[c-nsp] Output Drops

[Marc Steiniger]

Sorry I wasn't clear to state that this will only help identify why
you are seeing output drops (if in fact the link is being
overutilized), but it won't actually do anything to directly resolve
the problem.

-M



On 2/15/06, Marc Steiniger <marc.steiniger at gmail.com> wrote:
> Try changing your load-interval on Se1/0/0:13 to 30 from 600 (seconds).
>
> Your output shows a 5-minute load average, along with 40 output drops
> in 7 minutes.
>
> Output drops will occur anytime the link is overutilized, if even just
> for a moment.  By shrinking your load interval you will be reducing
> the number of samples used to create your average.
>
> HTH
> Marc
>
>
> On 2/15/06, Peder @ NetworkOblivion <peder at networkoblivion.com> wrote:
> > I've got a problem with output drops and I can't quite figure out what
> > the issue is.  I am running 12.2.29 on a 7505.  Here is the config for
> > the relevant interface:
> >
> > interface Serial1/0/0:13
> >   ip address x.x.x.1 255.255.255.252
> >   service-policy output CUSTOMER-MAP
> >   encapsulation ppp
> >
> > class-map match-all CUSTOMER
> >    match access-group name ToCustomer
> >    match ip precedence 5
> >
> > policy-map CUSTOMER-MAP
> >    class CUSTOMER
> >      priority 512
> >    class class-default
> >      fair-queue
> >
> > Basically, we are matching IP Prec 5 and a specific IP on the
> > access-list for priority of voice.  The customer is complaining about
> > quality issues every now and then.  When I check the inteface, I am
> > seeing output drops even though there is a small amount of traffic.  The
> > output below shows 40 packets dropped in 7 minutes.  I have a graph of
> > utilization that updates every 30 seconds and it is never above 500kbps.
> >   The 5-min average is ~115,000 bps.
> >
> >
> > 7505#sh int Serial1/0/0:13
> > Serial1/0/0:13 is up, line protocol is up
> >    Hardware is cyBus T3
> >    Description: Blah
> >    Internet address is x.x.x.1/30
> >    MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
> >       reliability 255/255, txload 18/255, rxload 7/255
> >    Encapsulation PPP, crc 16, loopback not set
> >    Keepalive set (10 sec)
> >    LCP Open
> >    Listen: CDPCP
> >    Open: IPCP
> >    Last input 00:00:00, output 00:00:01, output hang never
> >    Last clearing of "show interface" counters 00:07:03
> >    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 40
> >    Queueing strategy: VIP-based fair queuing
> >    Output queue: 0/40 (size/max)
> >    5 minute input rate 43000 bits/sec, 58 packets/sec
> >    5 minute output rate 114000 bits/sec, 62 packets/sec
> >       27965 packets input, 3012703 bytes, 0 no buffer
> >       Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
> >       0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
> >       29856 packets output, 9627702 bytes, 0 underruns
> >       0 output errors, 0 collisions, 0 interface resets
> >       0 output buffer failures, 0 output buffers swapped out
> >       0 carrier transitions no alarm present
> >    Timeslot(s) Used: 1-24, Transmitter delay is 0 flags
> >    non-inverted data
> >
> >
> > 7505#sh pol int Serial1/0/0:13
> >   Serial1/0/0:13
> >
> >    Service-policy output: CUSTOMER-MAP
> >
> >      queue stats for all priority classes:
> >        queue size 0, queue limit 128
> >        packets output 34124, packet drops 0
> >        tail/random drops 0, no buffer drops 0, other drops 0
> >
> >      Class-map: CUSTOMER (match-all)
> >        34124 packets, 2183936 bytes
> >        5 minute offered rate 48000 bps, drop rate 0 bps
> >        Match: access-group name ToCustomer
> >        Match: ip precedence 5
> >        Priority: kbps 512, burst bytes 12800, b/w exceed drops: 0
> >
> >      Class-map: class-default (match-any)
> >        11127 packets, 10132207 bytes
> >        5 minute offered rate 88000 bps, drop rate 0 bps
> >        Match: any
> >        queue size 0, queue limit 256
> >        packets output 11171, packet drops 0
> >        tail/random drops 0, no buffer drops 0, other drops 0
> >        Fair-queue: per-flow queue limit 64
> >
> > The policy doesn't show any drops due to bandwidth and the interface
> > isn't going down, so what is causing the drops?  Is there some other
> > commands I can use to try and figure that out?  Or does this sound like
> > a bug?  We've been running this version for ~ 40 weeks and they just
> > started complaining in the last 2-3 weeks.
> >
> > Thanks.
> >
> > Peder
> >
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