Technion - Israel Institute of Technology
		236341 - Internet Networking
		Winter 2011-2012
	Announcements Moed B Dear students, The exams have been checked and graded. The formula for the final grade is: Round(Min(100,(Avg(HW1, HW2, HW3, HW4, HW5, HW6))*0.15+(moed_b+2.5)*0.85)) FinalB average is 78.53. Appeals should be submitted by 26/3 to Ella's mail box on the 5-th floor. The solution of the exam is available in Ella's office. If you would like to have a look at the solutions, you can come to Ella's office on: Tuesday 20/3, 14:00-15:00 Wednesday 21/3, 13:30-14:30 Thursday 22/3, 9:30-10:30 Thanks, Course staff Created on 19/3/2012, 15:41:14   FinalA Histogram Hello, A histogram of the FinalA grades is available under "Course Material" (the average is slightly changed from the one published before, due to the appeals). Thanks, Ella. Created on 4/3/2012, 09:01:54   Moed A Dear Students, As you have probably noticed, we have published the final grades. The formula for the final grade is: Min(100,(Avg(HW1, HW2, HW3, HW4, HW5, HW6))*0.15+((1.03)*ExamA+3)*0.85). The course average is 80.36. A possible solution is posted in "old exams" Appeals can be submitted till 25.2.12 (in the box of Ella). They will be examined and returned a few days later. We were generous while checking some parts of the exam, so double check yourself before submitting an appeal. In particular, it is counter-productive to submit an appeal for 1 or 2 points. If someone already knows that he will need moed C due to miluim, please send an e-mail to Reuven asap (before moed B) in order to schedule a date. Regards, Reuven. Created on 13/2/2012, 14:51:42   HW4 & HW6 submittion Hello, If you submitted HW4/HW6 and still don't have a grade please contact Adi Omari: adiomarigmail.com Thanks, Ella. Last updated on 8/2/2012, 22:53:47   Ella's reception hour Hello, I will hold a reception hour before the exam on 5/2 at 11:00 at room 235. Please send me the questions ahead so that I'll be able to prepare. Thanks, Ella. Created on 31/1/2012, 09:47:42   Small typo in HW6 Question 2 Hello, In question 2c (about delayed-ACK), I meant the CE flag (and not EC flag). Thanks, Ella. Created on 30/1/2012, 22:04:33   Recitation 13 correction Hello, On slide 6 in recitation 13, the sentence: "Only TCP/UDP applications and ICMP queries are supported by NAPT" is not fully correct therefore it was removed. The updates recitation was uploaded. In addition, small note to Wednesday group: I said that FTP is problematic with NAT, but it can be treated (it requires specific treatment). Thanks, Ella. Created on 30/1/2012, 10:39:06   HW4 appeals Hello, The students whose ids are written here: 036724557-307739656 037052594-039667985 200586154-321380958 201011665-301437562 201209970-304864697 306667221-318109477 313034373-319431862 316690510 306786211 039404439 Please contact Adi Omari (omarics.technion.ac.il) about your HW4 (wet exercise) to schedule an appeal session (as your work failed the tests). Please come to the session with a working exercise (that compiles and produces at least the example output on the site - works correctly with the example on the site). You will integrate the changes you've made into the copy you have submitted and we'll rerun the tests. About 10-15 points will be reduced for the re-submission. Thanks, Ella. Last updated on 25/1/2012, 19:54:31   Small typo in HW6 Question 4 Hello, Please note a small typo in HW6 Q4: I wrote "if the second ACK doesn't arrive..." and it should be: "if the second segment doesn't arrive..." (It is on line #2) Thanks, Ella. Created on 24/1/2012, 23:04:52   Another note to Wednesday group. Another small note about Eifel (to be more precise): What we taught in the tutorial is mainly based on: "The Eifel Detection Algorithm for TCP" RFC (RFC3522) but the original proposal, the "Eifel algorithm", comprises both a detection and a response algorithm. Thanks, Ella. Created on 24/1/2012, 14:28:28   Allowed Material on the Exam Dear Students, The allowed material on the exam is a single A3 page (you can write on both sides). You can also bring 2 A4 pages, but attach them to each other, to form a single page. Good Luck. Last updated on 22/1/2012, 13:05:23   HW6 & Two notes Dear students, The last home assignment (HW6) is published on the site. The due date is 31/1/2011, 23:55. ECN will be taught on next lecture, it will be easier to solve the ECN question after the lecture. Two notes: 1. Regarding publishing additional exam solutions: There are no additional exams solutions. In addition, looking at too old exams is not very productive. 