计算机网络代写 | COMS3200 – Assignment 2

本次澳洲代写主要为计算机网络相关的assignment

Introduction
This assignment introduces the use of Network Layer and Link Layer (from OSI Models) as
well as socket programming (simulation) on each of these devices: adapters, switches and
routers. After finishing the assignment, you will understand how data is sent throughout the
internet.

This assignment contains three parts. For Part A and B, you will need to submit your answers
through Blackboard Quiz. for Part C, you will submit your code via COMS3200 subversion
(SVN). All submitted works are marked automatically. It is strongly recommended that you
read this spec carefully before you start working, as to avoiding any mistakes.

This assignment is to be your individual work. Using answers (or code) that you did not
calculate (or write) is against course rules and may lead to a misconduct charge.
Part A (21 marks)
Answer each of the following questions in the associated quiz on Blackboard, following the
specified instructions. All answers will be automatically marked.

You have established a new server for COMS3200 Inc, called RUSHBSvr (in assignment 1).
It works perfectly and has grown so much in users recently that the company must now
upgrade their network.

You, a supervisor of this project, has assigned the task of designing two (2) new networks, a
branch in Sydney and a local system for working at home. You also moved the File Server to
“somewhere” on the Internet to serve as a centralise data centre for your company. Then, you
ended up with the network map on next page.

To minimise spending for this system, you set up for only one DNS Server (D2) and one
DCHP Server (D1). You claimed that the system will run smoothly without paying more for
building extra servers, and it works.

You are now required to explain to your colleagues how your system works with some
scenarios given below. You can use these assumptions to support your answers:
1. The broadcast MAC address of all the LANs is FF:FF:FF:FF:FF:FF.
2. All forwarding tables in the switches and routers are up to date.
3. All valid protocols are HTTP, FTP, SSH, DNS, DHCP, UDP, TCP, ICMP, SNMP,
ARP, OSPF, and BGP. If there are 2 protocols used at the same time (e.g., SSH and
TCP), choose the lowest level (highest layer) only (e.g., SSH).
4. D2 is a DNS Server, and D1 is a DHCP Server.

You will have to fill out the table and answer some questions in Blackboard. Each student’s
questions will have different values (that is replaced by XXX…). Your question values will
be shown in the quiz. Please be careful to double-check before submitting your work to
Blackboard, as you can submit only once.

Task: Answer the questions below on Blackboard.

Question 1: Host A just joined the network and currently does not have an IP address. Please
complete the following table describing the four packets that will be transmitted through the

network upon this event (in the order they were sent), assuming that all requests succeed,
and Host A ends up with IP address XXX.XXX.XXX.XXX.

Protocol Opcode
Source
MAC address
Destination
MAC address
Source (or sender)
IPv4 address
Destination (or
target) IPv4 address

Question 2: After ending up with the IP address above, Host A wants to send a standard
DNS query to the DNS Server. Host A has already gotten the IPv4 addresses of the DNS
Server and its gateway router from the DHCP Server. Router 1’s ARP table contains all
hosts’ IP and MAC addresses in the network, and all other ARP tables are empty. Complete
the following table describing the first four packets transmitted through the network upon
this event, and no additional ongoing communications.

Protocol Opcode
Source
MAC address
Destination
MAC address
Source (or sender)
IPv4 address
Destination (or
target) IPv4 address

Question 3: Host A now wants to establish a HTTP connection with the Server S (see the
figure 1 above). You may assume that Host A knows S’s IP address and that all ARP tables
contain all required information to transmit any packet. Complete the following table
describing the packets that are sent to transmit Host A’s request to initialise the connection,
assuming the request is being sent from TCP port XXXX and the following available port
number in Router 1’s NAT table is XXXX. Give the TCP flags as an 8-bit binary number