What is STUN?

A STUN server,  which stands for Session Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs) or Session Traversal Utilities for NAT, helps manage your voice over IP (VoIP) network’s connection to the Internet when secured devices are encountered. It is a server-client communication protocol that helps to securely facilitate data transfer with a client device hidden behind a firewall. It is used by languages such as Session Internet Protocol (SIP). For our purposes, STUN servers are important because they help establish VoIP calls.

STUN Server Terminology:

  • Network Address Translators (NATs)–These systems help private IP networks with the Internet connection process. Private IP networks that lack registered IP addresses still need acceptable addresses in order to interact with other networks and devices on the Internet. This has two purposes. First, NATs assist with network security by allowing a private network to mask itself behind just one IP address. They also help to converse IP addresses, reducing the need for as many unique addresses for every device and network.
  • User Datagram Protocol (UDP)–A communication protocol and one of two that are typically used by STUN servers. UDP is very efficient with transmitting data, in the sense that it uses less bandwidth than TCP typically does. For applications where minimizing latency is important, such as gaming, UDP is usually better.
  • Transmission Control Protocol (TCP)–Also used by STUN servers to communicate. TCP uses more bandwidth than UDP, but it is still the more popular standard since it protects data against disorder and loss during transit by verifying information that is received. For uses where it is vital to maintain data integrity, TCP provides distinct advantages.
  • Voice over Internet Protocol (VoIP)–Phone calls can be conducted using the Internet instead of the traditional copper wire networks used with plain old telephone service (POTS). VoIP is the language with which this Internet phone data is packaged and communicated.

STUN servers enable VoIP phones to communicate with one another. VoIP technology can be used on a broad range of different types of phones, such as IP phones, analog phones with analog telephone adapters (ATAs) and other Session Internet Protocol (SIP) phones.

In this article, we will explain how a STUN works and why it is important for your VoIP phone service. A STUN server can help you initiate VoIP calls, so STUN server functionality is a key part of the process of using VoIP phone service.

Article Contents:

  1. STUN Server Basics
  2. STUN Server Functions
  3. Do I Always Need STUN Server Functionality?
  4. VoIP Services and STUN

1. STUN Server Basics

Your STUN server functionality is what helps to connect VoIP calls, whether it is a physical server or a software system that is hosted in the cloud. STUN servers have two different IP addresses and can communicate with client phones using UDP and TCP. STUN servers help to secure the VoIP system.

Networks, including with VoIP service networking, require security to protect from disruptions and unauthorized access. Online, client and server devices use IP address as they communicate. Within private networks, the addresses used are often not registered, allowing the private network itself to choose how addresses are assigned and structured. When one of these private networks tries to connect to the Internet, registered IP addresses are needed to “talk” with other networks. Some of the unregistered IP addresses may be identical with other machines connected online, making it difficult for servers to recognize individual systems. This is an important reason to have NAT translate unregistered addresses into IP addresses that can be successfully used on the Internet for networking.

2. STUN Server Functions

Typically, the STUN server functions are actually conducted by servers available on public networks. For instance, STUN functions can be done by STUN servers on the Internet. Both private networks have access to the STUN server. In the case of client VoIP phones attempting to connect a call, a signal is sent from the phone to the network’s NAT systems to obtain a proper translation to a registered IP address that can be used for the call. The STUN server helps the client find the NAT in the network. Not all NATs follow a standardized system for translating addresses and not all STUN servers can connect with all NATs, so these systems do have limitations.

If you are going to have a VoIP system, however, STUN server functions are likely to be part of your VoIP software system. Some PBX systems can handle these functions for you, but your VoIP system will typically use access to a public STUN server.

3. Do I Always Need STUN Server Functionality?

STUN server functions are important to many VoIP and other online communications services, but in some cases, STUN is not used. For instance, if a server does not have a firewall in front of it and uses a publicly-registered IP address, then the STUN server function is not needed to connect the call.

Typically, a phone that is a client device makes a request that passes through a gateway connecting to the STUN server. The STUN server then passes back data through the firewall to inform the client device. STUN servers have two IP addresses they can use to communicate with client devices.

A private branch exchange (PBX) may be able to help you by carrying on these functions. PBX devices are typically computers or maybe software-based and can run onsite or in the cloud. In order to use VoIP service, you may need a PBX for your business.

4. VoIP Services and STUN

If you are looking for VoIP services for your business, you will need phones, a PBX if you need PBX functions, an Internet connection and some type of VoIP service. STUN functions are part of how typical calls work since phones and servers must communicate voice data across the Internet for VoIP to work successfully. Securing these systems to protect from intrusion means that your system will probably regularly use STUN servers to reach NAT systems and work past firewalls. Your systems may have access to many different STUN servers at once, facilitating connection to the Internet and other servers.

STUN functions can be very technical, but they play an important role in how the Internet works. If you are having problems with your systems connecting to STUN servers properly, it may be a port issue or some other connection situation. Your VoIP vendor may be able to help you resolve this or help with other technical issues if you ask. If you are shopping for a vendor, be sure to ask how they handle technical support for their services and any systems you use, such as your phones, PBXs or servers. Not every vendor offers full support for every piece of equipment used to access VoIP, so it may be worthwhile to find out. Having a plan to help you resolve technical problems with your devices and service can help you keep your business from encountering more significant problems. Great technical support should be one of your considerations when shopping for a vendor, purchasing equipment or switching to another service. As always, if you are not sure where to begin, it is important to ask your vendor for help.

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