802.3



         


IEEE 802.3 is the IEEE standard defining the physical layer and transport layer of (a variant of) Ethernet. The maximum segment length is 500m and the maximum total length is 2.5km. The maximum number of hosts is 1024.

The maximum packet size is 1518 bytes. If the upper layer protocol submits a PDU (Protocol data unit) less than 64 bytes, 802.3 will pad the LLC Info field to achieve the minimum 64 bytes.

Although it is not technically correct, the terms "packet" and frame are used interchangeably. The ISO/IEC 8802-3 ANSI/IEEE 802.3 Standards refer to MAC sub-layer frames consisting of the Destination Address, Source Address, Length, LLC Info., and FCS fields. The Preamble and SFD are (usually) considered a header to the MAC Frame. This header plus the MAC Frame constitute a "Packet".

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Versions of Ethernet

This original Ethernet, today, is called "Experimental Ethernet". It is not in use anywhere, but is thought to be the only Ethernet by purists. However, as many standards have been developed that are based on Experimental Ethernet - the technical community has accepted the term Ethernet for all of them. Therefore, Ethernet can be used to name any of the following:


Ethernet Standard Date Description
Experimental Ethernet 1972 (patented 1978) 2.94 Mbit/s over coaxial cable (coax) cable bus
Ethernet II (DIX v2.0) 1982 10 Mbit/s over thin coax (thinnet) - Frames have a Type field
IEEE 802.3 1983 10BASE5 10 Mbit/s over thick coax - same as DIX except Type field is replaced by Length and LLC fields
802.3a 1985 10BASE2 10 Mbit/s over thin Coax (thinnet or cheapernet)
802.3c 1985 10 Mbit/s repeater specs
802.3d 1987 FOIRL (Fiber-Optic Inter-Repeater Link)
802.3i 1990 10BASE-T 10 Mbit/s over twisted pair
802.3j 1993 10BASE-F 10 Mbit/s over Fiber-Optic
802.3u 1995 100BASE-T Fast Ethernet at 100 Mbit/s (w/Auto-Negotiation)
802.3x 1997 Full Duplex
802.3z 1998 1000BASE-X Gigabit Ethernet over coax at 1 Gbit/s
802.3ab 1999 1000BASE-T Gigabit Ethernet over twisted pair at 1 Gbit/s
802.3ac 1998 Max frame size extended to 1522 bytes (to allow VLAN tag)
802.3ad 2000 Link aggregation for parallel links
802.3ae 2003 10 Gigabit Ethernet over fiber
802.3af 2003 Power over Ethernet


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See also

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References

This article was originally based on material from the Free On-line Dictionary of Computing and is used under the GFDL.

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