General

Ditching PCI cards in Asterisk for fun and profit

In the past, I’ve used PCI cards providing telephony TDM for my Asterisk-based projects. I’ve only worked with Digium’s FXO/FXS and T1/E1 cards, both in PCI and PCI-x formats, until a client asked for a gateway solution with FXO, FXS and E1, where using the PCI cards in a 1U IPBX was simply out of the question.Using Etheet gateways has always been a problem in those cases, since entry-to-medium level solutions lack the processing power for massive call handling, and signalling is poor, making the architecture unfit for reporting purposes and specialized apps such as call centers. But hey, that’s my experience with gateways.Therefore, I looked into Xorcom’s Astribank. They pack FXO, FXS and PRI/BRI ports inside a convenient 19″ 1U case, which can connect to an Asterisk-based IPBX server via USB and gets recognized as an integral DAHDI device in mode setups.So I ordered a composite 8xFXO, 8xFXS and 1xE1 PRI from Astribank, labelled XR0072. Getting the equipment from Arizona to Florida was easy, and since I worked with DHL, getting it to Guayaquil in Ecuador was a breeze (next-day delivery) but passing customs is, as always in Latin America, a time-consuming operation. After paying 12.5% taxes and then some for DHL operations, and 15 days waiting, I got the equipment in Quito.To my surprise, the Astribank was extremely light and small, slightly near 3 Kg in 1U form factor and under 1/4 depth in the rack. While it had a rack-mounting kit, which I used, it could also rest securely over my IPBX without rack screws.My Astribank uses a single USB cable to connect to the “master” PBX — it could also be connected to a secondary PBX and provide a fault tolerant setup. It also depends on a DC supply, which they included. Since I was using a mode Debian, with a mode Asterisk with already-compiled mode DAHDI (formerly called Zapata/Zaptel) drivers, I just connected the equipment via USB to the IPBX, issued an invoke-rc.d dahdi restart and we were good to go.Note: you do need the fxload package in Debian for firmware loading to the Astribank. And for “good to go” I mean you can check the registered spans with dahdi_registration and, as soon as you connect the E1 cable that comes from the CPE to the CPE port (which in my XR0072 is the first on the lower row for PRI) you get an OK status with dahdi_tool. Also note that I use an E1/CPE port, which is the default for the Astribank, otherwise I’d have to set the XPP_PRI_SETUP variable as indicated on the User Manual.DAHDI insists on configuring a crc4 parameter for the detected spans, which I needed to remove and restart DAHDI so the equipment could ‘sync’ with the CPE (that is, the box that the telco provided, with the balun and the crossover RJ45 cable) and avoid some nasty noise issues on the line, that also occur with Digium’s Wildcard for PRI.

usb:008/005          xpp_usb+     e4e4:1162 Astribank-modular FPGA-firmware LABEL=[usb:...]       CONNECTOR=@usb-0000:00:1d.7-1         XBUS-00/XPD-00: E1       (31)  Span 1  DAHDI-SYNC        XBUS-00/XPD-10: FXS      (8)   Span 2         XBUS-00/XPD-20: FXO      (8)   Span 3

Using DAHDI’s dahdi_genconf command writes an /etc/asterisk/dahdi-channels.conf file with the group and channel configuration as detected by DAHDI. It should be included by the chan_dahdi.conf file, which, in my case, is not necessary since I only wanted to enable one DAHDI group (DAHDI/g0) with my 31 E1 channels (1-15,17-31)

group=0context=from-pstnchannel => 1-15,17-31

That means that when I want to use the FXO/FXS ports, it’d probably be easier to include the dahdi-channels.conf (FXS ports, for example, belong to a different context, from-inteal) so I don’t have to type more than my laziness permits.I also found that, in my setup, some Asterisk parameters were superfluous, such as the switchtype (either national or euroisdn work, and the former is the default) or the echo-cancelling stuff, so I assume Astribank’s doing a great job in negotiating that with the CPE. Do take note, however, that in my case the CPE needed to be cold-restarted so I could get an ‘Up’ status in Asterisk (pri show spans) and that my only non-default, channel related configuration in chan_dahdi.conf is signalling=pri_cpe.So far, so good. I’m really happy with the Astribank and I can fully understand how useful it is in terms of price (quite competitive in comparison with traditional cards, specially when bought from resellers -like me-), size/weight and functionality/ease of setup and administration. Kudos!

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