Motorola 3352N, 7000, 3342, 2200 manual Sustained Cell Rate SCR

Administrator’s Handbook

ATM Traffic Shaping: You can prioritize delay-sensitive data by configuring the Quality of Service (QoS) characteristics of the virtual circuit. Click the ATM Traffic Shaping link.

You can choose UBR (Unspecified Bit Rate), CBR (Constant Bit Rate), or VBR (Variable Bit Rate) from the pull-down menu and set the Peak Cell Rate (PCR) in the editable field.

UBR (Unspecified Bit Rate) guarantees no minimum transmission rate. Cells are transmitted on a “best effort” basis. However, there is a cap on the maximum transmission rate for UBR VCs. In a practi- cal situation:

•UBR VCs should be transmitted at a priority lower than CBR.

•Bandwidth should be shared equally among UBR VCs.

UBR applications are non-real-time traffic such as IP data traffic.

CBR (Constant Bit Rate) guarantees a certain transmission rate (although the application may underutilize this bandwidth). A Peak Cell Rate (PCR) characterizes CBR. CBR is most suited for real time applications such as real time voice / video, although it can be used for other applications.

VBR (Variable Bit Rate) This class is characterized by:

•a Peak Cell Rate (PCR), which is a temporary burst, not a sustained rate, and

•a Sustained Cell Rate (SCR),

•a Burst Tolerance (BT), specified in terms of Maximum Burst Size (MBS). The MBS is the maximum number of cells that can be transmitted at the peak cell rate and should be less than, or equal to the Peak Cell Rate, which should be less than, or equal to the line rate.

VBR has two sub-classes:

a.VBR non-real-time (VBR-nrt): Typical applications are non-real-time traffic, such as IP data traffic. This class yields a fair amount of Cell Delay Variation (CDV).

b.VBR real time (VBR-rt): Typical applications are real-time traffic, such as compressed voice over IP and video conferencing. This class transmits cells with a more tightly bounded Cell Delay Variation. The applications follow CBR.

☛Note:

The difference between VBR-rt and VBR-nrt is the tolerated Cell Delay Variation range and the provisioned Maximum Burst Size.

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