ZyXEL p-660h-61 Guida Utente

Prestige 660H Series User’s Guide 

6-2 

WAN Setup 

By implementing PPPoE directly on the Prestige (rather than individual computers), the computers on 
the LAN do not need PPPoE software installed, since the Prestige does that part of the task. 
Furthermore, with NAT, all of the LANs’ computers will have access. 

Traffic Shaping is an agreement between the carrier and the subscriber to regulate the average rate and 
fluctuations of data transmission over an ATM network. This agreement helps eliminate congestion, 
which is important for transmission of real time data such as audio and video connections. 

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.  

 

 

To change your Prestige’s WAN remote node settings, click WAN, WAN Setup. The screen differs 
by the encapsulation.