cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 52

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

2.0 Architecture Overview
2.5 Advanced xBR Traffic Management
2.5.3 ABR Traffic
2.5.4 UBR Traffic
2.5.5 GFR Traffic
2-18
The CN8237 implements the ATM Forum ABR flow control algorithms. The
CN8237 acts as a fully compliant ABR Source and Destination, as defined in the
TM 4.1 ATM Source specification. The ABR service category effectively allows
low cell loss transmission through the ATM network by regulating transmission
based upon network feedback. The ABR algorithms regulate the rate of each
VCC independently.
the TM 4.1 specification. The SAR utilizes the dynamic rate adjustment
capability of the xBR Scheduler as the ATM Source’s variable traffic rate-shaper.
The CN8237 injects an in-rate stream of Forward RM cells for each ABR VCC.
When these cells return to the CN8237’s receive port as Backward RM cells after
a round trip through the network, the CN8237 processes these cells and uses the
data returned as feedback to dynamically adjust the rates on each ABR channel.
Destination. The reassembly coprocessor processes received Forward RM cells. It
turns around this incoming information to the segmentation coprocessor, which
formats Backward RM cells containing this information, and inserts these
Turnaround RM cells into the transmit cell stream.
Templates in SAR-shared memory. Each VCC is assigned to one of these
templates. The templates control such behaviors as the size of the additive rate
increase factors or multiplicative rate decrease steps. Each VCC’s rate varies
across the template independently.
The UBR service category is intended for non-real-time applications that do not
require tightly constrained delay and delay variation, such as traditional computer
communications applications like file transfer and e-mail.
categories covered previously are scheduled as UBR traffic. All UBR channels
within a priority are scheduled on a round-robin basis. To limit the bandwidth that
a UBR priority consumes, the system designer should use a CBR tunnel in that
priority level.
Guaranteed Frame Rate is a new service category defined by the ATM Forum to
provide a MCR QoS guarantee for AAL5 CPCS-PDUs not exceeding a specified
frame length. A GFR service connection is treated as UBR with a guaranteed
MCR.
both the VBR1 scheduling procedure (for the MCR rate value) and a UBR
priority queue, thereby providing fair sharing for all GFR connections to excess
bandwidth.
The CN8237 employs an internal feedback control loop mechanism to enable
The CN8237 also responds to an incoming ABR cell stream as an ABR
The exact performance of the rate-shaper is governed by one or more ABR
Those VCCs which have not been assigned to one of the other service
The CN8237 implements GFR by scheduling/shaping the connections using
Mindspeed Technologies
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
™
28237-DSH-001-C
CN8237