IEEE 802.3

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IEEE 802.3 is a collection of IEEE standards defining the physical layer and data link layer of wired Ethernet. This is generally a LAN technology with some WAN applications. Physical connections are made between nodes and/or infrastructure devices (hubs, switches, routers) by various types of copper or fiber cable.

802.3 is a technology that can support the IEEE 802.1 network architecture.

The maximum packet size is 1518 bytes, although to allow the Q-tag for Virtual LAN and priority data in 802.3ac it is extended to 1522 bytes. If the upper layer protocol submits a PDU (Protocol data unit) less than 64 bytes, 802.3 will pad the data 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/Type, data, 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".

Versions of 802.3

The original Ethernet is called "Experimental Ethernet" today. It was developed by Bob Metcalfe and was based in part on the wireless Alohanet protocol. It is not in use anywhere, but is thought to be the only Ethernet by some purists. The first "Ethernet" that was generally used outside Xerox was the DIX Ethernet. However, as DIX Ethernet was derived from Experimental Ethernet, and as many standards have been developed that are based on DIX Ethernet, the technical community has accepted the term Ethernet for all of them. Therefore, the term "Ethernet" can be used to name networks using any of the following standardized media and functions:

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. The Internet protocol suite use this frame format on any media.
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)
802.3b 1985 10BROAD36
802.3c 1985 10 Mbit/s repeater specs
802.3d 1987 FOIRL (Fiber-Optic Inter-Repeater Link)
802.3e 1987 1BASE5 or StarLAN
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-TX, 100BASE-T4, 100BASE-FX Fast Ethernet at 100 Mbit/s (w/Auto-Negotiation)
802.3x 1997 Full Duplex and flow control; also incorporates DIX framing, so there's no longer a DIX/802.3 split
802.3y 1998 100BASE-T2 100 Mbit/s over low quality twisted pair
802.3z 1998 1000BASE-X Gbit/s Ethernet over Fibre-Optic at 1 Gbit/s
802.3ab 1999 1000BASE-T Gbit/s Ethernet over twisted pair at 1 Gbit/s
802.3ac 1998 Max frame size extended to 1522 bytes (to allow "Q-tag") The Q-tag includes 802.1Q VLAN information and 802.1p priority information.
802.3ad 2000 Link aggregation for parallel links
802.3ae 2003 10 Gbit/s Ethernet over fiber; 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, 10GBASE-SW, 10GBASE-LW, 10GBASE-EW
802.3af 2003 Power over Ethernet
802.3ah 2004 Ethernet in the First Mile
802.3ak 2004 10GBASE-CX4 10 Gbit/s Ethernet over twin-axial cable
802.3an in work 10GBASE-T 10 Gbit/s Ethernet over unshielded twisted pair(UTP)
802.3ap in work Backplane Ethernet (1 and 10 Gbit/s over printed circuit boards)
802.3aq in work 10GBASE-LRM 10 Gbit/s Ethernet over multimode fiber
802.3ar in work Congestion management
802.3as in work Frame expansion

What is defined in earlier IEEE 802.3 standards is often confused for what is used in practice: almost any network frame you can find on a LAN will be an Ethernet II frame, since the Internet protocol suite will use this format, with the type field set to the corresponding IETF protocol type. IEEE 802.3x-1997 allows the 16-bit field after the MAC addresses to be used as a type field or a length field, so that Ethernet II frames are also valid 802.3 frames in 802.3x-1997 and later versions of the IEEE 802.3 Ethernet standard.

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