COMP8250 Advanced Topics in Computer Networks Assignment 1 Lecturer In-Charge: Dr. Rajan Shankaran Due: Week 7 – Tuesday, 20th of April 2021, 6 pm. Total Marks: 30 Weighting (Value): 20% Objectives This assignment will test your knowledge in the following areas: • IP Addressing - Classless Interdomain Routing (CIDR). • Inter Domain Routing. • Multicast. 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. [5 marks] Is it possible to create meaningful summary route/s (inclusive or exclusive) for the following address block? If yes, then please outline the steps to achieve this goal. If no, then explain why. (50-100 words) 194.1.96.0/24 194.1.97.0/24 194.1.98.0/24 : : 194.1.126.0/24 194.1.127.0/24 194.1.128.0/24 : : 194.1.158.0/24 194.1.159.0/24 2. [5 marks] A service provider usually advertises a single summary route which represents all networks within its jurisdiction to its peers. However, in some situations, the provider may choose to advertise a subset of more specific routes that fall within the summary route in addition to, and along with this summary route. Explain why the provider may follow this approach with the aid of an example. (250-350 words) 3. [8 marks] Consider the routing scenario shown in Figure 1 below. An autonomous system (ASX) is multihomed to two different providers using links via two separate routers. The router R1 in Sydney is using External Border Gateway Protocol (EBGP) to peer with a provider P1 over a T1 circuit. Similarly, the router R2 in Melbourne is using EBGP to peer with another provider P2 over a T3 circuit. ASX enforces a primary/backup policy to elect the MEL T3 link as the primary link. The SYD T1 link will act as a backup and will only be used in case the primary link goes down. Within ASX, the two border routers R1 and R2 communicate with each other using Internal BGP (IBGP). However, they are not physically and directly connected to each other. Consequently, all communication between R1 and R2 must pass through the internal routers R3, R4 and R5. These internal routers are non-BGP routers and exchange routes with all other internal routers as well as the two border routers using an Interior Gateway Protocol (IGP). In the current scenario, R1 and R2 are both receiving full routes from their providers P2 and P2, respectively. These two routers are also injecting a 0/0 default route inside ASX. Internal routers R3, R4, and R5 do not see any external routes and follow the default route towards R1 or R2 using the shortest path provided by the IGP. Identify and explain any one specific routing problem that is likely to surface in this scenario. Recommend any two alternate ways to avoid this problem. (350- 450 Words). Figure 1: Autonomous System ASX 4. (6 marks) Consider a situation in which a Customer Autonomous System (AS) is multihomed to the same provider at two different locations via two separate routers as shown in figure 2 below. The customer can decide which link to use for inbound/outbound traffic from/towards the provider’s network. Also note that C2, C3, C4 and C5 are other customers of this provider and can be directly reached via this provider’s network. The customer deploys Border Gateway Protocol (BGP) to interface with the provider. Using BGP explain how the customer can achieve each of the following goals: • (2 marks) Outbound Traffic: Traffic destined to C2 and C3 must be sent out on the SYD link and traffic to C4 and C5 must use the MEL link. (150-200 Words) • (2 marks) Inbound Traffic: Traffic from C4 and C5 must come into the customer’s AS via MEL router on the MEL link. Inbound traffic from C2 and C3 must come in via SYD router on the SYD link. (150-200 Words) • (2 marks) Default: For all the other routes not known to the customer (routes for destinations which reside outside the provider’s network - on the Internet) a default route must be selected for incoming/outgoing traffic in the primary and backup manner with MEL link acting as the primary link and SYD link acting as a backup link. (150-200 Words) Figure 2: A Customer with Multiple Connections to a Single Provider 5. [6 marks] A company has registered to receive 8 (eight) different channels of a high bandwidth video stream from a server via 8 (eight) different multicast groups. The company has support for multicasting and uses version 1 of Internet Group Management Protocol (IGMP) to manage its active groups. Assume also that the bandwidth available to each remote office in this company’s network has been sized to support two active video streams at a time. What problem do you foresee with the use of IGMPv1 in this scenario? Briefly explain the problem in your answer. (250-350 words) 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. • Assumptions (if any) must be stated clearly in your answers. Remember, 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 No extensions will be granted without an approved application for Special Consideration. There will be a deduction of 10% of the total available marks made from the total awarded mark for each 24 hour period or part thereof that the submission is late. For example, 25 hours late in submission for an assignment worth 10 marks – 20% penalty or 2 marks deducted from the total. No submission will be accepted after solutions have been posted. 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 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 Learning outcomes - L.O. 1 and 2 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. You should be well aware of the University's plagiarism policy.
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