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TCP versus UDP: Which is Better for VoIP?

TCP versus UDP for VoIP.

Voice over IP is the new standard when it comes to business telephony.

In VoIP, voice is converted into data packets and sent over the internet using communications protocols. Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) are both commonly used protocols for data transfer over the internet.

But how do you decide which is better for your business VoIP system? Here we compare TCP versus UDP, so you understand how these protocols affect VoIP calls.

Is TCP or UDP Ideal for VoIP?

The short answer is that UDP provides a better experience for VoIP users. Using UDP will help minimize network jitter and latency to ensure strong connections for your business phone calls.

Why Do TCP and UDP matter for VoIP?

Well, VoIP sends data packets over the internet.

These data packets consist of a header, which includes information about where the packet comes from and where it should go. They also have a payload, which is the actual data being transported by the packet.

TCP and UDP are just two different types of data packets. Both carry a payload and use internet protocols, but each works slightly differently.

Why is UDP Better Than TCP for VoIP?

Well, VoIP traffic is fast-flowing. A typical data packet contains 10 to 30 milliseconds of audio. Essentially, many, many data packets are sent one after the other. If a few packets are lost here and there, your conversation will probably remain unaffected.

Here’s an example:

Picture a well-trafficked highway; if one of the cars on the highway breaks down, you wouldn’t stop the flow of traffic just to wait for that one car. It’s better to just maintain the flow of traffic.

In the case of VoIP, TCP tries to recover lost packets, causing retransmission delays which stop the flow of voice traffic. UDP lets voice traffic continue to flow.

If you wait for and try to recover lost packets, the quality of your VoIP calls is going to be very low.

Let’s look at TCP and UDP in more detail.

Why is UDP better than TCP for VoIP?

UDP – User Datagram Protocol

This protocol is one of the core members of the IP suite.

UDP is generally better for real-time and high-performance applications like VoIP, which can’t afford retransmission delays. With UDP, there are no retransmission delays.

Here are some of the factors that make UDP ideal for VoIP:

  • Connectionless — Avoids the overhead associated with establishing a 3-way handshake.
  • No retransmission delays — If packets are lost, TCP will try to retransmit and recover lost packets, causing delays. This is not the case with UDP.
  • Speed — UDP is faster, simpler, and more efficient than TCP.

However, UDP also has some downsides compared to TCP:

  • No guaranteed ordering of packets — VoIP audio might be transmitted in a slightly different order than how it was sent.
  • No protection against duplicate packets.

In some cases, these disadvantages can lead to jumbled audio.

However, UDP is still always recommended for VoIP calls.

TCP – Transmission Control Protocol

This protocol is one of the most commonly used protocols within the IP suite because it ensures the integrity of end-to-end data delivery over a network.

Here is a quick overview of the Transmission Control Protocol:

  • Connection-oriented
  • Good failure recovery
  • High error rate handling and error-checking
  • Sequencing – packets arrive in order at the receiver
  • Relatively slower than UDP.

TCP is connection-oriented, which means that a connection must be established before data transmission takes place. The connection must also be closed after transmitting the voice packets. This comes with high overhead.

It also provides extensive error-checking mechanisms. If packets are lost, TCP will try to recover and retransmit those packets.

Your VoIP lines will become garbled due to packets trying to recover themselves, making it difficult to make sense of conversations.

TCP is ideal for applications like peer-to-peer file transfer, secure shell, and Internet Message Access Protocol (IMAP), for example. But, it’s actually harmful to low-latency connections like VoIP.

TCP versus UDP: What Do VoIP Experts Recommend?

As a network administrator or VoIP engineer, you’ll want to remember that UDP is ideal for VoIP and SIP connections.

Using UDP will help improve call quality significantly. It will also help with device registration. If you’re trying to register lots of VoIP devices on your network, TCP will slow down your servers.

To learn more about using the differences between TCP and UDP and which is better for VoIP, speak with one of our telecom experts.

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