Jumbo frames are Ethernet frames where the MTU is greater than the standard 1,500 bytes and a maximum of 9,000 bytes. The larger MTU provides greater efficiency because less overhead and fewer acknowledgments are sent across devices, drastically reducing interrupt load on endpoints. Jumbo frames are recommended for most workloads because the amount of data sent per message is far greater, reducing processing times and maximizing efficiency. While the general assumption is that jumbo frames provide performance advantages for all workloads, measure results in a lab environment simulating a specific workload to ensure performance enhancements.

For jumbo frames to take advantage of the greater efficiencies, they must be enabled end-to-end on all hops between endpoints. Otherwise, the MTU could be lowered through PMTUD or packets could be fragmented. The fragmentation and reassembly affect the CPU performance of each hop, which affects the overall latency.

For example, if a client is set to an MTU of 1,500 bytes while other hops are set to 9,000 bytes, transmission along the path will most likely set to 1,500 bytes using PMTUD, unless other options are configured.

Jumbo frames use the same Ethernet packet structure described in the previous section. However, the difference is the size of the data within the payload. The byte consumption of the other components within the frame remains the same, while each packet contains more data with the same overhead. A jumbo frame Ethernet payload is displayed in the following figure:

Figure 23.    Jumbo frames Ethernet payload