[c-nsp] cisco buffer misses

Booth, Ryan RBooth at pantex.com
Fri Apr 19 09:50:30 EDT 2013

This is true about the misses. From my own experience and what others have told me when a small or medium buffer is missed the frame/packet is usually dropped and requires a retransmission. For me this is evident in my IP-video traffic which suffers frame loss. Normal TCP traffic can just retransmit.

Ryan Booth

-----Original Message-----
From: Booth, Ryan 
Sent: Thursday, April 18, 2013 4:07 PM
To: 'Michael Sprouffske'; cisco-nsp at puck.nether.net
Subject: RE: [c-nsp] cisco buffer misses

No QoS will just degrade your performance. 3750s are notorious for having horrible buffer sizes and crappy ASIC performance. QoS will just carve this up into smaller chunks for each group of traffic making the situation worse

My initial guess is you are overloading and ASIC or the switch all together with either micro-burst or high levels of traffic. 

Check your ASICs to see if you are getting drops. Im not familiar with the ASIC performance and port-layout of the X series so you might need to move some heavy loaded links away from each other to even out the load across ASICS.

TAC can also give you specifics on ASIC performance and help.

Ryan Booth

-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Michael Sprouffske
Sent: Thursday, April 18, 2013 12:47 PM
To: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] cisco buffer misses

I'm thinking that some switch qos needs to be put in place to resolve this issue.  What does everyone think?  We currently don't have qos running in the switched network.  We only have qos running on the routers for the uplinks.

 From: Michael Sprouffske <msprouffske at yahoo.com>
To: "cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net> 
Sent: Thursday, April 18, 2013 9:40 AM
Subject: cisco buffer misses

Could someone give me some insight as to what is causing the misses?  I'm currently researching this on the inter webs.  I also notice an interface with several drops as well.


model: WS-C3750X-24T-S

Buffer elements:
     1061 in free list (500 max allowed)
     3479036431 hits, 0 misses, 1024 created

Public buffer pools:
Small buffers, 104 bytes (total 50, permanent 50, peak 119 @ 7w0d):
     49 in free list (20 min, 150 max allowed)
     1712506149 hits, 23 misses, 69 trims, 69 created
     0 failures (0 no memory)
Middle buffers, 600 bytes (total 25, permanent 25, peak 85 @ 7w0d):
     23 in free list (10 min, 150 max allowed)
     167702 hits, 58 misses, 174 trims, 174 created
     0 failures (0 no memory)
Big buffers, 1536 bytes (total 50, permanent 50,
 peak 119 @ 7w0d):
     50 in free list (5 min, 150 max allowed)
     244703400 hits, 39 misses, 117 trims, 117 created
     0 failures (0 no memory)
VeryBig buffers, 4520 bytes (total 16, permanent 10, peak 16 @ 7w0d):
     0 in free list (0 min, 100 max allowed)
     59 hits, 3 misses, 1429 trims, 1435 created
     0 failures (0 no memory)
Large buffers, 5024 bytes (total 0, permanent 0):
     0 in free list (0 min, 10 max allowed)
     0 hits, 0 misses, 0 trims, 0 created
     0 failures (0 no memory)
Huge buffers, 18024 bytes (total 4, permanent 0, peak 7 @ 7w0d):
     4 in free list (0 min, 4 max allowed)
     145363512 hits, 412449 misses, 822729 trims, 822733
     0 failures (0 no memory)

GigabitEthernet1/0/11 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is 649e.f3e2.7b8b (bia 649e.f3e2.7b8b)
  Description: server ports
  MTU 9000 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
 Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:16, output 00:00:01, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 54011
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 49000 bits/sec, 28 packets/sec
     837676 packets input, 118543994 bytes, 0 no buffer
     Received 492811 broadcasts (481207 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 481207 multicast, 0 pause input
 0 input packets with dribble condition detected
     670450255 packets output, 115399962776 bytes, 0 underruns
     0 output errors, 0 collisions, 1 interface resets
     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
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