slides09 Flashcards
why is collision detection difficult on wifi
But detecting another host’s radio signal can be very difficult as it can be a tiny fraction of the power of yours, and your signal will drown out the colliding signal and make it undetectable
RTS/CTS handshaking
asking if free, response, everyone sees response and know how much to wait until communication ends
when is it good and bad to have RTS/CTS
good for large or busy networks, good if restricted to large packets only, bad if small network, bad if small packets
802.11ac
MU-MIMO (a set of users or wireless terminals, each with one or more antennas, communicate with each other), 160MHz channel width support, support for more 5GHz channels, and four spatial streams
802.11ax
OFDMA (This allows simultaneous low-data-rate transmission from several users), QAM (It conveys two analog message signals, or two digital bit streams, by changing (modulating) the amplitudes of two carrier waves)
37% more data rate ac, x4 user throughput
describe wifi p2point
Each host communicates directly with each other without an access point
Basic Service Set
More common is Infrastructure or Basic Service Set (BSS), where a central hub (access point) relays traffic between hosts
This is more expensive to set up (as you have to buy an AP), but covers a larger area
Also the AP can connect into a wired network and so the rest of the Internet
Extended Service Set
Extended Service Set (ESS) connects several APs by a wired network
what is WEP
Wired Equivalent Privacy: Both ends of a communication share a secret key that is used to encrypt the traffic between them
how is WPA different from WEP
This introduced better secret key management (Temporal Key Integrity Protocol (TKIP), with RC4) and has a different key with each packet
WPA2 broken, how?
Essentially, KRACK breaks the WPA2 protocol by “forcing nonce reuse in encryption algorithms” used by Wi-Fi. In cryptography, a nonce is an arbitrary number that may only be used once. It is often a random or pseudo-random number issued in the public key component of an authentication protocol to ensure that old communications cannot be reused. As it turns out, the random numbers used on WPA2 aren’t quite random enough, allowing the protocol to be broken.
wpa3 features
Higher Security for Government, Defense, and Industrial Applications
An Easier Connection Process for Devices Without Displays
Protection Against Brute-Force Attacks
Privacy on Public Wi-Fi Networks
what is CCMP AND AES
CCMP is Counter Cipher Mode with Block Chaining Message Authentication Code Protocol
AES is the Advanced Encryption Standard
RADIUS
RADIUS is a networking protocol, operating on port 1812[1] that provides centralized Authentication, Authorization, and Accounting (AAA or Triple A) management for users who connect and use a network service
is The frame layout different from ethernet? if yes, how?
no :P
GSM
Rates of 9.6Kb/s to 14.4Kb/s
HSCSD
57Kb/s
GPRS
171.2Kb/s
EDGE
384Kb/s (3G)
HSDPA and HSDPA+
42Mb and 168Mb
LTE
300Mb/s (4G) LTE is data traffic only, and does not have a voice channel
Currently on most LTE systems if you want to make a voice call it has to drop back to 3G (or even 2G)
5G perks
5G is on track for about 2020 for widespread deployment
It uses the available spectrum much more efficiently than 4G, and employs frequencies up to 86GHz (LTE uses up to 6GHz)
Projections indicate users connected to a base-station will share 20Gb/s download and 10Gb/s upload rates
And base-stations will support “millions” of devices per square mile (enabling the Internet of Things)
A device will be able to connect even if it is moving at 500km/h (e.g., in a plane); latencies will be 1ms, compared to the current 20ms on LTE
one and 2 way satellites
oke
when use satellites
They cover a large area with a reasonably good bandwidth
They are good for remote and undeveloped areas with no other local infrastructure
