User`s manual

P-660R-F1 Support Notes

Peak Cell Rate (PCR): The maximum bandwidth allocated to this connection.

The VC connection throughput is limited by PCR.

Sustainable Cell Rate (SCR): The least guaranteed bandwidth of a VC.

When there are multi-VCs on the same line, the VC throughput is guaranteed by

SCR.

Maximum Burst Size(MBS): The amount of cells transmitted through this VC

at the Peak Cell Rate before yielding to other VCs. Total bandwidth of the line is

dedicated to single VC if there is only one VC on the line. However, as the other

VC asking the bandwidth, the MBS defines the maximum number of cells

transmitted via this VC with Peak Cell rate before yielding to other VCs.

The P-660R-F1 holds the parameters for shaping the traffic among its virtual

channels. If you do not need traffic shaping, please set SCR = 0, MBS =

0 and PCR as the maximum value according to the line rate (for examp le, 2.3

Mbps line rate will result PCR as 5424 cell/sec.)

7. What do the ATM QoS Types (CBR, UBR, VBR, rtVBR, nrtVBR) mean?

Constant bit rate (CBR): An ATM bandwidth-allocation service that requires

the user to determine a fixed bandwidth requirement at the time the connection

is set up so that the data can be sent in a steady stream. CBR service is often

used when transmitting fixed-rate uncompressed video.

Unspecified bit rate (UBR): An ATM bandwidth-allocation service that does not

guarantee any throughput levels and uses only available bandwidth. UBR is often

used when transmitting data that can tolerate delays, such as e-mail.

Variable bit rate (VBR): An ATM bandwidth-allocation service that allows users

to specify a throughput capacity (i.e., a peak rate) and a sustained rate but data is

not sent evenly. You can select VBR for burst traffic and bandwidth sharing with

other applications. It contains two subclasses:

Non-real time variable bit rate (nrtVBR) and Real time variable bit rate

(rtVBR).

8. The P-660R-F1 supports Bridge and Router mode, what's the difference

between them?

When the ISP limits some specific computers to access Internet that means only

the traffic to/from these computers will be forwarded and the other will be filtered.

In this case, we use bridge mode which works as an ADSL modem to connect to

the ISP. The ISP will generally give one Internet account and limit only one

computer to access the Internet.

For most Internet users having multiple computers want to share an Internet

account for Internet access, they have to add another Internet sharing device, like