PXF4336 Datasheet, PDF (65/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

3.4.1 Buffer Manager
ABM-P
PXF 4336 V1.1
Functional Description
3.4.1.1 Functional Overview
The basic function of the Buffer Manager (BM) is to decide whether an arriving cell is
granted access to the shared buffer or is discarded. This is done by running the Cell
Acceptance Algorithm (CAA) (see Chapter 3.4.1.7). The buffer manager tables
accessed by the CAA are summarized in Figure 3-15.
Local Connection
Identifier Table
16384 entries
Scheduler Block Occupancy Table
2 x 128 entries
Queue Configuration Table
2 x 8192 entries
Scheduler
SBID
Specific Data
LCI
Connection Specific
Data
QID ^{Queue Specific Data}
(up / down)
TCID
Traffic Class Table
2 x 16 entries
Queue / Traffic
Class Specific
Data
Global Buffer Data
Cell Acceptance Algorithm
Figure 3-15 Buffer Manager Tables
More generally, the buffer manager allocates the buffer resources needed to fulfill the
specific service guarantees of individual connections.
In a first step when receiving a cell, the Local Connection Identifier (LCI) that was
previously assigned by the Header Translation (see Figure 3-13), is mapped to a
corresponding Queue Identifier (QID). The QID represents the logical queue in which the
cell will be stored upon acceptance and serves as an index for subsequent table lookups.
In particular, the Scheduler Block and the Traffic Class of the received cell is identified
with the Scheduler Block Identifier (SBID) and the Traffic Class Identifier (TCID)
respectively.
With any incoming cell, the Cell Acceptance Algorithm (CAA) can access the current
buffer status information containing counters, thresholds and flags. Based on this data,
the cell is either discarded or accepted. The respective counters are updated
appropriately.
Data Sheet
65
2001-12-17