Homework for Class04

Due by the next class on February 11, 2009.

IP Basics
- Internet connectivity requires a unique IP address, a netmask, and a gateway.
- Use IP/netmask 152.23.64.89/21 and default router 152.23.64.1 for this question.
  - What is the IP address in hexadecimal?
  - What is the gateway in hexadecimal?
  - What is the netmask in dotted decimal?
  - What is the netmask in binary? (hint: this is easy!)
  - What is the highest numbered potential neighbor?
- Would 152.23.64.89/21 with a default router of 152.23.65.1 work?
- What would happen if the default router were 152.23.65.1 for 152.23.64.89/24?
ARP
- Re-write one of these for the case that your DNS is not local to you: LAN table, WAN table, or (re-draw) the flowchart.
Basic Network Tools
- Look at a traceroute to google.com and a traceroute to cnn.com. Comment on the results. Your answer does not need to be long.
- Send a few pings to the campus webserver. Did you learn anything about the connection between you and the server?
New Network Tools
- Open a web browser to NDT, and run the tool. What did you learn about your network connectivity? (Paste in the results, and make a few comments.)
- Use Internic Whois to look up information about the last named domains seen in your traceroute results. When I tried this, all but pure google.com were AOL! The classic (1.x) Unix command is whois google.com where you just give the domain name (not a FQHN).
Security
- Read about IPsec.
- What form of IPsec would you want to use for a P2P network, especially if you expect users to access this network from home?
IPv6
- Read about IPv6.
- Use ifconfig -a on Unix or ipconfig /all on Windows. Do you have IPv6 running on any interface?
- If so, what can you tell me about your IPv6 address(es)?
  - If your machine isn't running IPv6, use this information from my laptop:
    - ```
    lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
      inet 127.0.0.1 netmask 0xff000000 
      inet6 ::1 prefixlen 128 
      inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 
```
- ```
en2: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500
  inet6 fe80::201:23ff:fe45:6789%en2 prefixlen 64 scopeid 0x8 
  inet 10.37.129.2 netmask 0xffffff00 broadcast 10.37.129.255
  ether 00:01:23:45:67:89 
  media: autoselect status: active
  supported media: autoselect
```
- Read about 6to4 and Teredo.
  - Could you use 6to4 with the IPv6 address you used above, or would you have to use Teredo?
- There's lots more IPv6 information out there! Read about IPv6 tools for Mac OS X to learn about some of the Unix tools.
  - What would you use for ping? for traceroute?
  - If you can scan 255 (2⁸) IPv4 addresses in 3.228 seconds, how long would it take to sweep all 2¹²⁸ IPv6 addresses?
Thought Question: pick one for a very short discussion. Don't be afraid to wing it.
- Cellheads versus Airheads: A stateful application requires that a server, usually a centralized server, maintain state information. TCP maintains state information in its various states, from SYN_SENT to ESTABLISHED to CLOSE_WAIT and all the other states (however, it is maintained on the machine that needs to know the state information). Stateful applications are often upset by random resets, so a central server with state information really messes up the end points when it reboots. Do you think CellHeads or AirHeads maintain more state information? Where is it maintained, and is that location one that can upset the state information table?
- NetHeads versus BellHeads: Remember our discussion about network topology in Class01, where, for instance, the cost to add one more node to a fully-meshed network increases with the number of nodes. (To add node #(n+1), you have to run n cables to the existing n nodes so the cost increases with n. To add another node on a bus network, you just add a transceiver, so cost does not increase with number of nodes (until you need another cable run).) How does this argument apply to the NetHeads' network? How about the BellHeads network?

HW04

Homework for Class04