PXF4336 Datasheet, PDF (105/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

ABM-P
PXF 4336 V1.1
Functional Description
3.5.1.4 ABR Mechanisms
ABR Mechanisms are classified depending on the way congestion information is
conveyed to the ABR source and the way switches make use of the information
contained in the RM cells passing through. Table 3-43 shows this classification with
complexity increasing from top to bottom.
Table 3-43 ABR Mechanisms Supported in the ABM-P
ABR Mechanism
EFCI marking
Relative Rate Marking
Explicit Rate Marking
Reactive Switch
Control
VS/VD control
Description
ABM
Setting the PT bits in the user cell header to yes
“congestion experienced”
Setting CI and/or NI bits of forward or
yes
backward RM cells to 1 (binary feedback)
Updating the ER field of forward or
no
backward RM cells
Explicit rate marking and additional
no
reduction of the forward transmission rate in
switches to the ER in received BRM cells
Segmentation of the ABR control loop in a no
switch by building a virtual source (VS) and
virtual destination (VD)
ABM-P
yes
yes
yes
yes
yes
The implementation of the ABR mechanisms is mainly left to the manufacturer. It is
implicitly stated that the switch should update the RM cells in such a way that no cell
losses occur. The ABM-P supports all switch mechanisms mentioned above. The ABR
control loop with the different ABR mechanisms is shown below for one direction.
Source
Switch
Switch
Switch
Destination
adjust
ACR
BRM
Source and
sink RM cells
ä set
PTI
EFCI marking
user cell flow
RM cell flow
FRM
ä
update
BRM
ä
update
BRM
adjust
ACR
BRM
FRM
ä
BRM _update
Relative rate
or explicit rate
marking
Reactive switch control
ä traffic measurement
Turn-around
RM cells
Figure 3-44 ABR Mechanisms
Data Sheet
105
2001-12-17