qos problem

[sbjeong]

Hello,

I'd like to limit downloading traffic around max 2Mbps. So I configured like below. But, traffic is wave, no steady 2Mbps, so it looks like something wrong.

How can I make it correct ?

10.9.5.28 is my PC IPAddr.

---------------------------------

#show version

----

System image file is "sup-bootflash:s72033-ps-mz.122-18.SXD4.bin"

cisco WS-C6509-E (R7000) processor (revision 1.1) with 458720K/65536K bytes of m

emory.

----

#show run

class-map match-all traffic-limit

match access-group name bad_ip

!

!

policy-map traffic-control

class traffic-limit

police 2048000 1024000 1024000 conform-action transmit exceed-action drop

ip access-list extended bad_ip

permit ip any host 10.9.5.28

permit ip host 10.9.5.28 any

deny ip any any

interface FastEthernet9/47

description # To Internet #

bandwidth 5000

ip address 10.9.9.2 255.255.255.252

load-interval 30

service-policy input traffic-control

[Kevin Dorrell]

When you policy traffic, you can get a wave effect like this. It depends on the behaviour of the TCP in your client and/or server. Policing works by dropping packets when the CIR is exceeded. When a packet gets dropped, the TCP has to retry it. At the same time, it will increase its retry timers so that the average rate goes down. But once it has recovered from the lost packet, it will speed up again, and so round the circle.

One way to smooth out this behaviour is to do WRED, but I'm not sure whether this is an option on your switch. With WRED, it drops packets before the queue is full - the fuller the queue, the more packets it drops. This tends to make the graph smoother.

What you really need to do is to apply traffic shaping on transmission at the other end of this link. But I realise that might not be an option.

Kevin Dorrell

Luxembourg

[alfredshum]

WRED is only applied to output queue so seems like he has no choice but to use policing.

[Kevin Dorrell]

OK. I guess that makes sense 'cos in input you don't have the same sort of queue to drop packets from.

KJD

[sbjeong]

Thank you for your replies

alfredshum , Kevin.Dorrell, kumarapalani

Dear kumarapalani

My NIC is 10/100Mbps therefore 5% means 5Mbps.

Dear alfredshum

I've already tried set only CIR at the first time, but it was same pattern and lower bandwidth. And interface statistics show around CIR but wave pattern is the problem. In order to test this, only I used this network alone and downloaded one file.

Dear Kevin.Dorrell

Is this wave pattern natural?

If so, How can I make traffic pattern flat when I limit traffic?

[Kevin Dorrell]

I think the wave pattern depends on the reaction of the TCP stack on the client and/or server on losing packets. As an experiment, I would try the same test but running the FTP from a different operating system altogether - you may find it reacts differently. You may find it is nothing to do with the network itself. You might get some result by tuning the parameters of the TCP stack on the server - max window size etc.

Kevin Dorrell

Luxembourg

[emilo1405]

hi

try to use dscp

in the interface the the traffic comes attach a policy-map that places a dscp to all the packets coming to your ip 10.9.5.28

than conf an class to match those packets and after conf a policy-map to limit the traffic based on the dscp you configures before and this policy-map attach to the int where you are connected as an service policy output