Large Asterisk PBX test using Diva and 480 switched channels

The purpose of the test was to check usability of Asterisk with Diva hardware as solution for big enterprise switching systems (240 an more channels).

Following hardware used:

2 x Diva 8PRI PCIe in the system under test (16 x E.1 resulting in 480 channels)

2 x Diva 4PRI PCI and 2 x Diva 4PRI PCIe in the call generator

The system under test was used as PBX for switching calls between interfaces (between boards):

E.1[1...8] -> E.1[9...16]. Using "group" chan_capi syntax. This eliminates the need to check for free channel if switching the call, chan_capi provides management of channels within a group.

Two tests was used to check the quality of provided solution:

• Long term load on all 480 channels with control of PESQ (voice quality)
• High call frequency test on all 480 channels. Variable call length between 100 mSec and 2 Sec

Used Diva release: 9.02 (includes chan_capi)

Used Asterisk version: 1.6.1, 1.6.2, 1.4.29

OS: 64 Bit Debian lenny

Test results:

• In the first test all Asterisk versions exposed same behavior. The switching done by cross board (direct board to board access) BUS master DMA of Diva hardware does not depends on the host CPU and on the Asterisk version. This is why no quality changes, compared to original signal was detected (with and without echo cancellation).
• In the second test 1.6.X and 1.4.X versions of Asterisk exposed different behavior: while 1.4.29 was absolutely stable and no problem was detected 1.6.X crashed after several minutes of tests if used for more then 120 channels

Conclusion:

Using Diva 8PRI PCIe, Diva for Linux, chan_capi and Asterisk 1.4.29 this is possible to satisfy all needs of big enterprise marked using even one mid range server: the voice streaming is handled by Diva hardware in the independent from host CPU fashion, use of high density Diva hardware allows to provide 480 channels using only 2 x 4LANE PCIe slots.

Interesting aspect is the power consumption too. Every Diva 8PRI board uses approximately 20 W of power (20W for 240 channels). Combined with use of mid range CPU (1.2 ... 1.8 GHz) and use of power reduction technologies (ondemand power governer using SpeedStep, ...)

this provides significant reduction of power consumption.