HTTP Analysis

A case study on how web requests and responses appear in Wireshark, including HTTP versioning, cache validation, status codes, and TCP segmentation.

Overview

The HTTP lab traces browser requests to a web server and the server responses that follow. The captures show plain HTTP traffic, making request headers, response codes, and content-transfer behavior visible in Wireshark.

Objective

Inspect HTTP request and response flow, identify status codes and headers, observe conditional requests, and connect application traffic to the TCP segments that carry it.

Environment / Scenario

Client192.168.2.198

Server128.119.245.12

ProtocolHTTP/1.1 over TCP

ToolWireshark

What I Investigated

HTTP GET requests and matching server responses.
Headers visible in packet details and raw packet bytes.
Conditional GET behavior using If-Modified-Since.
How a larger HTTP response is carried by multiple TCP segments.

Key Observations

The browser and server used HTTP/1.1 in the selected request and response.
The first successful response returned HTTP 200 OK and content to the browser.
A later conditional GET included If-Modified-Since, allowing the server to validate cached content.
The server replied 304 Not Modified for the conditional request, meaning the cached copy was still valid and the file body did not need to be resent.
A larger HTTP response was reassembled from multiple TCP segments, showing how application data is delivered over the transport layer.

Annotated Screenshots

HTTP request and response showing HTTP 1.1 — Wireshark capture showing an HTTP/1.1 GET request and an HTTP/1.1 200 OK response between the browser and server.

HTTP conditional GET with If-Modified-Since — This frame illustrates a conditional GET using If-Modified-Since, which lets the browser ask whether its cached copy is still current.

HTTP 304 Not Modified response — Wireshark capture showing a 304 Not Modified response. The server confirms the cached object is valid without resending the full file contents.

HTTP response reassembled from TCP segments — This comparison demonstrates that an HTTP response can span multiple data-containing TCP segments before Wireshark reassembles it at the application layer.

Why It Matters for Troubleshooting

HTTP analysis helps distinguish server-side responses, cache behavior, missing content, and transport delivery. In real support work, status codes and headers can explain whether a browser issue is caused by the server, the cache, the requested resource, or the network path below HTTP.

Key Takeaways

HTTP headers and status codes provide direct evidence about web application behavior.
Conditional requests reduce unnecessary content transfer when cached data is still valid.
HTTP sits on top of TCP, so larger responses may require multiple TCP segments.