Communication Flashcards
(36 cards)
1
Q
Baud rate
A
The number of signal changes per second
2
Q
Bit rate
A
- The number of bits that are transmitted per second
- Baud rate * number of bits per signal
3
Q
Bandwidth
A
The range of frequencies that a communication medium is capable of transmitting
4
Q
Latency
A
The difference in time between an action being initiated and its effect being noticed
5
Q
Protocol
A
- A set of rules relating to communication between device
- Enables devices made by different manufacturers to communicate seamlessly
6
Q
Serial data transmission
A
- Data is sent one bit at a time over a single communication line
- Used for transmitting data over medium to long distances
7
Q
Parallel data transmission
A
- Numerous parallel communication lines that allows for multiple bits to be sent simultaneously
- Used for transmitting data over short distances
8
Q
Examples of data transmission
A
- Serial => USB
- Parallel => between parts of the processor
9
Q
Crosstalk
A
Signals from tightly packed communication lines can “leak” into other, causing data corruption
10
Q
Skew
A
- Each line in parallel transmission has slightly different electrical properties, leading to different times taken
- This means that bits sent together may not be received together, leading to bits being overlapping and the corruption of data
11
Q
Serial vs Parallel
A
- Serial data transmission does not suffer from skew or crosstalk, making it a more reliable communication method over long distances
- Serial mediums are cheaper to install
12
Q
Synchronous transmission
A
Data is sent on shared clock pulses at regular intervals, received in the same order that they were sent
13
Q
Uses of synchronous transmission
A
- Transmitting information in real-time systems
- Used by busses in the processor
14
Q
Asynchronous transmission
A
- Start and stop bits are used to indicated the duration of a transmission
- The sender and receiver must use the same Baud rate and synchronize their clocks for the duration of data transmission
15
Q
Physical star network topology
A
- Each client has its own direct connection to a central hub
- The hub receives packets for all clients and delivers them to the correct recipient
16
Q
Advantages of physical star network topology
A
- Packets are sent directly to the recipient so other clients cannot see packets that aren’t intended for them
- It is easy to add and remove clients to and from the network
- Each cable has just one device, removing the possibility of collisions
- The failure of one cable does not affect the rest of the network
17
Q
Disadvantages of physical star network topology
A
- If the central hub fails all communication is stopped
- Expensive to install due to the large amounts of cable
18
Q
Physical bus topology
A
- All devices are connected to a single central cable (the backbone)
- A terminator is at each end of the cable, preventing signals from bouncing back along the cable
19
Q
Advantages of physical bus topology
A
- No central hub, reducing the chance of a network failure
- Inexpensive to install due to minimum length of cable
20
Q
Disadvantages of physical bus topology
A
- Packets are sent through the shared backbone, allowing every client on the network to see packets that aren’t intended for them
- The backbone is used for communication by multiple clients, introducing the risk of collisions
- The entire network will fail if the backbone fails
21
Q
Logical network topology
A
The flow of data packets within a network
22
Q
Logical bus network
A
Delivers packets to all clients on the network
23
Q
Logical star network
A
Delivers packets only to their recipient
24
Q
Host
A
A device on a network that provides services
25
Client-server networking
- A central server provides services to multiple clients
- Allows for central management of clients and greater network security
- Requires higher levels of expertise to set up and manage
26
Peer-to-peer networking
- Services are provided by the clients themselves
- They are more effective than client-server networking as there is no need for a powerful server
- Easier to set up and maintain
27
Wireless networking
- Allows clients to communicate within a network without being physically connected to it
- Requires a wireless access point which connects to a wired network
- Requires a wireless network adapter in each device that connects to the wireless network
28
WiFi
- The standard that enables wireless local area networking
- Allows devices to connect wirelessly to a network using radio signals
- WiFi is based on international standards that enables global compatiblity
29
Components required for wireless networking
- Network Interface Card (built into devices)
- Wireless Access Point (sends and receives wireless signals)
- Router (routes data to and from the internet)
- Modem (connects the network to the wider internet)
30
Methods of wireless network security
- WPA/WPA2 encryption
- SSID Management
- MAC Address Filtering
31
WPA/WPA2 encryption
When a device tries to joins the network it must enter a pre-shared key
32
SSID Management
- The SSID is the name of a wireless network
- Broadcasting the SSID means it shows up when someone searches for it
- Hiding the SSID stops it from being publicly visible
33
MAC address filtering
- Every wireless device has a unique assigned MAC address
- MAC address whitelists allow only specific devices to connect to a network
- MAC address blacklists can be used to block specific devices from connecting to a network
34
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)
A protocol used in wireless networks to avoid data collisions caused by multiple devices communicating simultaneously
35
CSMA/CA process
- When a device is ready to transmit is listens to the communication channel to check whether it is idle
- If so the data is transmitted. If not, the device waits a random period of time and checks again
- An exponential backoff algorithm increases the time period for each check
- It cannot overcome hidden nodes
36
RTS/CTS
- A solution to the hidden node problem
- The sender sends a "request to send" message to the server when the channel seems idle
- If the server is idle it will respond with a "clear to send" message so transmission can begin
- If no CTS message is received the server is busy communicating and the transmitting data must wait
