PXF4336 Datasheet, PDF (74/425 Pages) Infineon Technologies AG – ABM Premium ATM Buf fer Manager

ABM-P
PXF 4336 V1.1
Functional Description
PPD may only be applied to non real-time connections. The mechanism is enabled by
the software configurable flag PPDen, specified per traffic class in the TCT.
Note: EPD/PPD functionality is offered by the ABM-P on a per VC basis. Hence, these
functions can be supported also for connections sharing a queue.
Note: Cell discarding due to EPD and PPD does not apply to non-user cells, e.g. an
OAM cell within a packet is not discarded.
GFR Packet Discard
The EPD mechanism in combination with the flag GFRen is used to support the GFR
service. GFR packet discard works only in conjunction with EPDen = 1 and discards only
a well defined subset of the packets normally eligible for EPD.
In particular, when EPDen = 1 and GFRen = 1, a packet is discarded only if:
[(BufEPDNg or SBMax or TrafClassMax) and QueueMax] or
any of the EPD CLP1 thresholds is exceeded.
GFRen and PPDen are independent. GFRen has no influence on PPD and PPDen has
no influence on GFR.
GFRen has no influence on the discard of CLP=1 frames. Therefore there is no
difference between EPD and GFR packet discard regarding CLP=1 frames.
3.4.1.6.4 Minimum Buffer Reservation
A minimum buffer reservation is provided on a per queue basis by setting parameter
MinBG. As long as the queue length has not reached this value, an incoming cell can be
stored without further checks, except the queue threshold checks. When the MinBG limit
is exceeded, the Cell Acceptance Algorithm checks if buffer space is available in the non
guaranteed buffer space.
Data Sheet
74
2001-12-17