I've been doing a number of network assessments recently and one of the factors that I use to determine network health is the number of TCP retransmissions that occur. I look at servers and user workstations as well as looking for retransmisisons using packet capture tools. There is a fair amount...

I just returned from a week at CiscoLive 2011. The show floor had a lot of network management products on display, making it an easy place to walk around and investigate various products. I did an informal product survey of functions that are important to a good NMS. Without going into the details of...

I'm helping a customer improve their network through better network management visibility into network problems. The result of a proof-of-concept is this graph, which I'll explain below. The customer loved the graph because it showed the total number of problems and, more importantly, it showed...

I just finished spending two days in San Jose, participating in the Gestalt IT Network Field Day , an event dreamed up by Stephen Foskett and Greg Ferro. Twelve delegates who are independent bloggers gather together to listen to presentations from a short list of interesting companies. The bloggers are...

I've been doing Data Center design recently and the customers are interested in what to monitor and why it should be monitored. At first, a data center is just another set of edge devices, albeit servers, connected to a set of access switches. But the traffic patterns and usage in the data center...

I've written in this blog about various reasons for using network automation but it is time to put them together. Counting down… 7. Performance and SLAs The first thing that network management does is performance monitoring. It's conceptually easy, but surprisingly challenging, primarily...

I'm a proponent of network management automation and found a related blog post, Why End Users Love BPM , by long-time friend Scott Menter, who is working at BP Logix. BP Logix makes products for automating business processes. Scott's post discusses what happens when people are forced to run errands...

Networks use the same devices in many different roles, so configuration validation based on device type isn't sufficient. There are some configuration things that can be checked across all the devices of a certain type in your network, such as checking the syslog and NTP configuration, or verifying...

My previous post talked about the basics of verifying a configuration prior to deployment as a way to minimize the number of incorrect configurations that are fielded. The second topic, which is closer to the original NANOG posting comments, is with respect to auditing existing configurations to make...

Jimmy Ray Purser, a blogger and video blogger for Cisco and Network World, just did a blog with that title . In that blog post, he makes several comments that are right on target with the deficiency of most network management systems: - It is a lot of manual correlation - Correlation, Correlation, Correlation...