The growth of internet-based and internet-dependent businesses has driven an associated growth in T1 line utilization. Over three million businesses in this country make use of T1 line bandwidth. Faster data transfer rates are available but none of the faster and more expensive options approach the T1 line market share. The T1 standard was developed by AT&T in the late 1950s. Based on empirical data from tests in Chicago, AT&T set the T1 standard at 1.544Mbps. That standard remains in effect.
Modern technology and rethinking of some of the early decisions could improve the throughput, however any changes will make existing infrastructure obsolete. The T1 standard is used in the United States, Japan and Korea with the rest of the world using the E1 standard. The actual usable T1 line bandwidth is 1.536Mbps due to certain framing overhead requirements.
If a single T1 line does not meet a business's requirements, T1s can be bonded together in up to usually 3 pairs for 9.216Mbps. T1 lines can support up to 24 full-duplex voice lines or up to 192,000 bps in unchannelized configuration. Available services can include voice, point-to-point data, VOIP, VPN, and most often internet backbone connectivity.
On paper, DSL seems to match T1 line bandwidth. Full speed DSL can easily transfer data at 1.54 Mbps but DSL service degrades over distance from the local phone switch center. Full DSL service is available only within a certain distance. DSL is offered as "best effort" service with no service availability guarantee. There is no real incentive for quickly restoring interrupted service.
On the other hand, T1 service is extremely reliable. Most T1 providers guarantee 99.9% or better service with service agreements setting forth penalties for loss of service. There is incentive to quickly re-establish service. Service interruptions are almost never measured in more than a few minutes.
The expense of a full T1 line may be hard for some small businesses to justify even though T1 reliability is needed. For these users some less expensive options are available. Fractional T1 provides some portion of the full T1 line bandwidth, often in multiples of 64k or 256kbps, at reduced lease rates. The reduced rates are not proportional to the reduction of the bandwidth. The non-bandwidth-related costs of T1 service make up most of the total cost and reducing bandwidth by 50% usually reduces lease rate by less than 20%. Once a fractional T1 service is installed it can be quickly and easily upgraded to full T1.
Two additional reduced cost T1 line options are available from some carriers. Metered T1 line service is charged based on the actual bandwidth used. This is one way to enjoy the reliability of T1 line service while only using full bandwidth a few times a month. Burstable T1 can deliver full bandwidth when required and throttle back when not in use. This is a good option for businesses that only need T1 line service a few times a month but still require the guaranteed availability.
This availability is very important to some businesses; more important than the data throughput. DSL can match data transfer speeds but cannot come close to the reliability. Some businesses need more bandwidth than the 1.544 Mbps of a T1 but cannot justify the expense of the next level technology - T3 lines. T1 lines can be bonded in pairs for more bandwidth but if that is not enough fractional T3 and Ethernet lines are offered by some broadband providers.
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