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Transcript of VoIP in Context Niall O’Reilly, University College Dublin IT Services HEAnet National Networking...
VoIP in ContextNiall O’Reilly, University College Dublin IT Services
HEAnet National Networking Conference 2006
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
VoIP in Context
• Strategic issues
• How VoIP works
• Interoperation
Strategic options
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
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 ...
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
How VoIP works
• Different flavours:Standards: SIP, H.323, Services: Skype, IP-TSPs
• Similar requirements:Find called partySet up call
Look at SIP ...
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
SIP — direct call
192.168.19.7610.17.243.34
INVITE sip:10.17.243.34100 Trying -
ACK
RTP session (voice, video, etc)
Artificially simple case:caller knows where my phone is
Caller’s
phoneMy
phone
200 OK180 Ringing -
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
SIP — where did he go?
10.17.243.34
Usual case:my phone is nomadic
Caller’s
phoneMy
phone
10.97.1.5
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
SIP servers keep track
10.17.243.34
SIP Registrar:tracks last REGISTER event
Caller’s
phoneMy
phone
10.97.1.5
SIP Registrar serversip.example.netCaller’s SIP server
(if any)
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
SIP — using servers
INVITE sip:[email protected]
ACK
RTP session (voice, video, etc)
Servers broker call using SIPPayload is carried peer-to-peer
INVITE
INVITE
200 OK
ControlTransport
Data
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
VoIP compared to e-mail
Submit
Difference:mail servers carry payload
Forward
Retrieve
Control & DataTransport
Messagequeue
Messagestore
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
VoIP compared to POTS
Place call
Difference:Payload travels over provider’s resources
Set upcircuit
Terminate call
Voice trafficover circuit
Vertically integrated:no separation of Control, Data,
and Transport
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
Interoperation
• Technology: gateways, mapping
• Service management
• Business model
POTS is centre-stage
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
POTS Interoperation
• Dial planwhat can be dialled (DTMF-12)
• Numbering planwhat can be reached (E.164)
• Interconnectionspecific number ranges — routing
codes
• Cascaded chargesterminating operator in control
• Fewer hops best for business
Originating Operator
TerminatingOperator
TransitOperator
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
• POTS uses [*#0-9]— VoIP side must accommodate
• Customer aliases facilitate this— Real POTS phone number
(E.164)— Two-stage dialling to
“extension”— [email protected]— [email protected]
VoIP/POTS Address Mapping
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
VoIP Interoperation
• Technology open — just like e-mail
• Operator business model varies— “walled garden” vs “public
park”
• Obstacles may be significant — NAT, firewall
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
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
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
• Example
• [Remember “!” and “%” for e-mail]
• *8 *4yy 8972xxxx
• sip:[email protected]
Address Mapping
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
• 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
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
Strategic options
• Global or local scope?
• Build, buy, or leave it to the users?
• Proprietary or standards-based?
Branding?
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
Local or global scope
• Technology substitution
• “Free” long-distance phone-calls
• Extend footprint of internal PBX— teleworkers, conference-
goers
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
Build, buy, or step aside
• In-house like e-maillinked to other administrative processes
• Outsource to existing IP-TSPestablished expertise
• Skype — just workswalled garden with gates (charged
Skype-in, -out)
Gizmo — has free SIP-out
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
Standard or proprietary
• Cisco, Nortel, ...
• Skype
• StandardInteroperabilityExploits DNS for provisioningOpen Source: SER, Asterisk
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
Branding• What goes on the stationery?
• Skype: joe_user
• IP-TSP: sip:[email protected]
• Own-brand: sip:[email protected]
E.164: +353-1-716-xxxx
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
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
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
VoIP Resources
• Terena VoIP Cookbook (2004)
• Richard Stastny’s Bloghttp://voipandenum.blogspot.com
iptel.org
Niall O’Reilly — UCD IT ServicesVoIP in Context — HEAnet NNC 2006
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