How to Stream Video over a Network or the Internet - Excercises

Pre-reading excercises

1. What do you know about the history of TV and radio?
2. Do you know the origins of the Internet?
3. Which kind of media do you find important and valuable?
4. Can you explain how connections are made between ‘users’ of radio, TV and the Internet?

Comprehension questions

1. Can you point out the differences between TV, radio and the Internet in terms of communication?
   • only broadcast communication (TV, Radio)
   • each of nodes can be both sender and recipient (the Internet)
   • information can be reviewed any time (the Internet)
2. Can you explain the process of establishing connections by telephone and on the Internet?
   • Telephone calls use many of the same wires used by the Internet. The telephone central office maintains devices called switches (automated versions of the classic telephone switchboard) that are used to connect the call to the next location. Telephone calls create a two-way circuit all the way from caller to receiver. The message “All circuits are busy”—usually heard only during disasters or radio call-in concert ticket giveaways—means the switch does not have any more slots in which to carry this call. The main barriers to telephone transmission are found at the beginning of the call— if there are not enough circuits to place the call. While a call is in progress, the entire route between the caller and recipient is reserved for their use only, even if there is silence and no one is talking. Telephones use what is called a circuit-switched connection.
   • What is the idea of “packet communication”?
     • The path from a website to a web browser is different than these other systems. Conceptually, it is similar to the telephone conversation: It’s a two way conversation in which the browser asks for a document and the server sends it. Unlike the telephone call, however, there is no reserved circuit. Data, in the form of requests and responses, are organized into chunks called packets and sent between the requesting web browser and the web server. In between the requester and the server are a series of routers. These machines route traffic between different smaller networks. Each time a packet crosses the boundary from one ISP (Internet Service Provider) to another or from one kind of network to another, it goes through a router. The packets “hop” from router to router like a bucket brigade. This type of data transmission is called packet switching, instead of circuit switching. Internet packet switching has some attributes that make it reliable and unreliable at the same time.
   • Explain, in general terms, how routing works.
     • Routing is the process of selecting paths in a network along which to send data or physical traffic, usually directs forwarding on the basis of routing tables which maintain a record of the routes to various network destinations. Thus constructing routing tables, which are held in the routers’ memory, becomes very important for efficient routing.
   • Give 5 reasons for packet delays.
     • a router is too busy and can’t keep up with traffic
     • a particular link between sender and receiver becomes saturated
     • a link goes down, causing traffic to be rerouted to a different link
     • one or more routers in between can’t think fast enough
     • a firewall looks at all the packets for viruses
     • delay is added due to the use of older technology, such as modems
     • other downloads on a pipe cause it to delay
     • packets are lost, resulting in resends, and other packets get bunched up behind
     them

Further exercises

1. Pre-prepare a list of features. Classify them into four groups: Internet, telephone, radio, television. The features could be taken from the text and/or worked out by students working in groups.

TV	Radio	Phone	Internet
broadcast	broadcast	direct	broadcast/direct
real-time	real-time	real-time	real-time/ prepared documents
		circuit-switched	packet-based
			routing
			streaming transmission

Possible topics for discussion

1. What do you think is the main cause of interruptions in internet transmission?
2. Why is audio data not transferred in the same way as telephone calls although both the Internet and telephone calls use the same wires?
   • Fundamentally, the Internet is far better suited for sending web pages than real-time media because web pages are far smaller and far less sensitive to delays. There is not much difference between a one- and two-second delay in getting a web page, but a one-second pause in real-time video is unacceptable.
3. How do you use the Internet? (Which Internet services do you use most often?)
4. Do you use the Internet for making phone calls? Why/why not? What are advantages and disadvantages?
   • low price
   • video transmission is possible
   • there is no difference (in costs) between long and short distance communication
   • the phone call quality depends on bandwidth of the connection
   • requires computer connected to the Internet