Homework 2 - ECE 2305 Introduction to Communications and...

ECE 2305: Introduction to Communications and Networks D-term 2014
Homework+Lab 2: Due at start of class on 01-Apr.
Please complete all five homework problems, and the twenty lab problems.
Homework Problems
1. Stallings Problem 2.4 from the “Problems” section, not the “Review Questions”.
2. Stallings Problem 2.7.
3. The signal x ( t ) =
1
2
sin( t ) (in volts) undergoes an attenuation of 6 dB. What is the peak-to-
peak voltage of the attenuated signal?
4. Suppose a communication system needs 11 dB SNR for reliable communication. Assume that
the noise floor is -100 dBm, and that a fiber optic cable with an attenuation of 0.12 dB/km
is chosen to connect the transmitter and receiver. What is the required transmit power (in
watts) if there is 40 km of cable between the transmitter and receiver?
5. Stallings Problem 4.3.
1

Lab 2: Application Layer DNS
[adapted from J. Kurose and K.W. Ross]
Before starting this lab, please make sure you have read section 24.2 in the textbook. As
described in the textbook, the Domain Name System (DNS) translates hostnames to IP addresses,
fulfilling a critical role in the Internet infrastructure. In this lab, we’ll take a closer look at the client
side of DNS. Recall that the client’s role in the DNS is relatively simple — a client sends a query
to its local DNS server, and receives a response back. As shown in Figure 24.6 in the textbook,
much can go on behind the scenes, invisible to the DNS clients, as the hierarchical DNS servers
communicate with each other to either recursively or iteratively resolve the client’s DNS query.
From the DNS client’s standpoint, however, the protocol is quite simple — a query is formulated
to the local DNS server and a response is received from that server.
What to hand in: There are twenty questions below which you will encounter as you complete
the lab. For each question, please provide the answer as well as necessary screenshots and packet
printouts to support your answer.
Part I: nslookup 1
In this lab, we’ll make extensive use of the nslookup tool, which is available in most Linux/Unix and
Microsoft platforms today. To run nslookup in Linux/Unix, you just type the nslookup command
on the command line. To run it in Windows, open the Command Prompt and run nslookup on
the command line.
In its most basic operation, nslookup tool allows the host running the tool to query any specified
DNS server for a DNS record. The queried DNS server can be a root DNS server, a top-level-domain
DNS server, an authoritative DNS server, or an intermediate DNS server (see the textbook for
definitions of these terms). To accomplish this task, nslookup sends a DNS query to the specified
DNS server, receives a DNS reply from that same DNS server, and displays the result.