Jumbo frame

In computer networking, jumbo frames or jumbos are Ethernet frames with more than 1500 bytes of payload, the limit set by the IEEE 802.3 standard. Conventionally, jumbo frames can carry up to 9000 bytes of payload, but variations exist and some care must be taken using the term. Many Gigabit Ethernet switches and Gigabit Ethernet network interface cards can support jumbo frames. Some Fast Ethernet switches and Fast Ethernet network interface cards can also support jumbo frames. Most national research and education networks (such as Internet2, National LambdaRail, ESnet, GÉANT and AARNet) support jumbo frames, but most commercial Internet service providers do not.

Each Ethernet frame must be processed as it passes through the network. Processing the contents of a single large frame is preferable to processing the same content broken up into smaller frames, as this makes better use of available CPU time by reducing interrupts. This also minimizes the overhead byte count and reduces the number of frames needing to be processed. This is analogous to physically mailing a packet of papers instead of several single envelopes with one sheet each, saving envelopes and cutting sorting time.

Jumbo frames gained initial prominence when Alteon WebSystems introduced them in their ACEnic Gigabit Ethernet adapters. Many other vendors also adopted the size; however, jumbo frames did not become part of the official IEEE 802.3 Ethernet standard.

Jumbo frames or 9000-byte payload frames have the potential to reduce overheads and CPU cycles. Recent work has also demonstrated the positive effect that jumbo frames have on end-to-end TCP performance. The presence of jumbo frames may have an adverse effect on network latency, especially on low bandwidth links. The frame size used by an end-to-end connection is typically limited by the lowest frame size in intermediate links. 802.5 Token Ring can use frames with a 4464-byte MTU, FDDI can transport 4352 byte, ATM 9180 byte and 802.11 can transport 7935 byte MTUs. The IEEE 802.3 Ethernet standard only mandates support for 1500-byte MTU frames, 1518 byte total frame size (1522 byte with the optional IEEE 802.1Q VLAN/QoS tag).

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