cn8236 Mindspeed Technologies, cn8236 Datasheet - Page 172

• Manufacturer Part Number: cn8236
• Description: Atm Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

6.0 Traffic Management
6.1 Overview
6.1.1 xBR Cell Scheduler
Figure 6-1. Non-ABR Cell Scheduling
6-4
System
Clock
Cell Scheduler
Parameters
and Priority
Schedule
Per-VCC
Dynamic
Table
xBR
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 CN8236
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 CN8236 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
CN8236 supports 16 priorities of non-CBR traffic.
flow for CBR, VBR, and UBR traffic. The Cell Scheduler tracks cell slots using
the system clock and decides which VCC should send during each slot. This
decision is based upon per-VCC parameters and the current condition of the
Dynamic Schedule table. Unlike ABR, these service categories are open loop,
and need no feedback from the network for run-time cell scheduling.
The Cell Scheduler selects individual channels based upon the dynamic
Figure 6-1
Mindspeed Technologies
VCC_INDEX
shows a high-level block diagram of the Cell Scheduler control
Segmentation
Coprocessor
ATM ServiceSAR Plus with xBR Traffic Management
™
CBR
UBR
GFR
VBR
Network
ATM
28236-DSH-001-B
CN8236
8236_035