Wireless Networks Flashcards
What are wireless Networks?
- Wireless local area networks (WLANs) use radio waves to connect devices, e.g. WI-FI
- Wireless signals can be intercepted more easily than wired signals as there is not physical connection to the network.
Wireless Network Fundamentals
- WLAN is based around a central communication device called a wireless Access Point (WAP)
- In homes, it is commonly known as a router provided by ISP (internet service provider)
- Larger buildings have several discreet WAPs
- Each wireless network is configured with a service Set Identifier (SSID) - known as network name
Connecting to a wireless Networks
- Can for networks within range on your devices
Open Networks
- An open network is one that has been configured so that a password is not required
- not secure
Interface with a wired Network
- most wireless networks are connected to a wired network
- this lets you run cables to some devices where you may want a reliable network performance
Wi-Fi
- Wi-Fi Alliance grants certification to products than meet the wi-fi standard
- wireless networks use a specific range of radio wave frequencies to transmit data
- Most WLAN devices will be dual band: operate on 2.4GHZ or 5.0GHZ
- Channels
What is a CSMA/CA protocol?
- Is a protocol used in wireless networking. It makes sure that network collisions are avoided
what is a carrier-sense?
- check for presence of any other signals, a decision is made whether to sen the message or try again later
what is a collision avoidance?
an end device, which is either sending or receiving data across the network — that wanted to send will wait for a period of time before trying again
What is a hidden node problem?
hidden node problem - which interferes with the data transmission.
How does a hidden node problem work?
- a device can be out of range from the broadcast of another device, but still be on the network connecting them
- both be sending data to the WAP at the same time, but ⇒ as a result, the WAP would not be able to receive any data due to the data collisions.
How does Request to send/clear to send work?
- Once the channel is determined to be idle, a signal is sent called Request to Send (RTS).
- The answering device then sends a Clear to Send (CTS) reply.
- ensures that only that device will send its message, by not responding to further RTS signals until the original sender has finished.
What is WI-FI?
Wi-Fi allows devices, such as smartphones, tablets and laptops to communicate wirelessly within a particular network area
What is an Wireless Access Point?
A wireless access point is device that allows wireless devices to connect to a wired network using Wi-Fi.
What is an Wireless adaptor?
A wireless adaptor performs a similar function to a network interface card (NIC) but wirelessly. The wireless adaptor can be built into the computer or it can be a portable device fitted into a USB port.
How does a wireless router work at home?
In a home or office network a wireless router transmits a Wi-Fi signal that can be shared by more than one device. This approach is used to share an Internet connection between several devices using a mixture of Wi-Fi and Ethernet cable connectivity.
What is a WPA/WPA2 (Wi-Fi Protected Access) ?
WPA/WPA2 (Wi-Fi Protected Access) are encryption protocols designed to protect a Wi-Fi connection.
This protocol is used whenever an attempt is made to connect to a secured wireless network, by prompting the user for a security key or passcode. This ensures that the connection is secured with encryption.
What is an SSID?
SSID (service set identification) is a unique 32-character identifier that is used to name a wireless network.
What is media access control?
A MAC (Media Access Control) address is the physical address of a networking device (for example a NIC). It is a unique identifier assigned by the manufacturer and is stored in the device’s read-only memory.
What is Carrier Sense Multiple Access with Collision Avoidance?
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) operates by the computer sending a signal indicating that it is about to transmit data. Other computers can then avoid a collision by delaying when they will transmit data.
CSMA/CA access methods can be used both with and without the Request to Send / Clear to Send (RTS/CTS) approach - With RTS/CTS?
1.RTS signal is sent by the sender of the package
2.then a CTS signal is sent by the intended receiver of the package
3.consequently the sender and receiver are aware of a data transmission and hold off for the duration of the main transmission
CSMA/CA access methods can be used both with and without the Request to Send / Clear to Send (RTS/CTS) approach - Without RTS/CTS?
1.The computer wanting to send a data packet senses if the channel is ‘idle’
2.then it is able to send the data packet
3.if the channel is sensed as ‘busy’, the sender will wait and try again
Where is the CSMA/CA method used?
The CSMA/CA method is widely used in WLANs although it has the disadvantage of reducing network performance since it increases the amount of network traffic.
