feat: complete section 1.5

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@@ -133,7 +133,53 @@ A safety margin (typically ρ ≤ 0.7-0.8) is often used to account for traffic
 
 ### 1.5 Web Caching (5%)
 
-[To be completed]
+#### What is Web Caching?
+
+**Web caching** is a technique where frequently requested web content (HTML pages, images, videos, etc.) is stored temporarily in locations closer to users than the origin server. When a user requests cached content, it can be served from the cache instead of fetching it from the distant origin server, reducing response time and network traffic.
+
+**Components:**
+- **Web cache/proxy server:** Intermediate server that stores copies of web objects
+- **Cache hit:** When requested content is found in the cache
+- **Cache miss:** When requested content is not in cache and must be fetched from origin server
+
+#### Web Caching Usefulness in Universities:
+
+Web caching is particularly useful in university environments due to:
+
+**1. Shared Content Patterns:**
+- Multiple students often access the same educational resources, research papers, and popular websites
+- High likelihood of cache hits for commonly accessed materials
+
+**2. Bandwidth Optimization:**
+- Universities typically have limited internet bandwidth shared among thousands of users
+- Caching reduces external traffic, preserving bandwidth for unique requests
+
+**3. Cost Reduction:**
+- Reduces bandwidth costs by serving content locally instead of repeatedly downloading from internet
+- Improves network efficiency during peak usage periods (class times, assignment deadlines)
+
+**4. Performance Improvement:**
+- Faster response times for students accessing cached educational content
+- Reduced load on university's internet connection during high-traffic periods
+
+#### Conditional GET in HTTP:
+
+**Problem Addressed:**
+The conditional GET mechanism solves the problem of **cache consistency** - ensuring that cached content is up-to-date without unnecessarily downloading unchanged content.
+
+**How it works:**
+1. **Initial Request:** When a web object is first cached, the cache stores the object along with its `Last-Modified` date or `ETag` (entity tag)
+2. **Subsequent Requests:** When the same object is requested again, the cache sends a conditional GET request to the origin server with:
+   - `If-Modified-Since: <last-modified-date>` header, or
+   - `If-None-Match: <etag>` header
+3. **Server Response:**
+   - **304 Not Modified:** If content hasn't changed, server responds with minimal 304 status (no content body)
+   - **200 OK:** If content has changed, server sends the updated object with new Last-Modified/ETag
+
+**Benefits:**
+- Maintains cache freshness without wasting bandwidth on unchanged content
+- Reduces server load and network traffic
+- Provides efficient mechanism for cache validation
 
 ### 1.6 Email Protocol Analysis (5%)