08-10-2009 11:47 PM - edited 03-04-2019 05:42 AM
With the following config...
policy-map COS
class IP-PREC4
set ip precedence 4
priority percent 50
class IP-PREC3
set ip precedence 3
bandwidth percent 30
class class-default
fair-queue
random-detect
policy-map SHAPING
class class-default
shape average 512000 5120
service-policy COS
!
interface FastEthernet0/0
description MPLS 2MB connection
FastEthernet5/1/1
bandwidth 2000
ip address 192.168.x.214 255.255.255.252
speed 10
full-duplex
max-reserved-bandwidth 100
service-policy output SHAPING
...would the priority percent use 50% of the shaped rate or 50% of the interface's bandwidth command for it's percentage calculation?
Cheers
Solved! Go to Solution.
08-11-2009 01:07 AM
To add some explanation to this:
With your configuration the queue system is built up the following way:
Interface Traffic -> LLQ -> Shaping Queue -> Transmit Queue -> Outgoing traffic
So if you configure the 'priority percent 50' command, the LLQ will allow 1000 kbps for the priority traffic.
But the shaping queue is configured for 512kbps only, so 1000 kbps priority traffic could overwhelm the shaping queue, leaving no space for other traffic.
Cheers:
Istvan
08-11-2009 12:52 AM
Hi Duncan,
The priority percent command uses the bandwidth setting to calculate the bandwidth allocated to the priority queue. In this case it will allocate 1000 kbps.
You should set the priority command to
"priority 256"
if you want the priority queue to use 50% of the shaped bandwidth.
Cheers:
Istvan
08-11-2009 01:07 AM
To add some explanation to this:
With your configuration the queue system is built up the following way:
Interface Traffic -> LLQ -> Shaping Queue -> Transmit Queue -> Outgoing traffic
So if you configure the 'priority percent 50' command, the LLQ will allow 1000 kbps for the priority traffic.
But the shaping queue is configured for 512kbps only, so 1000 kbps priority traffic could overwhelm the shaping queue, leaving no space for other traffic.
Cheers:
Istvan
08-11-2009 01:51 AM
Gotcha. Thanks Istvan.
Duncan
08-11-2009 03:46 AM
"...would the priority percent use 50% of the shaped rate or 50% of the interface's bandwidth command for it's percentage calculation? "
If I remember correctly, with the later IOS images, the bandwidth percentages will use the parent policy's shaped rate not the interface bandwidth setting (which whould be used by class percentages in the parent policy).
BTW, another interesting bandwidth issue is, you've explicity allocated 80%. For IOS on most platforms (pre 12.4[20]T?), you would be unable to do this without increasing the max-reserved-bandwidth from its default 75% (as you've done), although here too I think this would only apply to the parent policy, not a subordinate policy.
It also looks like you've clipped an actual CBWFQ implementation. What does a show policy-map interface indicate (since many IOSs will show class bandwidth allocations for percentages)?
08-11-2009 06:54 PM
Thanks Joseph. Where did you get this info? I've tried to find something definitive on the Cisco site regarding this but no luck to date.
Unfortunately it's a provider router (CE) so I don't have telnet access, but I do have GN3 so I'll give it a try on there.
Cheers
Duncan
08-12-2009 08:23 AM
Sorry, don't recall if I seen good Cisco documentation on this point.
BTW, I dropped your configuration into a lab router (2801 using 12.4.23) and it looks like my memory was confirmed.
class-map match-all IP-PREC3
match ip precedence 3
class-map match-all IP-PREC4
match ip precedence 4
!
