pxf4336 Infineon Technologies Corporation, pxf4336 Datasheet - Page 96

• Manufacturer Part Number: pxf4336
• Description: Abm Premium Atm Buf Fer Manager
• Manufacturer: Infineon Technologies Corporation

3.5
The support of the Available Bit Rate (ABR) service category is implemented in the
Enhanced Rate Control (ERC) unit of the ABM-P.
3.5.1
Available Bit Rate (ABR) is the only ATM service category with dynamic adaptation of
the transmission rate according to the currently available bandwidth. It uses an ATM
layer control loop carrying special Resource Management (RM) cells to convey
congestion and/or bandwidth information along a connection’s path through the network.
The RM cells are inserted in regular intervals by the source of a connection - usually the
terminal. At the destination of the connection, the receiving terminal loops the RM cells
back to the source. All the switches/bottlenecks on the way may update specific fields of
the RM cells. Based on this information, the source reacts by adapting its transmission
rate in a predefined and standardized way.
Refer to the ATM Forum Traffic Management Specification V4.1 [ 2 ] for a complete
operational description of the ABR source, destination and switch behavior.
Figure 3-34
with FRM denoting forward RM cells and BRM denoting backward RM cell flows. Note
that both sides A and B of the ABR connection have both source and destination
behavior.
Figure 3-34 User and RM Cell Flows of an ABR Connection
To summarize:
• Source behavior defines the rules for allowed cell rate (ACR) calculation and
• Destination behavior defines the rules for FRM cell turnaround.
• Switch behavior defines the rules for BRM cell update.
Data Sheet
multiplexing of user cells, FRM cells and BRM cells.
Available Bit Rate Support
ABR Service Description
ABR VC Source (A side)
ABR VC Destination (A side)
provides an overview of the cell flows in a bi-directional ABR connection
turnaround
RM cell
BRM
FRM
user cell flow (A to B)
RM cell flow (controlling source A)
≈ ≈ ≈ ≈
calculation
ACR
ATM Network
96
RM cell
update
FRM
BRM
BRM
FRM
calculation
RM cell flow (controlling source B)
user cell flow (B to A)
ACR
ABR VC Destination (B side)
≈ ≈ ≈ ≈
ABR VC Source (B side)
Functional Description
turnaround
BRM
FRM
RM cell
PXF 4336 V1.1
2001-12-17
ABM-P