User`s manual

P-660 Series Support Notes

The P-660 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 example, 2.3 Mbps line rate will result

PCR as 5424 cell/sec.)

15.Why do we perform traffic shaping in the P-660 ?

The P-660 must manage traffic fairly and provide bandwidth allocation for different

sorts of applications, such as voice, video, and data. All applications have their own

natural bit rate. Large data transactions have a fluctuating natural bit rate. The P-660

is able to support variable traffic among different virtual connections. Certain traffic

may be discarded if the virtual connection experiences congestion. Traffic shaping

defines a set of actions taken by the P-660 to avoid congestion; traffic shaping takes

measures to adapt to unpredictable fluctuations in traffic flows and other problems

among virtual connections.

ADSL FAQ

1. How does ADSL compare to Cable modems?

ADSL provides a dedicated service over a single telephone line; cable modems offer a

dedicated service over a shared media. While cable modems have greater downstream

bandwidth capabilities (up to 30 Mbps), that bandwidth is shared among all users on a

line, and will therefore vary, perhaps dramatically, as more users in a neighborhood

get online at the same time. Cable modem upstream traffic will in many cases be

slower than ADSL, either because the particular cable modem is inherently slower, or

because of rate reductions caused by contention for upstream bandwidth slots. The big

difference between ADSL and cable modems, however, is the number of lines

available to each. There are no more than 12 million homes passed today that can

support two-way cable modem transmissions, and while the figure also grows steadily,