Happy holidays

Class attendance and assignments records

By following this link you can check a copy of the records I keep about both attendance and assignments so you can double check them. If you detect an error please contact me ASAP to get it fixed.

Please bookmark it on your browser so you can return to it easily.

Map of the Internet's addressing space

I could not resist posting this link.

Second assignment is out

As promised here you have the second assignment work that deals with UDP network programming. As in the first assignment, it is a client/server application. Again you have to program a small server that receives files from the client and writes them down to disk.

I have chosen an "invented" protocol as there are lots of Java code out there for many standard protocols (including TFTP). The good news is that I tried to keep it as simple as possible. The bad news is that my skills at writing the protocol specification are not on par with a good RFC. As usual, feel free to ask me any question you may have about the assignment.

Although I know you can copy and paste the client's source code from the PDF file, you can also find the source code file here.

First assignment results

I want you to know that Javier, Edgar, Aitor, Ana, Ramazan and Manuel turned in their work. Unfortunately, one of them failed to meet the problem requirements but the rest pass the test with flying colors.

Congratulations, not bad for your first networking problem.

Those of you that did not turn in anything please remember there are still three other assignments to come.

Network programming is like riding a bike: None of you learnt it by reading a manual, did you?

The many uses this blog

I was reviewing last year's posts and I realized that many of the posts are applicable now as we are going through the same chapters at the same time. So instead of reposting the same entries I invite you to check last year's entries along the whole course and there you'll find useful information, interesting links and related material.

Please note that assignments are different.

Class attendance record

These are the attendance numbers so far (out of 13 classes).

Ayoub 10 Aitor 13 Martin 9 Luis Manuel 8 Edgar 10 Carlos 8 Erol 1 Ramazan 12 Jakub 1 Roberto 2 Ana 6 Manuel 6 Javier 11 Taha 9 Carlos S 1

Please note that some of you are joining the class quite late. I understand that you may have other subjects too, but please note you'll need some effort to catch up with the class.

Sample IM server application

I've created a server application like the one you have to write for assignment #1.

You'll find it running on port 7777 on the IP address 158.42.53.17. If for some reason it is not accepting your connections, please let me now, as a power outage might have happened on my side and manual restart would be needed.

Please note that the messages about a new client entering the server or a client leaving the server are not required on your code. I've just added them to give users a bit more of information.

News and reminders

Since Nov 16th we will be back to the "Seminari Nord" room. I've just posted the text of the first assignment, and I want to remind you that --although it is optional work-- doing it right will be worth 5 out of 100 points.

You do the four scheduled assignments right and you already have 20% of the subject.

You come to all the classes and you have 10% more.

Still not enough to pass the subject (you need 50%) but closer ...

Just a word of warning: Assignments are personal work, not team work. Your code will be checked against all the other submitters. If a copy is found all the involved parties will score 0% no questions asked. It is in your best interest to keep your work for yourself.

As with any other doubts you may have about the subject, I'm available during office hours for helping you solving them.

Programming Assignment #1

Instant Messaging Server

Your job is to write a Java application that will act as a the server for an Instant Messaging application. Clients will connect to the server [using a TCP connection] to talk to each other. Clients will type messages that are composed of one or more lines of text. Each time a user types a new line of text at the keyboard, that line will be transmitted to the server.

Each time the server receives a new line from any client, it will send a copy to all the clients but the one who sent it (i.e. to prevent a confusing double echo on the sending-client side).

Any client that wants to abandon the service MUST type a line with the text QUIT. Whenever the server receives such a line of text it will interpret its meaning, closing the socket this client was using. From them on, no attempt to send any more data to that client will happen (note: trying to send data to an already closed socket would trigger an exception).

Still, a client could leave the service by just closing the connection without the mandatory QUIT command. You do not need to manage that case though.

Your Code

Your code has to conduct the following tasks:

1. Accept any number of simultaneous clients, but it is safe to assume no more than one hundred simultaneous clients.

2. Retransmit any text line, including empty lines, to any active client but the one typing that text line.

3. Not to retransmit those lines which only contents is the QUIT command. Any combination of upper and lower case characters should be accepted and recognized (i.e: both QuiT and quit should work too).

4. The server program prints “NEW CLIENT” whenever a new client connects to the server and it prints “CLIENT GONE” when any client quits the system.

