SIP ALG Detection
What is SIP ALG?
SIP ALG stands for Session Initiation Protocol Application Layer Gateway. SIP ALG can and usually does exist on Routers, Modems or in rare cases a managed switch. It’s purpose is to help fix some VoIP traffic but it often causes problems when it shouldn’t. In general, you must disable this feature for any VoIP service to operate as expected.
Two methods can be used to detect SIP ALG on your network:
- Client Based Testing (.exe)
- Client Based Testing (.dmg)
- Web Based Testing
Client Based Testing
A small .exe agent that can test for the presence of a SIP ALG on the network the host PC is connected to.
After downloading, open the file and accept any permissions your machine may ask for.
If the results = False then a SIP ALG was not detected by the client.
If the results = True then a SIP ALG is active and must be turned off.
Web Based Testing
Visualware is a provider of internet based VoIP testng tools.
They offer a series of VoIP test tools that include a SIP ALG tester.
Below are 2 links to some of their web based test:
- This option must be run using internet explorer with java enabled.
- This option runs using HTML5 and their custom plugin.
Instructions:
This web test will simulate 1 VoIP Call using the G.711 codec and provide a realtime analysis of that call.
Note: The resulting analysis ONLY represents the quality of that single call and should not be used as a benchmark for real calling scenarios with multiple active calls during an extended period of time.
After the test completes click on the “VoIP” tab and look for “N” or “Y’ on the “SIP ALG Firewall” line in the lower white box.
- If you see “SIP ALG Firewall: Y” then a SIP ALG is active and must be turned off.
- If you see “SIP ALG Firewall: N” then a SIP ALG is was not detected.
Mac OSX Based Testing
A small APP agent that can test for the presence of a SIP ALG on the network the host MAC is connected to.
After downloading, open the DMG, move the contents to Applications and accept any permissions your mac machine may ask for.
Please note the Mac OSX based app is not an officially supported application of Telewyze.