cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 188

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

6.0 Traffic Management
6.3 ABR Flow Control Manager
6.3.7 Rate Decisions and Updates
6-32
6.3.7.2 Rate Adjustment
6.3.7.1 ABR Traffic
Overview
Shaping
The CN8237 schedules ABR VCCs as a single leaky bucket GCRA channel, but
the rate is subject to continual adjustment. At initialization, the host assigns flow
controlled VCCs I and L parameters corresponding to the negotiated ICR. The Cell
Scheduler rate-shapes the initial traffic according to these GCRA parameters. This
shaped cell stream includes in-rate Forward and Backward RM cells.
ABR Flow Control Manager overwrites the I and L parameters in the
SCH_STATE of the VCC. The updated rates fall within the range of MCR and
PCR, which are specified on a per-connection basis.
The CN8237 dynamically adjusts the rate of transmission for ABR VCCs based upon
network feedback, individual VCC parameters, and the current transmission rate. The
ABR Flow Control Manager uses all of these inputs to calculate the ACR of the
connection. This ACR corresponds to I and L GCRA parameters. The CN8237
updates the I and L parameters of the VCC with the new ACR I and L values.
types of events—the reception of a Backward RM cell or the transmission of a
Forward RM cell. The decision process is unique for each event type.
NOTE:
When feedback from the network results in flow control rate adjustments, the
The Flow Control Manager updates the transmission rate in response to two
Both of these event types may occur in one cell slot. In this case, the
CN8237 makes both decisions before updating ACR.
Mindspeed Technologies
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
™
28237-DSH-001-C
CN8237