PXF4336 Datasheet, PDF (93/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

ABM-P
PXF 4336 V1.1
Functional Description
3.4.3 Scheduler Block Usage
The ABM-P allows arbitrary assignment of connections to queues and of queues to
scheduler blocks. A scheduler block can be assigned to any UTOPIA PHY. Usage of a
scheduler differs in switch input (upstream) or output (downstream). For the Mini-Switch
application the upstream case does not exist.
At a switch output, the scheduler blocks provide constant cell streams to fill the payloads
of the PHYs. Either the entire cell stream of a PHY is provided or it is disassembled into
several VPCs as shown in Figure 3-32. A VPC may contain both real-time and data con-
nections. This is the case for a VPC which connects two corporate networks (virtual
private networks), for example. The scheduler block concept has the advantage that
data traffic is automatically adjusted after setup or teardown of a real-time connection.
The output rate of a scheduler block in both applications is usually constant.
The scheduler blocks always react to UTOPIA backpressure or can be controlled com-
pletely by backpressure instead of shaping. All scheduler blocks whose physical outputs
are asserting backpressure hold on serving. Scheduler blocks serving time slots which
are lost due to temporary backpressure are maintained and served later, if possible.
Therefore, the rate with some CDV will be maintained. The maximum number of stored
time slots which can be configured is equal to the maximum burst possible for that port
or path.
Switch
Fabric
Queue and Scheduler
Block Assignment
ABM-P for Port 1
SB
Virtual Paths, PHYs and Ports
PHY 1
SB
VPC 1
PHY n
SB
VPC m
Port 1
Figure 3-32 Scheduler Block Usage at Switch Output
At a switch input, each scheduler block is assigned to a switch output (Figure 3-33). A
switch with n ports needs n² scheduler blocks. The output rate of each scheduler block
Data Sheet
93
2001-12-17