VoIP Gateways Article

What is a VoIP Gateway?

January 04, 2017

VoIP gateways have the potential to make business operations much easier and more efficient. The problem is that many people don’t fully understand what they are or how they work. So, what exactly is a VoIP gateway?

According to VoIP Supply, a VoIP gateway is, “a piece of hardware with the standard purpose of converting TDM telephony traffic from the PSTN into digital packets IP packets for transport over an IP network (such as your LAN). A VoIP gateway can also convert digital IP packets into TDM telephony traffic for transport across the PSTN (Publicly Switched Telephone Network).”

However, it might be easiest to think of a VoIP gateway as a bridge between classic telephony technology and new VoIP technology. This bridge allows communications to cross from one form of technology to the other. Essentially, the primary purpose of this hardware is voice and fax compression/decompression, packetization, call routing, and control signaling. VoIP gateway provider beroNet provides an infographic in order to break down the purpose of the hardware:

Image via beroNet

To fully understand VoIP gateways, though, you need to understand how they work. A VoIP gateway works as a bridge between an IP network and the PSTN and, depending on where the voice traffic originates from, it converts the voice traffic into the proper form for receipt by the destination network (IP or PSTN).

This conversion is made possible thanks to protocols and codecs. A VoIP protocol determines how the voice packet is transported across a network. Typically, a VoIP gateway supports a single protocol; some of the most common are SIP, SCCP, MGCP and H.323. Meanwhile, voice codecs compress the voice stream within a digital packet. It also figures out the sound quality and bandwidth required to send the packet. The most common voice codecs are GSM, iLBC, G.711, G.722, G.726, G.728 and G.729.

So, for example, if the voice traffic originates from the PSTN, the VoIP gateway will convert the analog voice signal into a digital signal. From there, the digital signal is compressed using a codec and is broken into a series of packets that are transferred across the IP network using a signal protocol. If the voice traffic comes from an IP network, the opposite occurs.

The way a VoIP gateway works may seem confusing at first, but it’s worth it in the end because the hardware offers some beneficial features. Not all VoIP gateways are created equal, and different versions offer different features. However, the majority of VoIP gateways are compliant with multiple protocols, including SIP, H.323 and MGCP; support G.711, G.723.1, G.726, and G.729A voice codecs; are T.38 compliant (for faxing); offer echo cancellation, Jitter Buffer, VAD and CNG; have Web-based administration and management; offer automatic provisioning via TFTP/HTTP; and have call routing and least cost call routing capabilities. These are standard features found in most VoIP gateways, but some offerings have added benefits.

Many newer VoIP gateways have additional functionalities that allow them to act as more than a bridge between technologies. Some can be enhanced through the use of apps. For instance, apps can be used to turn the VoIP gateway into a Survival Branch Appliance, which then enables the gateway to act as a backup to hosted or off-site IP PBX (News - Alert) systems. Other features alert users when a device no longer functions properly, which is usually an indicator that there could be network problems at the gateway location.

VoIP gateways may seem difficult at first, but once you get the hang of the concept, the hardware can be used to make converting voice and fax calls between the PSTN and an IP network much easier.  

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