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New Member

mls qos problem

We have a 3750 stack include 48T and G-24T switch. The server is 1000/Full and workstation is 100/full. And we enable mls qos.

I got a very slow speed when copying file from server to workstation even off hour. From the sniffer it showed that some packet were lost. But I did show interface and did not see any drop packets. Where are those packet?

7 REPLIES
Silver

Re: mls qos problem

Please more infos: server/workstation OS, switch configuration, ...

Regards

Andrea

New Member

Re: mls qos problem

Here is the configuration:

===========================================

mls qos srr-queue input bandwidth 25 75

mls qos srr-queue input threshold 1 40 40

mls qos srr-queue input buffers 50 50

mls qos srr-queue input priority-queue 2 bandwidth 25

mls qos

!

interface GigabitEthernet2/0/1

description Server

switchport access vlan 10

srr-queue bandwidth share 10 20 40 80

srr-queue bandwidth shape 0 0 0 0

spanning-tree portfast

interface GigabitEthernet1/0/1

description Workstation

switchport access vlan 1

srr-queue bandwidth share 10 20 40 80

srr-queue bandwidth shape 0 0 0 0

spanning-tree portfast

===========================================

And the server is win2003, and workstation is win2000. This is a 3750 stack. I don't mark any traffic and all traffic is Cos 0.

Silver

Re: mls qos problem

have you already investigate it with a sniffer (like ethereal)?

Some years ago I've found a MS bug on Win2k server (with WinXP SP1 clients) about SMB retransmissions ... I don't know if that could help you, but ...

Set also duplex/speed statically on switch/server interface ... just a best practice for prevent a duplex mismatch or slow negotiation ...

HTH

Andrea

New Member

Re: mls qos problem

I did a sniff on the traffic. And it showed that some packets were dropped in the FE port. Dose anyone has a good mls qos configuration for this situation? I tried different mls qos setting, but everytime I enable mls qos the speed slow down dramatically.

New Member

Re: mls qos problem

What version of code are you running on the 3750s?

Re: mls qos problem

Following the previous post there are fundamental differences between 12.1 and 12.2 concerning QoS.

Certainly from 12.2 there is an additional queue-set for Gigabit interfaces. Previously all interfaces by default have queue-set 1 applied and therefore are restricted by thresholds configured regardless of port type.

Typically by default COS 0 or untrusted traffic will be mapped to the egress queue-4 unless you have changed your COS mappings.

Is there a specific reason why you have configured SRR in the first instance? You do not have any trust on either of the ports and will therefore be untrusted. Consequently all queue will be services accordingly, and COS 0 traffic will be the first to be dropped.

Congestion commonly occurs on egress, and your configuration unfortunately does indicate any output cos maps, output thresholds or buffers.

See the following example, like I said queue-set 1 is applied to FE and queue-set 2 is applied to GE.

mls qos map cos-dscp 0 8 16 26 32 46 48 56

mls qos srr-queue input bandwidth 90 10

mls qos srr-queue input threshold 1 8 16

mls qos srr-queue input threshold 2 34 66

mls qos srr-queue input buffers 67 33

mls qos srr-queue input cos-map queue 1 threshold 2 1

mls qos srr-queue input cos-map queue 1 threshold 3 0

mls qos srr-queue input cos-map queue 2 threshold 1 2

mls qos srr-queue input cos-map queue 2 threshold 2 4 6 7

mls qos srr-queue input cos-map queue 2 threshold 3 3 5

mls qos srr-queue input dscp-map queue 1 threshold 2 9 10 11 12 13 14 15

mls qos srr-queue input dscp-map queue 1 threshold 3 0 1 2 3 4 5 6 7

mls qos srr-queue input dscp-map queue 1 threshold 3 32

mls qos srr-queue input dscp-map queue 2 threshold 1 16 17 18 19 20 21 22 23

mls qos srr-queue input dscp-map queue 2 threshold 2 33 34 35 36 37 38 39 48

mls qos srr-queue input dscp-map queue 2 threshold 2 49 50 51 52 53 54 55 56

mls qos srr-queue input dscp-map queue 2 threshold 2 57 58 59 60 61 62 63

mls qos srr-queue input dscp-map queue 2 threshold 3 24 25 26 27 28 29 30 31

mls qos srr-queue input dscp-map queue 2 threshold 3 40 41 42 43 44 45 46 47

mls qos srr-queue output cos-map queue 1 threshold 3 5

mls qos srr-queue output cos-map queue 2 threshold 3 3 6 7

mls qos srr-queue output cos-map queue 3 threshold 3 2 4

mls qos srr-queue output cos-map queue 4 threshold 2 1

mls qos srr-queue output cos-map queue 4 threshold 3 0

mls qos srr-queue output dscp-map queue 1 threshold 3 40 41 42 43 44 45 46 47

mls qos srr-queue output dscp-map queue 2 threshold 3 24 25 26 27 28 29 30 31

mls qos srr-queue output dscp-map queue 2 threshold 3 48 49 50 51 52 53 54 55

mls qos srr-queue output dscp-map queue 2 threshold 3 56 57 58 59 60 61 62 63

mls qos srr-queue output dscp-map queue 3 threshold 3 16 17 18 19 20 21 22 23

mls qos srr-queue output dscp-map queue 3 threshold 3 32 33 34 35 36 37 38 39

mls qos srr-queue output dscp-map queue 4 threshold 1 8

mls qos srr-queue output dscp-map queue 4 threshold 2 9 10 11 12 13 14 15

mls qos srr-queue output dscp-map queue 4 threshold 3 0 1 2 3 4 5 6 7

mls qos queue-set output 1 threshold 1 138 138 92 138

mls qos queue-set output 1 threshold 2 138 138 92 400

mls qos queue-set output 1 threshold 3 36 77 100 318

mls qos queue-set output 1 threshold 4 20 50 67 400

mls qos queue-set output 2 threshold 1 149 149 100 149

mls qos queue-set output 2 threshold 2 118 118 100 235

mls qos queue-set output 2 threshold 3 41 68 100 272

mls qos queue-set output 2 threshold 4 42 72 100 242

mls qos queue-set output 1 buffers 10 10 26 54

mls qos queue-set output 2 buffers 16 6 17 61

Depending on your traffic profile, you may need to service queue depending on whether you have voice and/or videowhether. If you have neither of these requirements then configure SRR on the interfaces as follows:-

srr-queue bandwidth share 5 5 10 80

srr-queue bandwidth shape 0 0 0 0

Regards

Allan.

New Member

Re: mls qos problem

There is also this bug which you might be running into: CSCsc96037

Configuring Quality of Service on a CAT3560 or CAT3750 running any IOS can cause certain TCP

applications such as NFS to run slower.

This issue will be resolved in Cisco IOS 12.2(25)SEE1.

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