Re: Question about QoS on C3750

Hi,

As far as I know by default the 3750 has 25% of interface buffers allocated
to each queue and also 25% of interface bandwidth - which is not the same
thing as the buffers.
The buffers represent the storing place for each queue while the bandwidth
is the rate at which the queues are emptied. Both parameters are
configurable and usually if you are allocating more bandwidth for a queue
(more than the default 25%) you should decrease the buffer space as that
queue is going to be emptied quicker.
Regarding the priority queue, I know that this queue cannot be policed
meaning that if you put video traffic on it this traffic might overwhelm
other traffic on your port.

Hope this helps,
Adrian

On Tue, Jul 19, 2011 at 8:16 AM, Joe Astorino <joeastorino1982_at_gmail.com>wrote:

> That is actually a really good and tough question. When you are talking
> about interface buffers you are essentially just talking about memory that
> is allocated to store frames for a particular interface. I have never seen
> any numbers from Cisco that actually tell you what those buffers are in
> terms of bytes or anything else other than percentages. I guess I was
> assuming that 25% of the interface buffers would allow you to buffer 25% of
> the line rate, but I'm really not sure. Perhaps somebody can offer some
> more specific information on that topic.
>
>
>
> On Mon, Jul 18, 2011 at 11:02 PM, kawaii mak <kawaii00mak_at_gmail.com>
> wrote:
>
> > Dear Joe Astorino,
> >
> > Thanks. Means the percent of buffer is refer to the interface bandwidth
> ??
> >
> > Kawaii
> >
> > 2011/7/18 Joe Astorino <joeastorino1982_at_gmail.com>
> >
> >> I think you should be just fine with the default queueing mechanisms if
> >> you put your video traffic in the priority queue. The default buffers
> give
> >> you 25% of the interface buffer in the priority queue and 400% maximum
> >> (borrowing from the common pool). 25% of your Gig interface gives you
> >> 250Mb/s
> >>
> >> To see what you have allocated check out "show mls qos queue-set" and
> "sh
> >> mls qos interface <x/y> queueing"
> >>
> >> On Mon, Jul 18, 2011 at 4:10 AM, kawaii mak <kawaii00mak_at_gmail.com
> >wrote:
> >>
> >>> Dear Expert,
> >>>
> >>> I have a question about QoS apply on C3750 egree 1-GE uplink (Trunk)
> >>> interface with SRR queueing system. I need to allow the video traffic
> >>> (~200M) with high priority to use the GE uplink while the 1G uplink was
> >>> congested. How can I do that ?? The following is my question:
> >>>
> >>> Is it request to mark the cos of cs5 for the Video vlan traffic and set
> >>> the
> >>> cs5 with queue1 upder assigned queue-set as priority queue1 ??
> >>> Is the default queue set enough to priority the 200M streaming traffic
> go
> >>> first while the 1G link was congested ??
> >>> How to check the actually buffer bandwidth (e.g. bps) of the allocated
> >>> bandwidth for each queue ??
> >>> Or how to check the actually allocated bandwidth (e.g. in bps) for each
> >>> queue ??
> >>> For each queue, default configuration sets 400% as the maximum memory
> >>> before
> >>> dropped. How to check 400% is equal (in bps)??
> >>>
> >>> P'se help!!! Thank.
> >>>
> >>> Regards,
> >>> Kawaii
> >>>
> >>>
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> >>
> >>
> >> --
> >> Regards,
> >>
> >> Joe Astorino
> >> CCIE #24347
> >> Blog: http://astorinonetworks.com
> >>
> >> "He not busy being born is busy dying" - Dylan
> >>
> >>
> >
>
>
> --
> Regards,
>
> Joe Astorino
> CCIE #24347
> Blog: http://astorinonetworks.com
>
> "He not busy being born is busy dying" - Dylan
>
>
> Blogs and organic groups at http://www.ccie.net
>
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Received on Tue Jul 19 2011 - 11:26:50 ART