Please read the questions carefully before answering.Q1 is a short answer question, the first part asking to explain the ideas behind the design, and the second part asks why Option 2 is the best, and...

Please read the questions carefully before answering.








COMP3250 Computer Networks Assignment 1 Due: Week 8 – Tuesday 27th of September 2022, 6 pm. Total Marks: 30 Weighting (Value): 15% Objectives This assignment will test your knowledge in the following areas: • Intra-Domain Routing. • Classless Interdomain Routing (CIDR). • BGP. Assignment Type: Problem Solving (Individual Assignment) The purpose of the problem-solving assignment is to help the students to get accustomed to dealing with real world problem situations/issues. It is designed to help students analyse a particular problem and find its best solution. Questions 1. a. [4 marks] In an OSPF architecture, a network can belong to only one area. Briefly explain the rationale behind this design decision. [150-200 Words] b. [6 marks] When designing the OSPF routing protocol, the designers had the following choices with respect to the placement of this protocol within the protocol stack: i. Option 1: Place the OSPF protocol above the transport layer: OSPF packets are transported over either TCP or UDP segments. ii. Option 2: Place the OSPF protocol directly above the IP layer: OSPF packets are transported over IP datagrams. iii. Option 3: Place the OSPF protocol directly above the data link layer: OSPF packets are transported over data link layer frames. The designers opted for option 2. Briefly explain the rationale behind this design decision. In your answer, briefly highlight the potential drawbacks of using the other two options.[300-350 Words] 2. [6 marks] a. [3 marks] Determine the best summary route (inclusive or exclusive) for a block of addresses starting at 182.68.1.0/24 and going all the way to 182.68.120.0/24. Explain clearly how you arrive at the solution showing all relevant steps. b. [3 marks] Determine the best summary route (inclusive or exclusive) for the following block of addresses: 172.16.10.0/24 172.16.20.0/24 172.16.30.0/24 172.16.40.0/24 172.16.50.0/24 Explain clearly how you arrive at the solution showing all relevant steps. Note: For parts a and b, your strategy should be to first determine a single (best) exclusive summary. If this is not possible, summarize the addresses using more than one exclusive summary. If this is not possible, then determine the best inclusive summary. 3. [6 marks] Consider an Autonomous System consisting of two route reflectors RR1 and RR2 shown in figure 1. RR1 forms a cluster with its client A, and RR2 forms a cluster with its client B. The IGP and iBGP links along with IGP link costs are shown in the figure below. Both RR1 and RR2 receive advertisements from their respective external peers for a prefix N and both advertise this prefix to their respective clients. Explain briefly why this configuration is error prone. Figure 1: A Route Reflector Configuration 4. [8 marks] Consider the routing scenario shown in figure 2 below. An autonomous system (AS1) is connected to the Internet via two providers. The router R1 in Sydney is running EBGP with a provider P1 over a T1 circuit, and the router R2 in Melbourne is running EBGP with another provider P2 over a T3 circuit. Note: P1 and P2 are not shown in the figure. The two border routers R1 and R2 use IBGP to communicate with each other but there is no direct physical link connecting the two. The internal routers R3, R4, and R5 are non-BGP routers and exchange routes with one another using an Interior gateway Protocol (IGP). In the current scenario, R1 and R2 are receiving full routes from their parent providers P1 and P2 respectively. Both R1 and R2 are also injecting a 0/0 default route inside AS1. Furthermore, the MEL T3 link at R2 is configured as the primary link. The SYD T1 link at R1 will be used as a backup, and consequently all outbound traffic will exit the AS through R2. Interior routers R3, R4, and R5 do not see external routes and simply follow the early exit routing strategy (also known as Hot Potato Routing) by forwarding all packets to the nearest exit point. Give and explain one reason why this topology is error prone. Recommend and explain two solutions to fix or avoid this problem. [300 words]. Figure 2: Autonomous System AS1 with two border routers R1 and R2. Submission You must make an online submission on ilearn via Turnitin. Assignments will normally be marked and returned online. There are no hardcopy submissions for written assignments. Ensure you submit the correct file. The submission process shows you a complete preview of your entire assignment after you have uploaded it but before you have submitted it. Carefully check through every single page to ensure everything is there and the correct version has been uploaded, and only then press CONFIRM. Note: Multiple submissions may be possible via Turnitin prior to the final due date and time of an assessment task. Teaching staff will use the originality report to judge whether plagiarism has occurred and whether penalties should apply for breaches of the Academic Honesty Policy. Any similar text identified by Turnitin will be considered carefully to see if it is indeed a breach of the Academic Honesty Policy. Note • Answers must be within the specified word limit. This is an absolute word limit, and no excess will be allowed. This is an absolute word limit, and no excess will be allowed. If you exceed the word limit, you will be subject to a penalty of 5% of the available marks (irrespective of the number of words by which the word limit is exceeded). If you falsely claim the word-count of an assessment to be under the limit when it is in fact above the limit is a form of Academic Misconduct (deception) and can lead to even more severe penalties. • Assumptions (if any) must be stated clearly in your answers. Note that there may not be one right answer for some of the questions. Rather, your explanations do need to present your case clearly. The explanations you provide do not have to be long; a concise one is preferred to a rambling one. Late Submission From 1 July 2022, Students enrolled in Session based units with written assessments will have the following late penalty applied. Please see https://students.mq.edu.au/study/assessment-exams/assessments for more information. Unless a Special Consideration request has been submitted and approved, a 5% penalty (of the total possible mark) will be applied each day a written assessment is not submitted, up until the 7th day (including weekends). After the 7th day, a grade of '0' will be awarded even if the assessment is submitted. Submission time for all written assessments is set at 11:55 pm. A 1-hour grace period is provided to students who experience a technical concern. Assessment For all questions in this assignment not only the contents but also the presentation will affect your mark. You will lose marks (and not necessarily only a small portion) if there are problems with the presentation, particularly with clarity. This means that your answers to each question should be a coherent statement and that the https://students.mq.edu.au/study/assessment-exams/assessments spelling and grammar of your submission will be considered in assessing its presentation. For full marks, your answers should all be clear, coherent, and correct, and strictly within the word limits. The standards of marking described in the unit outline L.O. 1-6 will be applied to this assignment as relevant to the assignment topics. The questions will be marked individually, the marks totalled, and a final grade assigned that is no more than indicated by the total marks, and no more than allowed by the standards specified above and in the unit outline. Plagiarism In this assignment, you must be particularly careful to avoid plagiarising your articles or any other sources of information. Do not try to present someone else’s work as your own! The prescribed penalty is an ‘F’ grade for the assignment. When you use a source other than yourself to write a paper, you must cite that source. Sources available on the Internet must also be cited, including the Web address of the site. If you take an original source and modify it to turn in as your own work, you are also guilty of plagiarism. You need to write your own words and phrases that express your own ideas and understanding. You should be well aware of the University's plagiarism policy.