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MSAP2000 AAMS User's Guide
7.12.2.4 Cell Delay Variation Tolerance (CDVT)
Cell Delay Variation Tolerance (CDVT) is the accepted tolerance of the difference
between a cell's transfer delay and the expected transfer delay. CDVT controls
the time scale over which the PCR is enforced. CDVT is used to determine if a
cell arrived too early in relation to PCR.
7.12.2.5 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.
7.12.2.6 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.
Figure 32
7.13 VC Profile Screen
Click Basic Setting and then xDSL Profiles Setup in the navigation panel
and then VC Profile to open the following screen.
TAT, CDVT and BT in Traffic Shaping
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