Author Archives: Ooi Wei Tsang

OT: Protocol Jokes

by Ooi Wei Tsang

Sometime to lighten up your day while preparing for midterm. Feel free to share your own jokes :)

  • An IPv4 address space walks into a bar, “A strong CIDR please. I’m exhausted.”
  • A TCP packet walks into a bar “I want a beer.” Bartender responds “You want a beer?” Packet responds “I want a beer.”
  • DNS servers must feel sad, nobody calls them by their name.
  • I’d tell you the one about the CIDR block, but you’re too classy.
  • A UDP packet walks into a bar without a checksum. Nobody cares.
  • Chuck Norris doesn’t do TCP handshake – he does TCP roundhouse-kick to initiate the connection
  • Doctor: What seems to be the problem? Router: It hurts when IP.
  • I tried to come up with an IPv4 joke, but the good ones were all already exhausted.
  • The best thing about UDP jokes is that I don’t care if you get them or not.
  • People who tell routing jokes always exceed their time-to-live.
  • The problem with TCP/IP jokes is that when I tell them, all I want is an ACK but usually get FINs and RSTs
  • I had a funny UDP joke to tell, but I lost it somewhere…
  • The worst part about HTTP jokes is that you can never remember in which state you heard the last one.
  • HTTP jokes are rarely better than OK
  • I really don’t GET HTTP 404 jokes.

Credits: http://attrition.org/misc/ee/protolol.txt

  • “A UDP and a TCP sailor are getting ready to go into town on their evening leave from the ship. I have to go through a lot of handshaking to get to my favorite places in town. Most of the time, though, they just bounce me at the door. UDP: Hey! What are you complaining about? I get lost before I even get anywhere interesting.”

From: http://www.neowin.net/forum/topic/1095967-ip-protocol-joke/

  • A DHCP packet walks into a bar and asks for a beer. Bartender says: “here, but I’ll need that back in an hour!
  • You know it’s love when you memorize her IP number to skip DNS overhead.
  • IP packet with TTL=1 arrives at bar. Bartender: “Sorry, can’t let you leave… and you don’t get any beer either…”
  • “Hello, here’s a packet : “The problem with low MTU jokes is you can”. Hello, here’s a packet : “wait a long time before reading”. Hello, here’s a packet : “it.”
  • 192.168.0.1 jokes are best told in private.
  • We were supposed to be dressed in disguise. So I dressed as NAT.
Source: http://rekrowten.wordpress.com/list-of-network-jokes/

Assignment 1 Q&A Schedule

by Ooi Wei Tsang

This post will be updated at least once daily.

Wednesday, 5 March, 2014

The following takes place in MR6, AS6 #05-10

1100 OON ZI GUI, TAN MEI LING
1105 SUN HANG, GAO RISHENG
1110 WANG ZHE, KOH JUN XIANG
1115 DAO THAI DUY, HO TUAN DUONG
1120 NURWIDYA UTAMI JATI, LEWIS HARIS NATA
1130 LIM HONG HUI EUGENE, CAO YUBO
1135 TRAN THAI TRI TAN, NGUYEN VAN THE
1140 YANG HUIYU, YUEN SHU HUI
1145 LAI YIT HANN, TAN WEI YOUNG
1150 NGOC THANH, LIU PEIYU

The following takes place in Wei Tsang’s office, AS6 #05-14.

1040 SITI NORFAEQAH BINTE POWZAN, GANGADEVI D/O BALAKRISHNAN
1045 HUANG QINGHUI NICOLAS, CHENG WEN ZHAO
1050 SHIWANI AGARWAL, ASHISH TAYAL
1100 CHUA RUI JUN, LOW KIT YEE

1600 HUANG YUE, ZHOU WEI
1605 TAMANA ANNA THARAKAN, IPSITA MOHAPATRA
1610 JOANNE MAH JIA WEN, FAN YUXIN
1615 LIN BAOYU, LIM WEI KE
1620 CHIA WEI MENG ALEXANDER
1630 CHNG YUAN ZHANG MAURICE, GAN JIA HUI
1635 STEFANI LETICIA, LEE HUI SHAN
1640 TAN JUN KAI, QUEK JUN JIE
1645 XIE CHENHONG, SU HAN
1650 A YUSUF SHAMIR, ATUL NANDAKUMAR

1700 FLORENCE WAI TZE YUN, CHUA YI JING
1705 CHIAM ZHIJIE JONATHAN, IAN LEOW TZE WEI
1710 WANG YI, CHEN TONGTONG

The following takes place in DR5, AS6 #02-08.

