Institute of Technology, Carlow

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No:101a




Institute of Technology, Carlow

School of Science

Department of Computing & Networking

Autumn 2008 Examinations





Course Code:

KCSOFD (CW207)
/ KCCSYD
(CW217)





Course Title:

BSc in Software Development





Course Year:

3





Subject:

Wide
Area Networking







Date:

20/08 AM




Duration:

3 hours





Examiners:

Mr A Kinsella



Mr G Clynch



Mr E Townsend


Special Requirements:




Instructions to Candidate:

1.

Write your Name, Course, Course Year and Class Group on your answer
book.

2.

All questions carry equal marks. Section marks are shown in brackets.

3.


Answer
FIVE

questions.



1)

The Frame Relay Forum recommends choosing Frame Relay for WAN connectivity where the
requirement is for:

Connecting Multiple Sites

High Speed
connectivity

Multi
-
Vendor, Multi
-
Protocol Environment

Reducing

Networking Costs

Interactive or Bursty Traffic

Widely Separated Locations


Explain and comment on these recommendations.

(20)

2)

Explain the purpose and
operation of the Committed Information Rate (CIR) in a Frame Relay
Virtual Circuit (VC).

(10)


A group of fashion shops has eight branches around the country, and a distribution warehouse at
the Dublin head office. They currently operate a WAN with each br
anch connected to the head
office by 64kb/s leased lines in a star network. They are considering replacing the leased lines
with frame relay circuits, also in a star configuration.


Explain why there would be a saving in changing to Frame Relay.

(4)


What
capacity would you recommend for the access lines between head office and the FR
network?

(3)


What CIRs would you recommend for the virtual circuits between one of the branches and head
office?

(3)

3)

Firewalls for personal computers are often based on p
acket filtering. Explain how packet
filtering operates.

(8)


What are the limitations of packet filtering?

(4)


A home PC user connecting to the internet over DSL wants to set up packet filtering. Outline a
set of filtering rules that you would consider s
uitable.

(8)

4)

Virtual Private Networks built on the internet are often recommended as an alternative to a
WAN built using Frame Relay. Outline the advantages and disadvantages of each approach for
building wide
-
area networks for small and medium
-
sized bu
sinesses.

(20)

5)

Virtual Private Networks through the internet often use the IPSec suite of protocols. IPSec has
three principal architectures or configurations. Describe these architectures, and indicate the
situations where they might be used.

(12)


In
IPSec a Security Association (SA) is “the
relationship between two or more entities that
describes how the entities will use security services to communicate securely”.

List the typical
contents of an SA database.

(8)

6)

Describe the purpose and operation
of

Network Address Translation, and indicate how it
contributes to conservation of address space and to network security.

(16)


Outline the steps necessary to set up NAT on a Cisco router.

(4)

7)

In the ISDN S
-
bus:


(a) describe the encoding scheme used f
or transmitting bits;

(4)


(b) what is the purpose of the E bits in the NT to TE frame?

(4)


(c) indicate the sequence of events when multiple TEs start to transmit on the D
-
channel at the
same time;

(6)


(d) what is the purpose of the threshold, and why w
ill it not be exceeded during the data portion
of a D
-
channel transmission?

(6)