The beauty with Asterisk is you start with the software and you add  the hardware around it. Given these

The beauty with Asterisk is you start with the software and you add the hardware around it. Given these

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Extending Open Source PBX For Scalable Media Gateways Presented by: Nenad Corbic, B.Eng Chief Software EngineerSoftware Manager Sangoma Technologies2-Jun-08 / 1Limitations of Current Soft PBX Architecture• Monolithic/Single Server Architecture. • TDM Bottleneck (Zaptel/TDM Hardware)• Software Echo Cancellation & DTMF & D-Chan HDLC• Software Codec (g729)• Kernel / User Space Context Penalty• TDM Clustering Solutions limited and hard to configure• Customer need for 16 x E1 =~ 500 calls or greater !2-Jun-08 / 2Current Asterisk Open Source PBX ModelAsterisk PBXlibprichan_zap.sochan_sip.soIPIPZAPTEL Kernel SpaceTDM TDM T1/E1T1/E1Drivers/Hardware(Sangoma/Digium)2-Jun-08 / 3Hardware Interrupt Penalty: SW EC & DTMF Asterisk PBXsipiaxIPchan_zap.so / libpri/dev/zap/ 0 1 2 3 4 5 6 7 8 9 10 … 245 246… 500... 600Kernell ZAPTEL SpaceSpaceSoft EC and DCHAN HDLChw_isr() 1000 isr / sec * spans1ms 1ms 1ms 1ms 1ms1ms 1ms 1ms 1ms8byt 8byt 8byt 8byt 8byt8byt 8byt 8byt 8bytTDM Drivers/Hardware (Sangoma/Digium)T1/E1/BRI/Analog2-Jun-08 / 4HW Optimizations: EC & DTMF & DCHAN HDLC Asterisk PBX sipiaxIPchan_zap.so / libpri/dev/zap/ 0 1 2 3 4 5 6 7 8 9 10 … 245 246… 500... 600Kernell SpaceeZAPTEL hw_isr() 100 isr / sec10ms 10ms 10ms 10ms 10ms 10ms 10ms 10ms80byt 80byt 80byt 80byt 80byt 80byt 80byt 80bytHardware Echo Cancellellation & DTMF & DCHAN HDLCTDM Drivers/Hardware (Sangoma/Digium)T1/E1/BRI/Analog2-Jun-08 ...

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Extending Open Source PBX For Scalable Media Gateways
Presented by: Nenad Corbic, B.Eng Chief Software Engineer Software Manager Sangoma Technologies
2-Jun-08 / 1
Limitations of Current Soft PBX Architecture
Monolithic/Single Server Architecture. TDM Bottleneck (Zaptel/TDM Hardware) Software Echo Cancellation & DTMF & D-Chan HDLC Software Codec (g729) Kernel / User Space Context Penalty TDM Clustering Solutions limited and hard to configure Customer need for 16 x E1 =~ 500 calls or greater !
2-Jun-08 / 2
Current Asterisk Open Source PBX Model
IP
T1/E1
Asterisk PBX
chan_sip.so
libpri chan_zap.so
ZAPTEL
TDM Drivers/Hardware (Sangoma/Digium)
Kernel Space
2-Jun-08 / 3
Hardware Interrupt Penalty: SW EC & DTMF
IP
Asterisk PBX sipiax
chan_zap.so / libpri
/dev/zap/ 0 1 2 3 4 5 6 7 8 9 10 … 245 246… 500... 600
ZAPTEL Soft EC and DCHAN HDLC
hw isr() 1000 isr / sec * spans _
T1/E1/BRI/Analog
1ms 1ms 1ms 1ms 1ms 1ms 1ms 1ms 1ms 8byt 8byt 8byt 8byt 8byt 8byt 8byt 8byt 8byt
TDM Drivers/Hardware (Sangoma/Digium)
Kernel S p a c e
2-Jun-08 / 4
HW Optimizations: EC & DTMF & DCHAN HDLC
IP
Asterisk PBX sipiax
chan_zap.so / libpri
/dev/zap/ 0 1 2 3 4 5 6 7 8 9 10 … 245 246… 500... 600
hw_isr() 100 isr / sec
T1/E1/BRI/Analog
ZAPTEL
10ms 10ms 10ms 10ms 10ms 10ms 10ms 10ms 80byt 80byt 80byt 80byt 80byt 80byt 80byt 80byt
Hardware Echo Cancellation & DTMF & DCHAN HDLC TDM Drivers/Hardware (Sangoma/Digium)
Kernel Space
2-Jun-08 / 5
Kernel Context Penalty
Greater the number of kernel devices, the greater the context penalty. System doesn t scale over 500 individual channels. Where each channel receives its own kernel device. Solution is to move to a per span kernel device. This way all channels inside a span are read in a same kernel context. Stage two solution is to memory map user space into kernel space and have zero copy transfers from kernel to user space.
2-Jun-08 / 6
Create kernel device per Span
IP
Asterisk PBX
sip
iax
chan_zap.so / libpri
span channelization
/dev/zap/span/ 0 1 2 3 4 5 6 7 8 9 10 .. 28
ZAPTEL
TDM Drivers/Hardware (Sangoma/Digium)
Kernel Space
2-Jun-08 / 7
The Distributed TDM Architecture: Woomera
Started as a response to a business need
Providing a carrier-grade SS7 interface to Asterisk and others.
A need to support 16 + E1 lines.
Woomera Protocol: TCP Control Socket + UDP Media Socket (Woomera offers leverage)
Design a Generic Channel Driver using Woomera for Asterisk.
2-Jun-08 / 8
Woomera Asterisk PBX Model
IP
Asterisk Open PBX
chan_sip.so chan woomera.so _ (Client)
TCP Control Msg
UDP Media
Signal / Media Gateway
Woomera Server
voice
dchan
TDM API Drivers/Hardware
2-Jun-08 / 9
Woomera Control Protocol
TEXT based Call Control Messages (carried over TCP) HELLO, CALL, HANGUP, LISTEN, ACCEPT, ANSWER, DTMF, BYE/QUIT Each command is transmitted in ASCII text format
EVENT HELLO CALL Version: 1.0 bri:g1/9054741990 Supported-Protocols: Raw-Audio: 192.168.1.1:9000 h323,sip,iax.ss7,pri,bri Request-Audio: raw
ACCEPT EVENT MEDIA Unique-Call-Id: id1 Unique-Call-Id: id1 Raw-Audio:192.168.1.1:9000
UDP based: Media (ulaw,alaw,PMC-16…) RFC in progress…
2-Jun-08 / 10
Sangoma Woomera TDM Architecture
IP
chan_sip Aster isk
_ chan woomera
TCP Control
UDP Media
Sangoma Signal Media Gateway
Woomera Signal Server Translato r
T1/E1/BRI/Analog
LibSangoma (Media)
TDM API Flexible RX/TX Period Codec Translation B Channelizatoin
Signaling Stacks SS7 ISDN RBS
B{1-1 5 } |   D {1 6 } |  B { 1 7 -31}
MTP2 or Q921
2-Jun-08 / 11