cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 49

• 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
28237-DSH-001-C
2.5 Advanced xBR Traffic Management
The CN8237 implements ATM’s inherent robust traffic management capabilities
for CBR, VBR, ABR, UBR, GFR, and GFC. The CN8237 manages each VCC
independently and dynamically.
• The user assigns each connection a service class, a priority level, and a rate if
• In addition to reserved CBR bandwidth, the CN8237 provides
• The host submits data to be sent by writing entries to the transmit queues
• The CN8237 then submits this traffic demand to the xBR Traffic Manager
• The conforming traffic to be transmitted is further groomed in internal
applicable. The on-chip traffic controller (xBR Traffic Manager) optimizes
use of the line bandwidth according to the VCC’s traffic parameters and
control information stored in SEG memory. The xBR Traffic Manager
guarantees the compliance of each VCC to its service contract with the ATM
network at the UNI ingress point. It schedules all data traffic by acting as a
master to the segmentation coprocessor.
xBR Scheduler. The xBR Traffic Manager assigns segmentation traffic
from active VCCs to schedule slots, which the segmentation coprocessor
then complies to by segmenting VCC traffic in the sequence/schedule
dictated by the xBR Scheduler.
16 segmentation priorities. The user configures these priorities for the
remaining service categories, including the TM 4.1 defined ABR class.
The CN8237’s xBR Traffic Manager implements multiple functional
levels of traffic prioritizing. This is illustrated in
for segmentation. The SAR processes these transmit queues either in
round–robin order (transmit queue 0–31, looped back to 0), or in priority
order (with transmit queue 31 having highest priority). This scheme gives
the user or system designer some control of the delay between the host
submitting traffic and the SAR starting to process that traffic. For instance,
the user could assign CBR traffic to the highest priority transmit queue in
order to minimize any delay in processing and scheduling that traffic.
for scheduling. Traffic is scheduled based on the traffic class plus certain
parameters from the segmentation VCC table entries (primarily the GCRA
I and L parameters). And if the service category is ABR, the SAR also uses
certain parameters from the ABR templates to help determine that traffic’s
placement on the Schedule table.
priority queues. Each virtual channel is prioritized according to its
assigned scheduling priority. CBR channels are given pre-assigned
segmentation bandwidth, and channels for the remaining service
categories scheduled according to their priority number (priority 0 being
the lowest priority and priority 15 being highest).
Mindspeed Technologies
One of the functional components of the xBR Traffic Manager is the
™
2.5 Advanced xBR Traffic Management
Figure
2.0 Architecture Overview
2-9.
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