Positron Telecommunication's Innovative Asterisk-on-a-Card

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Tom Keating
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Positron Telecommunication's Innovative Asterisk-on-a-Card

In the January issue of Internet Telephony Magazine is a TMC Labs review of Positron Telecommunication Systems V114 analog PCI "Asterisk-on-a-card". They also have an ISDN version and a E1/T1 version. I thought I would share the review here since this is a very innovative product. It is pretty cool to have Asterisk running on a PCI card with some very interesting benefits.

But I won't steal my own review's thunder... Read it for yourself to find out the benefits:

Positron Telecommunication Systems Inc.
(514) 345-2220

Installation: 5
Overall: A-

Price: $630 USD MSRP

We've officially seen it all when it comes to Asterisk. We've seen Asterisk on a PC, in small boxes or small appliance form, and we've seen it in 1U rackmountable pizza boxes. But never have we seen Asterisk running on a PCI card - that is until now. Positron Telecom offers several Asterisk-on-a-card products, including the V114 (4 analog FXO), the V214 (4 ISDN BRI), and the V310 (E1/T1). Positron Telecom sent TMC Labs the analog V114 to test. Not only does this card have Asterisk integrated it also has 4 integrated FXO ports to support up to 4 analog trunk lines as well as a single FXS port for connecting a phone or fax machine. It also supports fax pass through as well.

TMC Labs spoke with Positron's President Richard McGravie to get some further insights into this product. One of the questions we were curious about was the target market for this product. Richard McGravie explained, "We are approaching vendors like Vyatta. We have a neat application for them because we're an Ethernet adaptor and they're just like a firewall/routing type appliance. They've got line interfaces from Sangoma and others, but it's not an application --it's just another interface. So it doesn't generate incremental sales for them. By installing one of our cards in their system you can then add secure VoIP routing and firewalling. So it becomes more for the reseller base to easily sell." He added that companies like their solution since they don't have to rewrite code or learn a new API interface to a card since Positron's solution is 100% SIP-based.

TMC Labs then inquired about their support for virtualization. Richard explained, "VMware was a fluke to be honest with you. We didn't design it intentionally, but because we install as an Ethernet adaptor, you go into your VMware session, you configure your virtual Ethernet adaptor, you configure as the default gateway and all of a sudden you've got the simplest, easiest solution to work inside of VMware environment that nobody else can do." He added, "In a VMware environment you have to configure an external switch and a router. You quickly end up with latency issues or a typical problem in VMware is timing due to clock drift. None of that happens in the VMware session anymore. It all happens on our card, so you don't have those issues." In fact, because the VM session communicates directly to the PCI bus to the 'virtual' network card as opposed to across an IP network infrastructure, there is less latency and less chance of a network issue causing a problem.

Interestingly, Richard told TMC Labs he has at least one company working on integration with Microsoft's popular unified communications platform - OCS 2007 R2. Positron is currently shipping with Asterisk 1.4.22 loaded, however they have ported over Asterisk 1.6 but they haven't ported over the GUI yet.

Installing the V114 was a breeze. When you install any Positron PCI card, you do not require a driver. The PCI card can therefore be installed in any host PCI slot running any operating system (Linux, Windows, etc.) and will simply communicate over Ethernet. Essentially, the card installs as an Ethernet network adaptor. Rather than using the full Asterisk IP-PBX functionality you can just send SIP traffic to the card and it will do SIP to TDM or SIP trunking making it a simple plug-n-play VoIP gateway. Because it is an Ethernet-based solution you can also use it with HMP applications as an IP-based TDM blade.

We installed the V114 into an old Windows XP machine and turned the PC on. Next, we browsed to, the default IP address for the Asterisk web management tool (See Screenshot 1). From here we added a couple SIP phones to the extensions list. It does support auto-provisioning, but currently it only supports the older Aastra series and some Polycom phones. We manually added a couple SIP phones, including a Yealink and an Aastra 67i IP phone and they registered with no problem.

Figure 1: Web-based tool for configuring Asterisk

Operational Testing
Next, we made an extension-to-extension test call. The voice quality was perfect. After our successful extension-to-extension call, we then tested the two built-in conference bridges. The bridges are PIN protected and feature your typical Asterisk moderator features, such as announcing your name when you join, increasing/decreasing volume, booting the last participant, and more. It also features music-on-hold if there is only one participant in the conference. All in all the conference bridges performed very well with excellent echo cancellation. A big part of that reason is because it uses Zarlink's ASIC hardware-based G.168 echo cancellation chipset (with up to 128ms tail length) to improve the sound quality.

