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Matric No: _________________
NAPIER UNIVERSITY
SCHOOL OF COMPUTING
NETWORK ACCESSIBILITY
CSN11104
Academic session: 2008/9 Diet: June
Exam duration: 2 Hours Reading time: None
(excluding reading time) Total exam time: 2 Hours
Please read full instructions before commencing writing
Exam paper information Total number of pages: 4 Number of
questions: 5 Answer any three questions from the five questions
shown. Put your answer into the script provided. Start each
question on a new page.
Special instructions Closed Book Exam.
Special items None
Examiner(s): Dr Gordon Russell , Mr Robert Ludwiniak
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1. MPLSa. Discuss the strengths and weaknesses of MPLS in
comparison to
more traditional backbone implementations
The idea behind MPLS was to replace routing done in software
with switching done in
hardware and offer higher speeds. MPLS is an improved method for
forwardingpackets it is not intended at replacing conventional IP
routing but to work alongside.MPLS is considered to be a layer 2.5
technology. MPLS is becoming widely adoptedas the preferred
backbone technology for service providers (SP) as it is
highlyscalable. Both ATM and MPLS support tunneling of connections
inside connections.MPLS uses label stacking to accomplish this
while ATM uses virtual paths .MPLSallows great flexibility in
network design as ATM is complex to set up.
Marks [5]b.
i. Using an example network, explain how MPLS sets up its
controlplane. Include the relationships between FIB, LFIB, and CEF,
andthe use of LDP.
Marks [10]ii. Discuss the advantages of using BGP within the
service
provided cloud when managing MPLS.
MPLS is used for forwarding packets over the backbone, and BGP
is used for distributingroutes over the backbone. The primary goal
that this method is used for is to support theoutgoing of IP
backbone services BGP/MPLS VPNs offer an alternative for secure
site-to-sitecommunication. BGP/MPLS VPNs have built within them
several mechanisms to providesecurity. Address space separation may
be a concern, especially considering the possibility of overlapping
address space. However, the use of VPN-IPv4 addresses allows for
independentVPNs to remain separate despite any addressing
overlap
Marks [5]c. Evaluate the use of MPLS VPN as a replacement for
normal VPN
over an MPLS network.
MPLS VPN combines enhanced BGP signaling, MPLS-based VPNs
enforce trafficseparation between customers by assigning a unique
VRF to each customers VPN.Compared to other types of VPN such as
IPSec VPN MPLS is more cost efficient andcan provide more services
to customers.
Marks [5]Total Marks [25]
2. Device Security
a. Discuss the progressive stages traditionally considered to be
involved inhacking a network.
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Marks [7]b.
i. Discuss using examples how the recommendations of RFC
2827could be used to police traffic from Martian packets entering
anetwork, and comment on their usefulness.
Marks [4]
ii. Describe the four stages considered good practice when
dealingwith a worm attack.
Marks [4]
iii. Discuss good practice networking rules for outgoing
networkconnections, commenting on why they are considered
important.
Marks [4]
c. Describe a common Distributed Denial of Service attack and
evaluate apossible Cisco-related approach to mitigating its effect.
Include syntaxexamples where appropriate.
Marks [6]Total Marks [25]
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3. Firewall Technologya. Discuss the advantages of using a
Layered Defense Strategy when
designing a firewall architecture.Marks [6]
b.i. Explain the function, advantages, and disadvantages of
Stateful
Firewall Systems.Marks [6]
ii. Produce an annotated Cisco IOS configuration to secure
thenetwork 20.5.5.0/24 using stateful rules, so that all
outgoingpackets are permitted, as well as allowing related
incomingpackets plus packets destined to the http server at
20.5.5.6.
Marks [7]c. Consider the difference between inband and
out-of-band control
channels for managing routers and switches, and discuss the
strengthsand weaknesses of both approaches.
Marks [6]Total Marks [25]
4. IPSECa. Describe the three main protocols specified by
IPSec.
Marks [6]b. Evaluate the main encryption algorithms used in
securing VPN
connections. As part of the answer, please provide suitable
examples of encryption techniques and compare their advantages
anddisadvantages.
Marks [12]c. Analyse possible failover solutions used in IPSec
VPN deployment. As
part of your answer, please discuss methods used to
achieveredundancy.
Marks [7]Total Marks [25]
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5. IDS and IPSa. Discuss six potential router service categories
that are considered
security threats.Marks [6]
b.i. Discuss and evaluate the strengths and weaknesses of IDS
and
IPS systems. Your answer should include network-based
andhost-based IDS and IPS.
Marks [7]ii. Describe the four categories of IDS and IPS
signatures?
Marks [6]c. IDS and IPS systems can be categorised based on
their approach to
identify malicious traffic. Discuss all three categoriesMarks
[6]
Total Marks [25]
.
END OF PAPER
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