261006 AstriCon Dallas

1
Implementing IAX2 In Java

• Tim Panton Director
• tim_at_mexuar.com

2
Introduction

• Demo Cards
• CorraletaTM
• IAX2 protocol
• Java
• Softphone
• 125kb
• Signed Applet
• Skinnable

3
History

• Westhawk Ltd
• Software consultancy for 20 years
• Open source SNMP in Java (gt10 years now !)
• CTI project v1 Sun BRI, v2 PRI dialogic
• Web services/security
• Old BRI exchange
• Redundant PRI line

4
Asterisk

• Installed Asterisk as office PBX
• With snom phones
• Neat dialplan
• Home/roam etc
• Firefly (IAX) on laptops
• ... all happy, except me, I have a Mac.

5
It begins...

• No good IAX client (then) for Mac
• IAX doc a bit thin, but... I could do that!
• Start from doc and packet inspection
• Use Java because... We just do
• Not a port of IAX client or chan_iax2

6
Why IAX ?

• Simpler than SIP
• Draft RFC is only 90 pages
• SIP/STUN/RTP has 90 RFCs
• Security background - SIP looks like FTP without
  pasv!
• Unix background - do just one thing, well!

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Problems 1

• Sequence numbers and Acks -
• Hard to get your head around, 'till you look at
  it from correct angle
• Every received packet is an ack of all packets
  sent up to the iseq number in that packet
  (thanks Mark!)
• Registration exchange is an audio-free call
• with a short lifespan.

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Problems 2

• Audio clock skew
• 1 of 10 mins is 6 sec!
• So insert or elide single samples
• Latency
• Can't buffer much or delay is audible
• Default ALSA buffer is 64k - 8 sec !
• Multiple buffer layers in JavaSound

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Problems 3

• UDP and packet loss
• Round trip time 100ms - too long
• Can't request retry
• Just wait as long as we dare for it to turn up
  out of order then make something up

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Problems 4

• Codecs all in higher layers of Java
• Too much buffering
• Re-implement
• Keeping buffer half full
• JavaSound blocks given the chance
• Use Java threads own ring buffer to help

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Problems 5

• WriteOnceRunAnywhere
• Or not
• Audio device capabilities/bugs vary
• Sound in Jdk1.5 much better

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Ok, done that, what next ?

• Built a simple UI for my application
• Used it on the Mac
• Bit dissatisfied with the UI, want it scriptable/
  skinnable
• Founded Mexuar

13
Where is the phone?

• Demo Hello Kitty
• CorraletaTM Technology SDK
• No need for a Java coder
• Interface is all JavaScript/DHTML
• We provide the skeleton
• You provide the skin
• And the users!

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Do you know what you have done?

• No
• But I'm beginning to...

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So what have we got?

• Asterisk flexibility
• Modern Java in browser
• IAX goes through NAT/firewalls
• ADSL adoption - plenty of bandwidth
• Skype etc. speed take up of microphones
• Portable
• Zero install

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What next?

• You tell me...
• Conference calls
• Low latency webcasts (auctions?)
• Webphones for ITSPs
• Dating
• Asterisk demos (Zork, parrot)
• Flash call centres
• Click to talk 2.0 -)

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CorraletaTM Connect

• Hosted ASP
• UK launch next month
• Context passing
• Any sufficiently advanced technology
• is indistinguishable from magic
• Arthur C. Clark

18
Questions ?

• Contact info
• tim_at_mexuar.com
• www.mexuar.com
• Visit us at booth 118 of the exhibition
• To find out more!