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• LINKSYS JUMBO FRAMES UPDATE

Simple additive checksums as contained within the UDP and TCP transports have proven ineffective at detecting bus-specific bit errors because with simple summations, these errors tend to self-cancel. As of IEEE 802.3-2015, allowed values are 1518 (only basic frames), 1522 (802.1Q-tagged frames), and 2000 (multi-tagged, envelope frames).

It allows frame length detection on a port by a two-octet field. IEEE 802.1AB-2009 and IEEE 802.3bc-2009 added LLDP discovery to standard Ethernet for maximum frame length ( TLV subtype 4). Most Ethernet equipment can support jumbo frames up to 9216 bytes.

Manufacturers have in turn adopted 9000 bytes as the conventional MTU size, with a total jumbo frame size of between 90 bytes with ethernet headers included. Their recommendation has been adopted by all other national research and education networks. The use of 9000 bytes as preferred payload size for jumbo frames arose from discussions within the Joint Engineering Team of Internet2 and the U.S.

LINKSYS JUMBO FRAMES UPDATE

The IEEE 802.3as update grandfathered in multiple common headers, trailers, and encapsulations by creating the concept of an envelope where up to 482 bytes of header and trailer could be included, and the largest IEEE 802.3 supported Ethernet frame became 2000 bytes. The IEEE 802.3 Ethernet standard originally mandated support for 1500-byte MTU frames, 1518 byte total frame size (1522 byte with the optional IEEE 802.1Q VLAN/ QoS tag). 802.5 Token Ring can support frames with a 4464-byte MTU, FDDI can transport 4352-byte, ATM 9180-byte and 802.11 can transport 7935-byte MTUs. The frame size used by an end-to-end connection is typically limited by the lowest frame size in intermediate links. The presence of jumbo frames may have an adverse effect on network latency, especially on low-bandwidth links. Jumbo frames have the potential to reduce overheads and CPU cycles and have a positive effect on end-to-end TCP performance. Many other vendors also adopted the size however, jumbo frames are not part of the official IEEE 802.3 Ethernet standard. Jumbo frames gained initial prominence in 1998, when Alteon WebSystems introduced them in their ACEnic Gigabit Ethernet adapters. 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. This also minimizes the overhead byte count and reduces the number of frames needing to be processed. 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. Each Ethernet frame must be processed as it passes through the network.