Burst Tolerance (BT)
Burst Tolerance (BT) is the maximum number of cells that the port is guaranteed to handle without any discards. BT controls the time scale over which the SCR is enforced. BT is used to determine if a cell arrived too early in relation to SCR. Use this formula to calculate BT: (MBS – 1) x (1 / SCR – 1 / PCR) = BT.
Theoretical Arrival Time (TAT)
The Theoretical Arrival Time (TAT) is when the next cell (in an ATM connection’s stream of cells) is expected to arrive. TAT is calculated based on the PCR or SCR.
The following figure illustrates the relationship between TAT, CDVT and BT. If a cell arrives at time A, then according to PCR or SCR, the next cell is expected to arrive at time B. If the next cell arrives earlier than time C, it is discarded or tagged for not complying with the TAT. Time C is calculated based on the CDVT or BT.
Figure13.4.3DSL Port VC Profile Setup Screen
Do the following to open the VC Profile screen:
Step 1. Click a DSL port's index number in the Port Setup screen to go to the DSL Port Setup screen.
Step 2. Click Channel Setup in the DSL Port Setup screen to go to the Channel Setup screen.
Step 3. Click VC Profile in the Channel Setup screen to open the VC Profile screen.
Virtual Channel Management |