A DS3 at full capacity is 45 Mbps. Many organizations graduate from multiple bonded T1s to some form of Fractional or Burstable DS3. Below are the most common forms this takes:

• Fractional DS3: Just as some smaller organizations have utilized Fractional T1s, a Fractional DS3 is typically delivered over a Full DS3 access loop, but the Internet port speed is set at the client's desired level.
  
  Typically, most carriers will require a minimum to deliver the service. Depending upon the carrier, they might require a customer to purchase at least 5-9 Mbps while others may require the customer to purchase 12 or more Mbps of Internet bandwidth over their fractional DS3.
  
  
• Burstable DS3: Unlike a Fractional DS3, a Burstable DS3 may have its Internet port speed configured to the full 45 Mbps. However, the customer is not necessarily billed for the full 45 Mbps. Instead, the customer is billed only for the amount of bandwidth they use, typically in a tiered structure.
  
  Carriers have different ways of partitioning these tiers, and may require a minimum usage while others may go strictly by usage. In other words, one carrier may bill one rate for 0-3 Mbps, 3.01-6 Mbps, 6.01-9 Mbps, 9.01-12 Mbps, 12.01-15 Mbps and so on. Their customer may use an average 11 Mbps one month and an average of 7 Mbps the next. This carrier would bill for the respective tier they fell into for each individual month. Another carrier may bill a minimum amount for 9 Mbps, for example, and then a predetermined rate for additional bandwidth.
  
  Regardless of the structure, it is a viable option for organizations in need of big bandwidth without paying for a Full DS3, while still having the bandwidth capabilities of a Full DS3, should they need it.
  
  
• Full DS3: This option is the full un-capped 45 Mbps. Sometimes, customers may start out with a Fractional or Burstable DS3, but when the time comes, there is a cost threshold where it makes sense to go ahead and provision the whole DS3 port. When you get into this type of circuit, the pricing and quality can vary, depending on the service provider.