What is SIP ALG?

SIP ALG stands for "Session Initiation Protocol Application Layer Gateway." It's a function often found in routers, and its primary purpose is to assist with certain types of internet traffic management. In simpler terms, it's a feature designed to help voice calls and video calls over the internet, like those from VoIP (Voice over Internet Protocol) services, to work more smoothly.

Why Can SIP ALG Be Problematic?

While SIP ALG is intended to be helpful, there are times when it can actually interfere with the proper functioning of VoIP calls. Here are some issues you might encounter if SIP ALG is affecting your service:

  1. Dropped Calls: You might find that your calls get cut off unexpectedly.

  2. One-Way Audio: You or the other party might not hear each other even if the call connects.

  3. Registration Failures: Your VoIP device or application might struggle to connect to the service.

  4. Call Setup Issues: Delays or difficulties in establishing a connection.

Many of these problems arise because SIP ALG often modifies the data packets associated with VoIP calls in ways that VoIP services don't expect. While the feature might work with some setups, in many instances, it can be more problematic than beneficial.

How Can I Resolve SIP ALG Related Issues?

If you suspect that SIP ALG might be causing problems with your VoIP service, here's what you can do:

  1. Check Your Router Settings: While some routers allow you to disable SIP ALG through their settings, this can be a technical process and may vary widely based on the router brand and model.

  2. Contact Your Internet Service Provider (ISP): We recommend this as the most straightforward approach for most users. Simply get in touch with your ISP's customer support and ask them about disabling SIP ALG on your connection. Some ISPs may have it enabled by default, and they can assist in turning it off if it's causing problems.

DTP Managed Networks vs Non-managed Networks

In environments where DTP manages the network, router, etc - we actively work to disable SIP ALG at the time of telephone deployments. In other networks such as home networks where corporate devices have been moved to for work-from-home situations, we are unable to manage these environments. For this reason, we ask home users to contact their ISP for assistance in disabling SIP ALG.