2. Small clarification from New Reno tutorial: I explained during the tutorial why deflating the cwnd upon receiving a partial ack makes sense mathematically. But the purpose of this deflation according to the New Reno RFC is: "This "partial window deflation" attempts to ensure that, when Fast Recovery eventually ends, approximately ssthresh amount of data will be outstanding in the network" Good luck, Ella. Created on 19/1/2012, 14:47:50   Clarification to Wedndsday group Hello, A clarification about Eifel: Eifel is a detection algorithm that allows a TCP sender to detect a posteriori whether it has entered loss recovery unnecessarily. But it doesn't define what should the sender do when it happens. "Based on the Eifel detection algorithm, a TCP sender may then choose to implement dedicated response algorithms." (from "The Eifel Detection Algorithm for TCP" RFC) However, such response algorithms are outside the scope of "The Eifel Detection Algorithm for TCP" RFC (RFC3522). Thanks, Ella. Last updated on 22/1/2012, 22:24:58   Correction in tutorial #10 Hello, Please note a small correction in tutorial #10, slide #5. It was previously said that loss of multiple packets from a single window of data will cause a use of retransmission time out. Which is not always true. You can read more about the performance of TCP Reno when multiple packets are lost in: ftp://ftp.ee.lbl.gov/papers/sacks.ps.Z Thanks, Ella. Created on 15/1/2012, 13:04:48   HW5 question 1a Hello, As PIM-DM wasn't covered enough neither in the lectures nor in the tutorials, please ignore question 1a ("seif a" in question 1). Thanks, Ella. Last updated on 12/1/2012, 10:59:42   HW5 Dear students, The 5th home assignment is published on the site. The due date is 19/1/2011, 23:55. Good luck, Ella Created on 9/1/2012, 15:16:37   A slide that explains the role of the cwnd variable when the sender is in the fast recovery state Dear students, The missing slides that explains the role of the cwnd variable when the sender is in the fast recovery state, was added under course material. The slide should be located between slides 190 and 191. Reuven. Created on 9/1/2012, 15:15:31   פרוייקט בתקשורת מחשבים שלום, כידוע לכם ישנו קורס בשם "פרוייקט בתקשורת מחשבים" הניתן מידי סמסטר ומזכה ב-3 נקודות אקדמיות. הפרוייקטים נערכים בקבוצות של שלושה סטודנטים בד"כ, ונמשכים סמסטר שלם. במידה ומישהו מכם מעוניין לעשות פרוייקט במתכונת קצת שונה ומתקיימים עבורו התנאים הבאים: 1) מעוניין לעשות את הפרוייקט לבד 2) יכול להתחיל את הפרוייקט בהקדם (לכל המאוחר עם סיום תקופת הבחינות) ולסיימו בתוך פרק זמן קצר (1-2 חודשים). 3) בעל ממוצע גבוה (כי מדובר בפרוייקט עם אופי מחקרי) נא לפנות לראובן. שימו לב: ההצעה יכולה להיות אטרקטיבית גם לסטודנטים שנותרו להם נקודות בודדות (1-2) לסיום התואר, שכן ניתן להתאים את דרישות הפרוייקט למספר הנקודות הדרושות. בברכה, ראובן. Last updated on 3/1/2012, 14:23:57   Reusing ports Hello, As you might have noticed, while working on the wet exercise, after establishing a connection and afterwards closing the socket, you can't open a connection on the same port for a while. The side that first sends FIN enters a state called TIME_WAIT for 2MSL when he gets the FIN from the second side. As a result it keeps the connection for 2MSL as if it was still open and you can't open a new connection on this port. For your tests you can change ports, or wait for a longer while to reuse the ports. 2MSL is usually 2 minutes. Thanks, Ella. Last updated on 2/1/2012, 15:24:47   Change in the tutorials Hello, As the material relevant for tutorial #10 (TCP New Reno) was not yet covered on the lectures, the tutorial today is cancelled. The tutorial on Wednesday will be given (but we'll do the "Max-Min Fairness" tutorial). In Monday group, "Max-Min Fairness" tutorial will be given next week. Sorry for the late notice, Ella Last updated on 2/1/2012, 15:14:19   HW4 FAQ Dear students, The FAQ for HW4 was added to the site under the F.A.Q. section. Ella. Created on 30/12/2011, 09:08:47   Wednesday tutorial next week is canceled. Dear students, Wednesday tutorial next week (on the 28/12) is canceled. The reception hours on next Wednesday move to 15:30. Thanks, Ella. Created on 22/12/2011, 15:03:14   Question and answers from the socket programming tutorial Hello, As many question that I wasn't sure in, were asked during the last tutorial, and as we won't have tutorials next week here are the questions and answers: Monday Group: ============= What is the port after accept? It is the same port as the listen port. It is possible as, as I mentioned in class, a connection is represented by [source IP, source port, destination IP,destination port]. You can see an example in slide 160 of the lecture. Should htons\htonl be used for the data sent? If the data is "per Byte" - no. But if you send 16/32 bit words you might want to apply these