Since last year I deployed the 'shape average BW' to fix the unexpected packet drop by Verizon's PE router. The BW is set to match the BW subscription with Verizon. Getting started the usage monitoring, I started seeing the OQD increasing daily but the Netflow reports the usage is below the max. Today I finally took the shaping away from one of the CE router and see if the packet loss becomes less. On the other hand, I started studying the effect of the parameters for the shaping command.
Below is the router configuration with Verizon link of 3Mbps.
class-map match-all critical
description critical apps
shape average 3000000 12000 0
no ip address
service-policy output QoS
encapsulation dot1Q 8
ip address x.x.x.x 255.255.255.252
ip flow ingress
ip flow egress
no snmp trap link-status
Initially I simply used 'shape average 3000000' and the OQD is large. Today I read some articles about the advanced QoS configuration, it's found that the byte limit is better to be multiple of 1500 (max MTU) and least sustain bit/int so as to get the minimum interval (Tc). Is it true?
Besides, I checked the network usage again by Netflow and found the usage is below the max. Unfortunately the OQD is not zero, as below, and that makes me puzzled.
Service-policy output: QoS
Class-map: critical (match-all)
668950 packets, 116032833 bytes
5 minute offered rate 150000 bps, drop rate 0 bps
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
3000000/3000000 1500 12000 0 4 1500
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 668738 116009290 62896 35730671 no
Class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
*: interface is up
IHQ: pkts in input hold queue IQD: pkts dropped from input queue
OHQ: pkts in output hold queue OQD: pkts dropped from output queue
RXBS: rx rate (bits/sec) RXPS: rx rate (pkts/sec)
TXBS: tx rate (bits/sec) TXPS: tx rate (pkts/sec)
TRTL: throttle count
Interface IHQ IQD OHQ OQD RXBS RXPS TXBS TXPS TRTL
* GigabitEthernet0/0 0 0 0 0 153000 119 181000 118 0
* GigabitEthernet0/1 0 0 0 213 185000 119 160000 121 0
* GigabitEthernet0/1.15 - - - - - - - - -
* Loopback0 0 0 0 0 0 0 0 0 0
NOTE:No separate counters are maintained for subinterfaces
Hence Details of subinterface are not shown
Thanks in advance.