!
policy-map COS
class IP-PREC4
set ip precedence 4
priority percent 50
class IP-PREC3
set ip precedence 3
bandwidth percent 30
class class-default
fair-queue
random-detect
policy-map SHAPING
class class-default
shape average 512000 5120
service-policy COS
interface FastEthernet0/0
ip address dhcp
duplex auto
speed auto
max-reserved-bandwidth 100
service-policy output SHAPING
Rtr1#sh policy-map i o
FastEthernet0/0
Service-policy output: SHAPING
Class-map: class-default (match-any)
122 packets, 18767 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
512000/512000 1280 5120 5120 10 640
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 122 18767 3 1006 no
Service-policy : COS
Class-map: IP-PREC4 (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip precedence 4
QoS Set
precedence 4
Packets marked 0
Queueing
Strict Priority
Output Queue: Conversation 40
Bandwidth 50 (%)
Bandwidth 256 (kbps) Burst 6400 (Bytes)
(pkts matched/bytes matched) 0/0
(total drops/bytes drops) 0/0
Class-map: IP-PREC3 (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip precedence 3
QoS Set
precedence 3
Packets marked 0
Queueing
Output Queue: Conversation 41
Bandwidth 30 (%)
Bandwidth 153 (kbps)Max Threshold 64 (packets)
(pkts matched/bytes matched) 0/0
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
122 packets, 18767 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 32
(total queued/total drops/no-buffer drops) 0/0/0
exponential weight: 9
class Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob
0 24/2604 0/0 0/0 20 40 1/10
1 0/0 0/0 0/0 22 40 1/10
2 0/0 0/0 0/0 24 40 1/10
3 0/0 0/0 0/0 26 40 1/10
4 0/0 0/0 0/0 28 40 1/10
5 0/0 0/0 0/0 30 40 1/10
6 98/16163 0/0 0/0 32 40 1/10
7 0/0 0/0 0/0 34 40 1/10
rsvp 0/0 0/0 0/0 36 40 1/10
08-12-2009 08:27 AM
(NB: prior post is throwing Apache errors?)
Sorry, don't recall if I've seen good Cisco documentation on this point.
BTW, I dropped your configuration into a lab router (2801 using 12.4.23) and it looks like my memory was confirmed.
class-map match-all IP-PREC3
match ip precedence 3
class-map match-all IP-PREC4
match ip precedence 4
!
!
policy-map COS
class IP-PREC4
set ip precedence 4
priority percent 50
class IP-PREC3
set ip precedence 3
bandwidth percent 30
class class-default
fair-queue
random-detect
policy-map SHAPING
class class-default
shape average 512000 5120
service-policy COS
interface FastEthernet0/0
ip address dhcp
duplex auto
speed auto
max-reserved-bandwidth 100
service-policy output SHAPING
Rtr1#sh policy-map i o
FastEthernet0/0
Service-policy output: SHAPING
Class-map: class-default (match-any)
122 packets, 18767 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
512000/512000 1280 5120 5120 10 640
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 122 18767 3 1006 no
Service-policy : COS
Class-map: IP-PREC4 (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip precedence 4
QoS Set
precedence 4
Packets marked 0
Queueing
Strict Priority
Output Queue: Conversation 40
Bandwidth 50 (%)
Bandwidth 256 (kbps) Burst 6400 (Bytes)
(pkts matched/bytes matched) 0/0
(total drops/bytes drops) 0/0
Class-map: IP-PREC3 (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip precedence 3
QoS Set
precedence 3
Packets marked 0
Queueing
Output Queue: Conversation 41
Bandwidth 30 (%)
Bandwidth 153 (kbps)Max Threshold 64 (packets)
(pkts matched/bytes matched) 0/0
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
122 packets, 18767 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 32
(total queued/total drops/no-buffer drops) 0/0/0
exponential weight: 9
class Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob
0 24/2604 0/0 0/0 20 40 1/10
1 0/0 0/0 0/0 22 40 1/10
2 0/0 0/0 0/0 24 40 1/10
3 0/0 0/0 0/0 26 40 1/10
4 0/0 0/0 0/0 28 40 1/10
5 0/0 0/0 0/0 30 40 1/10
6 98/16163 0/0 0/0 32 40 1/10
7 0/0 0/0 0/0 34 40 1/10
rsvp 0/0 0/0 0/0 36 40 1/10
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