Ethernet protocols refer to the family of local-area network (LAN) covered by the IEEE 802.3 standard. The Gigabit Ethernet is based on the Ethernet protocol, but increased speed tenfold over the fast Ethernet, using shorter frames with carrier Extension. It is published as the IEEE 802.3z and 802.3ab, supplement to the IEEE 802.3 base standards.

Carrier Extension is a simple solution, but it wastes bandwidth. Packet Bursting is "Carrier Extension plus a burst of packets". Burst mode is a feature that allows a MAC to send a short sequence (a burst) of frames equal to approximately 5.4 maximum-length frames without having to relinquish control of the medium.

The Gigabit Ethernet standards are fully compatible with Ethernet and Fast Ethernet installations. It retains Carrier Sense Multiple Access/ Collision Detection (CSMA/CD) as the access method. It supports full-duplex as well as half duplex modes of operation. Single-mode and multi mode fiber and short-haul coaxial cable, and twisted pair cables are supported. The Gigabit Ethernet architecture is displayed in the following figure:

Gigabit (1000 Mbps) Ethernet: IEEE 802.3z (1000Base-X), 802.3ab (1000Base-T) & GBIC

The IEEE 802.3z defines the Gigabit Ethernet over fiber and cable, which has a physical media standard 1000Base-X (1000BaseSX C short wave covers up to 500m, and 1000BaseLX C long wave covers up to 5km). The IEEE 802.3ab defines the Gigabit Ethernet over the unshielded twisted pair wire (1000Base-T covers up to 75m).

The Gigabit interface converter (GBIC) allows network managers to configure each gigabit port on a port-by-port basis for short-wave (SX), long-wave (LX), long-haul (LH), and copper physical interfaces (CX). LH GBICs extended the single-mode fiber distance from the standard 5 km to 10 km.

Protocol Structure

1000Base-X has a minimum frame size of 416bytes, and 1000Base-T has a minimum frame size of 520bytes. An extension field is used to fill the frames that are shorter than the minimum length.

• Preamble (PRE)- 7 bytes. The PRE is an alternating pattern of ones and zeros that tells receiving stations that a frame is coming, and that provides a means to synchronize the frame-reception portions of receiving physical layers with the incoming bit stream.
• Start-of-frame delimiter (SFD)-1 byte. The SOF is an alternating pattern of ones and zeros, ending with two consecutive 1-bits indicating that the next bit is the left-most bit in the left-most byte of the destination address.
• Destination address (DA)- 6 bytes. The DA field identifies which station(s) should receive the frame..
• Source addresses (SA)- 6 bytes. The SA field identifies the sending station.
• Length/Type- 2 bytes. This field indicates either the number of MAC-client data bytes that are contained in the data field of the frame, or the frame type ID if the frame is assembled using an optional format.
• Data-Is a sequence of n bytes (46=< n =<1500) of any value. The total frame minimum is 64bytes.
• Frame check sequence (FCS)- 4 bytes. This sequence contains a 32-bit cyclic redundancy check (CRC) value, which is created by the sending MAC and is recalculated by the receiving MAC to check for damaged frames.
• Ext C extension, which is an non-data variable extension field for frames that are shorter than the minimum length.

Packet Bursting Mode:

Gigabit (1000 Mbps) Ethernet: IEEE 802.3z (1000Base-X), 802.3ab (1000Base-T) & GBIC

Related protocols: IEEE 802.3, 802.3u, 802.3z, 802.2, 802.1, 802.3ae, 802.1D, 802.1Q, 802.1p, 802.1X, FDDI, Token Ring

Sponsor Source: Gigabit Ethernet is defined by IEEE (http://www.ieee.org) 802.3z and 802.3ab.

Reference:
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.
http://www.cis.ohio-state.edu/~jain/cis788-97/ftp/gigabit_ethernet/index.htm: Gigabit Ethernet
http://www.cis.ohio-state.edu/~jain/refs/gbe_refs.htm : Links and reference regarding Ethernet