Networking task-Computer Science Assignment help
NET 351 Computer Network Technologies
Written paper #1-Part 1 (individual)
The objective of part-1 the first assignment is to review the material we have covered in chapter 1.
Note: Your answers must be typed (if not, you will get ZERO), and the late assignments policy will be applied .
Due Date: See the date on Blackboard
IMPORTANT: you must follow the instructions below. If not, you will lose marks
· Have all your answers typed
· Be clear in your answers
· Don’t copy-past content from Internet, slides, or any other source (write in your own words)
· Follow the instructions in answering the questions when given (e.g. each step in a new line)
· Include references (e.g. web site links, book chapters, course chapters, …)
Chapter 1: Review of packet-switching and circuit-switching networks (20 Marks)
Consider the network below, where a client is using his laptop to access the intranet web site. There are two main end-to-end communications involved: a) when requesting the IP address of the web server from the DNS server; 2) when accessing the web site.
The standard server port numbers for DNS and HTTP are 53 and 80, respectively. The clients use random port numbers, which we consider in this case are 1030 for DNS and 1050 for HTTP.
Let’s start with the first communication, i.e. getting IP address from the DNS server. Answer the following questions based on the figure.
I. Switch Table (5 Marks)
At the beginning, all the switch tables are empty. Fill S1 switch table after each of the steps below. If the table will not change (i.e. no entry will be added to the table), write down “ NO CHANGE ” in the related row, and add an explanation why. Add more rows if needed.
NOTE: At each step, consider that the previous steps have already been processed (i.e. have already occurred).
a. (a1) The laptop sends an ARP request to get the MAC address of the default gateway. (a2) the gateway sends the reply.
b. (b1) The laptop sends a DNS request to the web server. (b2) the server replies.
c. The laptop sends a message to the desktop.
Step
MAC address
Output interface
time
a1
—–
a2
—–
b1
—–
b2
—–
c
—–
II. Switch functionality (5 Marks)
Following the steps in Q1 (i.e. the previous question), (1) where will the switch S1 send the frame in each step? list the interfaces via which the frame will be sent, separated by a comma. (2) which devices will receive the message? List all the devices in the figure that will receive/hear the message, except S1 and the message source, separated by a comma.
a1. Frame sent via interface: _______________________
List of devices receiving/hearing the message: _____________________
a2. Frame sent via interface: ______________________
List of devices receiving/hearing the message: _____________________
b1. Frame sent via interface: _______________________
List of devices receiving/hearing the message: ________________
b2. Frame sent via interface: ________ _______________
List of devices receiving/hearing the message: ________ ________
c. Frame sent via interface: _______________________
List of devices receiving/hearing the message: ____ _________________
III. Frame content (5 Marks)
Consider the case where the laptop sends a request to the DNS server. Fill-in the frame content in the following cases.
a. when sent by the origin source (the laptop)
src. IP
dst. IP
src-Port
dst-port
src. MAC
dst. MAC
Message Content
————–
b. when sent by the router R2
src. IP
dst. IP
src-Port
dst-port
src. MAC
dst. MAC
Message Content
————–
c. when sent by the router R5
src. IP
dst. IP
src-Port
dst-port
src. MAC
dst. MAC
Message Content
————–
IV. End-2-end communication (5 Marks)
The browser has got the IP address of the web server (using DNS) and sent a request to it (i.e. the second communication). What are the steps for the message to travel from the source to the destination? Assume the whole message can go in one packet then in one frame.
· Below are some of the nodes the message will go through in sequence. For each node, explain what it will do (in sequence). Be precise and brief in your description.
· Use bullets to present each step in a different line (each step should be presented using one -short- sentence). The steps for the laptop & the web server are already given as example.
· Describe all what the node will do (e.g. if it will check something, add something to a table, etc.)
a. Laptop:
i. Checks the destination network and finds out that the destination is outside of its network
ii. Gets the IP address of its default gateway (from local configuration)
iii. Sends the message to the default gateway
iv. The message gets to the switch S1
b. Router R1:
i. …
c. Router R4:
i. ….
d. Web server (i.e. destination):
i. Receives the request
ii. Checks if the requested page exists (we assume this is the case)
iii. Sends the page to the laptop
iv. The response gets the switch S2
A Note on Collaboration?
While students are encouraged to discuss ideas, copying another student’s answers is not allowed and a mark of zero will be assigned to all copied assignments.
What to Submit? You should type your answers in a Word document and submit that document via blackboard and also submit a print-out of the document.
