ATM Traffic Descriptors
PCR CLP=0 and PCR CLP=0+1 With Tagging
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/05B-3
Beta Draft Confidential
PCR CLP=0 and PCR CLP=0+1 With Tagging
You can select this option for CBR traffic. Traffic conformance is based on the PCR of
both the CLP=0 and CLP=0+1 cell streams with Tagging enabled. The cell streams are
checked for traffic conformance as follows:
• The switch checks the cell rate of the CLP=0 stream; CLP=0 cells arriving above
the PCR of CLP=0 are tagged as CLP=1 cells.
• 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 additional cells, based approximately on the
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-2 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/sec and the PCR for CLP=0+1 to 70,000 cells/sec.
All values in the table represent the measured traffic rate at a given point in time.
Table B-2. PCR CLP=0 and PCR CLP=0+1 With Tagging
CLP=0
(CPS)
CLP=1
(CPS)
Result
45,000 22,000 The switch does not tag or 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, 5,000 CLP=0 CPS are tagged as
CLP=1. This still leaves 72,000 CPS in the CLP=0+1 stream,
which exceeds the PCR of CLP=0+1. Therefore, 2,000 CPS are
dropped. 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 22,000 Since CLP=0 exceeds the PCR, 5,000 CLP=0 CPS are tagged as
CLP=1 cells. This still leaves 77,000 CPS in the CLP=0+1
stream, which exceeds the PCR of CLP=0+1. Therefore, 7,000
CPS are dropped. Since the ratio of CLP=0 to CLP=1 cells is 50
to 27, approximately 50 CLP=0 cells are dropped for every 27
CLP=1 cells that are dropped.
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