Practical Networking: Moving to 100 Mbit/s
Articles and Tips:
01 Sep 1998
To users, speed is everything. When you add users and applications to the network, however, the amount of time it takes to process users' requests may increase, causing users to complain about poor performance.
One way to satisfy users' need for speed is to migrate your company's 10 Mbit/s Ethernet network to a 100 Mbit/s Ethernet network. However, you may not have the time or budget to migrate the entire network to 100 Mbit/s Ethernet at one time: After all, you will need to purchase and install new hubs, new network interface boards in each workstation, and maybe even new workstations to replace older ones that do not have PCI slots.
To ease the pain of migrating to 100 Mbit/s Ethernet, many vendors have released products that allow you to migrate the network in stages. This article explains the types of products you can use to gradually migrate from 10 Mbit/s Ethernet to 100 Mbit/s Ethernet. This article also describes two migration scenarios to help you plan the migration for your company's network.
TYPES OF PRODUCTS
To begin the upgrade process, you need a product that allows you to run 100 Mbit/s Ethernet segments while retaining some 10 Mbit/s Ethernet segments. Until recently, the only available solution was a 10/100 switch, which creates a separate segment for each port. Because each port is independent of every other port, the traffic passing through one port affects only that port. However, a dual-speed switch can be expensive: A 10/100 switch typically ranges in price from U.S. $1,500 to U.S. $5,000, depending on the number of ports you need.
You now have the option of installing a 10/100 hub instead. A dual-speed hub actually contains two hubs that are connected internally by a dual-port switch module: One hub runs 10 Mbit/s Ethernet, and the other hub runs 100 Mbit/s Ethernet. When a port establishes a connection at a particular speed, this port becomes part of the segment that includes every other port which has established a connection at the same speed. As a result, all of the ports running at the same speed are connected to the same internal hub, thus sharing a single segment to access the network.
For example, if four ports established a connection at 100 Mbit/s and six ports established a connection at 10 Mbit/s, a dual-speed hub would create two segments--one for each speed. All of the ports running at 100 Mbit/s would share one segment, and all of the ports running at 10 Mbit/s would share one segment. A dual-speed switch, on the other hand, would create 10 segments--one for each port--thus providing better performance than a dual-speed hub.
The main benefit of a dual-speed hub is the price. The following products show how much dual-speed hubs cost:
You can purchase an eight-port CheetaHub from Accton Technology Corp. beginning at the suggested retail price of less than U.S. $500. (For more information about the CheetaHub family of products, go to http://www.accton.com/accton/products/hubs/hub_index.html.)
You can purchase a 12-port EZ Hub 10/100 from SMC Networks Inc. beginning at the suggested retail price of less than U.S. $900. (For more information about the EZ Hub 10/100, go to http://www.smc.com/network/hubs/ezhub10.html.)
In addition to installing a dual-speed switch or a dual-speed hub, you need to install dual-speed network interface boards in each workstation that you want to operate at 100 Mbit/s. Almost all of the latest network interface boards are dual-speed network interface boards, capable of running either 10 Mbit/s Ethernet or 100 Mbit/s Ethernet.
Dual-speed network interface boards have been available for some time, but vendors have only recently offered these products at an affordable price. For example, SMC Networks just lowered the cost of its PCI-based EZ Card 10/100, which now has a suggested retail price of less than U.S. $40. (For more information about EZ Card 10/100, go to http://www.smc.com/network/lan/ezc100ds.html.)
Because most dual-speed network interface boards are PCI based, you cannot install these network interface boards in older workstations that do not have PCI slots. If your company's network includes these workstations, you must replace them with new workstations that have PCI slots. Of course, if you have to replace workstations, the cost of running both 10 Mbit/s Ethernet and 100 Mbit/s Ethernet increases significantly.
