IEEE 802.3
|
|
IEEE 802.3 is a collection of IEEE standards defining the physical layer and transport layer of (a variant 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.
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 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".
| Contents |
Versions of Ethernet
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 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. 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 |
| 802.3y | 1998 | 100BASE-T2 100 Mbit/s over low quality twisted pair |
| 802.3z | 1998 | 1000BASE-X Gbit/s Ethernet over coax 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 infomation. |
| 802.3ad | 2000 | Link aggregation for parallel links |
| 802.3ae | 2003 | 10 Gbit/s Ethernet over fiber; 10GBASE-SR, 10GBASE-LR |
| IEEE 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 the IEEE 802.3 standard 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.
See also
- IEEE 802
- IEEE 802.11, the corresponding set of Wireless Ethernet standards
References
- This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
External links
- http://www.ieee802.org/3/ -- The IEEE 802.3 Working Group
- IEEE 802.3-2002 (pdf) (http://standards.ieee.org/getieee802/download/802.3-2002.pdf): Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specification.es:IEEE 802.3