B-21/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
ATM Traffic Descriptors
PCR CLP=0 and PCR CLP=0+1
Beta Draft Confidential
PCR CLP=0 and PCR CLP=0+1
You can select this option for constant bit rate (CBR) traffic. Traffic conformance is
based on the peak cell rate (PCR) of both the cell loss priority (CLP)=0 and CLP=0+1
cell streams with no Tagging. The cell streams are checked for traffic conformance as
follows:
• The switch checks the cell rate of the CLP=0 stream; if the cell rate exceeds the
PCR of CLP=0, the switch drops the CLP=0 cells arriving above that rate.
• The switch checks the cell rate of the CLP=0+1 stream; if the cell rate exceeds the
PCR of CLP=0+1, the switch drops cells arriving above that rate. Cells are
dropped according to a ratio of CLP=0 to CLP=1 cells.
For example, if the ratio of CLP=0 to CLP=1 cells is 8 to 5, approximately 8
CLP=0 cells are dropped for every 5 CLP=1 cells that are dropped.
Table B-1 illustrates what would happen to CLP=0 and CLP=1 cells in different
situations if you select this option. This example assumes you set the PCR for CLP=0
to 50,000 cells per second (CPS) and the PCR for CLP=0+1 to 70,000 CPS.
All values in the table represent the measured traffic rate at a given point in time.
Table B-1. PCR CLP=0 and PCR CLP=0+1
CLP=0
(CPS)
CLP=1
(CPS)
Result
45,000 22,000 The switch does not drop any cells because the CLP=0 and
CLP=0+1 streams did not exceed the PCR.
50,000 22,000 The switch drops 2,000 CPS because the cell transmission rate
exceeded the PCR of the CLP=0+1 cell stream. Since the ratio
of CLP=0 to CLP=1 cells is 50 to 22, approximately 50 CLP=0
cells are dropped for every 22 CLP=1 cells that are dropped.
55,000 17,000 Since CLP=0 exceeds the PCR, the switch drops 5,000 CLP=0
CPS. This leaves 67,000 CPS in the CLP=0+1 stream, which is
below the PCR of CLP=0+1. Therefore, no additional cells are
dropped.
55,000 22,000 Since CLP=0 exceeds the PCR, the switch drops 5,000 CLP=0
CPS. This leaves 72,000 CPS in the CLP=0+1 stream, which
also exceeds the traffic contract. Therefore, 2,000 additional
CPS are dropped. Since the ratio of CLP=0 to CLP=1 cells is 50
to 22, approximately 50 CLP=0 cells will be dropped for every
22 CLP=1 cells that are dropped.
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