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  • 1. VoIP in Context
    • Niall O’Reilly, University College Dublin IT Services
    • HEAnet National Networking Conference 2006
  • 2. VoIP in Context
    • Strategic issues
    • How VoIP works
    • Market issues
    • Interoperation with POTS
    • Interoperation among VoIP services
    • Strategic options
  • 3. VoIP in Context
    • What context would that be ... ?
  • 4. VoIP in Context
    • Strategic issues
    • How VoIP works
    • Interoperation
    • Strategic options
  • 5. VoIP: Strategic Issues
    • Global or local scope?
    • Build, buy, or leave it to the users?
    • Proprietary or standards-based?
    • Branding?
    • First, see how it works ...
  • 6. How VoIP works
    • Different flavours: Standards: SIP, H.323, Services: Skype, IP-TSPs
    • Similar requirements: Find called party Set up call
    • Look at SIP ...
  • 7. SIP — direct call INVITE sip: 10.17.243.34 100 Trying - ACK RTP session (voice, video, etc) Artificially simple case: caller knows where my phone is Caller’s phone My phone 200 OK 180 Ringing - 192.168.19.76 10.17.243.34
  • 8. SIP — where did he go? 10.17.243.34 Usual case: my phone is nomadic Caller’s phone My phone 10.97.1.5
  • 9. SIP servers keep track 10.17.243.34 SIP Registrar: tracks last REGISTER event Caller’s phone My phone 10.97.1.5 SIP Registrar server sip.example.net Caller’s SIP server (if any)
  • 10. SIP — using servers INVITE sip: [email_address] ACK RTP session (voice, video, etc) Servers broker call using SIP Payload is carried peer-to-peer INVITE INVITE 200 OK Control Transport Data
  • 11. VoIP compared to e-mail Submit Difference: mail servers carry payload Forward Retrieve Message queue Message store Control & Data Transport
  • 12. VoIP compared to POTS Place call Difference: Payload travels over provider’s resources Set up circuit Terminate call Voice traffic over circuit Vertically integrated: no separation of Control, Data, and Transport
  • 13. Interoperation
    • Technology: gateways, mapping
    • Service management
    • Business model
    • POTS is centre-stage
  • 14. Interoperation
    • Within POTS
    • VoIP/POTS
    • Within VoIP
  • 15. POTS Interoperation
    • Dial plan what can be dialled (DTMF-12)
    • Numbering plan what can be reached (E.164)
    • Interconnection specific number ranges — routing codes
    • Cascaded charges terminating operator in control
    • Fewer hops best for business
    Originating Operator Terminating Operator Transit Operator
  • 16.
    • POTS dominates (Metcalfe’s Law)
    • Address (URL, number) mapping
    • Media conversion
    • Business relationship
    VoIP/POTS Interoperation
  • 17.
    • POTS uses [*#0-9] — VoIP side must accommodate
    • Customer aliases facilitate this — Real POTS phone number (E.164) — Two-stage dialling to “extension” — extension@example.org — username@example.org
    VoIP/POTS Address Mapping
  • 18.
    • Numbering plan POTS: numeric only VoIP: URL space or per-operator number blocks
    • Interconnection must map (relevant parts of) numbering plans POTS to VoIP: ENUM can find matching URL for number VoIP to POTS: configuration; ENUM enables POTS bypass
    • Successive gateways degrade quality due to lossy trans-coding
    VoIP/POTS Interoperation
  • 19.
    • Different business model
    • Cascaded charges on POTS side from POTS: gateway immediately (keep entire fee! from VOIP: exit to POTS late (keep bigger share of fee!)
    • Paradox: VoIP is good for operator!
    VoIP/POTS Interoperation
  • 20.
    • Dial plan DTMF (0-9, #, *) URL (user@domain)
    • Numbering plan URL space
    • Interconnection Configuration tables — maintenance! DNS is so much simpler ENUM: maps number to URL SPIT: Spam over IP Telephony
    • Reachability decoupled from cost
    VoIP Interoperation Originating IP-TSP Terminating IP-TSP Internet: ISPs & Transit
  • 21. VoIP Interoperation
    • Can be just like e-mail: sip:user@domain
    • URL drives DNS to locate destination
    • DNS RR-types: SRV, A
    • Provider issues: — “walled garden” vs “public park”
    • Customer issues: NAT, firewalls
  • 22. VoIP Interoperation
    • Technology open — just like e-mail
    • Operator business model varies — “walled garden” vs “public park”
    • Obstacles may be significant — NAT, firewall
  • 23. VoIP Interoperation
    • Static routes support bilateral agreements
    • VoIP “islands” may need to route via POTS — involving duration charges, double transcoding
    • ENUM maps numbers to URLs — but not yet widely (enough) deployed
    • Not unlike e-mail before MX records
  • 24.
    • Example
      • [Remember “!” and “%” for e-mail]
      • *8 *4yy 8972xxxx
      • sip: 8972xxxx @example.org
      • sip:someuser@example.org
    Address Mapping
  • 25.
    • Encodes E.164 numbers as domain names — no “short codes” or “operator-specific”
    • Standard algorithm to determine URL — DDDS: RFC 3401ff
    • Not yet generally deployed
    ENUM
  • 26. Strategic options
    • Global or local scope?
    • Build, buy, or leave it to the users?
    • Proprietary or standards-based?
    • Branding?
  • 27. Local or global scope
    • Technology substitution
    • “Free” long-distance phone-calls
    • Extend footprint of internal PBX — teleworkers, conference-goers
  • 28. Build, buy, or step aside
    • In-house like e-mail linked to other administrative processes
    • Outsource to existing IP-TSP established expertise
    • Skype — just works walled garden with gates (charged Skype-in, -out)
    • Gizmo — has free SIP-out
  • 29. Standard or proprietary
    • Cisco, Nortel, ...
    • Skype
    • Standard Interoperability Exploits DNS for provisioning Open Source: SER, Asterisk
  • 30. Branding
    • What goes on the stationery?
    • Skype: joe_user
    • IP-TSP: sip:Niall.oReilly.UCD@example.ie
    • Own-brand: sip:First.Last@ucd.ie
    • E.164: +353-1-716-xxxx
  • 31. Strategic options
    • Global or local scope?
    • Build, buy, or leave it to the users?
    • Proprietary or standards-based?
    • Branding?
    • Know what you require, then decide
  • 32. VoIP Resources
    • Terena VoIP Cookbook (2004)
    • Richard Stastny’s Blog http://voipandenum.blogspot.com
    • iptel.org
  • 33. ?