We wanted to know how well Positron's E1/T1 cards scaled so we asked Richard McGravie. He responded, "If you take eight Digium or Sangoma E1/T1 cards and put them into a PC and you run those channels, it creates over a thousand interrupts per second since that's how Zap or DUNDi does its channel timing. That will bring any PC to its knees. So what Sangoma did is they went with Woomera [protocol]. It sticks all of the cards in a different PC and they have a protocol that talks from the host PC to the other PC. It has a TCP control channel and a UDP data channel." He then pointed out that debugging in this scenario is very difficult. He added, "With my cards you can put as many as you want into the system because the SIP overhead is so small that it doesn't really affect the processing power." The cards can intercommunicate via SIP or the IAX protocol.

You have full console access to the Linux operating system. We SSH'ed into the card . using an SSH client and the default root 'uClinux' password. Once logged in we were able to tool around the Linux shell, run various Linux commands, check out the default mounts and partitions, check out the tftpboot directory and modify some files, as well as peruse the /etc/asterisk/ directory which contains all the important Asterisk config files. The root level access is key to truly leverage the flexibility of Asterisk.

Of course, you can use the easy-to-use web-based admin tool to configure it as a SIP gateway or a full-fledged Asterisk-based IP-PBX. While using the web tool we initially thought that the changes we made were being applied as we did them. However, what was actually happening is that the configuration changes were being made to Positron's configuration files. We had to hover our mouse over System and then click Create Configuration. This would then write the changes to the Asterisk configuration files. We suggest a "Save Changes" button on the home page to make it clear you have to save the changes, but also it should be in a more prominent position for quickly saving configuration changes.

Figure 2: Main status screen-note the drop-down menus

The main status screen shows import stats such as SIP peers, available disk space, trunk line statuses and more. Importantly, out of the box it supports call recording and you can choose to save the recording to the removable CompactFlash memory on the PCI card. Additionally, you can configure the voicemail system to send your voicemails to your email as a .wav file.

• Blackfin ADSP-BF537 @600MHz
• Runs UClinux
• Asterisk v1.4.22 (v1.6 is coming)
• 4 FXO, 1 FXS
• Supports ring groups
• Two built-in conference bridges
• Call forwarding
• IVR/auto-attendant
• Personalize greeting schedules and follow-me support
• CallerID support
• Supervised and unsupervised transfers
• Single Compact Flash port
• PCI 2.2 compliant Ethernet interface
• 10/100Mbps auto MDIX Ethernet port
• G.711 ulaw & alaw, G.729 a/b, GSM, Speex
• LED indicators: Power, Fault, Network, Link speed

Pros: Cons:
• Hardware echo cancellation • Uses their own front-end Asterisk GUI
• Supports 40-50 simultaneous SIP calls • Limited space for permanent NAND Flash memory (256MB)
• Low Cost • Web GUI is for admins only, thus users can't access their recordings or personal settings from the web.
• Very scalable  
• Works with VMWare  
• Supports large CompactFlash memory sizes, i.e. 16GB, 32GB, etc.  
• Supports call parking, conferencing, and conference bridges  
• Supports fax pass-through.  
• Failover support to identical card  
• No CPU load - All processing happens on the card requiring no CPU power  
• Operating system independent  
• If the host PC crashes, the card keeps on running  

Although it only has 256MB of permanent NAND Flash memory to hold the OS and various Asterisk files, this is enough for most Asterisk deployments and certainly enough when using this as a SIP-based TDM and SIP-trunking blade. Still, might be nice to have a 512MB option in case power Asterisk developers want to load up a large custom application. The fact that it is OS-independent and it can even run under virtualized environments is a huge competitive advantage. Another winning element Positron has over their competitors is that they've made it easy to order. There is no need to figure out SKU numbers to add an additional echo canceller, FXS or FXO clip on cards - it is an all-in-one solution that comes with everything. Overall, we liked the versatility of their solutions and were very pleased with the feature-set of the Positron V114 4-port analog PCI card. We found it very easy to manage - even with yet another Asterisk GUI we had to learn. TMC Labs highly recommends VoIP developers, VoIP solution providers, and Asterisk users to check out Positron's PCI-based "Asterisk-on-a-card" solutions.

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