Cat 3750 Qos Understanding

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Mar 4th, 2010
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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  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  0 1 2 3 4 5 6 7
mls qos srr-queue output dscp-map queue 3 threshold 3  8 9 10 11 12 13 14 15
mls qos srr-queue output dscp-map queue 3 threshold 3  24 25 26 27 28 29 30 31
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 3  16 17 18 19 20 21 22 23
mls qos queue-set output 1 buffers 10 15 40 35


I understanding on Cat 3750 DSCP value are mapped to queue-ids seperately and done globally instead of interface level and different traffic types none IP and IP traffic can be mapped and service seperately.


Now Regarding the commands above, output queues are assigned DSCP values, for example queue-id 1 above is the expedite queue and have higer DSCP values for Voice packet with a threshold of 3 and so forth for the rest of queues 2  - 4


As for the "mls qos queue-set output 1 buffers 10 15 40 35" command, for output queue 1 buffer space, 10% of weight is assigned to top queue 1 for voice, and 10% to queue 2 and so forth. The values set in the qeueu-set are simple amount of memeory allocated to each queues.

Is my understanding correct about the "mls qos queue-set output 1 buffers 10 15 40 35" command?


Also does the queue-set works if not applied to an interace by issuing "queue-set 1" under the interface?

Cheers

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Lei Tian Mon, 03/08/2010 - 20:25
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Hi,


I understanding on Cat 3750 DSCP value are mapped to queue-ids seperately and done globally instead of interface level and different traffic types none IP and IP traffic can be mapped and service seperately.

That depends on the trust state on your interface; if it is trust dscp, yes the dscp to queue map will be used for egree queue.

Now Regarding the commands above, output queues are assigned DSCP values, for example queue-id 1 above is the expedite queue and have higer DSCP values for Voice packet with a threshold of 3 and so forth for the rest of queues 2  - 4


As for the "mls qos queue-set output 1 buffers 10 15 40 35" command, for output queue 1 buffer space, 10% of weight is assigned to top queue 1 for voice, and 10% to queue 2 and so forth. The values set in the qeueu-set are simple amount of memeory allocated to each queues.

Is my understanding correct about the "mls qos queue-set output 1 buffers 10 15 40 35" command?

Yes. The queue set 1 is the default queue set apply on interface; you can check it by show mls qos interface x/x buffer


HTH,

Lei Tian

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