Are Robo-calls tying up your IP codecs?

Many ACCESS and BRIC-Link users set their codecs to accept incoming SIP calls, which is required for the the system to be compatible with apps like LinPhone and WebRTC. But a side effect of opening these ports is that they will also answer calls from other SIP-based sources.

We are finding an increasing number of SIP-based "probes" or robo-callers, attempting to make connections with random IP addresses. When one of these hits your codec, it will attempt to answer the call. This typically results in a "hang" condition of the codec until the bad-call timer runs out, defaulted at 60 seconds. This is annoying but not usually a major concern.

Until recently, when we've started seeing a persistence of these dialers to hang on to a codec. When the codec disconnects, the dialer reconnects, resulting in a Denial-of-Service like condition. The user generally needs to reboot his system (maybe a couple of times) for the call to completely clear.

So we took a look at the incoming parameters of these calls to see if there was some way to reject them out-of-hand. And we found a series of "user agents" (the name of the software used to make the call) that were common among these calls.

We now have a beta-level version of firmware for ACCESS and BRIC-Link that adds a "blacklist" which defaults to the three most common user agents we have found in these dialers.  The list can be expanded by the user. If you're experiencing incoming SIP calls on your codecs that tie up your system, ask our support department about an upgrade.  You can reach them at techies@comrex.com.

Edit 3/17/15: Firmware 3.0p6, available at our support page for all models, has this fix. And our UML295s are in stock.

USB modem situation worsens on Verizon

It seems LTE USB modems are going the way of the Dodo bird and ISDN lines fast.  Verizon recently killed off it's line of Pantech modems, and the remaining one, the Novatel USB551L has a lot to be desired (see reviews from the Verizon site on left).

This is even more so on versions recently purchased from Verizon. We got some troubling reports, and got our hands on a sample.  This modem works fine on a computer, but there's a fundamental hardware timing issue that makes it unable to associate with our ACCESS codecs. It doesn't look like there's any work-around, either. So don't buy these.

We will be announcing a long-term solution to the USB modem issue next month at NAB. Until that solution is in place, we'll be stocking the Pantech UML295 (yes, we got a hold of a limited supply) for sale. This is the only USB modem that can take advantage of all of Verizon's LTE bands. And is hands down the best USB solution we have seen so far. Contact our sales department for more info.

Oh and don't forget the idea of using the ACCESS Wifi modem in conjunction with a hotspot device on Verizon! This lets you share your 4G with a computer in the field.