What is a Jumbo Frame?

Quick Definition: Jumbo frames refer to network frames or packets that are larger than the standard Maximum Transmission Unit (MTU) of 1,500 bytes. The most common size for a jumbo frame is 9,000 bytes.

Every bit and byte of data sent between devices is neatly packaged in a frame, also called a packet. Part of that “neatly packaged” anecdote refers to a standardized frame or packet size, any frame larger than 1500 bytes. A jumbo frame is any packet larger than that 1500-byte maximum size.

This article will discuss the difference between standard and jumbo frames, the benefits of using jumbo frames over standard packet sizes, and how to configure jumbo frames on supported systems.

What are Jumbo Frames?

First, let’s discuss the standard frame size of 1500 bytes. This is a bit of a misnomer since the true frame size is 1518 bytes, with 1500 bytes of payload data, 14 bytes of router heading information, and 4 bytes for the checksum. This standard frame is called MTU, or Maximum Transmission Unit. Smaller MTUs provide faster transfer speeds, but jumbo frames also have advantages. 

Jumbo frames can be much larger than 1500 bytes. Unlike the standard frame size, which was established by IEEE 802.3, jumbo frames do not have a standard frame size. The most common size for jumbo frames is 9,000 bytes, but they can be as large as 65,535 bytes — though that is rare. By using larger frames, you can optimize your network’s throughput, which we’ll discuss in more detail later in this article. 

You may be thinking that sending bulkier packets would hinder network performance, but that’s a common misconception about jumbo frames. In most cases (and yes, there are outliers), jumbo frames help with network optimization. Let’s think of jumbo frames through this practical example: shipping and logistics.

Say you just purchased one of those build-it-yourself backyard playgrounds for children, the one with a slide, a couple of swings, and some monkey bars. What sounds easier for both the shipping company and you as the customer:

1. Sending, tracking, and receiving multiple smaller packages with all the different parts. 

2. Sending, tracking, and receiving a single, giant box with everything you need to get started with assembly.

It’s much easier to deal with the one large delivery, right? Multiple smaller deliveries increase the risk of packages getting lost and the risk of reaching a point in the build where you don’t have the parts you need.

Similarly, your devices can send multiple smaller frames, but this increases the risk of issues. So, sending and receiving jumbo frames is generally the more efficient option.

What are the Benefits of Implementing Jumbo Frames?

Diving a bit deeper into our analogy, having everything you need to build and complete your playground requires less mental energy because you don’t need to track multiple deliveries and remember whether you have the parts you need. 

Similarly, dealing with jumbo frames is less CPU-intensive than sending multiple smaller packets because there’s no (or considerably less) packet fragmentation and reassembly occurring. This reduction in fragmentation and reassembly also decreases bandwidth usage, freeing up more space on the delivery truck compared to multiple smaller deliveries. 

Jumbo frames also reduce latency by minimizing the number of packets that need to be processed and improving performance for applications that require large data transfers, such as video streaming or data backup. 

Considerations for Jumbo Frames Deployment

Despite the benefits of jumbo frames, there are a few challenges to consider.  One of the main considerations is whether your hardware and network can handle the increased size of packets. Older hardware may not support jumbo frames, and network hardware may have limitations on the frame size it can optimally handle. 

It’s also important to note that jumbo frames must be configured the same across all devices that will send and receive the larger packets. Mismatched configurations may lead to performance and communication issues.

The most common issue is frame mismatch, which occurs when a jumbo frame is sent to a device that is either not capable of receiving or not configured to receive that same size frame. Frame mismatch can be the result of a few different issues:

1. Hardware variations: Unless you’re buying all new hardware at the same time, your network likely consists of different device types and versions from different manufacturers. It’s common for some devices to either not support jumbo frame configuration at all or to have inconsistent configurations.

2. Configuration errors: Even with an automated configuration process, it’s always possible one or more devices have an anomalous frame size in the configuration settings. This mismatch can disrupt the whole system.

3. Configuration changes: It’s crucial to ensure your standard firmware updates and other configuration maintenance do not manipulate the frame size settings on your hardware. Otherwise, you risk introducing mismatch errors into your network.

4. Multiple networks and mixed environments: All the physical and virtual hardware needs to be capable of working with jumbo frames and configured to the same frame size. This applies to the devices in your office, your data center, and any cloud environment you may be using.

If you need to troubleshoot networking issues and you suspect jumbo frames may be the culprit, here’s a quick overview of troubleshooting advice:

1. Validate the configurations between the troublesome devices to ensure they match. This includes ensuring the devices can use jumbo frames and the maximum MTU settings match.

2. Utilize ping testing—ping one device from the other and vice versa to confirm they can communicate with each other to some extent. Also, try pinging a neutral device from all the troublesome devices to verify the network connection.

3. Utilize network monitoring tools like Wireshark or tcpdump to view detailed information about the packets, including their frame sizes and where traffic may begin experiencing issues.

How to Configure Jumbo Frames in Port Settings

Configuring jumbo frames will look different depending on the makes, models, and versions of the devices you’re working with. For this reason, it’s always recommended you refer to your device’s specific documentation for configuration instructions. 

Thankfully, though, this can usually be done with a few commands in the command line interface, and it should look something like this:

1. Specify the interface(s) you want to configure.

2. Specify the MTU size. 

3. Save the changes. 

4. Verify the changes are persistent.

As always, more specific instructions can be found in vendor documentation specific to your devices. 

Conclusion

Jumbo frames are an excellent way to fully leverage newer, capable equipment to optimize your network’s performance. By sending and receiving packets larger than the standard 1500 bytes, you reduce the risks associated with packet fragmentation and reassembly. You also decrease CPU utilization and overall bandwidth usage. Jumbo frames are most effective on networks with newer hardware with low latency and high throughput. 

To learn more about networking and network optimization, check out CBTNuggets certification training.