By: thomas stocking

thomas stocking — Tue, 22 Jan 2008 19:31:38 +0000

From my point of view, the main question here is: do your users care? That’s not always easy to answer, so here are some techniques I’ve employed in the past to get a handle on this.
Know the Application
If you are using this link to provide connectivity to the Internet and the saturation occurs during lunch time and after 5pm, that’s a whole different problem from, say, providing connectivity from a branch office to an ERP application hosted at a global data center. The latter is far more important for productivity, and so a slow or congested link there will hit your bottom line faster than delays in surfing on the lunch break.
Measure Application Performance
Once you know the application, set up a response time measurement to see how long basic operations take. As a simple example, you can start with load times of the login page (if it is a web application), and just track that over time. Put this graph up on the same screen as the bandwidth graph to see if the saturation is really affecting performance of the application. There are lots of tools that can do this kind of measurement and graphing.
Know the Traffic
As was mentioned, if you have QoS measures for this link, use them to prioritize the traffic that you care about. Most QoS systems incorporate monitoring software to tell you what the traffic is composed of, but this is also relatively simple to obtain with commonly available tools, such as ntop or pmacct (http://www.pmacct.net/).

If, after taking these steps, or somewhere in the process, you realize there is a problem, consider that bandwidth may be cheaper than further analysis. As with all management decisions, know the cost of doing nothing and the cost of the simplest solution before you open the checkbook.

By: tbitner

tbitner — Thu, 17 Jan 2008 14:27:39 +0000

What is the average utilization on these links and what are they used for? Are people complaining and does the connection seem slow or is it performing satisfactory? Periodic spikes of 60% are not of concern unless it’s sustained. It could just indicate someone transferring files from your server or downloading from the internet (depending on what the link is used for), since these protocols try to use as much bandwidth as possible.

I have a threshold setup on my monitoring software to send me an email alarm if utilization is above 70%. It usually ends up being somebody copying from file shares or downloading from internet.

Are you running QoS on any of these lines?

Comments on: Bandwidth utilization: determining when to upgrade

By: thomas stocking

By: tbitner