Showing results for 
Search instead for 
Did you mean: 

QoS issue with video stream

david de sousa

                   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)


Best Regards

1 Reply 1

david de sousa

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


Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Recognize Your Peers