Chapter 12 - Onwards - From Wireless networking Flashcards
What are the effects of following :
- Using a higher frequency
- using a lower frequency
- Increasing the signal power
- If we use a wave with higher frequency, it will help us to increase the data throughput but it will decrease the transmitting distance.
- Using low frequency will give a longer transmitting distances but it will decrease the throughput
- By increasing the signal power, we will get longer transmitting distances but it can add distortion in wave.
What are the 3 main frequency bands that are used in wireless networking?
900 MHz, 2.4 GHz, and 5 GHz
Define 802.11b standard.
It uses 2.4 GHz band. Provides a maximum speed of 11 Mbps. It supports Data-rate-shifting technique. It uses DSSS - Direct Sequence Spread Spectrum as its modulation technique. It is susceptible to interference from devices that operate in 2.4 GHz range like Bluetooth, Microwave etc
Define 802.11g standard.
It also operates in 2.4GHz band. Provides maximum speed of 54Mbps. Uses OFDM - Orthogonal Frequency Division Multiplexing.
It is backward compatible with 802.11b standard but if any device that uses 802.11 b with the AP, all the other devices were forced to use DSSS modulation technique.
Define 802.11a standard.
Operates in 5GHz band. Provides a speed of 54 Mbps. Uses OFDM
Define 802.11n standard.
It can work in both 2.4 GHz band and 5 GHz band. It uses MIMO - Multiple Input Multiple Output.
Supports a speed of 100 Mbps to 300 Mbps. It gets this speed using MIMO and by doubling the channel bandwidth to 40 MHz from 20 MHz that is used in 802.11a,b,g
Define 802.11h standard.
It is an extension to 802.11a.
It provides 2 improvements ->
- DFS - dynamic frequency selection
- Transmit Power Control
- It also adds 11 more non-overlapping channels. Bringing the non-overlapping channels to 23 in this standard.
Rest of the things are same
Define 802.11ac standard.
Provides a speed of 1Gbps
- Uses MU-MIMO (Multi user)
What are non-overlapping channels in 2.4GHz
1, 6, 11
How many non-overlapping channels do we get in 802.11a standard?
11
What is goodput in wireless networks?
This is a actual speed that we get from a standard. Near about 70% of the throughput is used in the management of wireless network itself. So only 30% remains for data throughput.
Which standard provides more transmitting distance out of 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac?
802.11g provides longer transmitting distance as compared to 802.11a.
802.11n provides even longer distances than 802.11g and it’s transmitting distances are kind of similar to 802.11ac
What are the common antenna types used in wireless networking?
Omni antennas -> These antennas have a spherical coverage
Dipole antennas -> These antennas have coverage in the shape of a bagel. These have antennas in opposite directions.
Yagi antennas -> These are directional antennas that point only in one direction.
Patch antennas -> these antennas cover just half part of the sphere. These are usually deployed on walls.
These antennas unit is dBi (Isotropic) or dBd (dipole)
- dBd dipole antennas normally have 2.2 Db gain over its same value dBd antenna gain.
What are the 2 modes in which wireless device can be set?
We can either set it in ad-hoc mode or infra structure mode.
Ad-Hoc is also called Independent Basic Service set
APs are used in infrastructure mode. And in this mode, AP creates a Basic service set.
When APs work in a enterprise network and user can roam from one device to another in any fashion, it is called Extended Basic service set.
How does an AP work in a enterprise network?
In an enterprise network, AP is controlled by an Wireless controller.
So the job is divided between Light Weight AP and the WLC. LWAP is responsible for real time processes like data transfer over the wireless medium, encryption etc.
WLC deals with the RF management, security scheming, authentication etc.
WLC and LWAP talks to each other using Control and Provisioning of Wireless Access Point (CAPWAP) protocol.
What are the common reasons for signal degradation?
It can be degraded by distance, interference, walls and barriers, protocol used
Walls and barriers can decrease the wireless range to as low as 25 feet only.
what band is used by Bluetooth technologies and what is its operating range?
Bluetooth devices use 2.4GHz band and in optimal conditions, their range can be 30 feet.
Define one interesting thing about NFC - Near Field Communication
For NFC to work, actual antenna on receiver and the transmitter should be smaller than the wavelength used on both the transmitter and the receiver.
What are IoT - Internet of things?
This means almost everything in nowadays is connected to the internet. Like Refrigerators, Alarms etc
What is Z-wave technology?
It is a technology that is used in Home automation. In this technology, devices create a mesh network and they communicate from appliance to appliance using low energy radio waves.
Define PoE - Power Over Ethernet.
PoE is a standard that provided power over ethernet. PoE provides a power of 15.4 watts.
PoE+ provides a power of 30 watts.
What was the first Wireless security standard that was used in Wireless networking for encryption and authentication?
WEP - Wired Equivalent Privacy - This was the first standard that was created for encryption and authentication.
It used RC4 encryption algorithim. It used a initialization vector that was not very robust and it was 24 bits long. WEP used keys with with 2 key lengths - 64 bit and 128 bit out of which 24 bit was the Initialization vector. These were transferred in way which made them easily crackable.
WEP also provided shared key authentication which was not very secure.
Device WPA, WPA2 and which one is more secure?
WPA was the one who replaced WEP. IT was advertised as WPA + TKIP (Temporal Key integrity protocol). It still used RC4 algorithim. Can be easily cracked.
WPA2 - Wireless Protected Access 2 - it used AES encryption algorithim with CCMP (Some kind of Message integrity check). For authentication, we can either use pre-shared key on both the AP and the client or we can 802.1x standard that uses EAP - Extensible Authentication protocol.
Note - AES is a symmetrical standard that uses the same key for encryption and decryption. Thus it is faster than the RSA that uses public key encryption.
AES uses keys with 3 key lengths - 128, 192, 256
What is Client Isolation in todays Wireless networks?
With Client Isolation turned on, one Wireless client in a wireless network can’t see another wireless client.
What are some of the threats to wireless networks?
There can be rouge AP which can act as a Evil-Twin.
Define Point to Point protocol.
A PPP exists between 2 devices. For example - between 2 routers. It operates at Layer 2 of the OSI model and is used to transport the layer 3 protocols over serial links. Serial link can be a dial up, ISDN connection etc.
It consists of LCP (Link Control Protocol) and NCP (Network control Protocol)
LCP is responsible for establish a connection, authentication, error detection, multi link, load balancing
NCP worries about how to transport the Layer 3 data and what layer 3 data will be transported.
Does PPP support authentication and why do we need it?
One router uses PPP authentication to validate the far end router.
For authentication, either it can use PAP (Password authentication Protocol) - Not secure
Or it can use MSCHAP which is MS Challenge Handshake Authentication protocol.
CHAP uses MD5 algorithim.
What is SSL VPN?
It is the process of creating a secure tunnel using SSL (Secure Socket Layer) protocol.
SSL uses RSA public key encryption.
