Departamento de Engenharia Electrotécnica A C B Sistemas de
UNIVERSIDADE NOVA DE LISBOA
Sistemas de Telecomunicações
FACULDADE DE CIÊNCIAS E
Mestrado Integrado em Engenharia Electrotécnica e de
6th June, 2007
Departamento de Engenharia Electrotécnica
Secção de Telecomunicações
Duration: one hour and half
1. Explain how works the 1-persistent algorithm CSMA (Carrier Sense Multiple Access). Indicate, also, one advantage
and one disadvantage of this algorithm.
2. What is the disadvantage associated with the lowest addresses in the Binary Countdown protocol. How this
problem can be resolved?
3. In the Ethernet standard the length of the cable is limited. Explain the reasons for this limitation and the implications
in the frame structure.
4. Explain how the Swithed Ethernet works and why it is possible to increase the efficiency of the system. Identify
also the collision domains. Justify your answer.
5. The Standard IEEE 802.16 was drawn to support constant bit rate services, as well as services in real time with
variable rhythm, directly related with a process of dynamic allocation of band. Explain what are the techniques
used for band attribution that support this flexibility and which is the task of the Connection Identifier in the
6. The Bluetooth was designed to allow low requisites in equipment terms (processing, etc.). One of the aspects where
this became evident was the hierarchical structure Master-Slave. Describe the functions attributed to each one.
7. What are the differences between the promiscuous and not promiscuous operation modes. Which are the
implications of each mode in Lan security?
8. Consider the links between Lans shown in the figure. If we admit for initial condition that the addressing tables of
the bridges are empty, specify the content of these after the flooding.