Sangoma Hardware and Open Source Asterisk IP/PBX

Konrad HammelSoftware Engineer/Level 3 Tech

Sangoma Technologies

Voice and Data

Who is Sangoma?

-established in 1984

-publicly traded (TSXV:STC)

-started with hardware for Open Source data routers

-in the Linux Kernel since 1.01

-device drivers, X.25, Frame Relay, MLPPP

-award winning engineers

-contributors to open source telephony

-installed in 128 countries

-VOICE QUALITY and RELIABILITY

-Life Time Warranty

Voice and Data

What does Sangoma Manufacture?

• Analog TDM cards

– A200

– A400

• Digital TDM cards

– A101/102/104/108

– A500

• Serial Cards

– A142/A144

• ADSL Cards

– S518/S519

Voice and Data

Sangoma’s Award Winning Design

Voice and Data

Reliable Faxing

•Faxing from Digital to Analog = 2 different clocks

•Sync the clocks to get reliable faxing

•DSP is used to recover and pass clock

Voice and Data

Hardware Echo canceling

• Octasic DSP module (same as the telco’s use)

• 1024 taps = 128ms echo tails

• Hardware DTMF

• Noise reduction

• Comfort noise injection

• Tone detection for fax/modem pass through

• Field upgradeable

• Fully independent from system

Voice and Data

What is Echo?

• Your audio stream reflected back to you

• TX recorded and compared to RX

• Delays of 16ms+ are picked up by the human ear

• 3 main sources of echo

– Compression

• G.729 = ~15ms

– Distance

• Copper lines = ~1ms per 100 miles

– Transcoding (TDM to IP)

• Buffering = ~5-50ms

Voice and Data

Other Types of Echo

• Acoustic Echo

• Hybrid Echo

– 4 wires down to 2 wires

Voice and Data

Current Architecture

•Zaptel takes data from hardware and passes it to software transcoding if needed

•Due to software EC 1ms chunks, but Asterisk takes 20ms

•8 bytes every 1ms from every span = A LOT of interrupts (1000)

Voice and Data

A500/SS7 and future Architecture

•Removing Zaptel and it’s restrictions

•Per card interrupt rather then per span

•80 byte chunks every 10ms per card = a lot LESS interrupts

•Clustering/True Media Gateways

Voice and Data

Debugging Problems

• Remember the OSI model, start low and move high

– Check that hardware drivers start properly (/var/log/messages)

– Check that hardware is running properly (ifconfig)

– Make sure “ztcfg –vvv” has no complaints

– Verify that Asterisk loads the proper Zap channels

– Is the D-channel coming?

Voice and Data

Debugging Problems Cont’d

• Use the following useful commands:

– wanrouter hwprobe verbose

– wanrouter status

– wanpipemon –i wXg1 –c Ta

– wanpipemon -i wXg1 –c astats –m Y

– wanpipemon –i wXg1 –c trd

– wanpipemon -i wXg1 –c ehw

– wan_ec_client wanpipeX enable Y

– wan_ec_client wanpipeX disable Y

Voice and Data

Debugging Problems Cont’d

– cat /proc/interrupts

– cat /proc/zaptel/X

– zap show channels

– pri show span X

– pri intense debug span X

Voice and Data

Debugging Problems Cont’d

• Don’t forget the log files!

– /var/log/messages

– /var/log/asterisk/messages

• Use logger.conf to add or remove info from this file

– /var/log/sangoma_mgd.log