RTMMoIP RTMMoIP

Alfredo Terzoli / Mosioua TsietsiAlfredo Terzoli / Mosioua Tsietsi

PLAN: tiding up…PLAN: tiding up…

• ENUM: a few more wordsENUM: a few more words

• B/W calculation for VoIP B/W calculation for VoIP

• Plan for the rest of the weekPlan for the rest of the week

“Call setup”

PSTN to VoIP Call PSTN to VoIP Call via SIPvia SIP

Sipsip:paf@cisco.com

Query1.3.1.9.5.8.6.8.6.4.e164.arpa.?

Dial+4686859131

DNS-Server

Sip serverGateway

Responsesip:paf@cisco.com

(slide by Steven D. Lind,AT&T)

VoIP via SIP to VoIPVoIP via SIP to VoIPDNS-Server

“ENUM”

SIP-Server

SIP-Server

Gateway

Gateway

ENUM ‘strange’ format…ENUM ‘strange’ format…

• My telephone at home in ENUM My telephone at home in ENUM format: format:

5.3.6.3.2.2.6.6.4.7.2.e164.arpa5.3.6.3.2.2.6.6.4.7.2.e164.arpa

• Why not (it seems more logical!):Why not (it seems more logical!):

6223635.46.27.e164.arpa6223635.46.27.e164.arpa

ENUM ‘strange’ formatENUM ‘strange’ format

• The second way of representing makes The second way of representing makes explicit in the DNS search the current explicit in the DNS search the current format of e.164, which might change in format of e.164, which might change in futurefuture

• Using the first one (fully dotted), we Using the first one (fully dotted), we isolate ENUM from changes in the e.164 isolate ENUM from changes in the e.164 format by the ITU. The only assumption format by the ITU. The only assumption is that e.164 will be numbers, which is is that e.164 will be numbers, which is safesafe

A conversation becomes A conversation becomes DATADATA

And it is tranported…And it is tranported…

Another view!Another view!

VoIP bandwith VoIP bandwith calculationcalculation

• Let’s get more specific on B/W Let’s get more specific on B/W usage, for AUDIO transmissionusage, for AUDIO transmission

• Two families of CODECS: Two families of CODECS: – wave coding wave coding

• unrestricted, any sound (sound engineering)unrestricted, any sound (sound engineering)

– vocoding vocoding • good for voice, can reach very low bitratesgood for voice, can reach very low bitrates

• kbps: kilo bits per second (here kbps: kilo bits per second (here kilo=1000, not 1024!) kilo=1000, not 1024!)

‘‘Vocoders’ for Videos?Vocoders’ for Videos?

Voice Synthesisers & Voice Synthesisers & VocodersVocoders

• A voice synthesiser includes a A voice synthesiser includes a vocoder of some type, naturallyvocoder of some type, naturally

• In fact, using a voice synthesiser one In fact, using a voice synthesiser one can substantially reduce the can substantially reduce the bandwidth needed for the bandwidth needed for the transmission of voice. HOW?transmission of voice. HOW?

• (BTW, who knows how MIDI works?)(BTW, who knows how MIDI works?)

B/W consumption of a few B/W consumption of a few codecscodecs

VoIP bandwith VoIP bandwith calculationcalculation

VoIP bandwith VoIP bandwith calculationcalculation

• Bandwidth calculators at:Bandwidth calculators at:– http://www.newport-networks.com/http://www.newport-networks.com/

pages/voip-bandwidth-calculator.html pages/voip-bandwidth-calculator.html (btw, the white paper distributed to you on b/w calculation (btw, the white paper distributed to you on b/w calculation

comes from newport-networks)comes from newport-networks)

– http://www.packetizer.com/voip/http://www.packetizer.com/voip/diagnostics/bandcalc.htmldiagnostics/bandcalc.html

Reducing overheadReducing overhead

• cRTP compact RTP (RFC 2508):cRTP compact RTP (RFC 2508):– From 40 to 2 to 4 bytes, substantialFrom 40 to 2 to 4 bytes, substantial

• Trunking: same packet transport Trunking: same packet transport more than one conversation (of more than one conversation (of course, can be used only if on a course, can be used only if on a trunk)trunk)

Main PracMain Prac

• Building a service in AsteriskBuilding a service in Asterisk

• Possible dates:Possible dates:– WEDNESDA 16s: presentation of your WEDNESDA 16s: presentation of your

ideaidea– TUESDAY 29: demo of the implemented TUESDAY 29: demo of the implemented

serviceservice

A few URLs to follow (by A few URLs to follow (by Friday)Friday)

• http://www.start.com.my/blog/?q=google_talk_vs_skype (blog with comparison of skype and googletalk)

• http://gadgets.engadget.com/entry/1234000100055725/ (broadband providers VoIP (broadband providers VoIP dilemma)dilemma)

• http://voxilla.com/modules.php?op=http://voxilla.com/modules.php?op=modload&name=News&file=articlemodload&name=News&file=article&sid=170&newlang=eng&sid=170&newlang=eng (P2P SIP) (P2P SIP)

Questions?Questions?