Router’s SIP ALG

Posted on November 17, 2011 | By Voicent Support

Sometimes you get “line occupied” error even though your line (VOIP channel) is clearly not a problem. One of the cause of this problem is related to your router’s interfering with VOIP/SIP messages. A clear sign of a router problem can be found in the log files, where a SIP error message from your VOIP service contains: “400 Bad Request – Actual Content Shorter Than Content-Length”.

How to verify the problem is caused by your router?

You can try the following experiment.

1. Connect your computer directly to the Internet. If you are using a broadband modem (like a cable modem or a DSL modem), unplug the router from the modem, and connect your computer to the modem.
2. Reboot your computer and make sure you can browse the Internet
3. Try to use Voicent software

If the above experiment works, then it is almost sure that your router is the problem. Specifically, it is caused by your router’s ALG (see below for more info) feature is not working as expected.

How do I fix it?

You need to disable your router’s ALG feature. To access your router settings, you normally need to find its IP address and point your browser to that IP. In newer versions of Windows (i.e. Vista/win7) you can usually see your router under Network. Right click on it and select View device web pages. The following is an example for NetGear, specifically NetGear N150 (WRN1000/WRN2000 and similar series) and possibly other NetGear routers

Must do:
SIP ALG settings must be disabled
Visit http:///
You need to login (default user is “admin” and default password for it is “password”)
Go under WAN Setup and tick Disable SIP ALG and apply.

Additionally recommended:
WAN Setup > Disable SIP Firewall: check the box
WAN Setup > NAT Filtering: Set to Open
Maintenance > Router Upgrade: Click on Check and upgrade fireware version (take care and follow instructions)

What is SIP ALG?

Many of today’s commercial routers implement SIP ALG (Application-level gateway), coming with this feature enabled by default. While ALG could help in solving firewall/NAT related problems, the fact is that many routers’ ALG implementations are wrong and break VOIP/SIP.

An ALG understands the protocol used by the specific applications that it supports (in this case SIP) and does a protocol packet-inspection of traffic through it. A NAT router with a built-in SIP ALG can re-write information within the SIP messages (SIP headers and SDP body) making signaling and audio traffic between the client behind NAT and the SIP endpoint possible. This re-write feature, if not correctly implemented, will cause VOIP/SIP not working.

Posted in Predictive Dialer, voip |

Predictive dialer integrate with management system

Posted on October 26, 2011 | By Voicent Support

We are interested in Agent Dialer application. In the product description there is two arguments:

-Extensive interface for system integration (For developers)
-Integrate with any Window based software like SQL database and SugarCRM, Salesforce.com

Can you send me technical documents on what excatly can be done and how. Right now the software solution seems good, but we need to get the required client names and phone numbers over to AgentDialer from our own management system. Is this possible without the manual IMPORT/EXPORT method?

Yes, you can do this without manual import/export.

The way to do it is to write a separate program or script to query your management system or database, and then launch Agent Dialer program through its command line. In this program, you first get the required client names and phone numbers, using whatever your search criteria, and then launch Agent Dialer using the names and numbers. The following is a possible pseudo code snippet:


open "tmp.csv" file for write
ask user for search criteria
foreach client that meets the criteria {
save client name, comma, phone number to "tmp.csv" file
}

cmdLine = "adialer.exe tmp.aoc -pd -import tmp.csv"
execute cmdLine

For more information about using the command line interface, please see use predictive dialer command line interface.

You can run this program manually or use Windows task scheduler to automatically run it. In addition, you can enhance your own management system to include this feature.

Posted in Developer |

Predictive Dialer Dropped Calls

Posted on October 24, 2011 | By Voicent Support

we are getting many failed and drop calls, please advice as to how do we check if we have enough server or broadband to run properly

First, you want to use some online bandwidth speed testing sites to check your bandwidth. For Voicent software, it needs 128Kbps per line for both upload and download speed.

Second, choose only PCMU for gateway > setup > options > sip tab, click the codec button. Get rid of the rest of the selected codecs.

Third, we recommend 4-8 lines per CPU core. Your CPU utilization maybe low 4-8 lines. But since Voicent software has to handle a lot of real time events, it is better to have a computer with a faster computer. Also, since all the simultaneous calls are running in parallel, it is better to have a computer with multiple processors, and each with multiple cores.

Fourth, you can do some test runs. Start with a campaign with a few lines, if it works well, increase the number of lines. By doing test this way, you can see when the system starts to deteriorate.

And last, if you see “VOIP service error”, such as “service temporarily unavailable”, etc, you need to contact your VOIP service provider to see why some of your phone calls are not connected.

Posted in Predictive Dialer |