[j-nsp] fabric drops ?

[harry]

I believe that these represent packets that were received by an ingress
T-series FPC and destined to egress on a different FPC. This traffic must
transit the T-series switch fabric. In this case it seems that the traffic
was dropped because the destination FPC was not able to service the traffic
in the confines of the T-series delay-bandwidth buffer (some 100
milliseconds, if not mistaken). Packets that are not serviced in this
delay-bandwidth time-period are simply overwritten by newer traffic.

I would suspect that you have an issue of more ingress traffic being
directed to egress on a given FPC/PIC/port than that FPC/PIC/port can
handle. This many to one situation can lead to fabric drops; why send
traffic over the fabric to an egress FPC, only to have it dropped by the
egress FPC because it is unable to handle the offered load? This may also be
an issue of incorrect CoS related settings, or perhaps the use of
fabric-override, which is rarely used.  

Some information can be found at:

http://www.juniper.net/techpubs/software/junos/junos63/swcmdref63/html/cos-m
onitor6.html#1137498

HTHs



> -----Original Message-----
> From: juniper-nsp-bounces at puck.nether.net 
> [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of 
> Jerome Fleury
> Sent: Wednesday, May 12, 2004 9:59 AM
> To: juniper-nsp at puck.nether.net
> Subject: [j-nsp] fabric drops ?
> 
> 
> Hi,
> 
> does anyone know what fabric drops are ? (see last line)
> 
> we have this counter increasing on all of our routers, but 
> one of them has much more than the others.
> 
> Can someone point me on the exact definition of this ? Thanks.
> 
> jfl at RE0.BB1.COU> show pfe statistics traffic
> PFE Traffic statistics:
>         7887025183350 packets input  (1505803 packets/sec)
>         7861203968641 packets output (1492453 packets/sec)
> 
> PFE Local Traffic statistics:
>   675057223 local packets input
>   675182639 local packets output
>           0 software input high drops
>         187 software input medium drops
>           0 software input low drops
>           0 software output drops
>   393287161 hardware input drops
> 
> PFE Local Protocol statistics:
>           0 hdlc keepalives
>           0 atm oam
>           0 fr lmi
>    11617138 ppp lcp/ncp
>     5507027 ospf hello
>     3656359 rsvp hello
>    19263171 isis iih
> 
> PFE Hardware Discard statistics:
>           0 timeout
>           0 truncated key
>           0 bits to test
>           0 data error
>           0 stack underflow
>           0 stack overflow
>  4180034742 normal discard
>           0 extended discard
>       22104 invalid iif
>           0 info cell drops
>    61875452 fabric drops
> 
> 
> --
> Jerome Fleury
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