CMPS 396 Final, Fall 2004

AW eICAN UNIV ENSIT LIBRARY oF BEIROT Faculty of Arts & Sciences Department of Computer Sciences CMPS 396B Fall 2004-2005 Monday, January 24, 2005 Final Exam Name: Student Id: Signature: Duration: 100 minutes instructions * There are 6 problems and 12 pages. Make sure you have all of them. © The exam is closed book, closed notes, closed calculators, and closed neighbors. « Answer questions in the space provided. * The questions are not sorted by difficulty. Scan the whole exam before you start working. ¢ Your handwriting should be readable so it can be graded. Include all work or justification for partial credit. Problem } 18 Problem 2 19 Problem 3 13 Problem 4 13 Problem 5 25 Problem 6 12 Total 100 | Final Exam (2005-01-24) initials: Problem 1 [18 points] 1. The figure below shows the path from host | to host 3. Assume that a flow will be generated from host | to host 3. Show how the RSVP protocol can be used in order to guarantee that all routers on the path from host 1 to host 3 reserve the required resources for this flow. [5 points] er Bandwidth reserved for source 1 2. Suppose that Router E in the figure above loses its reservation state, but remains running. 2.1. What will happen to the existing reserved flow if the router handles reserved and non-reserved flows via a single FIFO queue? [2 points] 2.2. What might happen to the existing reserved flows if the router used weighted fair queuing to segregate reserved and non-reserved traffic? [3 points] CMPS 396B 2 Final Exam (2005-01-24) Initials: The network in the figure below uses RSVP with multicast trees for host 1 and host 2. Suppose that host 3 requests a channel of bandwidth 2 MB/sec for a flow from host | and another channel of bandwidth 1 MB/sec for a flow from host 2. At the same time host 4 requests a channel of bandwidth 2 MB/sec for a flow from host 1 and host 5 requests a channel of bandwidth 1 MB/sec for a flow from host 2. How much total bandwidth will be reserved for these requests at routers A, B, C, E, H, J, K, and L? [8 points] 4] \ 4 Receivers (a) CMPS 396B Final Exam (2005-01-24) Initials: Problem 2 [19 points] Answer the following questions. Make your answer as short as possible as you will not get credit for long answers. 1. Consider a cellular system with the following characteristics. Frequency bands are 815 to 845 MHz for mobile unit transmission and 870 to 900 MHz for base station transmission. A duplex circuit consists of one 30 KHz channei in each direction. The system 1s distinguished by a reuse factor of 4 cells. Suppose that the cluster of cells is duplicated 20 times. Find the number of simultaneous calls that can be supported by the system.[4 points] 2. What do we mean by saying that GSM uses both FOMA and TDMA techniques? Explain [2 points] 3. Consider the figure below then answer the following questions: HLR MSC/VLRI1 Border between two location areas CMPS 396B 4 Final Exam (2005-01-24) Initials: 3.1 What ts the main task of the followmg components? [6 points] ] | i | 1 3.2 Describe the sequence of event messages needed when the mobile node AN initiates a call to the mobile node M (call delivery procedure). [4 points} 3.3 In cellular networks, when and why location update procedure is performed? [3 points] CMPS 396B Final Exam (2005-01-24) initials: Problem 3 [13 points] Answer the following questions, Make your answer as short as possible. 1. What a handoff is? [3 points] 2. How the handoff decision is made? [2 points] 3. What would happen in case of handoff failure? [1 points] 4. What is the inter-BSC handoff and who controls this handoff? [2 points] 5. What is the main difference between soft handoff and hard handoff? [3 points] 6. Handoff can also be performed due to load balancing. What does it mean? [2 points] CMPS 396B 6 Final Exam (2005-01-24) Initials: Problem 4 [13 points] 1. Describe the "exposed terminal problem". You can use the figure below to illustrate your answer. [4 points} ¥ 4 2, Explain why Ethernet-type collision detection algorithm won't work in a mobile ad hoc network. [3 points} CMPS 396B 7 Final Exam (2005-01-24) Initials: 3. How IEEE 802.11 resolves the hidden terminal problem? You can use the figure below to illustrate your answer. [4 points] 4. In IEEE 802.11 what is the purpose of using Net Allocation Vector (NAV)? [2 points] CMPS 396B Fina] Exam (2005-01-24) Initials: Problem 5 [25 points] Answer the following questions. Make your answer as short as possible as you will not get credit for long answers. 1. Assume that Net 4 is the home network of a mobile node 4, Assume also that M moves to Net B a. What is the name of the entity that manages M in Net A? [1 point] b. What is the name of the entity that manages Min Net B? [1 point] c, What steps are taken when M moves from Net A to Net B? [2 points] 9 Assume that a node CN that helongs to Net C wants to communicate with node M. a. Describe the triangle routing when CN and M communicate. (If tunneling is used, specify where) [3 points] b. Why triangle routing is considered a problem? [2 points} CMPS 396B 9 Final Exam (2005-01-24) Initials: 3. Route optimization mechanism was proposed to solve the problem caused by the triangle routing. Describe the data flow between CN and M when route optimization is used. (If tunneling is used, specify where) [4 points] 4. Assuming route optimization is used, what would happen if Af moves from Net B to Net C while receiving packets from the CN?. [4 points] 5. What ts reverse tunneling? (describe the data flow between M and CN when both reverse tunneling and route optimization are used assuming that M is roaming in Net B and CN belongs to Net C) [3 points] CMPS 396B