[c-nsp] Monitoring congested links

[Rodney Dunn]

For accuracy for any drop I'm not sure you will be able
to beat a MQC policing policy that just matches
and permits. Then set the rate close to line rate
and watch for exceed and violate drops via SNMP polls
of the MQC mibs.

Or just watch for output drops because that is what should
happen when there is congestion causin packets to back
up in the output queue.

Averages are usually pretty good voer 5 minutes because
micro burst, if enough to drive the link over the
edge, will always be an issue unless you can quantify with
100% assurance what they will always be and at what rate.
That's pretty much impossible in a dynamic network with
various traffic streams.

Rodney

On Mon, Jul 02, 2007 at 10:09:24PM +0000, MKS wrote:
> Hello list.
> 
> The company I work for has some GigE circuits that are pretty long and
> therefore expensive, so it's important to get the most out of them.
> We are monitoring the load via basic tools like mrtg and  rtt/drop/jitter
> via cisco jitter probes (ip sla/rtr).. We have qos configured on the links
> because some of the traffic is sensitive (traffic groups: voip, multicast,
> business and internet)
> 
> I'm curious to know what is your preferred way of monitoring (congested)
> links? The mrtg graphs give 5min average traffic, so there must be
> considerable bursts. When do you consider the link to be full? Then the 5min
> average load reaches 50%, 60%, 70%, 80% or 90% load.
> 
> Or is it maybe better to monitor the link by using drop statistics, via
> jitter probes or interface drop/qos counters?
> When do you consider the link to be full? Then the average drop percent
> reaches 0.1%, 0.5%, 1%, 2%, 5% for best effort traffic? (internet)
> 
> Can someone suggest some tool(s) to graph the drop/qos interface counters?
> 
> Any comments will be great.
> 
> Regards
> MKS
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