rdized is Fast Ethernet hubs and switching hubs -- technology that adds value, but at a price that's mainstream.
Fast Ethernet
Fast Ethernet transfers data at 100 Mbps (or 100,000 bits per second), 10 times the rate of standard Ethernet. Until early 1996, there were two different competing Fast Ethernet technologies on the market, TX and VG.
While VG is still available, primarily from Hewlett-Packard, TX is now recognized as the preferred standard. This is true even though VG has some technology advantages over TX, namely, no collisions and no dropped packets. What is on the market, though, shows that TX has won out; even HP is now making TX products. The reason for TX's success is twofold. One is that Fast Ethernet TX switches allow for flow control. According to H
enry Ngai, customer service vice president for network products manufacturer D-Link, flow control allows the switching hub to send data until told not to by the receiver. The hub then switches to the next node, thus eliminating collisions and lost packets. The other reason is a marketing one. VG is a variation of the proprietary Token Ring technology. Ken Lu, R&D vice president for the network company Accton Technology, thinks that "VG is no good because nobody wants to follow a proprietary standard." The network market, like the information-technology (IT) market in general, is loath to support any kind of proprietary solution, for obvious reasons.
10-/100-Mbps Hubs
This year, mixed 10-/100-Mbps hubs and switching hubs will be the so-called cutting-edge product area for Taiwan's network makers. Various Taiwanese manufacturers have had Fast Ethernet hubs for more than two years, though sales have been limited. This year, though, all manufacturers agree that such products will have
wide market acceptance because of the favorable cost/performance ratio they offer.
It's been widely written that Fast Ethernet provides 10 times the performance at only twice the price. If this were true, the buyer's choice would be obvious. The 100-Mbps adapter cards run at about that cost differential but hubs and switches are still about six times the cost of a similar Ethernet product.
On the high-end, high-bandwidth front, most Taiwanese network manufacturers now offer pure, multiport 100-Mbps Ethernet hubs and switching hubs. D-Link offers an eight-port design. CNet and Network Peripherals, Inc. (NPI) both offer 12-port pure 100-Mbps Ethernet hubs and switching hubs. These products are expensive, however, and their popularity is limited to engineering workgroups or large LANs that have multiple enterprise servers. The Fast Ethernet hub services the enterprise servers and serves as their link to most of the network. It also acts as a dedicated 100-Mbps hub for heavy data users that need large th
roughput capability for activities such as sharing graphics files.
Mixed Speeds
All the Taiwanese firms offer the mixed-speed feature in their 100-Mbps hubs and switching hubs. Commonly called N-way, this feature allows the controller to auto-sense what a node can handle and to send data at either 100 or 10 Mbps. Again, though, this is an expensive solution for addressing mixed-speed environments. As a result, the Taiwanese have a large array of mixed 10-/100-Mbps hubs and switching hubs.
Few users need a total 100-Mbps network since most don't regularly handle extremely large files. Most networks, however, can see a marked performance improvement with mixed 10-/100-Mbps hubs and switching hubs. Prices for these products will in fact soon reach the magical "times-two" price of standard Ethernet. This makes these products especially attractive in Europe, where running fiber-optic cable between buildings is more common than in the U.S. For areas where fiber-optic cabling is not wide
spread, 100 Mbps could be a problem. Fast Ethernet can support distances up to 2 kilometers if fiber-optic cabling is used. Without fiber, category 5 unshielded-twisted-pair (UTP) cable is needed.
This is also known as "data quality" cable. The effective distance between hubs using UTP is only 200 meters using duplexing. Duplexing in networks is analogous to that in standard phone lines. The effect for the user is a doubling of bandwidth.
Reduced Chip Counts
One reason why mixed 10/100 hubs are coming down in price is the appearance of reduced chip count solutions for these products from many vendors. Basic network hub chip design calls for three types of chips: a controller chip, transceiver chips, and a physical (PHY) layer chip. Previous designs from Taiwan used a variety of mixed-chip solutions. Some were even as costly as one transceiver and controller chip per port. Several of the larger Taiwanese network manufacturers save money by having their own 10/100 hub and switching
hub chips developed.
D-Link's Ngai says, "We'll have a one-chip solution for a 2x100-Mb/12x10-Mb hub in the first quarter." Dik McLellan, product marketing manager at CNet Technology, agrees. He said, "In the first quarter, there will be single-chip solutions for mixed 10/100 hubs and switches." A few Taiwanese IC design houses also offer network chips, but they don't agree that one-chip solutions will be coming to market anytime soon, at least at the switching-hub level.
Mark Huang, president of Tamarack Microelectronics, says that "UTP transceiver chips still need to be done with a BiCMOS process. CMOS process yields are still only around 20 percent. There is a learning curve, however, so eventually yields will get better." Huang also said that Ethernet switching hub chips are a long way from moving to a single-chip from the present three-chip solution. He believes it won't happen until "we can move to 0.35-micron process fabrication with increased yields. If someone did have a single-chip solution
, though, they would make a lot of money."
Switching Hubs
Switching hubs are important for large networks for two reasons: They overcome TX's problem with collisions, and they offer an advantage over standard 100-Mbps hubs by partitioning an overloaded network. When a packet is forwarded to another node in the same segment, the switch confines traffic to that segment. If a packet is sent to a node in another segment, the switch will forward the packet only to that segment, isolating traffic from other segments. This increases network throughput and helps balance the network's load. Also, as Ken Lu points out, "You have to add a switch if there are more than two hubs in a network." With a much smaller forwarding delay than that of a bridge, you can connect as many hubs as needed. This overcomes the limitations of Fast Ethernet repeater hubs. The Taiwanese believe that, at a corporate level, mixed 10/100 hubs and switches will replace pure 10-Mbps products. They believe that it makes go
od planning sense to migrate to the higher performance mixed products. The 10-Mb switching hubs seem especially doomed to the technology graveyard. On the whole, however, the Taiwanese believe that 10 Mb will predominate in the network products sold this year because most of the world's companies are small and don't need the throughput of 100 Mbps.
Technology Limits
Fast Ethernet does not now support priority sorting of data, but Ngai at D-Link said that Fast Ethernet will soon have that capability. This is important for videoconferencing applications since the data flow of the videoconference must not be interrupted. Another limitation lies in the number of ports that can be supported, which is now 12. Lu at Accton believes that 24 ports will be available by midyear. The 100-Mbps switching hubs often outperform the systems they are made to support, which is something to consider when making purchase decisions. McLellan at CNet cites the example of customers buying ISA 100-Mb Ethernet
cards: Fast Ethernet transfers data at 12.5 MB but the ISA bus is running at only 8 MB.
Where to Find
Accton Technology Corp.
Hsinchu, Taiwan
Phone: +886 35 770 270
Phone: +886 35 783 839
Internet:
http://www.accton.com.tw
The Cost/Performance Network Shuffle
