ZyXEL Communications Prestige 661H Series, User Manual

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Prestige 661H/HW Series User’s Guide
Chapter 7 WAN Setup 106
Peak Cell Rate (PCR) is the maximum rate at which the sender can send cells. This parameter
may be lower (but not higher) than the maximum line speed. 1 ATM cell is 53 bytes (424 bits),
so a maximum speed of 832Kbps gives a maximum PCR of 1962 cells/sec. This rate is not
guaranteed because it is dependent on the line speed.
Sustained Cell Rate (SCR) is the mean cell rate of each bursty traffic source. It specifies the
maximum average rate at which cells can be sent over the virtual connection. SCR may not be
greater than the PCR.
Maximum Burst Size (MBS) is the maximum number of cells that can be sent at the PCR.
After MBS is reached, cell rates fall below SCR until cell rate averages to the SCR again. At
this time, more cells (up to the MBS) can be sent at the PCR again.
If the PCR, SCR or MBS is set to the default of "0", the system will assign a maximum value
that correlates to your upstream line rate.
The following figure illustrates the relationship between PCR, SCR and MBS.
Figure 43 Example of Traffic Shaping
7.5 Zero Configuration Internet Access
Once you turn on and connect the Prestige to a telephone jack, it automatically detects the
Internet connection settings (such as the VCI/VPI numbers and the encapsulation method)
from the ISP and makes the necessary configuration changes. In cases where additional
account information (such as an Internet account user name and password) is required or the
Prestige cannot connect to the ISP, you will be redirected to web screen(s) for information
input or troubleshooting.
Zero configuration for Internet access is disable when
• the Prestige is in bridge mode
• you set the Prestige to use a static (fixed) WAN IP address.