Chapter 14 Flashcards
"Communication and Internet Technologies"
what is a protocol?
a set of rules for successful transmission and receiving of data, which must be agreed between sender and receiver. enables cross communication between devices functioning on different platforms
explain why a protocol is used in communication between computers
- provides a set standard for communication (gives accepted set of rules for transmitting and receiving data)
- enables communication between different platforms
therefore if two devices were sending messages to each other but using different protocols, they would not be able to communicate properly
list the TCP/IP Protocol stack
- application layer
- transport layer
- internet layer
- data link layer
application layer
- sends files to transport layer
- contains all programs that exchange data e.g. web browser
- to allow access to network resources
- presents data to the user, (allows user to communicate with the server?)
HTTP, SMTP, DNS, FTP, POP3, IMAP
transport layer
- handles data packets - data is broken into packets and a packet header is added
- data is sent to the network layer/receives from application
- controls the flow of packets, ensures that packets arrive in sequence without errors
- handles packet loss/corruption
- protocols in this layer: TCP (transmission control protocol - standard for exchanging messages)
internet layer
ensures correct routing over the internet // handles the transmission of data using IP addresses
- identifies the intended network and host
- routes packets independently through the optimum route
- transmits packets to the data link layer
- addresses packets with their source and destination IP addresses
- then uses an IP address and port number to form a socket
IP
data link layer
- handles how data is physically sent
- ensures network/internet protocols are followed
- delivers data/communicates with other computer
- maps IP addresses to physical/MAC addresses
- formats the data into frames for transmission
ethernet protocol, wifi protocol, bluetooth protocol
IMAP
internet message protocol
- a pull protocol
- used to receive/download email messages from the mail server
- allows a copy of the email to be downloaded from the mail server
- same purpose as POP but mail doesn’t get deleted and can be accessed from different devices
POP3
post office protocol,
for receiving/downloading emails from the server. pull protocol
HTTP(S)
hypertext transfer protocol, for sending and receiving web pages
(every time a user accesses a website using a browser, HTTP is used. browser sends a request for a web page to a web server)
FTP
file transfer protocol, for sending and receiving files over a network/between devices
SMTP
simple mail transfer protocol, for sending/uploading emails. a push protocol
ethernet
a protocol primarily focused on LANs, transmitting data in frames. each frame has a course and a destination address, being the physical or MAC address, uniquely defining one NIC. used in the data-link layer
what is stored in a packet header
- source IP address and destination IP address
- checksum
- protocol used
- message data, known as the payload
- ID number of that packet
- packet length
purpose of a packet header
- to store data about packet
- …and its routing to ensure that it reaches its destination
- to ensure that messages can be properly reconstructed
function of TCP protocol
Transmission Control Protocol and works at the Transport layer.
- allows applications to exchange data
- ensures delivery of data - establishes and maintains connection until exchange of data is completed
- determines how to break application data into packets
- adds packet header
- sends packets to and from the network layer
- manages flow control of data to avoid congestion
function of the IP protocol
internet protocol, functions at the internet/network layer.
* provides rules for exchange of packets over the internet
* decides the path for transmission of each packet
* passes packet to the link layer for transmission on the LAN
bit torrent
a peer-to-peer file sharing model. peers act as both clients and servers. the swarm shares a torrent
swarm
all the connected peer computers
that have all or part of the file to be uploaded/downloaded
they share a torrent
tracker
central server
stores details of other computers/swarm
store IP addresses of other peers in swarm allowing them to connect
leeches
peers who download much more than they upload
seed
a peer computer that has 100% of the file it is uploading
BitTorrent downloading/uploading process
torrent file is made available
file to be shared is split into pieces
bit-torrent client software is made available to other peers which allows them to work as seeds or leeches
once a peer has a piece of a file it can become a seed for the parts downloaded
tracker keeps record of all the peers and the parts of the file they have and can pause and restart at any time
packet switching
- data is split into same-size packets
- packets have a header and a payload (the message)
- The header contains a source IP address, destination IP address, and serial number
- each packet is given its own independent route that may be different.
- routes determined based on congestion
- packets are reassembled in the correct order at the receiver’s end
- if packets are missing, re-send
used for: high-volume data transmission, more secure, e.g. email, text messages, VOIP
not for: real-time transmission e.g. live streaming
(a circuit does not have to be established at the start of communication)
(packets can travel different routes independently)
circuit switching
- a dedicated circuit is established which lasts for the duration of the connection (is released after transmission ends)
- between sender and receiver
- data is transferred using the whole bandwidth,
- all data is transferred over the same route
- the link that makes up the circuit is then removed
used: real time communication, where a dedicated path needs to be sustained, where the whole bandwidth is required
e.g. video streaming, voice calls, private data networks
not used:
advantages of packet switching
doesn’t use whole bandwidth (allows simultaneous use of channel)
more secure as packets are sent by different routes and hashed
packets can be rerouted if there are problems or take the least congested route
transmission error is more easily detected
- missing packets can be resent
disadvantages of packet switching
unsuitable for real-time transmission
time delays to correct errors
requires complex protocols
advantages of circuit switching
- data arrives in same order
- data cant get lost
- dedicated communication channel increases the quality of transmission
- simple method
- data is transmitted with fixed data rate
- fast method of data transfer - no waiting time at switches
disadvantages of circuit switching
- A dedicated connection doesnt allow other data transmission even if the channel is free//bandwidth is wasted during periods when no data is sent
- no alternative route in case of failure (not flexible)
- less secure as only one channel is used (easier to intercept)
- time required to establish physical link between two stations can be too long
- whole bandwidth is required, can’t be shared
differences between packet switching and circuit switching
- circuit switching transfers data over a dedicated channel, packet transmits its packets over a digital network
- dedicated path for circuit switching must be established before the transfer, unlike packet switching
- message is split into packets vs message remains itact
- packet switching - packets may be sent out of order for reassembly, unlike circuit
- circuit switching is implemented at the physical layer whereas packet switching is at the network/internet layer
- circuit uses the whole bandwidth
- packet switching allows packets to be resent
- circuit switching is a simpler process than packet switching
router
- examines packet header,
- reads the destination IP address,
- decides on the next (optimum) route to send it on, and sends it
- has access to a routing table (e.g. gateway used, available hops/routes)
- and the status of routes along the way (congestion)
- most intelligent
hub
ensures that any incoming communication is broadcast to all connected devices
switch
has the function of a hub but can also keep track of the addresses of connected devices (more specific).
can send communication to specific devices
server
central computer that stores all files to be downloaded
