add traceroute 4

1 files changed, 41 insertions, 43 deletions

diff --git a/assignments/1/README.md b/assignments/1/README.md
index d00afa6..e3d8e48 100644
--- a/assignments/1/README.md
+++ b/assignments/1/README.md
@@ -109,6 +109,25 @@ traceroute to google.com (142.251.215.238), 64 hops max, 40 byte packets
     172.253.79.231 (172.253.79.231) 76 bytes to 192.168.0.139  22.211 ms  21.499 ms
 ```
 
+### Trace 4
+
+```bash
+モ traceroute -v google.com
+Using interface: en0
+traceroute to google.com (142.251.215.238), 64 hops max, 40 byte packets
+ 1  192.168.0.1 (192.168.0.1) 48 bytes to 192.168.0.53  5.041 ms  2.739 ms  2.033 ms
+ 2  10.139.230.1 (10.139.230.1) 48 bytes to 192.168.0.53  3.232 ms  3.904 ms  4.116 ms
+ 3  * * *
+ 4  * * *
+ 5  * * *
+ 6  * * *
+ 7  192.178.105.146 (192.178.105.146) 36 bytes to 192.168.0.53  29.061 ms
+    142.251.249.236 (142.251.249.236) 36 bytes to 192.168.0.53  22.413 ms
+    108.170.255.196 (108.170.255.196) 36 bytes to 192.168.0.53  23.130 ms
+ 8  172.253.79.231 (172.253.79.231) 76 bytes to 192.168.0.53  23.171 ms
+    sea09s35-in-f14.1e100.net (142.251.215.238) 36 bytes to 192.168.0.53  22.844 ms  22.020 ms
+```
+
 ### Analysis
 
 The traceroute runs show different destination IPs due to Google's
@@ -208,56 +227,35 @@ In packet-switched networks, four main delays can occur (Kurose & Ross, 2021):
 
 ## 1.5 Web Caching (5%)
 
-> What is Web-caching? When may Web-caching be more useful in a university? What problem does the conditional GET in HTTP aim to solve?
-
-### 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 (Kurose & Ross, 2021, Section 2.2.5). 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
+> What is Web-caching? When may Web-caching be more useful in a
+> university? What problem does the conditional GET in HTTP aim to
+> solve?
 
-### Conditional GET in HTTP
+Web caching stores frequently requested web content (pages, images,
+videos) closer to users so it can be served locally instead of from
+the origin server. This reduces response time and network traffic.
 
-Problem Addressed:
+* Cache hit: Requested content is found in the cache
+* Cache miss: Content is not in the cache and must be fetched from the server
 
-The conditional GET mechanism solves the problem of cache consistency - ensuring that cached content is up-to-date without unnecessarily downloading unchanged content (Kurose & Ross, 2021, Section 2.2.6).
+Usefulness in universities:
 
-How it works:
+* Shared content: Many students access the same resources, increasing cache hits
+* Bandwidth optimization: Reduces external traffic, preserving limited bandwidth
+* Cost reduction: Cuts repeated downloads from the internet
+* Performance: Faster access to educational content, especially during peak usage
 
-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
+Conditional GET in HTTP ensures cached content is up-to-date without
+downloading unchanged objects:
 
-Benefits:
+1. Cache stores object with `Last-Modified` date or `ETag`
+2. On subsequent requests, cache sends a conditional GET with `If-Modified-Since` or `If-None-Match`
+3. Server responds:
+   * 304 Not Modified: Content unchanged -> no download
+   * 200 OK: Content changed -> new object sent
 
-- Maintains cache freshness without wasting bandwidth on unchanged content
-- Reduces server load and network traffic
-- Provides efficient mechanism for cache validation
+Benefits: Maintains cache freshness, reduces bandwidth use, lowers
+server load, and validates cache efficiently
 
 ## 1.6 Email Protocol Analysis (5%)