Re: traffic shaping for C2620 on IOS12.5

Hello Ronnie,

- 'bandwidth percent 45' command reserves 45% of interface bw in the case
that interface is congested (there are some packets in the outbound queue or
you may even see some outbound queue drops).
- 'priority percent' sends packets for that traffic class before the other
traffic no matter if interface is congested or not. This could lead to
starvation of other non-priority classes, but ensures so called low latency
QoS because reduces latency at the minimum possible. So, it's mainly used
for VoIP, because VoIP takes a little bw, but it needs a minimum latency
possible.
In both cases if traffic rate for those classes rises above 45 % of
interface bw traffic then QoS stops and this traffic is treated as best
effort unless otherwise configured.

You may wish to investigate:
http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_book09186a0080435d50.html

B.R.
Igor

"Ronnie Corny" <ronniecorny@xxxxxxxxxxx> wrote in message
news:ed3ajl$upl$1@xxxxxxxxxxxxxxxxxxxxxxxxxx
Hi Igor and James

thanks for taking time to help out...

my main traffic is only http and smtp... with very minor domain (DNS) and
others (ntp, ssh, etc.), would these be affected by the priority command?

I think our bandwidth consumption comes out like 95% smtp and the other 4%
http and 1% all other protocols... i was thinking of getting a better
read on this usage, that's why i was thinking of monitoring bandwidth
consumption per protocol using mrtg...

what's the difference between "bandwidth percent 45" and "priority percent
45" in the policy-map?

I'd really like to get this right for our system... currently, i've got
it set at "priority percent 45" but we haven't seen how it affects the
line yet.

rgds,

- ron

"Igor Mamuzic" <someone@xxxxxxxxxxx> wrote in message
news:ed16r6$cso$1@xxxxxxxxxxxxxxxxxxxxxx
You shouldn't use priority command because it could lead to starvation of
other traffic... This is suitable only for delay non-tolerant apps such
as VoIP. You should use bandwidth percent command, but keep in mind that
if prioritized traffic rate exceeds bandwidth percent rate this traffic
becomes best effort if not otherwise specified, so it's suitable only for
small bw traffic such as RDP and telnet, but it works relatively ok for
http traffic in my case. So, if you want to absolutely ensure that smtp
traffic doesn't eat all bw you have even if your prioritized classes
exceeded their reserved bw then you must shape smtp traffic:
instead of bandwidth percent, just type shape average under policy-map
config mode. Of course, if there is a little amount of traffic other then
SMTP this could be a wasting of bw since SMTP is no longer able to posses
the whole bw even if there is no other traffic currently flowing trough
the link.

B.R.
Igor


"Ronnie Corny" <ronniecorny@xxxxxxxxxxx> wrote in message
news:ectm4f$bjh$1@xxxxxxxxxxxxxxxxxxxxxxx
hi James

thanks for the tips... this really helps a lot...

you're right, i mistyped my IOS version... it's 12.3(5b)... haven't
taken time to upgrade the IOS yet as i have to schedule the few minutes
of downtime...

rgds,

- ron








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