07-27-2006 09:01 AM - edited 03-03-2019 04:15 AM
Is the max-reserved bandwidth only important when working with Qos classes and the bandwidth statement? Is the default 75% available bandwidth only used then?
In other words if I have a 100MB link with a service policy applied for Voice, Call-Control and video. After that I notice the available bandwidth on thie 100MB link is 61280 kilobits/sec.
If I put in a 'max-reserved bandwidth 95' would I reclaim another 20MB of bandwidth for the class-default? Would leaving 5% on the 100MB link for routing and other stuff be acceptable?
Here is the config and show commands:
class-map match-any Call-Control
match ip dscp cs3
match ip dscp af31
class-map match-any Video
match ip dscp af41
class-map match-any Voice
match ip dscp ef
policy-map QOS_classes_to_ACN
class Voice
priority 10000
class Call-Control
bandwidth 500
class Video
bandwidth 3220
class class-default
fair-queue
random-detect
interface FastEthernet6/0
description 100MB Link to ACN
ip address xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
ip route-cache flow
no ip mroute-cache
load-interval 30
duplex full
speed 100
service-policy output QOS_classes_to_ACN
ROC-RT7206-QMOE#sh int f6/0
FastEthernet6/0 is up, line protocol is up
Hardware is i82543 (Livengood), address is 00b0.4a28.3ca8 (bia 00b0.4a28.3ca8)
Description: 100MB Link to ACN
Internet address is xxx.xxx.xxx.xxx/xx
MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
reliability 255/255, txload 183/255, rxload 21/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s, 100BaseTX/FX
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:03, output 00:00:00, output hang never
Last clearing of "show interface" counters 01:13:30
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 5211742
Queueing strategy: Class-based queueing
Output queue: 70/1000/64/5211742 (size/max total/threshold/drops)
Conversations 2/35/256 (active/max active/max total)
Reserved Conversations 2/2 (allocated/max allocated)
Available Bandwidth 61280 kilobits/sec <--- Available bandwidth
30 second input rate 8615000 bits/sec, 6860 packets/sec
30 second output rate 71788000 bits/sec, 7484 packets/sec
31692173 packets input, 4263195179 bytes
Received 1204 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog
0 input packets with dribble condition detected
34536300 packets output, 2513155446 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
07-27-2006 09:02 AM
Here is the output of show policy-pam int:
ROC-RT7206-QMOE#sh policy-map int f6/0
FastEthernet6/0
Service-policy output: QOS_classes_to_ACN
Class-map: Voice (match-any)
3417571 packets, 934178998 bytes
30 second offered rate 1722000 bps, drop rate 0 bps
Match: ip dscp ef (46)
3417571 packets, 934178998 bytes
30 second rate 1722000 bps
Queueing
Strict Priority
Output Queue: Conversation 264
Bandwidth 10000 (kbps) Burst 250000 (Bytes)
(pkts matched/bytes matched) 1908656/521903140
(total drops/bytes drops) 0/0
Class-map: Call-Control (match-any)
615085 packets, 48926098 bytes
30 second offered rate 84000 bps, drop rate 0 bps
Match: ip dscp cs3 (24)
588857 packets, 47299978 bytes
30 second rate 81000 bps
Match: ip dscp af31 (26)
26228 packets, 1626120 bytes
30 second rate 2000 bps
Queueing
Output Queue: Conversation 265
Bandwidth 500 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 337953/26882724
(depth/total drops/no-buffer drops) 0/0/0
Class-map: Video (match-any)
146136 packets, 82165408 bytes
30 second offered rate 90000 bps, drop rate 0 bps
Match: ip dscp af41 (34)
146136 packets, 82165408 bytes
30 second rate 90000 bps
Queueing
Output Queue: Conversation 266
Bandwidth 3220 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 81687/45950190
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
35227089 packets, 47492000208 bytes
30 second offered rate 87718000 bps, drop rate 14714000 bps
Match: any
Queueing
Flow Based Fair Queueing
Maximum Number of Hashed Queues 256
(total queued/total drops/no-buffer drops) 0/5171786/0
exponential weight: 9
class Transmitted Random drop Tail drop Minimum Maximum Mark
pkts/bytes pkts/bytes pkts/bytes thresh thresh prob
0 30181523/39910255774 1297726/1944176143 3893194/5836883998 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 1213/88749 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
07-27-2006 06:37 PM
In a simple ans., Yes, increase the max-reserve bandwidth then you can use more bandwidth. How much you allocate the bandwidth is quite difficult to decide, it depends on how much traffic will be the control, routing protocol, etc.
If your network is simple and not much routes & route update there, I believe you can increase the ratio, 75% is only a default value and you can fine tune it.
So, in this case, if you decided the ratio then you have to recalculate the bandwidth allocation in each class to reflect to the correct throughput.
Hope this helps.
07-28-2006 01:32 AM
Hi,
just for clarification (maybe unnecessary, but ...): you always have 100 MB used bandwidth. Queueing, which uses max-reserved and bandwidth to calculate "bandwidth ratios" between different classes, only kicks in once your link is overloaded. Unless this is the case any traffic will be forwarded with line speed.
So max-res and bandwidth (interface command) only modify your per-class bandwidth guarantees in an overload situation.
Hope this helps!
Regards, Martin
07-28-2006 02:32 AM
Hi
I had a similar post sometime back but there was no QOS policy applied.
With default queuing too i find the available bandwidth is less than the bandwidth on the link.
And if i just change the bandwidth command to say some arbitrary value on the interface (although it will not increase my line bandwidth), these values change..
So if i have a T1 line and no policies, what would ideally be the available bandwidth?
Thanks in advance
Narayan
07-28-2006 07:43 AM
So if I understand you correctly traffic in the class-default will have full line rate available to them unless there is congestion?
The reason I ask is on this link, along with the classes for voice, video and call control, we are now transferring one huge volume of traffic for data backup. This is a one time operation and it is over a terrabyte. The data transfer folks say they've throttled the application that is transfering this data to 75mbs, which is 3/4 of the bandwidth on this 100mb link. My confusion comes from the 'available bandwidth' that is shown in the 'show int' which is around 61mb. With only 61mb available, and the transfer application is sending at 75mbps there is massive congestions as can be seen by all the dropped packets on the 'show int'.
I thought that if I used the 'max-reserved bandwidth 95' I would gain up to 20mb of throughput. But I guess this isn't the case? Is it true then that increasing the max-reservered bandwidth won't free up more bandwidth for class-default traffic?
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