ZyXEL Communications MSAP2000 manual VC Profile Screen, Cell Delay Variation Tolerance Cdvt

MSAP2000 AAMS User’s Guide

7.12.2.4Cell 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.

7.12.2.5Burst 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.

7.12.2.6Theoretical 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 TAT, CDVT and BT in Traffic Shaping

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.

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