functions. Where recvfrom stores the pending packets? It has a buffer in the kernel. What is the Protocol parameter in socket function? "The protocol specifies a particular protocol to be used with the socket. Normally only a single protocol exists to support a particular socket type within a given protocol family, in which case protocol can be specified as 0. However, it is possible that many protocols may exist, in which case a particular protocol must be specified in this manner." (taken from man socket). Why should address length be included? The length and format of the address depend on the address family of the socket. Other options for address family: Please see the manual of the socket function. Wednesday group: =============== What is the typical backlog size? It depends on a lot of factors (for instance, the possible load and the memory available). You can take a look at various applications' code and see what is used there. Is recvfrom blocking? As I said in class there is a flag which determines it. If it is blocking, it will wait until something arrives. You can see the options of the flags in the manual of the function. Thanks, Ella. Last updated on 22/12/2011, 14:59:13   HW4 Dear students, The 4th home assignment is published on the site. The due date is 5/1/2011, 16:00. Good luck, Ella Last updated on 22/12/2011, 12:23:46   HW3 FAQ Dear students, The FAQ for HW3 was added to the site under the F.A.Q. section. Ella. Created on 15/12/2011, 10:16:49   HW3 Dear students, The 3rd home assignment is published on the site. The due date is 19/12/2011, 23:55. Good luck, Ella Last updated on 7/12/2011, 17:30:08   HW2 FAQ Dear students, The FAQ for HW2 was added to the site under the F.A.Q. section. Ella. Created on 4/12/2011, 22:34:32   Note about DUAL Hello, In the tutorial we teach a "simplified" version of DUAL which can lead to paths that are not the shortest paths. The full version, available in:http://ccrg.soe.ucsc.edu/publications/jj.dual.ton93.pdf assures also shortest paths. In the 1st question in the HW you are required to follow the algorithm taught in the tutorial (the "simplified" version). Thanks, Ella. Last updated on 30/11/2011, 12:46:58   A typing mistake in HW2 Dear students, In HW2 question 3.3 appears a quote taken from an RFC. It was taken from RFC792 and not RFC729 as written in the HW. Thanks, Ella. Created on 30/11/2011, 09:01:22   HW2 Dear students, The second home assignment is published on the site. The due date is 7/12/2011, 16:00. Good luck, Ella Created on 23/11/2011, 15:39:42   A small clarification to Monday's tutorial group In the ping example we saw the TTL was set to 255. But generally (in ping) it can be set to other values as well, for instance 128. Thanks, Ella. Created on 21/11/2011, 20:43:12   HW1 FAQ Dear students, The FAQ for HW1 was added to the site under the F.A.Q. section. Ella. Created on 17/11/2011, 14:56:35   Complementary lecture Dear students, A complementary lecture in "Internet Networking" will be held on Sunday, 27/11/2011 between 16:30 and 18:30 in Taub 9. Thanks, Reuven. Created on 17/11/2011, 14:34:42   Reception hour on 16/11 Hello, As a one-time change, Ella's reception hour on 16/11 is moved to 11:30 (instead of 10:30). Thanks, Ella. Created on 15/11/2011, 10:54:53   Complementary tutorial on 14/11 - Room change Hello, The complementary tutorial on 14/11 will take place in Taub 8. Thanks, Ella. Last updated on 14/11/2011, 10:45:15   Next lecture Dear students, The next lecture in Internet networking, to be held on Monday 14/11/2011, is cancelled. You will be notified about a supplementary lecture later on during the semester. Thanks, Reuven. Created on 10/11/2011, 10:34:13   HW1 Dear students, The first home assignment is published on the site. The due date is 23/11/2011, 16:00. Good luck, Ella. Created on 9/11/2011, 13:02:54   Complementary tutorials Hello, Due to the strike, tutorial 4 will be given in a complementary tutorial. It is scheduled to: 1. Monday, 14.11, 18:30 - 19:30, Taub 5. 2. Wednesday, 16.11, 10:30-11:30, Taub 3. Regards, Ella. Created on 6/11/2011, 13:43:47   The strike is over Hello, The strike is over. Starting next week tutorials will be held. Please bring the first 2 tutorial notes to the first tutorial. Ella. Created on 3/11/2011, 16:48:12   Welcome to Internet Networking Dear Students, Welcome to the "Internet networking" course. First meeting will be held tomorrow (Monday), 23/10/2011 at 12:30, in Taub 7. To get the location of the lecture notes please contact Ella. In addition, please note that due to the "segel zutar" strike, there will be no tutorials until further notice. Good luck, Course staff. Last updated on 1/11/2011, 09:29:31