Extending Open Source PBX For Scalable Media Gateways

Transcription

1 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

2 Limitations of Current Soft PBX Architecture Monolithic/Single 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

3 Current Asterisk Open Source PBX Model Asterisk PBX IP chan_sip.so libpri chan_zap.so ZAPTEL Kernel Space T1/E1 TDM Drivers/Hardware (Sangoma/Digium) 2-Jun-08 / 3

4 Hardware Interrupt Penalty: SW EC & DTMF IP sip Asterisk PBX iax chan_zap.so / libpri /dev/zap/ ZAPTEL Soft EC and DCHAN HDLC Kernel Space hw_isr() 1000 isr / sec * spans 1ms 8byt 1ms 8byt 1ms 8byt 1ms 8byt 1ms 8byt 1ms 8byt 1ms 8byt 1ms 8byt 1ms 8byt TDM Drivers/Hardware (Sangoma/Digium) T1/E1/BRI/Analog 2-Jun-08 / 4

5 HW Optimizations: EC & DTMF & DCHAN HDLC IP sip Asterisk PBX iax chan_zap.so / libpri /dev/zap/ hw_isr() 100 isr / sec ZAPTEL Kernel Space 10ms 80byt 10ms 80byt 10ms 80byt 10ms 80byt 10ms 80byt 10ms 80byt 10ms 80byt 10ms 80byt T1/E1/BRI/Analog Hardware Echo Cancellation & DTMF & DCHAN HDLC TDM Drivers/Hardware (Sangoma/Digium) 2-Jun-08 / 5

6 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

7 Create kernel device per Span Asterisk PBX sip iax IP chan_zap.so / libpri span channelization /dev/zap/span/ ZAPTEL Kernel Space T1/E1/BRI/Analog TDM Drivers/Hardware (Sangoma/Digium) 2-Jun-08 / 7

8 The Distributed TDM Architecture: 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. Protocol: TCP Control Socket + UDP Media Socket ( offers leverage) Design a Generic Channel Driver using for Asterisk. 2-Jun-08 / 8

9 Asterisk PBX Model Asterisk Open PBX chan_sip.so Signal / Media Gateway IP chan_woomera.so (Client) TCP Control Msg UDP Media voice dchan T1/E1/BRI/Analog TDM API Drivers/Hardware 2-Jun-08 / 9

10 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/ Supported-Protocols: Raw-Audio: :9000 h323,sip,iax.ss7,pri,bri Request-Audio: raw ACCEPT EVENT MEDIA Unique-Call-Id: id1 Unique-Call-Id: id1 Raw-Audio: :9000 UDP based: Media (ulaw,alaw,pmc-16 ) RFC in progress 2-Jun-08 / 10

11 Sangoma TDM Architecture Sangoma Signal Media Gateway IP TCP Control Signal Translator Signaling Stacks SS7 ISDN RBS chan_sip Asterisk LibSangoma (Media) chan_woomera UDP Media TDM API Flexible RX/TX Period Codec Translation B Channelizatoin MTP2 or Q921 T1/E1/BRI/Analog B{1-15} 15} D{16} B{17-31} 2-Jun-08 / 11

12 Object Oriented Telephony Design Each piece is well defined Reuse of debugged modules Reduced Bugs Increased Stability Increased Asterisk Stability 2-Jun-08 / 12

13 Distributed TDM Architecture Asterisk over TCP Media over UDP Client Media over UDP over TCP SIP/H323/T SMG TDM Gateway SS7 ISDN RBS SIP/H323 over IP voice TDM API TDS Hardware dchan T1/E1/BRI/Analog 2-Jun-08 / 13

14 Distributed Clustering TDM Architecture Signaling over TCP Asterisk SIP/IAX Client SMG TDM. Gateway Media UDP ISUP/IP SMG TDM Gateway TDM API Hardware TDM API Hardware SS7 TDM API Hardware 2-Jun-08 / 14

15 Distributed TDM Architecture ASTERISK over TCP Media over UDP Client over TCP Media over UDP VOIP Protocol VOIP Protocol SMG TDM Gateway SS7 ISDN RBS TDM API / ZAPTEL Hardware T1/E1 2-Jun-08 / 15

16 Auto Asterisk Load Balancing Scaling ASTERISK SIP/IAX ASTERISK SIP/IAX chan_woomera chan_woomera 250 calls 250 calls 500 Voice Channels Media SMG TDM Gateway TDM API / ZAPTEL Hardware SS7 ISDN RBS 2-Jun-08 / 16

17 Distributed Clustered Scaled Asterisk & SS7 SIP/IP ASTERISK SIP/IAX ASTERISK SIP/IAX ASTERISK SIP/IAX ASTERISK SIP/IAX chan_woomera chan_woomera chan_woomera chan_woomera 250 calls 250 calls 250 calls 250 calls 500 Voice Channels Media SMG TDM. Gateway TDM API Hardware SS7 TDM API Hardware ISUP/IP SS7 TDM API Hardware SMG TDM Gateway TDM API Hardware 500 Voice Channels Media 2-Jun-08 / 17

18 Sangoma Wanpipe RTP TAP : Voice Recording Asterisk PBX IP chan_sip.so chan_zap.so User Space ZAPTEL Kernel Space Voice ulaw/alaw RTP TAP UDP/RTP Wanpipe TDM Voice Drivers AFT Series HW eth0 Ethernet Device LAN 2-Jun-08 / 18

19 Distributed Performance Asterisk can handle 500+ SIP-SIP calls channels are lighter than SIP/RTP Asterisk should be able to handle 500+ distributed TDM to TDM or SIP to TDM calls. 2-Jun-08 / 19

20 Future of Open Source PBX/Gateways Demand is growing! Need for 16 + E1 media gateways. Distributed model works Asterisk is the answer Asterisk Telco Grade? 2-Jun-08 / 20

21 Thank You! Questions and Comments? 2-Jun-08 / 21