State and FCC regulations mandate minimum cost escalation, defined quality levels, and customer service responsiveness. Circuit cost escalations, defined quality levels, and customer service responsiveness are at the discretion of Verizon or other local Bell and the third party DSL provider.
Speed is dependent on distance from telco central office - the farther away, the slower the speed.
Synchronous transmission cannot be guaranteed. Circuit Availability T1 circuits are widely available. Limited availability -not all towns served. Physical Circuit T1 circuits are engineered for digital data transmission and may be delivered via fiberoptic. DSL connections are made from voice-grade copper telephone circuits.