IT415: Transport Layer

Which of the following is an incorrect pairing of a TCP port number and its use?

All of the above are correct associations between port numbers and their applications.

Your friend always has the greatest tech in her house. She has owned a 4K TV for a while, and Netflix recently started 4K streaming so she checked it out. When she tries to 4K stream, though, the video stutters even though her Internet connection is 100Mbps and a 4K stream is only 15Mbps. The normal HD streams that use 7Mbps are very smooth, and she is actually able to download those more than twice as fast as they play. Since you have taken IT 415, she considers you a networking expert. Why can't she watch 4K streams normally?

Her window size field in TCP is set big enough for HD streams, but too small for 4K streams.

Your friend was charged recently with Criminal Tresspass because he was caught in the Constant Hall computer lab at 1:05 am. The police claim that he was hiding out in there after wrapping the lion statue with tiolet paper. If he can prove that he was using the computer to study for his pre-med class on pathology, the police will drop the charges. In the firewall logs for that day, there is an entry at 1:04 am with the source address and port 10.22.104.70:53059 and destination address and port 208.80.154.225:80. 10.22.104.70 is the IP address of the computer he was seated at, and 208.80.154.225 is the IP address for en.wikipedia.org. Which of the following is true about providing a reasonable doubt against the police claim that he was not using the computer?

It provides doubt because it indicates that someone used a web browser to access wikipedia.org.

What does your computer do after it receives a message via TCP?

It sends a return segment with the ACK bit set to 1 and the Acknowledgement Number set to the Sequence Number of the original segment.

When I play minecraft with my son at home, he connects to my computer at IP address 10.0.1.201. However, when I type "What is my IP address" into a Google search box from my computer, it says my address is 72.218.131.111. Which of the following explains why I am seeing different values?

My computers all share the IP address 72.218.131.111 via NAT.

On my computer right now, three applications are running that are all simultaneously using the Internet: an email client, a web browsing client, and a web server. How does my computer decide which application should receive an incoming TCP segment?

The destination port number on the TCP segment indicates what application should handle the incoming segment.

TCP uses a four-way close. Why so many messages?

The hosts on either end of the connection want to be sure that there will be no more communication before they free up their memory.

The first time I tried BitTorrent, my Verizon-provided home DSL router crashed because of the large number of connections that a BitTorrent client makes. Which of the following describes why a router would crash from too many connections being made?

The router's NAT module had too little memory to handle the number of connections made by my BitTorrent client.

I have been helping my son develop a browser-based application. We update the HTML, Javascript, and CSS files on our home computer, and I want him to be able to test them on his iPod. Before he can access them on his iPod, though, I have to start up a web server program on my computer. Why can't he download these files to the web browser on his iPod without my having to start an extra program?

The web server program opens port 80 on my computer, which is the port that his web browser will use to access the files.

What is the purpose of the source and destination port fields in TCP and UDP?

They identify a specific connection between applications running on different hosts.

Which of the following is false about why a UDP datagram has such a smaller header than a TCP segment?

UDP is unreliable, so there is no reason to check for errors.