AP Computer Science Principles: Unit 2

What does TCP/IP stand for?

Transmission Control Protocol/Internet Protocol

What do routers do?

devices that act as traffic control for the Internet; provide various pathways, or routes, to get information from one computer to another

What do routers allow for?

redundancy, or the fact that if one pathway fails, the routers can reroute the information to get it where it needs to go

What is the Internet?

a global network of computers and servers allowing communication between them

What is bandwidth?

the transmission capacity of a connection measured in bit rate

What is bit rate?

number of bits that can be processed in a given amount of time

What is latency?

time it takes for a bit to travel the distance between computers

What would happen without transfer protocols?

each computer would have to decide for itself what the binary string actually meant

What do effective transfer protocols have to agree on?

order of information, timing of information, common language, indicators (01000001 would be the number 65 or the letter A)

What are the two main forms of IP adresses?

IPv4

IPv6

What format are IPv4 addresses in? What is the reason for this?

0-255.0-255.0-255.0-255

so that each part is represented by one byte, or 8 bits

32 bits used in total

What format are IPv6 address in?

0000-FFFF:0000-FFFF:0000-FFFF:0000-FFFF:0000-FFFF:0000-FFFF:0000-FFFF:0000-FFFF

represented by 8 groups of 4 hexadecimal digits, each group representing 16 bits

128 bits used in total

For an IPv4 address, what do the first two sets refer to?

Ex: 28.10.204.16

the network

(28.10)

For an IPv4 address, what do the last two sets refer to?

Ex: 28.10.204.16

the specific node in the network the computer is attached to

(204.16)

For an IPv4 address, what sets refer to what if the network uses subnets, or subnetworks? (often used at universities, companies, and governments)

the first two sets would be the university network, the next set would be the individual school, and the last set would be the node

What are static IP addresses?

permanent IP addresses, mostly for major servers that will never move, like google.com or espn.com

What are dynamic IP addresses?

IP addresses that are temporarily assigned by the Internet Service Provider, or ISP, when the computer or device logs on; this allows devices to switch from network to network easily, like phones on WiFi

Why was DNS created?

because people can't remember IP addresses

What is DNS?

Domain Name System

Format: thirdleveldomain.secondleveldomain.topleveldomain

Ex: apclassroom.collegeboard.org

Only a set number of top level domains (.com, .edu)

What happens when a domain name is registered?

it is linked to an IP address, and because of this, the IP address almost always has to be static

What is one way to take out a website temporarily?

DoS (Denial of Service) attack

What is a DoS attack?

-a cyber-attacker will flood a specific IP address, or series of IP addresses, with many requests almost simultaneously

-in order to do this they write a program (sometimes called a bot program) to send the requests at the appropriate speed which overloads the servers, causing them to crash

What is the difference between a DoS attack and a DDoS (Distributed Denial of Service) attack?

they're the same thing, except a DDoS attack is coordinated with other computers so the attack comes from multiple sources at once

What does a computer use to access a site/understand packets on the Internet?

Hypertext Transfer Protocol (HTTP)

What happens after your computer sends a request to the server?

The server sends back a response:

-if the server finds the requested file, it returns a Code 200, and begins to send the information to your computer

-if it can't it sends back an error code, the most common of which is Code 404

-your browser is designed to read and interpret the resultant code to put it on the computer

More and more websites are converting to HTTPS, which is what?

Hypertext Transfer Protocol Secure

-sets up a secure connection with your computer, and sends a certificate to your computer that authorizes the secure connection

-helps prevent cyber-criminals from intercepting information from your computer and/or information packets sent from the server

What are cookies?

-one of the ways websites track user information

-a file that stores information like search queries, form inputs, and other data that might be useful to them

-plus side is it helps the site remember what you put in your shopping cart or what your searches were

-downside is that it allows other sites to see the same information

-geolocation

How is data sent over the Internet?

packets

-packets are the units of data that are sent over the network

-must be labeled with metadata (from address, to address, and size of data in packet)

What is a packet? How do they work?

-the units of data that are sent over the network

-the layout of a packet is defined by a protocol

What does the Internet Protocol, or IP, require all packets to have? (Internet Protocol is for single packets being sent by two computers on a network to each other)

-a destination IP address

- a from IP address

-the actual data being sent

What is TCP (Transmission Control Protocol)?

-a protocol that allows for sending multiple packets between two computers

-TCP checks that all packets arrived and that they can be put back together in the proper order

-TCP adds a packet number to each packet, so that we can track the order of packets (TCP/IP)

-if the packets arrive out of order, the number allows them to be pieced back together

-if a number is missing, TCP will re-request the missing packet

What are the steps of an HTTP Request and Response?

1: The URL- the domain is where in the Internet you need to look, the path is what resource you are requesting

2: Create an HTTP request

3: Use DNS to get IP address

4: TCP/IP breaks the Request into Packets (and labels them with the proper metadata)

5: Packets are routed to the proper IP address

6: the original request is pieced together from the packets

7: the server creates an HTTP response (includes a status code, and if code=200, then the actual HTML file as well)

8: TCP breaks up the response into packets

9: the response packets are routed back to the computer

10: the original response is pieced together from the packets

11: the page is rendered

What is sequential computing?

completes one task at a time, in order; slower

easier to find bugs, no setup needed

What is parallel and distributed computing?

completes multiple tasks at a time, simultaneously; faster

difficult to find bugs, difficult to use and set up correctly

What is distributed computing?

parallel computing (more than one processor in a computer) but utilizing multiple computers and distributing tasks between computers

-scalable, fault-tolerant, and reliable

-complex and expensive to maintain