Some tips

• Server listens on port 7777

• You may use several telnet windows as clients of your server (for testing purposes) by just typing;

telnet localhost 7777

Due date

Your Java source code has to be submitted by email (address available on the front page) by Nov 30th.

If you have any doubt about the assignment I strongly suggest you to stop by my office during office hours (posted on the web).

News

I mentioned in the class this sample server program.

Next class will be held on Aula Informática, on the ground level, see the plane (click on the image to get a larger view).

A bird's eye view of the Internet

There are several projects aimed to provide such a view. This is just one of them.

A tree is built connecting lower level networks. As you can see a huge hierarchical view is shown, and that is just part of how it was the Internet some time ago as it is evolving on a daily basis.

Changing location

During the two first weeks of November we will have our classes in the "Aula Informática" so all of you can try for yourself with a networked computer how things really work. This will be from November the 2nd till November 10th.

FYI: For Your Information

Any submission to the IETF intended by the Contributor for publication as all or part of an IETF Internet-Draft or RFC and any statement made within the context of an IETF activity is considered an "IETF Contribution". Such statements include oral statements in IETF sessions, as well as written and electronic communications made at any time or place, which are addressed to:

• the IETF plenary session,
• any IETF working group or portion thereof,
• the IESG, or any member thereof on behalf of the IESG,
• the IAB or any member thereof on behalf of the IAB,
• any IETF mailing list, including the IETF list itself, any working group or design team list, or any other list functioning under IETF auspices,
• the RFC Editor or the Internet-Drafts function

All IETF Contributions are subject to the rules of RFC 3978 and RFC 3979.

Statements made outside of an IETF session, mailing list or other function, that are clearly not intended to be input to an IETF activity, group or function, are not IETF Contributions in the context of this notice.

Please consult RFC 3978 for details.

Welcome to all of you

I've just returned from a trip to a Finish university and I've discovered there are thrity eight people enrolled on the subject this year. This is definitely our best score ever and I just hope most of you will actually stick to the English group (I'm afraid that some of you might have ended in this group because other groups are full).

I'll see you all on Thursday,

Miguel

September news

I am glad to inform you that Rami passed the subject.

Antonio: I'm glad to see you again enrolled in the subject. You are welcome to come to the class too, work permiting.

Still reading this blog?

Well, maybe you failed the subject, sorry.

On the other hand, if you are planning joining us next course, please be welcome and feel free stoping by my office (I'll be out of town week 38th though).

There is just another opportunity for you to take an exam next September 14th, Thursday, at 16:00.

Best of luck (not that I think it has lots to do with the outcome),

Dr. Sanchez

Solved Exam

It is here.

Please contact me if you want to have a look at your exam. Marks will be final in a few days.

What not to do this summer

This list contains some of the IP ranges that you better avoid if you do not want a free trip to Guantanamo or another sunny place with the latest fashion in orange suits.

Subject's marks

Several students did not show up at the exams and they have no marks:

ANTONIO, ALBERTO, JOSE LUIS and RAMON

The rest of you, brave people, did get the following results:

NAME            EXAM    LAB    ASSIG.     ATT.    TOTAL   COURSE_MARK
--------------  ----    ---    ------     ----   -------  -----------
DIEGO           44      35        1        20    53.05        63.25
JORGE           62      70        0         0    64.60        67.29
TOMASZ          70      70        2        17    83.39        82.85
IGNACIO         62      45        1        17    71.49        79.05
LUISMANUEL      22       0        0         2    20.67        28.73
VLADISLAV       82      55        1        21    90.23        86.24
RAMI            38       0        0         2    36.37        21.15

Congratulations on your results. Unfortunately those below the 50% course mark have failed the subject, please remember we will have another exam in September covering THE WHOLE SUBJECT (assignments or lab exam are not available in September).

Your exam is available for you to check your results (just email me for a revision slot). In a few days I'll post the 2nd term exam answered.