MIGRATION SCENARIOS
Now that you know what products to purchase, you should know how to gradually move your company's network from 10 Mbit/s Ethernet to 100 Mbit/s Ethernet. You can use two migration scenarios to help plan the migration process. The first migration scenario features a small network with one server and 10 workstations, and the second migration scenario features a larger network with two servers and 50 workstations. Each migration scenario has different requirements to make the migration process seamless, without causing any network downtime.
These migration scenarios are based on the assumption that you are running a 10Base-T Ethernet network and that you are using Category 5 unshielded twisted-pair cabling. Category 5 cabling is designed to support speeds of up to 100 Mbit/s, while Category 3 cabling is designed to support speeds of only 10 Mbit/s. Using cabling that is not designed to support the speed at which you are running can cause connectivity problems that prevent the network from functioning properly.
Migration Scenario for One Server and 10 Workstations
If your company's network had one server and 10 workstations, you would begin the migration process by replacing the existing 10 Mbit/s Ethernet hub with a 12- or 16- port dual-speed hub. You would simply swap cables from the old hub to the new hub.
After you had installed the dual-speed hub, you would replace the existing network interface board in the server and in each workstation you wanted to operate at 100 Mbit/s. You would then install and configure the new dual-speed network interface board. In most cases, you would run the configuration utility that comes with the network interface board and select the Auto option or the 100 Mbit/s option, depending on the available options.
Because a dual-speed hub automatically detects the correct speed for each connection established to the hub, some workstations could continue to run 10 Mbit/s Ethernet. As a result, you could keep the existing network interface board in these workstations, rather than installing a dual-speed network interface board.
Migration Scenario for Two Servers and 50 Workstations
If your company's network had two servers and 50 workstations, this network would include more 10 Mbit/s Ethernet hubs. In the past, you had to replace all of the 10 Mbit/s Ethernet hubs at once with 100 Mbit/s Ethernet hubs. With dual-speed hubs, however, you no longer have to replace all of the hubs at one time. You could implement dual-speed hubs in two ways, depending on where the existing 10 Mbit/s Ethernet hubs reside on your company's network:
If the existing 10 Mbit/s Ethernet hubs were distributed throughout the network, you might want to purchase and install only one dual-speed Ethernet hub. You could then daisy-chain this hub to each 10 Mbit/s Ethernet hub. With this configuration, you could gradually replace each 10 Mbit/s Ethernet hub with a dual-speed hub or with a 100 Mbit/s Ethernet hub. If some users did not need the extra speed, you could keep one or more 10 Mbit/s Ethernet hubs indefinitely for these users.
If the existing 10 Mbit/s Ethernet hubs resided in a central location, such as in a server room, you might want to purchase and install a stackable dual-speed hub. Both of the dual-speed hubs mentioned earlier--Accton Technology's CheetaHub and SMC Networks' EZ Stack 10/100--are stackable, enabling you to add other dual-speed modules as necessary.
Most stackable dual-speed hubs offer anywhere from eight to 96 ports per module, providing a lot of flexibility in how you implement the migration process. When you were ready to replace a 10 Mbit/s Ethernet hub, you could simply purchase a dual-speed module with the number of ports you needed. You could then add this module to the stackable dual-speed hub.
After you had implemented dual-speed hubs in one of these ways, you would replace the existing network interface board in the server and in each workstation you wanted to operate at 100 Mbit/s. You would then install and configure the new dual-speed network interface board.
CONCLUSION
By implementing dual-speed hubs and dual-speed network interface boards, even small companies without a huge networking budget can push the envelope to 100 Mbit/s. No matter the size of your company's network, dual-speed hubs and dual-speed network interface boards offer an easy, cost-effective alternative to single-speed products. As a result, you no longer have to let high-speed networking technologies pass you by.
Mickey Applebaum has worked with NetWare for more than 14 years. Mickey provides technical support on the Internet for The Forums (http://theforums.com.)
NetWare Connection,September 1998, pp. 32-33
* Originally published in Novell Connection Magazine
Disclaimer
The origin of this information may be internal or external to Novell. While Novell makes all reasonable efforts to verify this information, Novell does not make explicit or implied claims to its validity.