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A problem arises when configuring the two GCRA functions as recommended by
TM 4.1 if you specify VBR service and set PCR and SCR to the same value
(PCR=SCR). The Maximum Burst Size (MBS) parameter then becomes irrelevant
and both GCRA functions end up with the same increment and limit values. This
occurs because in every available VBR policing configuration, the action taken for
nonconforming cells by the first GCRA function is a superset (more severe or at
least as severe as) the action taken by the second GCRA function; the second
GCRA function has no effect. Therefore, if you specify a VBR service category and
set PCR equal to SCR, the line card uses a single GCRA with the increment based
on PCR and limit based on CDVT. The line card ensures conformance only to the
PCR value within the CDVT range (specified or default). The MBS parameter has
no effect.
Procedure
To configure ATM traffic profiles:
8335-A2-GB20-70
1. Select the Index number (1–10) of the traffic profile you wish to modify, or 0 to
add a new traffic profile. Factory default traffic profiles are read-only.
To scroll to the previous or next group of profiles, type u (for Up) or
d (for Down) in the Index field.
2. Position the cursor in the field you wish to modify. Type the value you want
and press Enter.
For . . .
Profile Name
Class
PD
POL (Models 8335,
8365, and 8385 only)
PCR (Models 8335,
8365, and 8385 only)
February 2003
Enter . . .
Up to 12 alphanumeric characters.
The class of service (listed below in priority order):
CBR – Constant Bit Rate.
rt-VBR – Real-time Variable Bit Rate.
nrt-VBR – Non-real-time Variable Bit Rate.
UBR – Unspecified Bit Rate. This is the only class available
for Model 8355.
The Early Packet Discard (EPD) and Partial Packet Discard
(PPD) features setting:
Yes – EPD and PPD are used when congestion is
detected.
No – EPD and PPD are not used.
The Policing mode:
N – None. All cells are forwarded to the SCM.
T – Tag. All cells are forwarded to the SCM, but
nonconforming cells (cells which do not comply with the
traffic contract) have their Cell Loss Priority bits set to 1.
D – Drop. Nonconforming cells are dropped.
The Peak Cell Rate. Permitted values are 1 up to the
DSL line rate.
3. Configuration
3-35
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