Internet Flashcards
What is the internet?
interconnected group of computing devices that uses open protocols to standardize how information is sent and received across our planet
What is the relationship between servers and clients?
clients request information that exist on servers
What is defined by protocols?
form of the client request, and how it is sent through the network
What is a server?
computer connected to internet that responds to requests – machine that ‘serves’ content
What lives in server?
HTML (or other website info)
Server Example
canvas.ubc.ca
NO ‘WWW’
What is a file server?
machine that serves up files
ie. machine www.cs.ubc.ca lives in ICICS/CS building
this machine is networked with a file server, which allows different machines on cs.ubc.ca network to access same files
What do most interactions over the internet use?
client/server interaction protocol
What is the client/server interaction protocol?
- when you click web link, computers gets the page for you… beginning the client/server interaction
- computer = client
- computer with web page = server (web server)
- client gets services from server
- when the page is returned, operation is completed and client/server relationship ends
What is synchronous communication?
both sender and receiver are active at same time (ie. talking on telephone)
What is asynchronous communication?
sending and receiving occur at different times (ie. email, answering machine)
Can servers handle many clients at a time?
yes – server is busy only for as long as it takes to perform your request
ie. between two consecutive client requests from your browser (getting page, and asking for another), that server could have serviced hundreds of other clients
What is data transmitted via?
open protocols
What do protocols do?
standardize communication, so all data is sent by same rules for sending and receiving data
What are open protocols?
protocols available for use by anyone to ensure that anyone can build systems that connect to internet
What are two of the most important protocols?
- transmission control protocol (TCP)
- internet protocol (IP)
TCP/IP
How do packets travel?
- information is divided into numbered packets
- packets are sent over the internet by the most expedient route
- don’t necessarily all take the same route
- don’t necessarily arrive in sequential order
- arranged in order after they all arrive, and reassemble
TCP/IP
What information do packets hold?
- one unit of information
- destination IP
- their sequence number (which packet they are)
TCP/IP
Why is each packet independent?
because each packet can take different route – congestion and service interruptions do not delay transmissions
How does TCP/IP protocol work under adverse conditions?
if traffic is heavy and pack progress is slow, protocol allows packet to be thrown away
What do routers do?
perform traffic directing functions on internet
In what form is data sent through internet (such as webpage or email)?
data packets
Where do packets travel?
forwarded from one router to another router through networks that constitute an internetwork until it reaches its destination node – routers direct the packet through the network to the server with the given IP address
What is point-to-point routing?
computers send data to their neighbours, which send data to their neighbours… somehow, data gets from one computer across network to another
How is each packet sent along a path?
routing algorithm
Why is the internet fault-tolerant?
it is a redundant network
Whys is the internet a redundant network?
there are multiple pathways among its physical connections to create redundancy
even if one pathway is unavailable, there is still another way to transmit message from sender to receiver
- software in connection points knows how to re-route data if one connection fails
What are 3 types of addresses?
- email address
- URL
- domain name
What are addresses for?
key to performing networking tasks
What do email addresses do?
identify people
What do URLs do?
identify webpage
What do domain names do?
identify computers?
Do email addresses and URLs have domain names?
yes
What is uniform resource locator (URL)?
specifies location (address) of web resource, and mechanism to retrieve it
kemiola@cs.ubc.ca
user ID = kemiola
computer addressed by cs.ubc.ca will figure it out for us
cs.ubc.ca is an address designed for humans
What is an address designed for computers?
IP address
What does a transport layer do?
switches from human-readable domain names to machine-friendly IP addresses
What is an internet protocol address (IP address)?
unique address (series of numbers and letters separated by dots) that each computer connected to internet is given
Is IP address temporary or permanent?
either temporarily or permanently assigned by internet service provider (ISP)
- old IPv4 (1983): 4 billion (109) IPv4 addresses (32 bits) – we’ve almost run out
- new IPv6 (2017): about 1038 IPv6 addresses (128 bits) – enough addresses for every atom in every person
What is a domain name?
name that identifies one or more IP addresses
Can a server have more than one IP address attached to them?
yes
What are domain name servers (DNSs)?
keep a directory connecting domain names to IP addresses
- every computer connected to internet needs IP address of its ‘nearest’ DNS
- this DNS is used to resolve, or translate, a domain name to IP address
- DNS names need to be constantly updated
URL = http://www.phdcomics.com/comics.php
protocol = http://
domain = www.phdcomics.com
file, directory, and additional information = /comics.php
What does a URL have to begin with?
protocol
- most of the time, protocol is http (hyper text transfer protocol), but it can be other things
- https = secure hyper text transfer protocol
How do domain names form a hierarchy?
- each ‘.’ separates a different level
- higher level = further towards end
- read from right to left (←)
Hierarchy – Domain Names
www.students.cs.ubc.ca
top-level domain is Canada (ca)
which contains UBC domain (ubc.ca)
which contains computer science department domain (cs.ubc.ca)
which contains undergrad domain (students.cs.ubc.ca)
which contains computer (www.students.cs.ubc.ca)
File Organization
http://imgs.xkcd.com/comics/phishing_license.png
protocol = http://
domain = imgs.xkcd.com/
directory = comics/
file = phishing_license.png
Hierarchy – File Paths
- each ‘/’ separates different level
- higher level = closer to front
- read from left to right
How can file paths end?
can end in ‘file type’ (after trailing period) that provide important information
What is ‘?’ in a URL?
everything after ‘?’ is data needed to process the request
What is spam?
unsolicited or undesired messages sent in bulk by email
What is phishing?
type of social engineering where attacker sends fraudulent (‘spoofed’) message designed to trick human victim into revealing sensitive information to attacker, or to deploy malicious software on victim’s infrastructure (like ransomware)
What is encryption?
taking data and changing it so that it’s hard to understand
What are cookies?
store information about your web browsing
What are first party cookies?
save information about you for that website
- relevant to experience you are trying to have
ie. that you’ve authenticated yourself, Fahrenheit vs. Celsius, language option
What are third party cookies?
save information about you that is not used for that website
- largely why we see targeted ads
What is disinformation?
false information that is deliberately created and spread “in order to influence public opinion or obscure the truth”
What are filter bubbles (echo chambers)?
algorithms have isolated you from info & perspectives that you haven’t already expressed an interest in
Why are filter bubbles (echo chambers) dangerous?
- don’t ask for your permission
- don’t tell you when they’re active
- don’t say what they’re keeping from you
What is end to end encryption?
only you and the people you talk to can decrypt the message
no one else has the ability to see what you are saying
Will your information be encrypted if you back it up to a third party?
no
