Jumbo Frames
Each network device has a Maximum Transmission Unit (MTU) that defines the largest packet that can be transmitted though its interfaces. A standard Ethernet frame will carry a 1500 byte payload (MTU = 1500 bytes). Since Ethernet was invented, around 1980, it has used a 1500 byte payload size, with a total frame size of 1518 or 1522 bytes. In order to maintain backward compatibility, 100 Mbps Ethernet and 1 Gbps Ethernet used the same standard MTU. This was done so that a packet to or from any combination of 10/100/1000 Mbps Ethernet devices could be transmitted without any Ethernet frame fragmentation or reassembly.
Initially, the 1500 byte MTU for Ethernet was utilized due to the low speed of network communications and the high error rates. As a result, if a corrupted frame was transmitted, only 1500 bytes must be resent to correct the error. However, each frame requires network hardware and software processing. By increasing the frame size, the same amount of data can be transferred with less effort on the end-systems and network hardware.
Other commonly used network devices have utilized different MTU sizes, for instance: Fiber Distributed Data Interface (FDDI) = 4470, Asynchronous Transfer Mode (ATM) = 9180, Packet Over SONET (POS) = 9180, and High-Performance Parallel Interface (HIPPI) = 65280.
Jumbo Frames extends the Ethernet MTU from 1500 to 9000 bytes. The 9000 byte MTU will improve network data transfer performance on networks with 1 Gbps or higher links.
Why 9000 Bytes?
- The 9000 MTU is supported across a broad variety of a hardware and software elements.
- Secondly, the 9000 byte MTU is large enough to carry an 8 kilobyte application datagram (e.g., Network File System [NFS]) plus packet header overhead.
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Experimental results showing the impact of increased MTU on network throughput is shown here.
Note: In order to take advantage of Jumbo Frames, the end-to-end path must have Jumbo Frames enabled. If the LAN, WAN, or firewall infrastructure does not support Jumbo Frames, then the MTU will be constrained by the device of the smallest MTU in the entire path.
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Additional information on Jumbo Frames:
+ Configuring Jumbo Frames
+ Jumbo Frame Information
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Customer Service: Jumbo Frames