1645 CHRISTOPHER MARSHALL LAIRD, AI YUE GUO
1650 ADINDA AYU SAVITRI, ONG CHEE CHIN

1700 CHU BING HAN BRYAN, SAN WENYIN
1705 KHAN SAIM SAEED, SENGUPTA DEBOPAM
1710 HE LINGFEI, XIA LU
1715 GUNESS VARSHA, MICHELLE SINN SHWE YE OO
1720 CHANG YAN QIAN, LIM YU DE
1730 SEAH SHAO CHENG, JACOB TAN JIA WEN
1735 LI HO YEUNG, KIN FUNG ANTONY TSE
1740 SONG YI, LI YUANDA
1745 WANG WENZHU, WANG GAOYING

1800 JOEY HOK WAI YI, JAYARAMAN ARCHANA
1805 YE SHUJIAN, LU XI
1810 ZHANG MENGDI, YEO JEONG HOUN

Continue reading →

Lecture 7: Routing

by Ooi Wei Tsang

3 March, 2014.

Millions of Routers Work in Concert to Route Packets on the Internet, Based on This One Simple Equation. Amazing.

This week we will look at how routing is done on the Internet, focusing on distance vector routing protocol and RIP, used in intra-AS routing.

Slides: PDF

Please read the following sections in the textbook. Reading:
Chapter 4 of KR.

  • 4.5 Routing Algorithms
    • 4.6.1 Intra-AS Routing in the Internet: RIP

Assignment 1 Q&A

by Ooi Wei Tsang

Please book your slots for Q&A here.

Here are the rules:

  1. Each team will indicate the one-hour slots where both team members are available, from which we will allocate 5 minutes for each team.
  2. We will need to stick to the clock exactly, so you must come on time and end on time.
  3. We will randomly ask each student to explain a random part of the code.  Your answer will constitute 2 marks of your individual Assignment 1’s grade.
  4. If you missed your slot or is late, there will be no rescheduling and no extra time.
  5. Both team members must show up on the same time slot.
  6. At the doodle site, in the column that says “Your Name”, please enter the matriculation numbers of both team members.
  7. You will receive an email confirming your slots. Further schedule will be updated in another blog post.
  8. The last slot will be 6pm, 5 March, 2014. After this time, no further booking online possible.

NextGen@ICAAN

by Ooi Wei Tsang

The following email snippet from National Youth Council is referred:

—
We have been approached by an organisation to nominate youths from university/tertiary students, to participate in the inaugural NextGen@ICANN program that will engage them on the areas of internet policy and governance, and get them familiarized with the ICANN (Internet Corporation for Assigned Names and Numbers) processes. ICANN is an international organization responsible for coordinating the unique identifiers – top level domains (TLD), such as ‘.com’, ‘.org’ and ‘.net’, etc, between computers across the world and building the global Internet. The youths should preferably be those who are interested in the area of ICT, internet governance or whose study is related to this area. More details on the program can be found in the attached.

Would you be interested to nominate some of your students to participate? There are 15 slots for students, Uni Year 1 and above (or equivalent, aged 18-29).
—

If anyone is interested, please email me.

Midterm Review Questions

by Ooi Wei Tsang

Here are the midterm review questions, selected from past CS2105 midterms and finals. No solution will be posted, but you are more than welcome to show the teaching staff your solution and discuss them with us, either online or during our office hours. I encourage you to discuss online as well, on the blog with your peers, and we will chip in when the discussion is heading in the wrong direction.

CS2105 in The News: Whatever happened to the IPv4 address crisis?

by Ooi Wei Tsang

Whatever happened to the IPv4 address crisis?

Unallocated IPv4 address blocks are gone forever. However, carriers still have IPv4 addresses available for allocation, so IPv4 addresses will remain in use for some time to come. And though there may be no immediate crisis for service providers, businesses, or customers, there is steady pressure to enable IPv6 in every segment of the network ecosystem as the best way to address IPv4 address scarcity.

Assignment 1: Clarifications II

by Ooi Wei Tsang

A few clarifications/tips related to Assignment 1.

  • You can assume that the browsers generate properly formatted HTTP requests. You only need to handle user errors, such as, when users enter a URL pointing to a non-existing file.
  • Beware of Runtime.exec(String[] cmdarray, String[] envp). If the standard environmental variables, such as HOME is missing from the parameter envp, the perl script will not run properly. The script expects that HOME to be set to the user’s home directory. The symptoms of this bug is that todo.pl tries to create a folder /a1/data, which it does not have permission to.
  • Beware of readline(). It returns only after it encounters a new line character. Note that neither HTTP request or response BODY guarantees that it ends with a new line character. If you use readline(), you may have to wait forever for it to return.
  • If you are ssh-ing into cs2105-z from Windows ssh client, you may have key mapping issues when you use vim. You can copy my .vimrc from ~ooiwt/.vimrc on cs2105-z, which maps the keys properly, to resolve this issue.