Question

A user calls and says that she is able to work on all applications except Internet explorer web browsing. When she tries to access a website, she receives this error: "Page cannot be displayed—cannot find server or DNS error."

What can be the cause of the problem and on which layers can the problem exist? Provide possible solutions to each cause of the problem

List the various troubleshooting steps that Alex should conduct to resolve the issue, assuming he approaches the most common error first and the least common error last.

Another user who manages a tremendous amount of data on a daily basis has encountered a network problem. He has an idea that the problem is related to usage of TCP and UDP.

How is data transmitted through the different layers of the TCP and UDP? Describe the specific layers in which data is transmitted using TCP and UDP.

Do you agree with this statement that "TCP is always more reliable than UDP?" Why or why not? List and compare the security considerations of both the data transfer techniques.

Can TCP and UDP be used interchangeably? Which factors will influence their interchangeable use? Describe the difference of TCP and UDP. Also, list and compare the factors of transmission with respect to the data transmission technique used by them.

Answer 1

TCP/IP is a protocol used by devices to communicate over the Internet and local networks. It is named two of it’s protocols as the Transmission Control Protocol (TCP) and the Internet Protocol (IP) whereas User datagram protocol is an open systems interconnection (OSI) transport layer protocol for client- server network applications.

TCP divides the data(from the application layer) into proper sized chunks and then passes these chunks onto the network. It acknowledges received packets, waits for the acknowledgments of the packets it sent and sets timeout to resend the packets if acknowledgements are not received in time. When you click a link, or do anything else, your web browser sends TCP packets to the server and the server sends TCP packets back.

UDP stands for User Datagram Protocol — a datagram is the same thing as a packet of information. The UDP protocol works similarly to TCP, but it throws all the error-checking. When using UDP, packets are just sent to the recipient. The sender will not wait to make sure the recipient received the packet — it will just continue sending the next packets. UDP is used when speed is desirable and error correction is not necessary.

TCP is more reliable than UDP, and has acknowledgement segments. Also has guarantee that the order of data receiving same as on sending. TCP is reliable it guarantees the delivery packets uncorrupted, Connection Oriented in a way that data travel both ways, guarantees that packets arrive in order unlike UDP, it does not guarantee delivery of packets, Connectionless, and packets can be delivered out of order.

TCP for sending information that is sent infrequently, but should be guaranteed to arrive reliably.

If you just need to send some reliable data and do not want to worry about retransmission and implementing a reliable protocol, and you know the rate will be low, then there wont be any problems with using both TCP and UDP.

The difference between TCP and UDP is:

TCP has a connection establishment phase with the SYN,SYN-ACK and ACK request whereas UDP has no connection establishment phase or ACKs which means the sender has no way of knowing if the receiver has listened to anything that the sender has been sending.  

1. TCP can establishes a Connection and UDP cannot.
2. TCP provides a stream of unlimited length, UDP sends
small packets.
3.TCP gurantees that as long as you have a connection data
sent will arrive at the destination, UDP provides not
guarantee delivery.