NR-115126: update docs

docs/network_troubleshooting.md

@@ -43,11 +43,35 @@ RawContentLength  : 284
 
 **Linux**
 
-```bash
-$ curl -v https://infra-api.newrelic.com/cdn-cgi/trace
+1. **Resolve the domain:** Use nslookup or dig to validate that the Linux system can resolve the domain to an IP address:
+
 ```
+$ nslookup infra-api.newrelic.com
+```
+
+The output should contain a name and IP address.
 
+2. **Ping the server:** Try pinging the IP address obtained above to ensure you can reach the server.
+
+```
+$ ping 162.247.241.2
 ```
+
+The server should be reachable.
+
+3. **Traceroute:** Use traceroute to check the network path between your system and the server:
+
+```
+$ traceroute -I infra-api.newrelic.com
+```
+
+Analyze the output to identify potential network issues, such as high latency or packet loss.
+
+4. **Curl:** Use curl to check if the endpoint is reachable:
+
+```bash
+$ curl -v https://infra-api.newrelic.com/cdn-cgi/trace
+
 fl=366f101
 h=infra-api.newrelic.com
 ip=XX.YY.ZZ.ZZ
@@ -125,6 +149,22 @@ time="2023-10-04T17:08:10+02:00" level=debug action=WroteRequest component=HttpT
 time="2023-10-04T17:08:11+02:00" level=debug action=GotFirstResponseByte component=HttpTracer duration=1208ms requester=testing
 ```
 
+Each log line represents a different part of the network request process:
+
+1. GetConn → create a new request
+
+2. DNSStart & DNSDone → backend IP was resolved
+
+3. ConnectStart & ConnectDone
+
+4. TLSHandshakeStart & TLSHandshakeDone
+
+5. GotConn
+
+6. WroteHeaders & WroteRequest  → Request written into backend
+
+7. GotFirstResponseByte → Response from backend
+
 ## Configuration
 
 1. Enable trace logs with the HttpTracer feature
@@ -169,6 +209,24 @@ To fix the issue, Let’s Encrypt root authority certificates must be installed
 
 #### Proxy being used without proper configuration
 
+```
+time="2023-08-25T12:00:58+01:00" level=error msg="metric sender can't process" component=MetricsIngestSender error="error sending events: Post \"https://infra-api.newrelic.com/infra/v2/metrics/events/bulk\": context deadline exceeded (Client.Timeout exceeded while awaiting headers)" postCount=19310 sendErrorCount=1
+```
+
+1. Verify all the Proxy configuration values are provided to the infra-agent. Filter the agent logs to find the used configuration:
+
+```
+$ cat newrelic-infra.logs | grep "Loaded configuration."
+```
+
+Assert the corresponding [values](https://docs.newrelic.com/docs/infrastructure/install-infrastructure-agent/configuration/infrastructure-agent-configuration-settings/#proxy-variables).
+
+2. Use `curl` to check if the endpoint is reachable via the proxy:
+
+```
+$ curl --proxy http://YOUR_PROXY:80 https://infra-api.newrelic.com/
+```
+
 #### DNS issues
 
 If the agent logs contain the following error, it might be related to a system’s DNS issue.