Computer Networks Answers

use of Wireshark, a packet sniffer, to briefly examine the 802.11

Use the “wlan_packet_capture” file to answer the following questions. After opening the file, enter the string wlan in the filter field and then apply the filter. Find the first probe request message in the trace and use that to answer the following questions.

a. What are the MAC address fields in the 802.11 frame?

b. Which MAC address in this frame corresponds to the wireless host (give the hexadecimal representation of the MAC address for the host)?

i. To the access point?

ii. To the first-hop router?

use of Wireshark, a packet sniffer, to briefly examine the ethernet

Use the “ethernet_packet_capture” file to answer the following questions. After opening the file, find the first DHCP message in the trace and use that to answer the following questions

a. What is the 48-bit Ethernet source address of the frame?

b. What is the 48-bit destination address of the Ethernet frame?

c. Is this destination Ethernet address associated with the destination IP address?

d. Give the hexadecimal value of the two-byte Frame type field.

e. What upper layer protocol does this correspond to?

use of Wireshark, a packet sniffer, to briefly examine the IP

Using the “tcp_packet_capture” file and the first HTTP GET message, answer the following questions:

a. Within the IP packet header, what is the value in hex of the upper layer protocol field? b. Is the checksum Validation enabled for this datagram?

c. Explain your answer for b

d. Has this IP datagram been fragmented?

e. Explain how you determined whether or not this datagram has been fragmented.

f. State one major disadvantage of IP fragmentation

TCP

Open the “tcp_packet_capture” trace file and find the first HTTP GET message from the trace with

packet length equal to 517 bytes and sequence number 2398008939. Hint: To limit yourself to TCP

messages, enter the string tcp in the filter field and then apply the filter. Answer the following

questions:

a. What are the IP address and TCP port number used by the client computer to retrieve

the file? [1]

b. What is the next sequence number of the TCP SYN segment? (Give the relative sequence

number). [2]

c. What is the flag field set to? [1]

d. Based on the value of the fields what flags are set in this TCP message?

UDP

Open the “udp_packet_capture” trace file and select the first DNS query packet from the trace. Hint: To limit yourself to DNS packets, enter the string DNS in the filter field and then apply the filter.

a. By consulting the displayed information in Wireshark’s packet content field for this packet, determine the length in bytes of each of the UDP header fields.

b. By examining the UDP header explain whether or not UDP can provide reliability.

c. What is the maximum number of bytes that can be included in a UDP payload?

d. What is the protocol number (in hex) for UDP?

e. What is the source port number for the query?

f. What is the destination port number for the response? 

HTTP

Open the “tcp_packet_capture” file and select the HTTP get message from the trace with Sequence Number: 3559289491. Hint: To limit yourself to http packets, enter the string http in the filter field and then apply the filter. To get the actual sequence number instead of the relative sequence number, right click go to protocol preferences and make sure the relative sequence numbers option is not selected.

a. What is the IP address of the machine that generated the HTTP request? [1]

b. What is the IP address of the server that will handle this request? [1]

c. Does the client request a persistent connection? [1]

d. How do you know? [1]

e. What operating system was this request sent from? [1]  

Horizontal cabling in a structured cabling system connects the telecommunications room to the work areas on the buildings. This method of cabling is typically installed when the building is being initially assembled. Horizontal cabling is normally an unshielded twisted-pair cable or UTP. Some Special standards or principles regulate how long the cables should be installed in the building and where the horizontal cabling should be mounted to prevent electromagnetic interference. This kind of cabling is like “last mile” cabling before reaching a computer in a work area. Various components such as mechanical terminations, jumpers and patch cords located in the Telecommunication room are also involved. With the aid of a diagram, illustrate how horizontal cabling systems get connected from the telecommunications room to the work areas in the buildings. In your illustration, ensure you indicate various details that need to be involved, such as meters, etc.

Design an implementable routing and bridging solution for the network. Your solution must address the following design and operation aspect of all routers.

4.1. 1 Functionality of the network layer. 

4.1.2 Design and implementation of data plane.

Design an implementable routing and bridging solution for the network. Your solution must address the following design and operation aspect of all routers.

4.1. 1 Functionality of the network layer.

4.1.2 Design and implementation of data plane.

4.1.3 Design and implementation of control plane.

4.1.4 Interconnection of networks using bridging systems.

Q.4.2 Draw a detail diagram showing the design and implementation of Q.4.1 above.