T-1
 1.544 Mbps
 A 24 channel cirucit that can be used for Frame Realy, Private Line, VPN or, most commonly, Internet access.
 Connects a company's LAN into the Internet or carrier's Frame Realy network.
 Provides access straight into the carrier?s backbone. Only slightly more expensive than a Fractional T-1. 99% availability in U.S. Very reliable.
 Setup and monthly costs can be prohibitive.
 Approx. $900-$1,200/month. Required router is additional. 
T-3
 44.736 Mbps
 A dedicated connection made up of the equivalent of 28 T-1s.
 Provides access from a location into the Internet for a large business or ISP (Internet Service Provider).
 Circuit runs directly into the carrier's backbone. Bandwidth guaranteed by SLA (Service Level Agreement). Very reliable.
 Setup and monthly costs can be prohibitive. 
 Starts at $10,000/month for the 45 Mbps. Local loops range from $2,000 - $4,000/month 
OC192  9.6 Gbps  9.6 Gbps optical fiber sometimes called SONET. Uses ATM Switches. Costs are extremely high
 
DS3 =  44.73 Mbps 672 (28 DS-1s) 
OC-48
 2.488 Gbps (Gigabytes per second)
 Optical carrier (multiple strands of fiber) connected by equipment capable of speeds up to 2.488 Mbps. 
 Large enterprise or ISP backbone.
 Extremely high speed and throughput.
 Extremely high cost.
 Several hundred thousand dollars a month, plus several hundred thousand dollars in setup costs.