CN8237EBGB Mindspeed Technologies, CN8237EBGB Datasheet - Page 51

• Manufacturer Part Number: CN8237EBGB
• Description: ATM SAR 622Mbps 3.3V ABR/CBR/GFR/UBR/VBR 456-Pin BGA
• Manufacturer: Mindspeed Technologies

Specifications of CN8237EBGB

• Package: 456BGA
• Traffic Class: ABR|CBR|GFR|UBR|VBR
• Utopia Type: Level 1|Level 2
• Host Interface: PCI
• Maximum Data Rate: 622 Mbps
• Typical Operating Supply Voltage: 3.3 V
• Minimum Operating Supply Voltage: 3.135 V

CN8237
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
2.5.1 CBR Traffic
2.5.2 VBR Traffic
28237-DSH-001-C
The CBR service category requires guaranteed transmission rates, and
constrained CDV. The CN8237 facilitates these needs when generating CBR
traffic by pre-assigning specific schedule slots to CBR VCCs. For each
CBR-assigned cell slot, the CN8237 generates a cell for that specific VCC unless
data is not available. The CN8237 also minimizes CDV by basing all traffic
management on a local reference clock.
CBR channel to the rate of its data source. To accomplish this rate-matching, the
host can occasionally instruct the xBR Scheduler to skip one transmit opportunity
on a channel.
However, instead of one VCC, several UBR, VBR or ABR VCCs can be
scheduled within this CBR tunnel, in round-robin order.
of other service categories by the xBR Scheduler.
The CN8237 takes advantage of the asynchronous nature of ATM by reserving
bandwidth for VBR channels at average cell transmission rates without
pre-assigning hardcoded schedule slots, as with CBR traffic. This dynamic
scheduling allows VBR traffic to be statistically multiplexed onto the ATM line,
resulting in better utilization of the shared bandwidth resources. The xBR
Scheduler supports multiple priority levels for VBR traffic. Through the
combination of VBR parameters and priorities, it is possible to support real-time
VBR services.
GCRA algorithm. The GCRA I and L parameters control the per-VCC Peak Cell
Rate (PCR) and Cell Delay Variation Tolerance (CDVT) of the outgoing cell
stream on any channel. This guarantees compliance to policing algorithms
applied at the network ingress point. The user can control the granularity of rate
by dictating the number of schedule slots in the schedule table.
definitions. VBR1 controls PCR and CDVT. VBR2 controls PCR and CDVT, as
well as Sustained Cell Rate (SCR) and Burst Tolerance (BT). VBRC (also called
VBR3) controls PCR and CDVT on all cells, but controls SCR on only CLP = 0
(that is, high priority) cells.
The CN8237 provides a mechanism to exactly match the scheduled rate of a
The CN8237 manages CBR tunnels in the same manner as a CBR VCC.
Unused CBR and Tunnel time slots are automatically made available to VCCs
The outgoing cell stream for each VBR VCC is scheduled according to the
Channels can be rate-shaped as VCs or VPs according to one of three VBR
Mindspeed Technologies
™
2.5 Advanced xBR Traffic Management
2.0 Architecture Overview
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