Cisco BPX 8650, Installation And Configuration Manual

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21-53
Cisco BPX 8600 Series Installation and Configuration
Release 9.3.30, Part Number 78-12907-01 Rev. E0, May 2005
Chapter 21 Configuring ATM Connections
Traffic Policing Examples
Figure 21-28 UBR Connection, UPC Overview
CLP=1
5
CLP=0
4
CLP=1
3
CLP=0
2
CLP=0
1
+
PCR(0+1)
CDVT(0+1)
Time
interval
variations
Leaky Bkt 1
CLP(0+1) cells to Leaky Bkt 1
S6351
Leaky Bkt 1
discards
if depth >
CDVT(0+1)
Admit to network
+
SCR=0
BT + CDVT
Leaky Bkt 2
CLP=1
5
CLP=1
3
CLP=0
4
CLP=0
2
CLP=0
1
CLP=0
4
CLP=0
2
CLP=0
1
CLP(1) cells compliant with Leaky Bkt 1, admit to network
CLP(0) cells
compliant with
Leaky Bkt 1,
applied to
Leaky Bkt 2
For UBR connections, the first bucket
polices PCR compliance within the
CDVT(0+1) limits. The second bucket,
used when CLP is set to Yes, tags all
CLP(0) cells.
UBR Traffic
CPE
Multiple PVCs
To UPC for each
individual PVC
Time
Cells
per
sec.
PCR
SCR=0 when CLP=Yes (UBR.2)
Clumping
(Cells arriving early, i.e, at a
higher than contracted rate)
Cells arriving late
(at a less than
contracted
cell rate)
TAT TAT TAT TAT TAT TAT TAT TAT
Verify
VPIs,
VCIs
Policing
Note: The notation 0, 1, and 0+1 refers
to the types of cell being specified:
cells with CLP set to 0, CLP set to
1, or both types of cells, repectively.
For example, CLP(0), CLP(1), and
CLP(0+1)
For CLP = No, (i.e., UBR.1),
Leaky Bkt 2 sees no traffic.
For CLP = Yes, (i.e., UBR.2), CLP(0)
cells that were compliant with Leaky Bkt 1
are sent to Leaky Bkt 2. Since SCR = 0
for Leaky Bkt 2, the bucket is essentially
always full, and all cells are therefore
tagged with CLP being set to 1. This
allows the network to recognize these
UBR cells as lower priority and
available for discard in the event of
network congestion.