U14 communication and network tech Flashcards
what is a protocol
- set of rules
- for successful transmission and receiving of data
why are protocols essential for communication between computers
- provides a set standard for transmission of data
- that basically gives accepted set of rules for transmitting and receiving data
- enables communication between different platforms
POP3/4
post office protocol: downloads email from server
HTTP
hypertext transfer protocol: responsible for correct transfer of hypertext files
FTP
file transfer protocol: allows files to be transferred from one computer to another
SMTP
simple mail transfer protocol: responsible for sending emails
IMAP
internet message protocol: same purpose as POP/receiving mails but does not get deleted and can be accessed from different devices
bit-torrent
protocol used for peer-to-peer file sharing
TCP/IP protocol suite
- conceptual model for networking
- consists of 4 layers: application, transport, network, data link
application layer
- sends files to transport layer
- contains all programs that exchange data
- e.g: web browser
transport layer
- data is broken into packets and are sent to network layer
- uses TCP
- ensures that packets arrive in sequence
- without errors
transmission control protocol
- uses positive acknowledgement with re-transmission
- automatically resends the data packets if it has not received positive acknowledgement
- connection oriented (connection is required b/w devices => host-to-host)
- re-transmits missing packets
- re-assembles packets in correct order
function of TCP
- allows application to exchange data
- establishes and maintains connection until exchange of data is completed
- determines how to break application data into packets
- sends packets to and accepts packets from the network layer
- manages flow control of data to avoid congestion
function of IP
- ensures correct routing of packets of data over the internet
- takes a packet from your transport layer and adds its own header, including IP address of both recipient and sender
- encapsulates data into datagram (felt cute might delete later)
- passes datagram to the link layer for transmission on the LAN
purpose of 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
contents of TCP header
- source port number
- sequence of packets
contents of IP header
- IP address of sender
- IP address of destination
- IP version
IP data packet contents
- message data
- IP version
- size of packet
- sequence number
- source IP address
- destination IP address
link layer
- protocols in this layer provide the means for the system to deliver data to the other devices
- ethernet protocol, wifi protocol, bluetooth protocol
function of 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 that have all/part of files to be downloaded
- store IP addresses of other peers in swarm allowing them to connect
leechers
- peers who download much more data
- and upload less data
- negative impact on network
data exchange using bit-torrent
- 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 and leeches download much more than they upload
- 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
- a circuit does not have to be established at the start of communication
- data to be sent is divided into packets
- can travel different routes
- from node to node
- packets are reassembled in the correct order at the receiver’s end
- must wait until the last packet is received to put the data back together
circuit switching
- dedicated communications channel b/w 2 communicating devices
- a circuit is established at the start of the communication
- between sender and receiver
- lasts for the duration of the call/data transfer
- the link that makes up the circuit is then removed
packet switching pros
- packets can be re-routed if there are problems
- packets can take the least congested route
- transmission error can be detected
- missing packets can be resent
packet switching cons
- packets can be delayed
- a real time conversation is not possible
pros of circuit switching
- person communicating can see each other in real time
- better synchronization // full bandwidth available
cons of circuit switching
- bandwidth // channel not available to other users
- extra time required to set up circuit at start of conversation
- alternative route not available without restarting the conversation
- less secure as easier to intercept data if only one channel is used
- failure in single route used means failure of transmission
server
central computer that stores all files to be downloaded
command
ensures that user can send instructions such as delete, copy which are carried out on the server
anonymous
allows user to access files and user does not need to identify themselves to the server
network layer
- ensures correct routing of data over the internet
- takes a packet from transport layer and adds its own header which includes the IP address of sender and recipient
- encapsulates data into datagram
- passes datagram to datalink layer for transmission on the LAN
data link layer
- protocols in this layer provide the means for the system to deliver data to other devices
- ethernet protocol, wi-fi protocol, bluetooth protocol
