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QoS issue with video stream

                   hi all,

i'm facing an issue with quality of service (srr-queuing).

i explain:

i have a cisco ws-c3560X and i have different VLANs on it, i have one VLAN who support video encoders. i want to fix priority on the video VLAN and make sure the stream to pass trough the uplink in priority.

so i made a qos vlan-based, i catch the flow and i mark it to dscp 40, then by default, the dscp 40 use the queue 1 for output, and it works well i can verify it with a "show mls qos inter gi1/4 statistic"

the flow is bigg because we have 4 stream at 20Mbps (more or less) so i configured a shaping on the egress side with this command:

bandwidth 100000

srr-queue bandwidth share 85 5 5 5

srr-queue bandwidth shape 85 0 0 0

mls qos trust dscp

so i reserve 85% of bandwidth to queue 1 in case of congestion.  Am i ok for the moment???

then, i looked the stream and it have a lot of drop, after revision, i saw a lot of dropped in the "output queue drop" corresponding to the first queue, first threshold.

i wanted to adapt the buffers and threshold by reading and following the cisco recommandations (i guess)

i did that :

i reserve buffer for queue 1 (the same as the srr queue shaping)

mls qos queue-set output 1 buffers 85 5 5 5

and i adapt the threshold for queue 1 too

mls qos queue-set output 1 threshold 1 400 400 100 400

to be sure :

Queueset: 1

Queue     :       1       2       3       4

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

buffers   :      85       5       5       5

threshold1:     400     200     100     100

threshold2:     400     200     100     100

reserved  :     100      50      50      50

maximum   :     400     400     400     400

so i thinked i was good, but nothing do, i loose 1 packet over 2, and i don't know why, for more detail, the stream who's working for now is only 12Mbps and no congestion over the link.

do you see what's wrong??

do you need other explanation?

i was thinking about reserved bandwidth, is it good as i made? i have to reduce the other reserved threshold on other queues?

any help can be valuable (and sorry for my bad english)

thanks

Best Regards

1 REPLY
New Member

QoS issue with video stream

for more, just for you to know, if i disable the mls qos, everything works fine

thanks

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