RS8234EBGC Mindspeed Technologies, RS8234EBGC Datasheet - Page 182

• Manufacturer Part Number: RS8234EBGC
• Description: RS8234EBGC ATM XBR SAR
• Manufacturer: Mindspeed Technologies

6.0 Traffic Management
6.3 ABR Flow Control Manager
6.3.1 A Brief Overview of TM 4.1
6.3.2 Internal ABR Feedback Control Loop
Figure 6-12. ABR Service Category Feedback Control
6-22
Variable
Shaping
Rate
Source
(Backward_RM)
6.3 ABR Flow Control Manager
This section briefly describes the TM 4.1 ABR Flow Control algorithms.
However, it is strongly recommended that the reader be familiar with the ATM
Forum’s TM 4.1 specification before attempting to understand the RS8234’s ABR
implementation.
As a complete implementation of the UNI ATM layer, the RS8234 acts as both an
ABR Source and Destination, complying with all required TM 4.1 ABR
behaviors. The RS8234 utilizes the dynamic rate adjustment capability of the
xBR Cell Scheduler as the Source’s variable rate shaper. An internal feedback
mechanism supplies feedback from the received cell stream to the ABR Flow
Control Manager, a special purpose state machine. This state machine translates
the feedback extracted from received Backward RM cells, to instructions for the
xBR Cell Scheduler and segmentation coprocessor. It supports both binary and
ER flow control methods.
BW_RM
Figure 6-12
Mindspeed Technologies
illustrates this basic concept.
(
³
Congestion
1 Switches)
Algorithms
Network
Switch
ATM
ATM ServiceSAR Plus with xBR Traffic Management
FW_RM
(ForWard_RM)
™
(TurnAround_RM)
Internal Congestion
Destination
Backpressure
TA_RM
28234-DSH-001-B
RS8234
100074_051