cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 159

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

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
6.1.1 xBR Cell Scheduler
28237-DSH-001-C
segmentation on each active VCC by controlling the segmentation coprocessor.
By intelligently selecting when each VCC transmits a cell, the Traffic Manager
guarantees that the output of the CN8237 conforms to the negotiated traffic
contract. This selection process (called scheduling) executes dynamically, based
upon per-VCC parameters.
Dynamic Cell Scheduler, which provides for CBR, VBR, UBR, and GFR traffic.
Second, for ABR service classes, is the ABR Flow Control Manager, an additional
state machine, which works in conjunction with the xBR Cell Scheduler.
achieve full rate performance—one which reacts to feedback from the network
and adjusts cell transmission accordingly. This specification models ABR to align
with the TM 4.1 ABR specification. The CN8237 supports the rate based flow
control and service models specified for ABR in TM 4.1.
complements the GFC algorithm by allowing switches to significantly
overallocate port bandwidth.
The Cell Scheduler maintains the QoS guarantees for each service category. It
rate-shapes all segmentation traffic according to per-channel parameters. This
provides each channel with appropriate transmission opportunities and guarantees
conformance with network traffic contract policing algorithms applied to the
outputs.
schedule table. Schedule Slots in this table can be pre-reserved for CBR services.
The VPs and VCs with CBR service reserve cell slots for transmission, and are
intended for highly regular data sources, such as voice circuits. The CN8237
schedules all other traffic dynamically. The proprietary dynamic scheduling
algorithm uses the remaining bandwidth to statistically multiplex all other service
classes onto the line. The CN8237 can manage VCC traffic on either a VC or a
VP level. In addition, it can schedule traffic as a CBR tunnel (or pipe), that is,
several VCCs assigned to a single CBR scheduling priority, with individual VCCs
within that tunnel scheduled based on their traffic parameters. Traffic into this
CBR tunnel can be of types UBR, VBR and ABR. To enhance flexibility, the
CN8237 supports 16 priorities of non-CBR traffic.
In order to supply these services, the xBR Traffic Manager directs the
The xBR Traffic Manager consists of two primary components. The first is the
Due to the complexities of ABR, a dedicated state machine is required to
The CN8237 also provides Generic Flow Control. This XON/XOFF protocol
The Cell Scheduler selects individual channels based upon the dynamic
Mindspeed Technologies
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6.0 Traffic Management
6.1 CN8237 Overview
6-3