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Understanding T-1's
"T-1" is a commonly used word that has many meanings in the world of telecom and the Internet.
Generally speaking, it refers to the underlying "dedicated" telephone connection between two points that is sold by the local telephone company. This connection has a throughput rate of 1.54 Megabits per second (Mbps) in both directions. ISP's like BluegrassNet use these T-1s to connect to their customers. These connections can be delivered via copper or fiber lines running to a facility.
There are several different types of T-1's that are sold on the market today:
The Internet T-1: This is a connection to an ISP over one of these T-1 loops, thereby delivering the Internet conneciton at 1.54Mbps. It usually means that all that is running over that T-1 is Internet data (also referred to as IP)
The Voice T-1: This is where the T-1 is used to deliver voice services exclusively. A T-1 can support up to 23 or 24 telephone lines depending on whether it is provisioned as a "channelized T-1" or a "PRI". These 23 or 24 voice lines are delivered to a location via a T-1 loop, and subsequently connected to a phone system. The channelized T-1 has 24 X 64kbps channels. The PRI has 23 X 64kbps voice channels and one 1 control channel. They are just T-1's that are provisioned a certain way.
The Integrated T-1: This is where a channelized T-1 has its 24 channels split up between voice and data. For example, if 7 X 64k channels are allocated to voice, then the remaining 17 channels are allocated to data. On the integrated T-1, this division is static. Which means it never changes.
The Dynamic T-1: This is where the use of the connection fluctuates between voice and data. This type of service means that when there are no voice calls in progress, the full 1.54Mbps is allocated to Internet traffic. When a voice call is initiated, the needed bandwidth is carved out to deliver the phone call, and the remaining bandwidth continues as the dedicated Internet connection. When there are more phone lines being used, there is less Internet bandwidth available.
Why would someone buy a T-1?
Customers looking for dedicated Internet connections now have more choices than ever. However, oftentimes a T-1 is still the best choice for a customer. Here are some reasons why:
- The customer needs a "mission critical" service level. Keep in mind that the telephone companies are required by law to fix these circuits quickly. You get preferential treatment when things need to be fixed.
- The customer needs consistent upstream bandwidth because they're hosting servers that need to be accessed from the outside.
- The customer can not afford to have fiber installed at their facility (preventing ethernet)
- The customer can not receive Wimax or some type of reliable wireless service that will deliver consistent upstream bandwidht.
- The customer is outside of the metropolitan area, and T-1's are still the best dedicated connection that extend to rural areas.
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