Reference no: EM132218870

Computer Networks

Question-1:

1) Your company has recently been expanded and currently 40 users of your company need simultaneous access to the internet. However company has only one public IP address. The network diagram of the company is presented below.

Consider an example situations when three computers in switch-1 are communicating with remote server at the same time using one public IP

Assume PC-1 under switch-1 is using TCP port (1020) for this example. The public IP is assigned to the border router's (NAT router) serial interface. Explain (for PC-1) how
packet is sent to and received from the destination remote server by PC-1 through the steps:

1. source and destination addressesin outgoing packetsfrom PC-1;

2. how router keeps track of incoming packet from remote server and forwards to correct sources with private IP inside the company host by using router's entries.

Question-2:

In the following network diagram, you want to test the connectivity from PC-A to PC-B which are connected through a router in the middle. As part of this you pinged PC-B's IP address from PC-A. Eventually this causes ICMP at PC-A to create an ICMP echo request packet which is to be delivered to PC-B. List and briefly describe the detail of IP routing and frame forwarding of the processes that deliver the above ICMP echo request packet to PC-B at the ICMP protocol of PC-B.

Address the following points in your explanation:

1) How IP packet is created from ICMP packet at PC-A, i.e., describe the encapsulation of the ICMP payload into an IP packet (indicating values of relevant IP header fields).

2) How IP at PC-A determines whether PC-B is a local or remote destination including any calculations performed.

3) Once the location is determined in (2), a destination MAC address is required to prepare a frame. If PC-B is in remote, which device's MAC address will be used for encapsulation of IP packet into a frame; mention the IP of that devices? Explain why this device.

4) Once the frame is prepared and given to the physical layer of PC-A, list and briefly describe the remaining steps to deliver the frame to next device's IP protocol, including decapsulation, routing decisions, and encapsulation, until the ICMP payload can be processed at PC-B.

Question-3:

In the following network diagram two routers are connected through a WAN link. The IP addresses are mentioned for different interfaces of routers and hosts. You have studied different types of dynamic routing in the lecture and practical classes. You are required to configure the routers in the diagram below using dynamic routing protocols.

1. Identify two dynamic routing protocols that will work for the routers below.

2. Also mention a dynamic routing protocol that will not work.

3. Explain your answer for 1 and 2, why (1) will work and (2) will not work.

4. What will be the network addresses when you configure the dynamic routing in the routers?

5. Compare the routing protocols in the above with respect to their convergence properties.

Question-4:

Two processes at the application layers of sender and receiver are communicating each other. Transport layers of both ends are using a stop-and-wait protocol for flow and error control for this communication. An example flow diagram of data and acknowledgement exchange between the nodes has been presented in the following.

Create a flow diagram of data and acknowledgement exchange using stop-and-wait protocol similar to the above diagram where sender sends three packets. The first two packets arrived in time and acknowledgement also received. However third packet was delayed and resent. The duplicate third packet was received after the acknowledgement of original one.

a) Show all the exchange of data and acknowledgement for above three packets in your diagram.

b) Show all timer activities (starts and so on) at the sender side with clear indication of sending and receiving time (receiving side).

c) Show all data acknowledgment, sender and receiver sliding windows and with appropriate sequence numbers in the windows for both sides and next packet indicator.

d) Explain the fact how the duplicate third packet and acknowledgements were exchanged.

Attachment:- Problem-solving-report.rar