[c-nsp] Outbound drops on ME-3600X-24FS-M microbursts

[Steve Dodd]

The only reliable method we've found to mitigate OutDiscards on the ME36/3800 platform when coming from the 10G to the 1G interfaces has been to set a queue-limit per class. 

class-map match-all COS_ZERO
 match cos  0 
!
policy-map QUEUEFIX
 class COS_ZERO
  bandwidth 100
  queue-limit 2000 us
 class class-default
  queue-limit 2000 us
!
Int g0/1
 service-policy output QUEUEFIX
!

The command will be rejected if you just try to use a default class, thus why the config includes the COS_ZERO portion.


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Abel Alejandro
Sent: Saturday, January 28, 2012 7:48 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Outbound drops on ME-3600X-24FS-M microbursts

Hello,

I have a ME-3600X-24FS-M with a 10GE interface facing an LTE core network and a 1GE interface to a remote node.
The client wants to achieve 50Mbps on a single tcp session with an RTT of 50ms, so the BDP is about 300KB, however the congestion window seems to be stuck at around 44KB due to packet drops due to the microbursts.

The offending interface appears to be:

GigabitEthernet0/23 is up, line protocol is up (connected)  Hardware is Gigabit Ethernet, address is 24b6.574b.5297 (bia
24b6.574b.5297)
 Description:
 MTU 1610 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
    reliability 255/255, txload 1/255, rxload 1/255  Encapsulation ARPA, loopback not set  Keepalive not set  Full-duplex, 1000Mb/s, media type is LX  input flow-control is off, output flow-control is unsupported  ARP type: ARPA, ARP Timeout 04:00:00  Last input never, output never, output hang never  Last clearing of "show interface" counters 05:10:14  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
1815
 Queueing strategy: fifo
 Output queue: 0/2512 (size/max)
 30 second input rate 1000 bits/sec, 1 packets/sec
 30 second output rate 48000 bits/sec, 11 packets/sec
    31938 packets input, 2874462 bytes, 0 no buffer
    Received 31938 broadcasts (31938 multicasts)
    0 runts, 0 giants, 0 throttles
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
    0 watchdog, 31938 multicast, 0 pause input
    0 input packets with dribble condition detected
    13997301 packets output, 19484128487 bytes, 0 underruns
    0 output errors, 0 collisions, 0 interface resets
    0 unknown protocol drops
    0 babbles, 0 late collision, 0 deferred
    0 lost carrier, 0 no carrier, 0 pause output
    0 output buffer failures, 0 output buffers swapped out

We increased the output queue but still getting drops, any tips?

(Please discard a duplicate mail from another account, thought it was filtered).

Thanks,
Abel.
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