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Jumbo Frames — Are You Sure Your Network TAPs Support Them?

January 28, 2016

There are certain things you can always rely on in this world. The refreshing taste of a drink after a long day at work. The other side of your pillow always being cooler. And the fact that if your network TAP supports Ethernet it inherently supports jumbo frames—at least we thought this one was reliable. It turns out there are many network TAP customers out there who implement their solutions only to find that Ethernet support doesn’t mean jumbo frame support for some vendors.

With network traffic demands increasing everyday, we should be able to rely on Ethernet standards to include jumbo frames.

Ethernet Frames vs. Jumbo Frames—What’s the Big Deal?

The difference between standard Ethernet frames and jumbo frames is fairly simply. Standard Ethernet frames support packet sizes up to 1,522 bytes whereas jumbo frames support packets up to 9,216 bytes. Support for larger packets means greater network speeds can be achieved, which is essential as data demands continue to rise.

The problem is that there is a gray area in Ethernet standards that many vendors exploit. Vendors can meet IEEE 802.3 standards with a wider range of frame-size support than you might expect. Even though gigabit Ethernet is becoming a standard, jumbo frame support isn’t quite keeping up. If you unknowingly deploy network TAPs that don’t support jumbo frames, you’re in for quite the surprise.

When network TAPs only support standard 1,522 byte frames in a gigabit environment, anything larger can’t be processed and is ultimately dropped. You deployed network TAPs to ensure visibility, but you’ll be dropping packets more than ever before. 

Jumbo frame support should be assumed in a gigabit network TAP; but it can’t be and you must be prepared to notice the missing specification.

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Don’t Rely on Ethernet Standards—Do Your Jumbo Frame Due Diligence

The jumbo frame dilemma boils down to one key piece of advice—as you’re building your network, you need to ensure that all of your components can support your desired speed and packet size. 

When your network TAPs don’t support jumbo frames, you’re accepting the fact that you’ll soon hit a wall with your network. You’ll max out on standard frame data transfer rates and be left with a network that requires a complete overhaul of its components. In short, you need to support jumbo frames if you want to continue growing your network.

Garland Technology network TAPs supporting 1G and higher speeds are all guaranteed to support jumbo frames and your growing network. If you want to learn more about how you can implement Garland’s network TAPs in your infrastructure, contact the visibility experts now and discover how to see every bit, byte and packet®—no matter how big the packets are.

Looking to add a visibility solution to your industrial deployment, but not sure where to start? Join us for a brief network Design-IT consultation or demo. No obligation - it’s what we love to do.

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Heartbeats Packets Inside the Bypass TAP

If the inline security tool goes off-line, the TAP will bypass the tool and automatically keep the link flowing. The Bypass TAP does this by sending heartbeat packets to the inline security tool. As long as the inline security tool is on-line, the heartbeat packets will be returned to the TAP, and the link traffic will continue to flow through the inline security tool.

If the heartbeat packets are not returned to the TAP (indicating that the inline security tool has gone off-line), the TAP will automatically 'bypass' the inline security tool and keep the link traffic flowing. The TAP also removes the heartbeat packets before sending the network traffic back onto the critical link.

While the TAP is in bypass mode, it continues to send heartbeat packets out to the inline security tool so that once the tool is back on-line, it will begin returning the heartbeat packets back to the TAP indicating that the tool is ready to go back to work. The TAP will then direct the network traffic back through the inline security tool along with the heartbeat packets placing the tool back inline.

Some of you may have noticed a flaw in the logic behind this solution!  You say, “What if the TAP should fail because it is also in-line? Then the link will also fail!” The TAP would now be considered a point of failure. That is a good catch – but in our blog on Bypass vs. Failsafe, I explained that if a TAP were to fail or lose power, it must provide failsafe protection to the link it is attached to. So our network TAP will go into Failsafe mode keeping the link flowing.

Glossary

  1. Single point of failure: a risk to an IT network if one part of the system brings down a larger part of the entire system.

  2. Heartbeat packet: a soft detection technology that monitors the health of inline appliances. Read the heartbeat packet blog here.

  3. Critical link: the connection between two or more network devices or appliances that if the connection fails then the network is disrupted.

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