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Cork Institute of Technology
Bachelor of Science (Honours) in Software Development and
Computer Networking - Stage 3
(KDNET_8_Y3)
March 2008
Internetworking and Security
(Time: 3 Hours)
Answer any FOUR questions All questions carry equal marks
Examiners: Ms.Olivia Brickley Mr. J. Buckley Mr. A. Kinsella
Q.1 a. Many public carriers are deploying ATM in their core networks as an infrastructure for carrying voice, video and data traffic. Describe how ATM facilitates these services simultaneously, addressing the following:
- Cell switching
- Traffic contract
- Traffic control techniques (10 marks)
b. An ATM network consists of a set of ATM switches interconnected by point-to- point ATM links or interfaces. Illustrate a typical ATM network, identifying the four types of ATM interface. (5 marks) Illustrate and explain how the interface type influences the ATM cell header? (5 marks)
c. Compare and contrast PVCs and SVCs. A soft PVC provides the flexibility of SVCs and the stability of PVCs. Explain (5 marks)
Q2. a. Explain, with the aid of a diagram, the Q931 call setup procedure for ISDN BRI. (5 marks)
b. What is enbloc sending? How does this differ from overlap sending during the Q931 call setup procedure? (5 marks)
c. A Frame Relay PVC has an agreed data rate, the committed information rate. Identify the relationship between CIR and committed burst size, excess burst size, and explain how frames are transmitted on a PVC taking into account these parameters. (8 marks)
d. What is the purpose of the FECN and BECN bits in a LAPF frame? How is the DE bit used? (6 marks) In Frame relay, multiple connections are configured over one physical connection. How is this possible? (1 mark)
Q3. a. What is a security policy and what are its benefits? (2 marks)
b. The three security policy components are identity, integrity and active audit. Describe the aspects of network security addressed in each, identifying possible solutions. (9 marks) c. Describe the AH and ESP protocols defined in IPSec, outlining the services they provide. Using diagrams, explain the difference between tunnel and transport mode. (8 marks)
d. What is a Denial of Service (DoS) attack? Identify four types of DoS attack, outlining how these could be thwarted. (6 marks)
Q4. a. Explain the function of a DIFS, SIFS and PIFS in 802.11, giving possible values for these parameters. (6 marks)
b. DCF uses CSMA/CA to allow multiple independent stations to share the wireless channel. Explain its operation. (8 marks)
c. Given the network address 192.159.145.0/26 and assuming the use of subnet#0, use VLSM to design an efficient subnetting scheme to allow for: i. 2 subnets with up to 30 hosts ii. One subnet with up to 10 hosts iii. One subnet with up to 6 hosts iv. 2 subnets with 2 hosts (6 marks)
d. What is IP multicast? List its advantages and drawbacks. (5 marks)
