[c-nsp] 3CXL limitations

[Андреев Андреевич]

Hi list,

Today one of our 7600 transit router was under dos attack and we saw 
serious performance degradation.
Cpu was not affected but i saw transit traffic drops.

Firstly i think about pps lookup limit on 3CXL PFC but the command 
"show platform hardware capacity forwarding" shows me that peak-pps 
was about 12606022 packets amd the cisco documents says that limit is 
much higher.

#show platform hardware capacity forwarding
...
      Forwarding engine load:
                      Module       pps   peak-pps
                      5        2693808   12606022


At the same time some packets was droped:

#show platform hardware central-rewrite drop details
slot channel drop_id description          packet drops         total 
overruns
----+-------+-------+--------------------+--------------------+--------------+
2    0       0x5ED   DROP NON BPDU        0                    0
2    0       0x5EB   DROP BPDU            0                    0
3    0       0x5ED   DROP NON BPDU        0                    0
3    0       0x5EB   DROP BPDU            0                    0
3    1       0x5ED   DROP NON BPDU        0                    0
3    1       0x5EB   DROP BPDU            0                    0
5    0       0x40A   DROP RED             4280398              37
5    0       0x425   DROP RE              0                    0



I cant find the root cause of this issue.

Please explain me what is "central-rewrite drop" exactly means.
I also dont understand "RED" and "RE" differences in the output.



And some diag commands from this box:


#show mod
Mod Ports Card Type                              Model
--- ----- -------------------------------------- ------------------
   2   24  CEF720 24 port 1000mb SFP              WS-X6724-SFP
   3    4  CEF720 4 port 10-Gigabit Ethernet      WS-X6704-10GE
   5    2  Route Switch Processor 720 (Active)    RSP720-3CXL-GE


#show platform hardware pfc mode
PFC operating mode : PFC3CXL


Thank you.