![](http://datasheet.mmic.net.cn/330000/PM7329-BI_datasheet_16444382/PM7329-BI_93.png)
PM7329 S/UNI-APEX-1K800
DATASHEET
PMC-2010141
ISSUE 2
ATM TRAFFIC MANAGER AND SWITCH
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
79
DirMaxThrsh
QDirMaxThrshErr
Check WANCnt or LoopCnt
FreeCnt = 0
QFreeCntZeroErr
N/A
EFCI marking may be performed on cells as they are transmitted out of the
queue, based on the state of congestion at the time of transmission. Marking of
EFCI is per VC selectable to occur at either the CLP1 thresholds or the CLP0
thresholds. A cell will be marked if hierarchical count values exceed one of the
CLP1 thresholds (VcCLP1Thrsh, ClassCLP1Thrsh, PortCLP1Thrsh,
DirCLP1Thrsh) or one of the CLP0 thresholds (VcCLP0Thrsh, ClassCLP0Thrsh,
PortCLP0Thrsh, DirCLP0Thrsh), and the third bit of the PTI field in the cell is
zero (PTI = 0xx).
There are three unique congestion discard rules. The selection of the rule to be
applied is based on the cell type (user or non-user), the queuing mechanism,
and finally the congestion type. If it is a non-user cell, the congestion mode is
always cell discard. If shaping is not enabled for the destination port/class, the
discard rule is selected on a per-VC basis, and is a function of the queue
mechanism selected (VcQueue), as well as a per-VC congestion context
parameter (VcCongMode). If the port/class is shaped, only two of the three rules
is available, and is selectable on a per-VC basis. Table 10 below illustrates how
the congestion discard rule is selected.
Table 10
- Congestion Discard Rules Selection
Cell
Shaped
VcQueue
VcCongMode
Congestion Mode
User
No
0 (WFQ)
0
EPD/PPD discard
User
No
0 (WFQ)
1
Cell discard
User
No
1 (FCQ)
x
FCQ discard
User
Yes
x
0
EPD/PPD discard
User
Yes
x
1
Cell discard
Non-user
x
x
x
Cell discard
OAM cells that are redirected to the microprocessor are subject to cell discard
rules applied to the uP congestion counts at the per-port and per-class levels.
There is no congestion control at the VC level for these redirected OAM cells.