Alice in wonderLAN: high capacity office networks.

Executives responsible for office local area networks can think they're at a tea party with Alice and the Mad Hatter when it comes to choosing the office network that's best for their company. Many executives know they know they need to start planning to upgrade their networks to handle more users, graphics, images, and new applications like desktop video conferencing. What do they do to fix the problems they have today at the lowest cost, with the least disruption, and with an eye to the future?

NETWORKS ARE LIKE HIGHWAYS

Networks are designed to carry information traffic, the same way highways are designed to carry automobiles. You can compare most office networks to the roads in a neighborhood. As you add more people to the neighborhood, or make more trips, or start using larger vehicles, the networks become congested -- there are traffic jams. That's what's happening to office networks. Larger, more capable servers lead to more users per server -- larger neighborhoods and more trips to the store. OS/2 and Windows applications use more data. It takes 2,000 characters for a page of text, but more than 100,000 characters for a page with a picture -- larger vehicles. Multimedia applications like distance learning, desktop video conferencing, remote medical consultations, and others will require even more information. As you interconnect offices, and give employees the ability to collaborate interactively between locations, the office network equivalent of the interstate highway is needed.

UNDERSTANDING THE LINGO

Almost all office networks are based either on Ethernet or Token-Ring, two well understood, mature technologies with ubiquitous support. You are seeing and hearing terms like FDDI, AnyLAN, Fast Ethernet, ATM, switching, full duplex, and shared (or dedicated) networks. These are all ways to add capacity to your network. FDDI, or Fiber Distributed Data Interface, is like a Token-Ring, but runs at 100,000 bits of information per second (Mbps), instead of the 4Mbps or 16Mbps for Token-Ring, or 10Mbps for Ethernet. FDDI can be used for an office work group, but is especially well suited for carrying information on a backbone between offices. FDDI is newer than Ethernet or Token-Ring, but still well established. There are two 100Mbps technologies for work groups; AnyLAN, which can be used to add capacity to either Ethernet or Token-Ring work groups; and Fast Ethernet, which extends Ethernet work groups only. No one has had much experience with either AnyLAN or Fast Ethernet yet. FDDI, AnyLAN, and Fast Ethernet are each extensions of existing office network technologies. They expand the capacity of office networks letting information go faster. ATM, on the other hand, is a new type of networking that can operate at much higher speeds than traditional networks, is better suited for new multimedia applications, and can be used for both local area office and wide area company networks. ATM is even newer than AnyLAN and Fast Ethernet, but is getting a lot of attention because of its promise.

There is a new way of looking at office networks that adds capacity to networks not by operating at higher speeds but by using the existing networks more efficiently. Each user of an Ethernet or Token-Ring network shares the road with other users. Information on the network flows by each workstation. A technique called switching eliminates the need to share by making direct, instantaneous connections between communicating users. Since information only flows between the two workstations involved, those two workstations can use the full network capacity. Switching is relatively new to office networks, but is simple, inexpensive, and requires minimal changes. With full duplex, you can double the additional capacity provided by switching. Switching is the most promising solution for many of today's office network problems.

OPEN ROAD, TRAFFIC JAMS, OR GRIDLOCK?

You know you'll need higher capacity office networks in the future, but do you need them now? You should carefully examine your networks, and try not to change more than you have to. The vast majority of networks are operating well within their limits, with only a few trouble spots. Congestion, the cause of most of the problems, is typically localized to backbones between offices, access to servers, and occasionally, a few "power users."

Traffic jams on a backbone between offices require more capacity. You can add capacity with higher speeds, with FDDI, or ATM, or get more from your existing capacity with a switch. When too many people try to use the server at the same time, they can be delayed. Accidents can occur, and servers can loose information, causing applications to fail. Breaking the network up into neighborhoods, or segments, or adding a switch reduces the amount of sharing, and can eliminate jams. Adding another adapter to the server is another way to reduce jams by getting more information into and out of the server. Power users can get workstation adapters with higher performance, or their own segment. Each of the above, is an effective, non-disruptive, low cost solution with a minimum number of changes.

There are probably a few groups in any company that strain the capacity of the network no matter how much capacity you give them. They typically are the groups that generate and exchange large amounts of information: pictures, or large blocks of data, or use advanced applications like multimedia. These are the first groups that will need higher capacity to the workstation. These groups can be separated from the others, upgraded to higher speeds with workstation adapters and hubs to support the new speeds. The existing wiring can often be used. These groups communicate with others through interconnecting bridges that translate between the network types. As additional groups require higher speeds, they can be upgraded one at a time. To minimize changes to applications and retraining, you should upgrade with the technology that meets your needs and is closest to what you have today. Ethernet users who need more than network reconfiguration or switching should consider Fast Ethernet first, then AnyLAN, then ATM, unless the ability of AnyLAN and ATM to better handle multimedia information is required. Token-Ring users should consider AnyLAN or ATM. Fast Ethernet will be the least expensive upgrade path, but also the most constrained. AnyLAN and ATM are more expensive, but have more latent capabilities. Of the two, ATM is clearly the most likely long term choice.

WHAT TO DO?

The high capacity office network market place is like a village square on Saturday morning, with lots of sellers, each loudly proclaiming the merits of their products. Before you buy, you need to make sure you understand how much capacity you need, where you need it, and how you will deploy it in the least expensive way, with an eye to future needs. You may only have to put in a traffic switch to fix an office traffic jam, rather than adding capacity to your entire network.

Don't let others sell you more than you need, because that's all they have to sell. Pick a partner who sells a wide range of products from which you can choose, and who also has the experience to help you with that choice, and the commitment to sell you neither more than you want nor less than you need.

Bob Roth is manager of Campus Network Systems at IBM. He is a frequent speaker at trade shows and conventions.