Re: CBWFQ behavior change - 12.4 Mainline vs 12.4T (124-24.T1)

thnks Nick, makes sense now.

On Mon, Aug 10, 2009 at 4:45 PM, Nick Matthews <matthn_at_gmail.com> wrote:

> There was a big change in 12.4(20)T. Namely:
>
> http://www.cisco.com/en/US/docs/ios/qos/configuration/guide/qos_frhqf_support.html
>
> There was also a CEF re-write. I believe that WFQ was one of the main
> components changed in the new architecture.
>
>
> -nick
>
> On Sun, Aug 9, 2009 at 3:24 PM, Swap<ccie19804_at_gmail.com> wrote:
> > Hi group,
> >
> > There is a significant difference in CBWFQ based QoS on 12.4 and 12.4T
> >
> > In 12.4T (24), CBWFQ behaves as if it has an inbuilt policer for the
> > reserved BW. The reserved flow stays within the reserved bandwidth during
> > congestion. Other flow get their share out of the remaining bandwidth.
> >
> > In 12.4 Mainline and before, the reserved flow eats up all the bandwidth
> > based on the higher weight. Other flows don't get enough bandwidth at
> all.
> > (ofc shaping can be manually configured to restrict the CBFWQ flows).
> >
> > has something officially changed? I couldn't find any explicit
> documentation
> > stating this difference.
> >
> >
> > Details:
> > -----------
> >
> > E.g.
> >
> > Out pipe = 10Mbps
> > In traffic-:
> > 1. UDP1000 with CBWFQ reserved BW=6000kbps received at the rate of 8MBps
> on
> > router LAN on fa0/0
> > 2. UDP1001 received at 20Mbps on router LAN on fa0/0
> >
> > Topology-
> > ------Clients-
> >
> --100Mbps----(fa0/0)--LAN-router-----(fa0/1)-----10mbps-------(fa0/1)----WAN
> > -router----
> >
> >
> > In 12.4T,
> >
> > WAN#sh policy-map int fa0/1
> >
> > FastEthernet0/1
> > Service-policy input: PM_QOS_STATS
> >
> > Class-map: CM_UDP1000 (match-all)
> > 226396 packets, 281183832 bytes
> > 30 second offered rate 5945000 bps ----> CBWFQ gets 6Mbps even when
> > sending at 8Mbps. The excess BW is auto-policed like it happens in LLQ.
> >
> > Match: access-group 100
> >
> > Class-map: CM_UDP1001 (match-all)
> > 146264 packets, 181659888 bytes
> > 30 second offered rate 3864000 bps -> other flow gets remaining
> 4MBps
> > (approx)
> > Match: access-group 101
> >
> >
> >
> > In 12.4 Mainline,
> >
> > WAN#sh policy-map int fa0/1
> > FastEthernet0/1
> >
> > Service-policy input: PM_QOS_STATS
> > Class-map: CM_UDP1000 (match-all)
> > 1185545 packets, 1472446890 bytes
> > 30 second offered rate 8161000 bps ----> CBWFQ gets 8.0Mbps when
> > sending at 8Mbps based of the higher weight
> >
> > Match: access-group 100
> >
> > Class-map: CM_UDP1001 (match-all)
> > 373738 packets, 464182596 bytes
> > 30 second offered rate 1649000 bps-> other flow get only around 2
> Mbps
> > Match: access-group 101
> >
> > Configs:
> > --------------
> > WAN-RTR
> > WAN#sh run policy-map
> > Building configuration...
> >
> > Current configuration : 142 bytes
> > !
> > policy-map PM_QOS_STATS
> > class CM_UDP1000
> > class CM_UDP1001
> > class CM_UDP1002
> > class CM_UDP1005
> > class CM_UDP1004
> > class CM_UDP1003
> > !
> > end
> >
> > WAN#sh run int fa0/1
> > Building configuration...
> > Current configuration : 164 bytes
> > !
> > interface FastEthernet0/1
> > ip address 192.168.58.2 255.255.255.0
> > load-interval 30
> > duplex auto
> > speed 10
> > no keepalive
> > service-policy input PM_QOS_STATS
> > end
> >
> >
> > LAN-RTR
> > ------------
> >
> > LAN#sh run int fa0/1
> >
> > Building configuration...
> > Current configuration : 202 bytes
> > !
> > interface FastEthernet0/1
> > bandwidth 10000
> > ip address 192.168.58.1 255.255.255.0
> > load-interval 30
> > duplex auto
> > speed 10
> > no keepalive
> > max-reserved-bandwidth 100
> > service-policy output PM_QOS
> > end
> >
> >
> > LAN#sh run policy-map
> >
> > Building configuration...
> > Current configuration : 313 bytes
> > !
> > policy-map PM_QOS
> > class CM_UDP1000
> > bandwidth 6000
> > class CM_TELNET
> > priority 100
> >
> >
> > Swap
> > #19804
> >
> >
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> >
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Received on Mon Aug 10 2009 - 22:02:44 ART