated hardware • Hard to add new apps like caller-id, 800 calling etc Tandem Office Local Office Local Office User A User B

39. Advanced Intelligent Network • Out-of-band signaling • Introduce adv services like caller-id easily • Reduced wastage of circuits in voice network • Signaling could be over a packet network • E.g. SS7 stack Signaling Network Customer Info for Advanced services Voice Network Local Office User A User B Sometimes also called Intelligent Network, arrival of services other than voice

40. Analog line Central Office (CO) Digital Trunks The PSTN – Architecture • PSTN – Public Switched Telephone Network • Uses digital trunks between Central Office switches (CO) • Uses analog line from phones to CO Analog Digital Analog

41. The PSTN – Digitization • Voice frequency is 100 - 5000 Hz, with the main portion from 300 – 3400 Hz • Nyquist Theorem states that sampling must be done at twice the highest frequency to recreate. 4000 Hz was chosen as the maximum frequency, thus sampling at 8000 Hz • PCM = 8kHz * 8 bits per sample = 64 kbit/s

42. Quantization

43. Companding

44. The PSTN – Digitization • The PCM encoding used in the PSTN is standardized as G.711 by the ITU • Each sample is represented by one byte • The voice signal is companded to improve voice quality at low amplitude levels (Which most conversation is at) • The ITU standards for companding are called A-law and u-law • G.711 A-law is used in Europe • G.711 -law is used in the US and Japan

45. The PSTN – Digital Voice Transmission • The digital trunks between the COs are based upon the T-carrier system, developed in the 1960s • Each frame carries one sample (8 bits) for each 24 channels, plus one framing bit = 193 bits • 193 * 8000 (samples/sec) = 1.544 Mbit/sec = T-1 Channel 1 Channel 2 Framing Bit Channel 3 TDM Channel 1 Channel 2 Channel 3 … Channel 24 … Channel 24 1 D4 Frame

46. The PSTN – Architecture, Switches • PSTN – Public Switched Telephone Network • As the name says, it’s switched… • Each conversation requires a channel switched throughout the network • Circuit setup uses a separate out-of-band intelligent network (SS7) 1. Call is requested 3. Channel is established 2. Call is accepted

47. Legacy Digital Circuit Switch • Centralized Intelligence • Proprietary Code • Proprietary service deployment • Very expensive

48. Class 5 Located at the edge of the network Trunk to Line/Line to Line Aprox. 30,000 deployed Services: Caller ID, call waiting, voice mail, E911, billing, etc. Ex: Lucent 5ESS, Nortel DMS, Siemens EWSD Class 4 Located in the Core of the network Trunk to Trunk Aprox. 800 deployed Services: call routing, screening, 800 services, calling cards, etc. Ex: Lucent 4ESS, Nortel DMS, Siemens What’s the difference between a Class 5 and a Class 4 switch?

49. 4210 IXC 212 LEC 555 The PSTN – NANP • NANP – North American Numbering Plan • 3 digits area code + 3 digits office code + 4 digits phone • Each Local Exchange Carrier (LEC) switch are assigned a block of at least 10,000 numbers • The Inter-Exchange Carrier (IXC) switches are responsible for transmitting long distance PSTN (212) 555 4210

50. SS7 1+212+555+5644 555+5644 5644 212 5644 The first LEC receives a call, seeing ‘1’ as the first digit and then passing the call on to the IXC switch. The IXC then routes the call to the remote IXC responsible for ‘212’ The ‘212’ IXC looks at the office code and passes it on to the ‘555’ LEC switch The ‘555’ LEC switch then checks the station code and signals the appropriate phone The PSTN – Call Routing • Both NANP and International Numbering Plan – E.164, use prefix-based dialing 408 555 PSTN