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Internet Telephony (VoIP)

Internet Telephony (VoIP). Henning Schulzrinne Dept. of Computer Science Columbia University Fall 2003. Overview. new Internet services: “telephone”, “radio”, “television” why Internet telephony? why not already? Internet telephony modalities components needed: audio coding

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Internet Telephony (VoIP)

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  1. Internet Telephony (VoIP) Henning Schulzrinne Dept. of Computer Science Columbia University Fall 2003

  2. Overview • new Internet services: “telephone”, “radio”, “television” • why Internet telephony? • why not already? • Internet telephony modalities • components needed: • audio coding • data transport • quality of service – resource reservation • signaling • PSTN interworking: gateway location, number translation

  3. Name confusion • Commonly used interchangeably: • Internet telephony • Voice-over-IP (VoIP) • IP telephony (IPtel) • Also: VoP (any of ATM, IP, MPLS) • Some reserve Internet telephony for transmission across the (public) Internet • Transmission of telephone services over IP-based packet switched networks • Also includes video and other media, not just voice

  4. New Internet services • tougher: replacing dedicated electronic media vs. new modes (web, email) • distribution media (radio, TV): hard to beat one antenna tower for millions of $30 receivers • typewriter model of development • radio, TV, telephone: a (protocol) convergence?

  5. The phone works – why bother with VoIP

  6. Emergency Calling • 911 in North America, 112 in Europe, others elsewhere • First implemented 1968 in US, now roughly 95% of US population • Basic 911 service: route emergency call to nearest emergency call center (public safety answering point – PSAP) • Later, enhanced 911 (E-9-1-1) for selective routing and conveying caller location information to PSAP • Roughly, 150 million 911 calls per year (2000) • 45 million wireless • For wireless: Phase I and Phase II • Phase I conveys call back number + Pseudo-ANI (cell face identifier) to PSAP • Phase II provides caller location (e.g., via GPS or TOA)

  7. Wireless 911 Phase II - TDOA BellSouth

  8. Wireless 911 Phase II - EOTD BellSouth

  9. Wireless 911 Phase II • Example: Sprint PCS and Nextel use GPS • Implementation just starting • VolP has similar problems as wireless: • devices change “network attachment point”

  10. Recent Change Links Update Links E9-1-1 Call flow elements - wireline E9-1-1 Tandemw/SRDB End office Public Safety Answering Point ES Trunks EM Trunks PSAP ALI Data Links PSAP Loop Access Control ie DLC System The Local Loop ALI SCP GATEWAY (Firewall) DBMS Service Providers ALI Database Elements

  11. Public Safety Answering Point PSAP E9-1-1 CALL FLOW ELEMENTS - WIRELESS MPC ALI/SR DBASE 8 PDE E2 7 4 3 9 TDL’s 6 5 E9-1-1 Tandemw/SRDB 2 MSC #9 is only applicable in a CAS-Hybrid architecture, such as BellSouth’s WLS911 Solution 1

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