N-Tier Application Performance Issue

Scenario

Users report slower-than-expected response times from an in-house web application. This application follows an N-tier architecture, and its performance as experienced by clients depends on several factors:

• DNS latency when resolving the web server name from the client host (see DNS Response Time)
• Connection time to the server
• Data Transfer Time between these hosts
• DNS latency when resolving other server names accessed by the web server (such as database servers, see DNS Response Time)
• Connection and data transfer times between these hosts
• Server response time of these servers

Identifying the Culprit

To determine whether the observed slowdown originates from the web front-end, evaluate each component of the EURT as follows:

• If the Server Response Time (SRT) is fast but the Round Trip Time (RTT) and/or Data Transfer Time (DTT) (see also Connection Time) are high, this indicates a network-related slowdown. Refer to earlier sections of this guide for detailed troubleshooting steps.

• If the SRT is significantly higher than both DTT and RTT, the performance issue likely stems from the application itself. Investigate further to identify the underlying cause.

Next, assess the EURT between the web server and all other involved servers (such as databases).

• If any of these EURTs show degradation, perform recursive checks on those hosts.

• If no degradation is found, review the web server’s load average to identify potential resource constraints.