IEEE 802.3
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IEEE 802.3 is a collection of IEEE standards defining the physical layer, and the media access control (MAC) sublayer of the 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 protocol data unit (PDU) less than 64 bytes, 802.3 will pad the data field to achieve the minimum 64 bytes. The minimum Frame size will then always be of 64 bytes.
Although it is not technically correct, the terms packet and frame are often used interchangeably. The ISO/IEC 8802-3 and ANSI/IEEE 802.3 standards refer to MAC sub-layer frames consisting of the destination address, the source address, length/type, data payload, and frame check sequence (FCS) fields. The preamble and Start Frame Delimiter (SFD) are (usually) together considered a header to the MAC frame. This header and the MAC frame constitute a packet.
The original Ethernet is called Experimental Ethernet today. It was developed by Robert Metcalfe in 1972 (patented in 1978) 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[who?]. The first Ethernet that was generally used outside Xerox was DIX Ethernet, followed by Ethernet II. IEEE defines a 802.3 standard where the Type field is replaced by Length, and an 802.2 LLC header follows with the Type field. 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:
IEEE 802.3 Standards
| Ethernet Standard | Date | Description |
|---|---|---|
| Experimental Ethernet |
1972 | 2.94 Mbit/s (367 kB/s) over coaxial cable (coax) cable bus |
| Ethernet II (DIX v2.0) |
1982 | 10 Mbit/s (1.25 MB/s) over thin coax (thinnet) - Frames have a Type field. This frame format is used on all forms of Ethernet by protocols in the Internet protocol suite. |
| IEEE 802.3 | 1983 | 10BASE5 10 Mbit/s (1.25 MB/s) over thick coax - same as DIX except Type field is replaced by Length, and an 802.2 LLC header follows the 802.3 header |
| 802.3a | 1985 | 10BASE2 10 Mbit/s (1.25 MB/s) over thin Coax (thinnet or cheapernet) |
| 802.3b | 1985 | 10BROAD36 |
| 802.3c | 1985 | 10 Mbit/s (1.25 MB/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 (1.25 MB/s) over twisted pair |
| 802.3j | 1993 | 10BASE-F 10 Mbit/s (1.25 MB/s) over Fiber-Optic |
| 802.3u | 1995 | 100BASE-TX, 100BASE-T4, 100BASE-FX Fast Ethernet at 100 Mbit/s (12.5 MB/s) w/autonegotiation |
| 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 (12.5 MB/s) over low quality twisted pair |
| 802.3z | 1998 | 1000BASE-X Gbit/s Ethernet over Fiber-Optic at 1 Gbit/s (125 MB/s) |
| 802.3-1998 | 1998 | A revision of base standard incorporating the above amendments and errata |
| 802.3ab | 1999 | 1000BASE-T Gbit/s Ethernet over twisted pair at 1 Gbit/s (125 MB/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 |
| 802.3-2002 | 2002 | A revision of base standard incorporating the three prior amendments and errata |
| 802.3ae | 2003 | 10 Gbit/s (1,250 MB/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 (1,250 MB/s) Ethernet over twin-axial cable |
| 802.3-2005 | 2005 | A revision of base standard incorporating the four prior amendments and errata. |
| 802.3an | 2006 | 10GBASE-T 10 Gbit/s (1,250 MB/s) Ethernet over unshielded twisted pair(UTP) |
| 802.3ap | 2007 | Backplane Ethernet (1 and 10 Gbit/s (125 and 1,250 MB/s) over printed circuit boards) |
| 802.3aq | 2006 | 10GBASE-LRM 10 Gbit/s (1,250 MB/s) Ethernet over multimode fiber |
| 802.3ar | On Hold | Congestion management |
| 802.3as | 2006 | Frame expansion |
| 802.3at | exp. 2008 | Power over Ethernet enhancements |
| 802.3au | 2006 | Isolation requirements for Power Over Ethernet (802.3-2005/Cor 1) |
| 802.3av | exp. 2009 | 10 Gbit/s EPON |
| 802.3aw | 2007 | Fixed an equation in the publication of 10GBASE-T (released as 802.3-2005/Cor 2) |
| 802.3ax | exp 2008 | Move Link aggregation out of 802.3 to IEEE 802.1 |
| 802.3ay | exp 2008 | Maintenance to base standard |
| 802.3az | exp 2007 | Energy Efficient Ethernet |
| 802.3ba | exp. 2009 | Higher Speed Study Group. 40 Gbit/s over 1m backplane, 10m Cu cable assembly (4x25 Gbit or 10x10 Gbit lanes) and 100 m of MMF and 100 Gbit/s up to 10 m or Cu cable assembly, 100 m of MMF or 40 km of SMF respectively |
What is defined in earlier IEEE 802.3 standards is often confused for what is used in practice: most network frames you will find on an Ethernet will be DIX frames, 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 DIX frames are also valid 802.3 frames in 802.3x-1997 and later versions of the IEEE 802.3 Ethernet standard.
See also
- IEEE 802
- IEEE 802.1, the network architecture
- IEEE 802.11, a set of wireless networking standards
- IEEE 802.16, a set of WiMAX standards
- IEEE_802.11g-2003 a set of wireless networking standards
References
This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.
External links
- http://www.ieee802.org/3/ -- The IEEE 802.3 Working Group
- http://www.ieee802.org/3/eee_study/index.html -- IEEE 802.3 Energy Efficient Ethernet Study Group
- Get IEEE 802.3 LAN/MAN CSMA/CD Access Method -- Download 802.3 specifications.
