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SRR shaping

diondohmen
Beginner
Beginner

Hi there,

I am learning the basics of QoS on the 3560 platform. To begin I applied the "auto qos voip trust" command on two interfaces. This command enabled some basic mls qos statements in the config.

The specific interface looked like this:

interface GigabitEthernet0/20

srr-queue bandwidth share 10 10 60 20

srr-queue bandwidth shape 10 0 0 0

queue-set 2

mls qos trust cos

auto qos voip trust

end

Then, I wanted to understand the SRR shaping command. So what i did was, configure two interfaces, with two hosts, and removed the SRR share commands. The two interfaces, with the two hosts (same VLAN), now look like this:

interface GigabitEthernet0/1

duplex full

speed 100

queue-set 2

mls qos trust cos

auto qos voip trust

spanning-tree portfast

end

!

interface GigabitEthernet0/2

duplex full

speed 100

srr-queue bandwidth shape 10 100 220 120

queue-set 2

mls qos trust cos

auto qos voip trust

spanning-tree portfast

end

With this config i did some bandwidth tests, by copying a big file between G0/1 and G0/2. Copying a file from G0/1 to G0/2 resulted in a speed of 0.83mbit

Copying a file from G0/2 to G0/1 resulted in a full speed bandwidth of 100mbit.

This behavior is exactly the opposite of what i expected to get with this config. Apparently the "srr-queue bandwidth shape" statement on G0/2 did reduce the inbound traffic (download). From what I've learned from the docs, SRR shaping applies to the egress queues, also called outbound, so from port G0/2 to G0/1 and not vice versa?

Any hints will be appreciated..

4 REPLIES 4

gogasca
Advocate
Advocate

Your concern makes sense to me, afaik SRR bandwidth shape is for egress queues.

Can we see the following:

show mls qos

show mls qos interface (interface #)

show mls qos interface [interface #] queueing

and the sh run and sh ver.

Which COS value the file is set to? 0, 3 ?

If you remove mls qos trust cos or add mls qos trust dscp? same behaviour?

Thanks

gogasca, thanks for your reply.

I don't do anything with the CoS/DSCP value, so it hits Q4, 1/120 of the total bandwidth.

I've included a txt with all of the requested show commands.

gogasca, i have added the wrong txt before.

This time it's the right txt.

Pavel Bykov
Contributor
Contributor

Well, SRR is set up in the inverse proportion. So you have set up "10" for the first queue, which means 1/10, or 10%. 10% of 1 gigabit is 100 Mbps...

So, isn't everything working correctly?

Also, did you check your settings with show mls qos commands? Do you have mls qos enabled globaly?

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