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CMSI 355 Networks, Spring 2020

Assignment 0204

This first assignment is all about knowing your way around the network, particularly the parts that most users never see.

Background Reading

Most of the information needed can be found in the Internet Basics page from Dr. Toal’s website. Not included in this page is information on arp, the Address Resolution Protocol command. There’s a bunch of documentation available on the web for this, though at varying levels of detail. This one is example-oriented and is likely the best fit for what we’re doing, but don’t hesitate to look for other sources if you want more detail.

Deeper background and details can be found in Chapters 20, 21, 23, and 26 of the Comer book (chapter 27 if you are on the 5th edition). Don’t be alarmed that we jumped from Chapter 3 to Chapter 20—there are whole sections on data communication basics and hardware-level network technologies that are elided for this course.

For Submission: A Network Exploration Log and Map

Getting to know a network at a technical level for the first time feels (to me) a lot like pioneering exploration: you encounter strange new names and places, make discoveries about how information gets around, and gain some insight on how environments that you take for granted are actually set up. This assignment adapts this “exploration theme” as a way for you to introduce yourself to networks by having you look around the very networks that you use frequently.

Step 1: Explore and Record

For the following network environments…

  • LMU
  • Private network outside LMU (apartment, office [when appropriate], house)
  • Public network (coffee shop, shopping area, restaurant)

…and on at least two distinct occasions per environment (“distinct” meaning that you leave/disconnect from that environment at least once between sessions), perform the following explorations:

  1. Note your computer’s IP address, subnet mask, router, and domain name server(s)
  2. Examine your computer’s full routing table
  3. Use arp to discover hosts that are on the same network
  4. Use ping to make contact with:
    • A host you discovered via arp
    • The default router
    • One of your domain name servers
    • www.lmu.edu
    • A host on the Internet (most likely a website, but for more variety, see if you can find a different kind of public host, such as a game server, mail server, chat server, or cloud storage)
  5. Use traceroute to discover the path taken to these same hosts
  6. For www.lmu.edu and the chosen Internet host, use dig to discover their IP addresses
  7. Use nmap to see what ports are open on these hosts
  8. Use nmap to see what ports are open on one of the intermediate “stops” discovered by traceroute to any host outside of your network

Take screenshots of each of these activities and look for what’s common or consistent and what changes either across networks or across different sessions. Take note of when an operation fails as well.

Step 2: Journal/Log

Gather these screenshots and provide commentary on them to form a coherent “explorer’s log” of sorts, to serve as a record of your explorations and discoveries.

Step 3: Map

Based on the information you gather, try to sketch out a “map” of the networks and hosts that you explored. Where are they connected? What do the IP addresses in each environment look like? How do each of them get to www.lmu.edu and your chosen Internet host?

Think of this map as similar to one that early seafarers and explorers might have drawn: admittedly just a small part of the world (Internet), but as accurate and grounded as you can figure, based on the commands that you used.

Optional: Work with a Friend or Classmate

Embarking on this exploration with a friend or classmate can give you some additional insight on how different computers on the same network are set up and may feel more comfortable when doing an nmap (i.e., so that you aren’t doing nmap on some random person’s computer—it’s still a pretty harmless exercise but you may still feel more comfortable if you’re nmap-ing somewhat that you know). However, if doing this with a classmate, each of you must still submit individual, distinct logs and maps: no sharing of work or screenshots.

Overall: Imagine

Add a dash of fancy and imagination to your explorations by giving your log and map a fanciful theme that befits an exploration. Examples include:

  • A starship captain’s log and charts
  • A fantasy world such as Westeros or Middle Earth
  • A certain popular monster game with its many regions and leagues
  • Alternate dimensions or universes

In a way, you are playing the role of an explorer, and the amazing thing is that you will be encountering places and paths that are all around us and yet are virtually unseen by nearly everyone, except at the very surface where websites and applications dwell.

How to Turn it In

  • Commit your journal/log to your allocated repository as a Markdown file. Make sure to embed your screenshots in this file alongside your fanciful (but technically accurate!) commentary. Call this file log.md.
  • Your map may use any visual medium, ranging from something that is legibly hand-drawn then scanned/photographed to something made with a drawing tool—whichever approach you choose, upload the final result to the allocated repository as well. Name this file map.* where * indicates the format of the map file (e.g., map.pdf, map.jpg, etc.).

Specific Point Allocations

This assignment covers outcomes 1a1c, 2a, 2c, and 4d4f as described in the syllabus. For this particular assignment, graded categories are as follows:

Category Points Outcomes
IP address 0.25 points each, 1.5 points total 1a, 1b
Subnet mask 0.25 points each, 1.5 points total 1a, 1b
Router 0.25 points each, 1.5 points total 1a, 1b
Domain name server(s) 0.25 points each, 1.5 points total 1a, 1b
Routing table 0.25 points each, 1.5 points total 1c, 2a, 2c
arp findings 0.5 points each, 3 points total 1b, 1c, 2a, 2c
ping LAN host 0.25 points each, 1.5 points total 2a, 2c
ping router 0.25 points each, 1.5 points total 2a, 2c
ping DNS 0.25 points each, 1.5 points total 2a, 2c
ping www.lmu.edu 0.25 points each, 1.5 points total 2a, 2c
ping external host 0.25 points each, 1.5 points total 2a, 2c
traceroute LAN host 0.5 points each, 3 points total 1c, 2a, 2c
traceroute router 0.5 points each, 3 points total 1c, 2a, 2c
traceroute DNS 0.5 points each, 3 points total 1c, 2a, 2c
traceroute www.lmu.edu 0.5 points each, 3 points total 1c, 2a, 2c
traceroute external host 0.5 points each, 3 points total 1c, 2a, 2c
dig www.lmu.edu 0.5 points each, 3 points total 2a, 2c
dig external host 0.5 points each, 3 points total 2a, 2c
nmap LAN host 0.5 points each, 3 points total 2a, 2c
nmap router 0.5 points each, 3 points total 2a, 2c
nmap DNS 0.5 points each, 3 points total 2a, 2c
nmap www.lmu.edu 0.5 points each, 3 points total 2a, 2c
nmap external host 0.5 points each, 3 points total 2a, 2c
nmap intermediate stop 0.5 points each, 3 points total 2a, 2c
Overall log 13 1a, 1b, 4d
Overall map 25 1a, 1b, 1c, 4d
Fun theme 5 🤩😎🤓🧐🤔
Version Control deduction only 4e
Punctuality deduction only 4f
Total 100
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