RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 177

• Manufacturer Part Number: RS8234EBGC
• Description: RS8234EBGC ATM XBR SAR
• Manufacturer: Mindspeed Technologies

RS8234
ATM ServiceSAR Plus with xBR Traffic Management
6.2.5 UBR Traffic
28234-DSH-001-B
6.2.4.7 Real-Time VBR
6.2.4.6 Rate Selection
6.2.4.5 CLP-Based
and CDV
Buckets
The third option allows both buckets to apply to CLP=0 cells. CLP=0 means high
priority cells; CLP=1 means cells are subject to discard. CLP=1 cells are
scheduled from the second bucket only. Therefore, the second bucket should
correspond to PCR. This controls the PCR of the total cell stream, but only
controls the SCR of CLP=0 cells. The user enables this scheme by setting the
SCH_MODE bits to “110” (VBRC — also called VBR3).
The I and L parameters of the GCRA algorithm represent cell slots in the
schedule table. Therefore, the VBR channels have the same maximum rate
available as the CBR channels. Since VBR channels are internally scheduled by
the Cell Scheduler based on that channel’s I parameter, a floating point value, they
are not constrained to repeat at some n integer value of R
Thus, VBR channels have a much finer rate granularity.
Real-time VBR traffic should be assigned the highest scheduling priority to
minimize cell delay variation. The worst-case CDV for rt-VBR traffic is
calculated as:
The remaining priority levels not already assigned to ABR, VBR or CBR tunnel
traffic, are scheduled as UBR traffic. All UBR channels within a priority are
scheduled on a round-robin basis.
tunnel in that priority level. Another method of limiting the bandwidth that a
UBR priority consumes is described in
The minimum rate for VBR channels is R
To limit the bandwidth that a UBR priority consumes, the user can use a CBR
((# VBR VCCs at same-or-higher priority)+TX_FIFO_LEN)/(line rate in cells/sec).
Mindspeed Technologies
Section
™
6.2 xBR Cell Scheduler Functional Description
max
6.2.8.
/(TBL_SIZE –1).
max
6.0 Traffic Management
/(TBL_SIZE – n),
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