Let's Talk About Bandwidth.

This is an explanation of the various terms used with bandwidth capacity or "Pipe Size".

A bit is One - A byte can be 4,8,10,12,16 depending on the thing we are talking about - The Tele-communcations industry uses bits - so we do to. Please never confuse the two. From a PC standpoint 8 bits equal one byte. So if you promise a customer 150,000 bytes per month you just gave him a T1.

T1 or DS-1 - This is the equipvalent of 24 phone lines. The capacity is 1.5 million bits per second [1.5Mbps]. The key word is BITS not bytes. Bits are much smaller than bytes.

T2 or DS-2 - This is the equivalent of 4 T1's. The capacity is 6.3 million bits per second [6.3Mbps].

T3 or DS-3 - This is the equivalent of 28 T1's. The capacity is 45 million bits per second [45Mbps].

T4 or DS-4 - This is the equivalnet of 6 T3's. The capacity is 274 million bits per second [274Mbps].

OC-1 - Sometimes called SONET. OC-1 uses ATM switches [as all OC-X does] and runs at 51 million bits per second [51Mbps], and uses Fiber.

OC-3 - This is the equivalent of 155 million bits per second [155Mbps].

OC-12 - 600 million bits per second [622Mbps].

OC-48 - 2.4 gigabits per second [2.4 Gbps].

Frame Relay -A standardised form of fast packet switching in which packets are switched in hardware and at the Data Link layer. Basically dead and gone as far the Internet is concerned. Especially with the bandwidth requirements the way they are. Frame relay runs around 64kbps to 1.5Mbps [64,000 bits per second to 1.5 million bits per second]. Frame Relay is shared line with other people and your bandwidth depends on the current utilization of the line.

ATM, (Asynchronus Transfer Mode) - is a very expensive switching solution that is used in carry OC-3 and OC-12 lines