Four steps to more effective network services - Page 2

 By Paul Strauss
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Older technologies sometimes can't be decommissioned without changing the applications involved. Sometimes it's not cost-effective to make the switch. In addition, many of those older services and technologies work pretty well. Don't abandon them without careful thought.

For instance, there are signs of increasing competition on long-haul and, in the future, local-access communications. New carriers with a flood of new capacity are already driving down prices. But don't forget the price and service advantages of signing long-term contracts with the established carriers.

It's all about priorities
Here are the main questions to ask when making a choice among leased lines, frame relay, and ATM:

Are you choosing a network service for an individual connection or for the entire network? If just one, it's probably best to stick with whatever service you're using for the rest of the network.

Can you create a hybrid solution (leased lines for some connections, ATM for others, for example)? If you can create a hybrid, consider whether you will want to keep it, or move to a single service at a later date.

Is the overall network mainly many points to one point, many points to many points, or a few points that can be connected in a triangle, square, or rough circle? Your choice will be determined more by the configuration than by the cost, because leased lines are often cheaper than packet services for short distances and point-to-point connections.

Do you plan to use individual links nearly constantly, and do you require a guaranteed amount of bandwidth? If so, leased lines are the clear choice.

Does your network require guaranteed security? Leased lines again have the advantage. Security specialists recommend encryption on any shared service.

How much bandwidth do you expect to use on each circuit or virtual circuit for the foreseeable future? It's advisable to buy more than you need because network traffic is growing so rapidly.

Do you require backup services? Leased lines can only be backed up by other leased lines or dial-up services. frame relay and ATM lines can be backed up interchangeably through multiple service carriers . (for instance, you could back up an AT&T frame relay service with one from Sprint.)

What is the total cost, including local access and installation for a specified time (usually three years) for each alternative? --Paul Strauss

Migrate to new technologies and services where it makes sense to do so.
Migrating to better approaches means weighing the pros and cons of various network services, while bearing in mind that any new service or technology must support the organization's business objectives.

The choice of a service shouldn't be based on whether it's theoretically cheaper or better than another, but on whether it truly and dependably is. In the case of frame relay services, carriers allow users to "burst" over a Committed Information Rate, and most corporate networks rely on using the burst rate constantly. But the situation could be temporary. If carriers restrict over-use of the "burst" capability, the attractiveness of frame relay as a voice/data service will fade.

Tough choices

Users are constantly faced with a choice between leased lines and frame relay, and sometimes they must choose between frame relay and Asynchronous Transfer Mode (ATM) (see sidebar, "It's all about priorities").

Here's how those services stack up.

Leased lines are the clear choice for organizations that plan to use individual links nearly constantly, that have networks covering short distances, or that require a guaranteed amount of bandwidth. If you have a lot of traffic between Atlanta and Chicago, for example, it would be far better to lease a 56Kbps or T1 (1.544Mbps) circuit instead of making constant modem calls or Integrated Services Digital Network (ISDN) calls. Leased lines also are a good choice for organizations whose networks require guaranteed security.

It's relatively easy to compute the cost/benefit tradeoffs among different kinds and different speeds of leased lines. But in many situations it's not clear whether firms should take leased lines at all.

Of the two kinds of leased lines, local-access circuits and long-haul circuits, there have been some price declines in the former over the last 18 months. These declines have been caused by new competitors offering Internet access services, often by reselling the service offerings of the entrenched local service companies.

In general, local-access price declines have ceased and prices are tending to rise slightly in major markets, says Thomas Jenkins, a senior consultant with TeleChoice, a consulting firm in Owasso, Okla. Although prices of local access vary significantly by metropolitan area, the list price of long-haul leased lines varies little by area or by carrier and has not changed substantially in years. If anything, long-distance circuit prices are tending to increase slightly, Jenkins says.

Most companies find that leased local-access and long-haul circuits are terribly expensive in the absolute sense, consuming a major portion of the annual WAN budget. A T1 between Atlanta and Boston runs around $5,000 a month these days. And naturally, the expenditure seems overwhelmingly onerous if circuits are not constantly being used.

New technologies to some extent ameliorate the wastefulness of taking leased lines and not using them for periods of time. More significantly, they deal with the problem of multipoint connectivity. Today's digital leased lines are only point-to-point circuits (unlike analog circuits, which offered multidrop options). This means that a circuit runs only from Atlanta to Chicago, for example. It's possible to connect Atlanta to Chicago to Boston by using multiplexing technology, but that takes two leased lines. Four points take three leased lines, five four, etc. More expensive still is the creation of a matrix network, in which all points connect to all other points. Connecting five cities in a full matrix requires a star configuration of 10 leased lines.

An additional drawback of leased lines is that they can only be backed up by other leased lines or dial-up services.

Packet services, which make more efficient use of circuits, evolved as an answer to the problems of leased lines. Packet services often are cheaper than leased lines because the carrier can aggregate the packets from various users on the same circuits.

Frame relay was created by the telecommunications standards bodies because by the mid-1980s, X.25 was considered a slow network transport protocol. Frame relay allows for faster transmissions than X.25 because it doesn't require error checking at each switch. Recent survey data from Datamation and SG Cowen show marked increases in interest and use of frame relay.

Many organizations think they save money by putting voice on frame relay services. Doing this can save money, but only when there is unused capacity on a subscribed frame relay permanent virtual circuit (PVC)--which is essentially a connection. With the exception of international calls, which are often tremendously expensive, it rarely saves money to put voice on a data service if you have to pay to increase capacity of that service.

Frame relay can provide up to T1 speed in the United States and E1 (2Mbps) in Europe, and it has been tested at 45Mbps. But few carriers offer such fast frame relay services because those speeds are considered to be ideal for ATM, which apparently has no top speed.

ATM can and does carry voice and data. Much of the dialed voice traffic in the United States already travels over carrier ATM switches, and recent Datamation/SG Cowen surveys indicate ATM use is soaring. But ATM does not yet carry much corporate voice/data traffic.

This is surprising because communications carriers are clearly using ATM to carry both voice and data. If carriers use ATM for voice and data, why don't corporate users? Largely because corporate users cannot obtain the economies of scale the carriers have.

Also, carriers use ATM differently from the way corporate users want it. Carriers use an ATM format known as the constant-bit-rate format for voice, and another format, the variable bit rate, to carry user data services. Corporate users were hoping to obtain a single ATM service for both voice and data. Having to buy two different formats raises the cost and diminishes the flexibility of ATM.

This article was originally published on Sep 1, 1999
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