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

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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Received on Mon Aug 10 2009 - 08:45:42 ART