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:niall@example.net

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”— extension@example.org— username@example.org

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:8972xxxx@example.org

sip:someuser@example.org

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:Niall.oReilly.UCD@example.ie

• Own-brand: sip:First.Last@ucd.ie

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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