Section 6 - Communication: technology and consequences Flashcards
what is serial data transmission
bits are sent one at a time over a single wire
what is parallel data transmission
several bits are sent simultaneously over a number of parallel wires
what are the advantages if serial over parallel transmission
- the bits could travel at different speeds over the wires (data skew)
- bits can interfere with each other across the wires and cause corruptions (cross-talk)
what does bit rate mean
the speed at which data is transmitted serially (bits per second)
what does baud rate mean
the rate at which the signal changes
how can baud rate be higher than bit rate
if more than one bit is encoded in each signal change
what is bandwidth
the range of frequencies that a transmission medium can carry (bits per second)
the larger the range, the greater amount of data that can be transmitted in a certain time
what is latency
the time delay between the moment that transmission of the first byte starts and when it is received
what is synchronous transmission
when data is transferred at regular intervals that are timed by a clocking signal
what is asynchronous transmission
when one byte is sent at a time that is preceded by a start bit and followed by a stop bit
the start bit alerts the device and synchrnoises the clock inside the receiver
the stop bit is a stop period
what is protocol
a set of rules relating to communication between devices
what is a local area network (LAN)
a LAN consists of a number of computing devices on a single site or in a single building connected together by cables
users on the network can communicate with each other as well as sharing data and hardware devices
what is the physical topology of a network
the networks actual design layout
what is the logical topology of a network
the shape of the path the data travels in, and how components communicate
what is a physical bus topology
all the computers are connected to a single cable
the ends of the cable are plugged into a terminator
what are the advantages of bus topology
- inexpensive to install as it doesn’t require that much cable or any additional hardware
what are the disadvantages of bus topology
- if the main cable fails, no network data can be transmitted
- the performance gets worse with heavy traffic
- all the computers on the network can see all data transmission
what is a physical star topology
a network with a central node (switch or computer) that acts as a router to transmit messages
the central node has a record of the unique MAC addresses to identify which computer to send the data to
advantages of star topology
- if one cable fails, only one station is affected
- the performance stays consistent even when a network is being heavily used
- no collisions
- messages are sent directly to the central computer and cannot be seen by other stations
- easy to add new stations without disrupting the network
what are the disadvantages of star topology
- may be costly to install
- if the central device goes down, no data can be transmitted
what is a MAC addess
every device has a network interface card (NIC) that has a unique media access control address (MAC address) which is hard coded into the device
what is client-server networking
computers known as clients are connected to a powerful central computer (server)
each client holds some of its own files and resources and can also access resources held by the server
advantages of a client-server network
- security is better as access rights are managed by the server
- backups are done centrally so individual users don’t need to back up their data
- resources and data can be shared easily
disadvantages of a client-server network
- expensive to install and manage
- professional IT staff are needed to maintain the servers
what is a peer-to-peer network
there is no central server, instead individual computers are connected to each other locally or over a WAN to share files
each computer has equal status
advantages of a peer-to-peer network
- cheap to set up
- enables users to share resources
- not difficult to maintain
disadvantages of peer-to-peer networks
- widely used for online piracy
what is wifi
a local area wireless technology that enables you to connect devices to a network or the internet via a wireless access point (WAP)
what are some methods to secure a wireless network
- WPA and WPA2: wi-fi protected access
- whitelist: controls what MAC addresses are allowed on the network
- CSMA/CA
- CSMA/CA with RTS/CTS
what is CSMA/CA
carrier sense multiple access/ collision avoidance is a protocol for transmission in wireless LANs
1. assemble a frame
2. check if the channel is idle
3. if yes transmit the data
if no wait a random period of time and try again
4. end
what is CSMA/CA with RTS/CTS
the station wanting to transmit data sends a request to send (RTS) signal and the WAP sends a clear to send (CTS) signal back if the channel is idle
