UNIVERSITY EXAMINATIONS: 2016/2017
EXAMINATION FOR THE DEGREE OF MASTER OF SCIENCE IN
DATA COMMUNICATIONS
MDC 6101 COMPUTER NETWORKS
DATE: AUGUST, 2017 TIME: 2 HOURS
INSTRUCTIONS: Answer Question One & ANY OTHER TWO questions.
QUESTION ONE [20 MARKS]
a) More and more companies are finding it beneficial to have teleworkers. With advances in
broadband and wireless technologies, working away from the office no longer presents
the challenges it did in the past.
(i) Describe the benefits of the teleworker solution. 2Marks
(ii) Teleworkers typically use diverse applications (for example, e-mail, web-based
applications, mission-critical applications, real-time collaboration, voice, video, and
videoconferencing) that require a high-bandwidth connection. Describe any three
infrastructure services options that are available. 3 Marks
b) (i) On a corporate network, hosts on the same VLAN can communicate with each
other, but they are unable to communicate with hosts on different VLANs. What is
needed to allow communication between the VLANs? Explain. 2 Marks
(ii) While troubleshooting a connectivity issue from a PC you obtain the following
information:
Local PC IP address: 10.0.0.35/24
Default Gateway: 10.0.0.1
Remote Sever: 10.5.75.250/24
You then conduct the following tests from the local PC:
Ping 127.0.0.1 – Successful
Ping 10.0.0.35 – Successful
Ping 10.0.0.1 – Unsuccessful
Ping 10.5.75.250 – Unsuccessful
What is the underlying cause of this problem? 2 Marks
c) State four major differences between WLANs and wired Ethernet. 4 Marks
d) Describe
(i) four limitations of layer 1 of the OSI reference model. 2 Marks
(ii) how layer 2 addresses each of the above limitations 2 Marks
e) (i) A receiving host has failed to receive all of the segments that it should
acknowledge. What can the host do to improve the reliability of this communication
session? 1 Mark
(ii) What kind of cable should be used to establish a trunked line between two
Catalyst switches? 1 Mark
(iii) Assuming you build networks to exact specifications, what is the recommended
maximum length a 10BaseT cable can be before it has to be segmented or repeated?
1 Mark
QUESTION TWO [15 MARKS]
a) (i) Two buildings on the Ruaraka campus of KCA University must be connected to
use Ethernet with a bandwidth of at least 100 Mbps. Our main concern is about possible
problems from voltage potential differences between the two buildings. Explain which
media type should be used for the connection 2 Marks
(ii) You are installing IP phones in a new office. The phones and office computers
connect to the same device. To ensure maximum throughout for the phone data sessions,
the company needs to make sure that the phone traffic is on a different network from that
of the office computer data traffic. What is the best network device to which to directly
connect the phones and computers and what technology should be implemented on this
device? 2 Marks
b) What factors would you take into account when choosing between a layer 3 switch and a
router? 3 Marks
c) Describe any four major benefits associated with hierarchical network designs.
4 Marks
d) Discuss the following in relation to hierarchical network designs:
(i) Performance 1 Mark
(ii) Security 1 Mark
(iii) Network Diameter 1 Mark
(iv) Bandwidth aggregation 1 Mark
QUESTION THREE [15 MARKS]
a) The transition from IPv4 does not require upgrades on all nodes at the same time. Many
transition mechanisms enable smooth integration of IPv4 and IPv6. Other mechanisms
that allow IPv4 nodes to communicate with IPv6 nodes are available. Different situations
demand different strategies. Discuss the dual stacking and tunneling techniques to
transition from IPv4 to IPv6. 4 Marks
b) Explain the following switch operations:
(i) Learning 1 Marks
(ii) Flooding 1 Marks
(iii) Selective forwarding 1 Mark
(iv) Filtering 1 Mark
c) Explain the three major characteristics of WANs. 3 Marks
d) Explain any four factors to consider when selecting a Network Operating System (NOS).
4 Marks
QUESTION FOUR [15 MARKS]
a) Your company has a class C network address of 200.10.57.0. You want to subdivide your
physical network into 5 subnets (A, B, C, D and E). You will need at least 20 hosts per
subnet. Based on the given information, fill in the table below. 10 Marks
Discuss the benefits and drawbacks of using Network Address Translation (NAT).
5 Marks
