Troubleshooting and analyzing performance of WAN-deployed applications is an evolving business. Many products and services are available on the market to accommodate the needs of large and small WAN companies. Generally, there are two schools of thought on the analysis and performance of applications deployed over the WAN: active and passive technologies.
Active technology, also called active agents, is used by installing clients on strategically placed machines within the environment to analyze the performance of applications from remote desktops. The active agent technology has several advantages and disadvantages.
First, the active agent will consistently monitor typical transactions from the end-user. This provides a more appealing set of strategic data but also has a costly overhead of maintaining the scripts that run as well as the deployment of the clients on the desktops.
The data represented in these transactions also reflect an entire end-to-end transaction framework. However, when problems occur, the statistics gathered do not identify any particular component of the transaction that might cause the delay. Due to caching servers, several applications may cache the queries used in these transactions, giving a 'green light' when in fact performance problems are being encountered.
Alternatively, a more recent technology has been developed to utilize passive application monitoring.
Passive technology can provide a more meaningful analysis of the transaction by identifying the application, network and server portion of the transactions. Instead of a subset of the transactions like the active agent technology, all transactions are monitored by the passive approach. Often a single user, server or single query can be isolated as to the root cause of a performance problem. With the passive approach, analysis on the number of users, TCP session counts, volume and other metrics not obtained through the active agent technology also assist the network engineers with analysis and troubleshooting.
As an added bonus, the passive technology works passively in the environment without deploying agents to the desktops of users. By utilizing port mirroring capabilities on the switches located near the servers, the passive approach does not require any agents to be deployed on the clients. Also, the passive technology does not put additional loads on the network. If the network or servers are already busy servicing requests from the end-users, the passive technology is far preferable since it does not add any requests or transactions for performance purposes.
Feature sets and budget affect the tools that adequately meet the requirements for troubleshooting and analysis in WAN deployed environments. However, a larger portion of enterprises are moving toward a passive technology for this type of troubleshooting due to less configuration overhead and a more feature-rich environment. For a comprehensive listing of tools, visit this website.
Lindi Horton is a performance engineer for NetQoS and the network administration expert for SearchNetworking.com.
