interface drops issue

rec stalmaski · ‎05-14-2012

Hi I would like to ask assistance regarding QOS issue i'm facing my customer. Currently they have 60Meg BW, and we allot 2048 to their realtime trafic. The problem is that they are seeing drop rates even we if we are not reaching the full capacity of set priority. One thing i've noticed is that we are seeing total drops also on the main interface. I tweaked shape average to full 60000, configure max reserve BW to 90 & also 100, i even increased the hold que both in & out but trouble still in occur.

Relevant configuration that i can provide:

class-map match-any realtime
match dscp ef
match ip dscp cs5 ef
match dscp cs5
!
----snipped-----
!
policy-map etm-CSR_1
class realtime
    priority 2048
    police 2048000 conform-action transmit exceed-action drop
class priority
    bandwidth remaining percent 39
!
----snipped-----
!
policy-map shape-etm-CSR_1
class class-default
    shape average 60000000
service-policy etm-CSR_1
----snipped-----
!
!
interface GigabitEthernet0
bandwidth 60000
no ip address
no ip redirects

----snipped-----

CSR_1#sh int g0
GigabitEthernet0 is up, line protocol is up
MTU 1500 bytes, BW 60000 Kbit/sec, DLY 100 usec,
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1139439
!
----snipped-----

Class-map: realtime (match-any)
   33633081 packets, 30883004811 bytes
   5 minute offered rate 135000 bps, drop rate 2000 bps
   Match: dscp ef (46)
     9832 packets, 2038052 bytes
     5 minute rate 0 bps
   Match: ip dscp cs5 (40) ef (46)
     33623249 packets, 30880964243 bytes
     5 minute rate 135000 bps
   Match: dscp cs5 (40)
     0 packets, 0 bytes
     5 minute rate 0 bps
   Priority: 2048 kbps, burst bytes 51200, b/w exceed drops: 0



   I'm thinking of replacing the cable in used towards the WAN side and also, there is another port which we can use but FastE. This is to elminate any cabling and port issue I'm seeking your expertise why we are seeing drops even if we are not reaching the full capacity set to realtime traffic. Also current utilization is very minimal which is playing around 30-50% during business hours.

paolo bevilacqua · ‎05-14-2012

You cannot ever judge the instaneous traffic based on the average of 30 or even 5 seconds. If there are burst of traffic, packes will be dropped eaxtly because you have configured policing.

So, either relax the parameter ands let traffic flow, or configure shaping, or anything else, but do not assume the router is wrong because some traffic graph suggest "little utilization".

Leo Laohoo · ‎05-14-2012

policy-map Parent-Policy
 class class-default
 shape average percent 95

This is our policy map to shape the traffic to 95%. It's simple but effective. You up the bandwidth, there's nothing to change.