The IEEE defines Gigabit Ethernet in standards 802.3z for optical cabling and 802.3ab for electrical cabling. Like Fast Ethernet, Gigabit Ethernet retains many familiar features of slower Ethernet variants. CSMA/CD still is used and can be disabled for full-duplex support. The 802.3z and 802.3ab standards call for the use of the same old IEEE 802.3 MAC and 802.2 LLC framing for the LAN headers and trailers. The most likely place to use Gigabit is between switches, between switches and a router, and between a switch and a server.
Gigabit Ethernet is similar to its slower cousins in several ways. The most important similarity is that the same Ethernet headers and trailers are used, regardless of whether it's 10 Mbps, 100 Mbps, or 1000 Mbps. If you understand how Ethernet works for 10 and 100 Mbps, then you know most of what you need to know about Gigabit Ethernet.
Gigabit Ethernet differs from the slower Ethernet specifications in how it encodes the signals onto the cable. Gigabit Ethernet is obviously faster, at 1000 Mbps, or 1 Gbps.
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