> ## Documentation Index
> Fetch the complete documentation index at: https://docs.zayo.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Diagnosing Poor Application Performance

> A step-by-step workflow for diagnosing application slowdowns, leveraging the platform to distinguish between network, server, and DNS issues.

This playbook provides a systematic workflow for diagnosing application slowdowns.

### Step 1: Differentiate Latency

The investigation begins in the **Network Observability** dashboard. Analyze the "Latency" tab for the affected application's server IP. Compare the "Network Latency" and "Application Latency" graphs.

* **If Application Latency is high while Network Latency is low,** the network is not the bottleneck. The issue lies with the server. **Proceed to Step 3.**
* **If both latencies are high,** the issue is network-related. **Proceed to Step 2.**
* **If both latencies are stable and low, but users report access issues,** the problem may be DNS-related. **Proceed to Step 4.**

### Step 2: Investigate the Network Path (If Network Latency is High)

* Check for saturation and drops in the **Cloud and Connections** dashboard. Are the traffic graphs for the relevant link approaching maximum bandwidth or showing a high number of dropped packets?
* Use the **Looking Glass (Traceroute)** tool to trace the path to the application server. This will identify the specific hop where latency increases or packet loss begins.
* Use **Looking Glass (Path MTU Discovery)** to check for an MTU mismatch along the path.

### Step 3: Investigate the Server/Application (If Application Latency is High)

* Pivot to the **Application Observability** dashboard. Use the "Top Applications Table" to confirm if the issue is isolated to a single application or if multiple applications hosted on the same server are also experiencing high latency.

### Step 4: Investigate DNS (If Latency is Fine but Access Fails)

* In the **Application Observability** dashboard, navigate to the **DNS** tab.
* Filter by the source IP of an affected user. Verify that DNS queries for the application's hostname are being generated.
* Check which DNS server is responding and if the resolution is successful. The absence of queries or queries to a non-responsive server points directly to a DNS issue.