Gigabit Ethernet

Tens years ago, compared to when I was writing this chapter in April 2003, Ethernet technology was just getting to the point that 10BASE-T networks were becoming common. Those networks shared 10 Mbps between all devices. On the horizon at that time was the promise of Ethernet switching, with which you could actually have 10 Mbps on each port of the switch.

Ethernet has gone from being one of many competing LAN technologies, with several competitors, to the king of the LAN in 10 years. With "10 Gig E," as it is commonly called, Ethernet has increased its speed a thousandfold in 10 years and has won the war in terms of LAN technologies. Just as the last 10 years have seen the emergence of TCP/IP as the most prolific Layer 3 protocol, Ethernet has become the most prolific Layer 1 and Layer 2 LAN standard.

10 Gig Ethernet, defined in IEEE 802.3ae, runs at 10 Gbps—it would be poorly named if not! It uses the same 802.3 MAC and 802.2 LLC as the other types of Ethernet. But it does have some differences with the other types:

■ It allows only a point-to-point topology because it is intended for connectivity between switching devices.

■ It allows only full-duplex communication.

■ It specifies only optical fiber—no copper cabling. (Support for copper wiring might be added later.)

It will be a while before 10 Gig E becomes a cost-effective alternative for the wiring closet, but it is becoming a part of high-speed core enterprise networks already. Also, 10 Gig E has some very interesting applications for service providers as a trunking mechanism between switching locations. And with support for 10 Gig E using SM fiber for up to 40 km, 10 Gig E might help Ethernet continue its movement from a LAN technology into the WAN arena.

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