Later This Year: 1-GB Ethernet Switches

An Ethernet network transferring data at 1 Gbps is the Ethernet vendor's answer to ATM technology. Dik McLellan at CNet said, "Ethernet people don't want ATM to happen, so 1 Gb is their move to keep ATM on the back burner."

The 1-Gb Ethernet products began to appear in the U.S. in late 1996, all using proprietary technologies. We should see standard protocols for 1-Gb networking equipment by midyear. As a result of the lack of a standard, the Taiwanese are waiting to introduce 1-Gb switches, but most agree that 1 Gb has potential for late this year, though volumes will be low. Some manufacturers see problems in commerci ally implementing 1-Gb products, notwithstanding 1 Gb's use of the same technology as Ethernet and Fast Ethernet. For the Taiwanese, 1-Gb technology is mostly a fancy tweaking of standard Ethernet technology. Mark Huang, of Tamarack MicroElectronics, says, "Basically, 1-Gb Ethernet uses the same technology as 100-Mb, but at a higher frequency. This heightens the problem of collisions. As a result, every node needs a switch. You can't use standard hub designs." Lu at Accton adds that the technology "not only increases the signal frequency but also splits data into three channels from the one channel used by 10- or 100-Mb Ethernet." Cabling is another potential problem with 1 Gb. Current designs call for either the use of four-pair, category 5 unshielded twisted pair (UTP) or fiber-optic cabling. Ken Lu at Accton disagrees, however, thinking that fiber-optic cable is the only way to go.

The problem of increased cabling costs pales in comparison to basic flaws in 1-Gb techno logy. Due to the high speed of packet transfer, collision detection greatly reduces the effective transfer distance of 1-Gb Ethernet. McLellan says that because of the need for collision control, 1-Gb Ethernet is limited to a distance of 10 meters, or 20 meters duplexed. Henry Ngai at D-Link concurs but sees a potential way around this distance limit in a move back to VG technology. He says, "If you go to 1 Gb, VG technology begins to get attractive again. That's because you don't need a switch and you can go farther than the 20-meter limit."

Even if the distance barrier is overcome, however, most Taiwanese doubt the basic need for 1-Gb. Their question is one of total system data flow. Officials at D-Link, CNet, Accton, and Tamarack all say that at 1 Gb you get CPU and software bottlenecks in the total system. McLellan says, "Even at 100 Mb, the network is not the bottleneck. System constraints are. Current systems certainly can't match 1-Gb-level bandwidth." Ngai concurs, pointing out that at 10 Mbps yo u get 1000 packets per second with interrupts. At 100 Mbps you have 10,000. At 1 Gb you have 100,000 packets per second with interrupts, which is more than any current or planned CPU or software can handle. Ngai doubts the mainstream need for 1 Gb. "Since most traffic in a network is intradepartmental," he says, "1 Gb is not really cost-effective. A better solution is a 12-port 100-Mb switching hub."

Most Taiwanese agree that 1 Gb will not be mainstream until 1998, but most still plan to offer some type of 1-Gb product this year. Accton, in particular, will offer a mixed 100-Mb/1-Gb switch at the end this year. As is usual in the PC market, though, the Taiwanese suggest caution when buying first-edition products.

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Speed and Reach

                 Packets           Effective
                per second         distance

 10 Mb              1000               1 K
100 Mb            10,000             100 m
  1 Gb           100,000              10 m