P-793H v 2 Support Notes
Traffic shaping parameters (PCR, SCR, MBS) can be set in Menu 4 and Menu
11.6 and is valid for both incoming and outgoing direction since G.shdsl is
symmetric.
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-793H v2 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.)
12. What do ATM QoS Types (CBR, UBR, VBR-nRT, VBR-RT) 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 busty traffic and bandwidth
sharing with other applications. It contains two subclasses: Variable bit rate non
real time (VBR-nRT) and Variable bit rate real time (VBR-RT).
13. Why do we perform traffic shaping in the P-793H v2?
The P-793H v2 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-793H v2 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
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