Wold Cup telnet fun

I've just learned that some people are using the old and aged telnet application for new uses:

                                   _ajjaa                             
                                 _Q???4Qf                            
              _,...,_            ) a/]QQb                            
            .'@/~~~\@'.              jQQba                           
           //~~\___/~~\\          _, .?QQ#[ _                        
          |@\__/@@@\__/@|         ]m _.7   "asLaas_a/                
          |@/  \@@@/  \@|        , ,\J#L -!4Wba                      
          \\__/~~~\__//       [aL[    \    \jmm     jP               
            '.@\___/@.'    ,b#'"[     \jmmmmm    _P.                
              `"""""`        a##'      "4P#mmm#   _ya                
                            _P          !4####m  ?]aa/               
                           /'        aaJ#U###m#   4QP'               
                          '         aa,/4!44! '                      
                      jf         _'jQQQQyb7b /                       
                      '.         '.QQQQ4QQPb  )?                     
                                   QQQ'QQP?'  jg/ f                  
                                 _yQP']QQb aa                        
                               a#W?'..QQQQ?)?   ?'                   
                              "##'  _jQQP'                           
                             .j?  [ jQQ'                             
                        aJ  jmaaX#L???                               
                        ? am'                                        
                      _QjQQQ/                                        
                      )QQQP?                                         
                       4QQQ/                                         

So try any of these live-streams based on telnet:

telnet ascii-wm.net 2006
             
                        MIRRORS: 

telnet diego.ascii-wm.net 2006
telnet pinguin.eikon2.fs.ei.tum.de 2006

Warning: Exam ahead

As a reminder: Written exam will be held on June 23rd at 4:00pm. You either have to do the second term exam if you passed the first term or a final exam covering first and second terms if you didn't.

If you have attended to all the lab sessions please remember you are eligible for a written laboratory test, to be held afterwards (same day). Any score you get there will only add to your total score (it is my way of telling you should do it if you are eligible).

Those who fail the subject will have an exam in September covering all the subject.

Remember the final grade will include the marks from you class attendance and the assignments you turned in.

Till the exam, I'll be available to address any of your questions on my office hours (Mon & Tue 9:00 - 12:00).

Encryption ... rap?

Rapper MC Plus+ has created a song titled "Alice and Bob" based on the improbable theme of computer cryptography. It is freely available online. I'm not sure this will become a huge hit but, who knows?

New software threats

As I mention in the last class, I read this post where new types of malware activity are commented. While I am not afraid this will have a wide effect it is a new twist as to how some people can turn out a benefit from creating this particular type of sofware.

Last assignment is out

This last assignment is about finding the best route in a graph. This is part of what a routing algorithm does. Actually, a routing algorithm will search for all the best routes to all the destinations.

Moore's law of networking?

Apparently, there is a Metcalfe's law about the value of a network I have never heard before. All it all, it does not seem to make everybody happy. I guess Metcalfe will be better recalled because of Ethernet technology.

Getting to know an autonomous system

In this link you can learn more about this ISP's set of addresses. Comsat Colombia is the local branch of an international ISP that offers satellite Internet access. In the report all the BGP-related information is shown, so you can learn about their addressing space and the other AS they are routing through.

For those of you that feel happier with a closer ISP. Here you have the ONO-CableEuropa AS details.

Third assignment

As we are studying IP fragmentation, it seems appropriated to get some hands-on experience on the topic. This is what this third assignment is all about.

Please remember this is just an optional programming exercise dealing with computer network's concepts. But if you decide to go for it you'll get the double benefit of learning plus scoring a bit towards your final grade.

Back to work

Exams' period is over. We've got an interesting second term where we'll cover from IP network-layer to LANs and network security. For those of you new in the subject I want you to know that we'll have a couple programming assignments this term. For you all remember that attendance to the lectures while not mandatory is recorded and it will be marked (sometimes you can even learn something new).

See you in class next Feb, 16th.

Exam results

You may want to get a copy of the exam with all the answers too. It's already here.

               EXAM      LAB.TEST   ATTENDANCE  TOTAL
Jorge          63%         55%         1        70%
Luis Manuel    38%                     7        37%
Ignacio        73%         55%        27        87%
Alberto        41%                     6        39%
Diego          59%         40%        22        73%
Johan          57%         20%        19        65%
Tomasz         67%         80%        20        82%
Vladislav      63%        100%        22        82%

Solved lab test is also available.

The column "total" includes your assignments too (if any).

Marks are calculated as follows:

TOTAL = EXAM * (9 - #ASSIGN) / 10 + #ASSIGN * 10 + ATTENDANCE * 10 / 27 + LAB.TEST / 10

Fall term is over

Lectures are interrupted till the beginning of Spring term. I guess we'll keep you busy with exams. Please remember there is still one week to turn in assignment #2.

My best wishes with the exams.

Johan, we'll miss you.

Maybe some new students will join us next term.