S/UNI®-ATLAS-3200 Telecom Standard Product Data Sheet
Preliminary
3. MCR conformance test. This test is performed using GCRA2, however, it differs slightly
from the normal cell policing. The MCR conformance test is only performed at the start of a
frame. If the first cell of a frame is a conforming cell, then all remaining cells in that frame
will be processed as if they are conforming to the MCR conformance test. If the first cell is
non-conforming, then the action specified by Action2[1:0] will be performed on the entire
frame. Normally, the MCR conformance test will be programmed to tag non-conforming
CLP=0 frames (Action = 01, CLP0 cells policed). If the first cell of a frame is a non-
conforming CLP=0 cell, then that cell and all other cells in that frame (including the EOM)
will be tagged. However, the MCR may be programmed to discard (Action = 11), in which
case a complete packet discard will be performed on frames whose first cell is non-compliant
to MCR.
In order to support AAL5 frame-aware policing on connections that do not support full GFR,
the GFR_MCR_PPD bit in the Policing Configuration register is provided. If this bit is a
logic 1, then the MCR is permitted to perform PPD, if configured to discard; tagging will
still be performed only on frame boundaries.
4. CLP conformance test: This test is performed on every cell in a frame, including the EOM.
The CLP conformance test can be enabled on a per-connection basis; this is controlled by the
CLPCC_CLP1_Discard bit of the Policing Configuration field in the VC Table. If the Start
of Frame is a CLP = 1 cell, then any subsequent CLP=0 cell will be tagged. If the first cell of
the frame is a CLP=0 cell, then if the CLPCC_CLP1_Discard bit is logic 1, any subsequent
CLP=1 cell received in the frame will result in a partial packet discard being executed.
The relevant GFR fields in the VC are described below:
Name
GFR
Description
If this bit is a logic 1, the S/UNI-ATLAS-3200 will utilize GFR policing on
the connection as described above. If this bit is logic 0, the connection
will not use the GFR policing, rather it will use the normal cell-based
policing described previously.
GFR_MCR_PPD
If this bit is logic 1, GFR policing is enabled and the MCR test is enabled
to discard (i.e. Action 2 = Discard) then the policer will perform partial
packet discard when a connection begins to fail MCR. If this bit is logic
0, then the MCR is only permitted to perform actions on frame
boundaries, as per the GFR standard.
CLPCC_CLP1_Discard
If the CLP Conformance Check CLP1 Discard bit is set to logic 1, then
during GFR policing, if a cell arrives with CLP = 1 in a frame whose first
cell had CLP = 0, then the frame will undergo Partial Packet Discard. If
the CLP=1 cell is the end of packet, then every cell until the next CLP =
0 end of packet will be discarded. If this bit is logic 0, then CLP = 1 cells
in CLP = 0 frames will not be treated as non-compliant.
Maximum Frame Length
Remaining Frame Count
This field indicates the maximum permissible length of a frame for GFR
connections. Frames exceeding this length will undergo PPD. A
maximum frame length of zero is invalid, and is treated as an MFL of 1.
When an End Of Message cell in a packet is received, the Remaining
Frame Count field of the VC Table is loaded, after testing for MFL
conformance with the current value, with the value programmed in the
Maximum Frame Length field in the VC Table. The Remaining Frame
Count is then decremented with each cell received in the new frame. If
this value reaches zero before an End Of Message cell is received, the
remainder of the frame is discarded (the EOM cell is identified by having
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990553, Issue 4
102
PMC [ PMC-SIERRA, INC ]
