Chapter 3: Networks Flashcards
What is the internet?
The Internet is the totality of all wires, fibers, switches, routers, satellite links, and other hardware for transporting information between addressed computers.
It is a “network of [wide area] networks [WANs]” using point-to-point asynchronous communication.
What is synchronous communciation?
Synchronous communication requires that both the sender and the receiver are active at the same time (e.g. telephone call)
What is asynchronous communication?
In asynchronous communication, the sending and receiving occur at different times (e.g. postcards, text messages)
Describe broadcast, multicast, and point-to-point communication - give an example of each
Broadcast communication involves a single sender and many receivers. Radio and television are examples of broadcast communication. The term multicast is used when there are many receivers, but the intended recipients are not the whole population. Magazines, often covering specialized topics, are an example of multicast communication. The opposite of broadcasting and multicasting is point-to-point communication. Telephone communication and text messages are point-to-point because there is one specific sender and one specific receiver. The property of broadcast versus point-to-point communication is separate from the property of synchronous versus asynchronous communication.
What is client/server interaction?
It is the communication protocol used in the Internet for most communication between computers (e.g. web server: As a result of your client request (clicking on the web link), the server sends the page back over the Internet, fulfilling the request. That completes the operation started when you clicked on the link, and it ends that client/server relationship.) It is a very brief relationship, lasting from the moment the request is sent to the moment the service is received. There is a client-to-server transmission for requests and a server-to-client transmission for replies.
What are “cookies”?
Cookies are small files stored on the client computer by the server, and returned to the server with each page request. The file contains enough data from the server, such as a unique identifier, that it can connect you to earlier interactions.
What are URL parameters?
URL Parameters are information added by a client to a URL when it connects to the server. You notice this information, for example, when you’re buying airline tickets: flybynite.com/buytix.php?trip=round&leg1=ORDtoLAX&dep=041114&ret= … It’s the information following the question mark.
What are the 2 ways websites use to give the illusion of a continuous connection?
Cookies and URL parameters
What is an IP packet?
A computer communicates with another computer by sending an IP packet to its IP address. The packet is like a letter: It has the IP address of the computer being contacted and the return IP address; it also has a sequence number (more about that later), a few bits used for technical purposes, and a payload. The payload is what’s being sent—it may be one byte, or thousands.
What is a “hop”?
It is when a router transfers an IP packet to another router to get it towards its destination
How do computers send information to one another?
Using TCP/IP (Transmission Control Protocol/Internet Protocol) - independent packets of information
Describe internet vs ethernet communication?
Internet = asynchronous point-to-point communication = TCP/IP protocol. Ethernet = broadcast medium that can be used for point-to-point communication = “multipoint data communication channel with collision detection.” = party protocol. The difference is that with the Internet, multiple communications can take place at once over different wires, but with the Ethernet, only one communication can take place at a time because there is just one wire. This limitation is usually not a problem, because Ethernets usually carry much less traffic.
What 2 TCP/IP qualities allow system communications to recover from unusual situations?
Being “independent” and “robust”
Describe an ISP connection
Your ISP company gives you a modem for your house. Modems convert the bits a computer outputs into a form (the dashed orange line in the figure) that is compatible with the carrier. These signals are sent to the carrier’s business where they are converted (via another modem) into a form suitable for the server that connects to the Internet via the Internet gateway. The digital subscriber line (DSL or ADSL, for asymmetric DSL) and cable (the same folks that bring you TV) are two very common service providers. When you use your smartphone, it has a modem for connecting to the so-called “wireless broadband” network such as the 4G network provided by phone carriers; its radio signals behave just like the dashed orange line to connect you to the Internet.
What is DNS?
domain name system (DNS) is the hierarchical structure we use to name computers. People use hierarchical domain names. Computers use IP addresses. For you to visit facebook.com, the computer needs to know that you mean 31.13.69.128. Figuring that out is the task for the Domain Name System (DNS) servers.
