Time
3 hours 38 minutes
Difficulty
Beginner
CEU/CPE
2

Video Description

WIFI- Wireless fidelity

  • LAN Protocol
  • IEEE 802.11
  • Standards: a,b,g, and n

    • Frequency
    • Speed
  • Works in ISM band
  • Uses 2.4 GHz and 5GHz
  • Frequency band divided into channels
  • Governed by WiFi Alliance

    802.11 Standard- WLAN standard

  • Uses air as transmission media
  • Concerned with the 2 lower layers of the OSI model
  • Data link layer

    • Logical link control (LLC)
    • Medium access control (MAC)
  • Physical layer

    • Physical layer convergence procedure (PLCP)
    • Physical medium dependent (PMD)

Infrastructure vs Ad-Hoc Modes- Infrastructure

  • Uses access point
  • Star topology
  • More commonly used
  • Ad-Hoc

    • Direct communication
    • Exists for short period
    • Suitable for meetings and conferences
    • More flexible in setup
    • Point-to-point

SSID- Service Set Identifier

  • Used to identify wireless LAN
  • Can be broadcasted or hidden
  • Length: 32 alphanumeric characters
  • Can be composed of several access points
  • Single access point can connect to several SSIDs

CSMA/CA- Carrier Sense Multiple Access Collision Avoidance

  • Uses request to send RTS and clear to send CTS to avoid collisions
  • Possibility of collision still exists
  • Lead to slower performance
  • Recovered by resending

Video Transcription

00:00
Now let's talk about the wireless networks protocol, the WiFi,
00:06
the wife I stands for Wireless fidelity. It's a land protocol. It is used to connect.
00:14
The virus is in the limited geographical area wirelessly. It has the standard off 802.11 from the IEEE.
00:23
We have several standards for the WiFi
00:27
A, B G and then are the names of these standards.
00:32
They differ in the frequents used and the speed achieved for the wireless communication.
00:38
The wife, I generally works in the ice and bend, so it needs no license from the regulatory authority.
00:45
It uses the frequencies off 2.4 gigahertz and five gigahertz, according to the Standard. Either it is a B, G or end.
00:54
This frequency band is divided into a number of channels with a guard frequency
01:00
or a guard band between each channel and the other. These channels are used for the communication off
01:08
excess points that are near to each other without allowing for interference between
01:15
their frequency ranges. WiFi is governed by the WiFi alliance.
01:23
The 802.11 standard is the wireless land standard. If uses air as the transmission media, such as the rest off the wireless standards. It is concerned with the two lower layers off the S. I model the physical and the datalink layers in the datalink. Clear.
01:44
It divides the Datalink lair into two sub layers. One of them is the logical in control layer, and the other is the medium access control layer, and the physical air is also divided into two sub layers. One of them is called the Physical Layer Convergence Procedure PLC P.
02:01
The other is the physical medium dependent P M D. Layer. So we have in this diagram this division, tow the datalink and physical air according toe the WiFi standard.
02:15
We can establish two types of wireless networks
02:20
amazed on the WiFi standard, either an infrastructure network or ad hoc network.
02:25
The infrastructure not accuses the excess point to communicate to devices to each other.
02:30
It is a start apology. It is more commonly used to establish a wireless network inside an office meeting room or a corridor is, or something like this. The excess point is used to connect the wireless devices, so the wired infrastructure sometimes you need toe establish an ad hoc network wirelessly.
02:51
You need to establish direct communication between two laptops or two mobile phones that happened to exist in the same place.
02:59
This ad hoc network is established for short period inside, for example, a meeting inside the meeting room between two persons that need to communicate their business cards or to exchange some information between their laptops. They can do this using the ad hoc network.
03:15
It's suitable for meetings and conferences. It is more flexible in set up. It can be set up for some short period of time. And then these holds. If these two laptops or mobile phones are away from each other, it uses the point to point communication
03:32
apology. Meanwhile, the infrastructure, while it's not, loses the start apology. Since there is a connecting device, which is the excess point,
03:43
the S s I D. Which is the service set. Identify Rh. This is the name off the network. This is the name that you can see when you scan the surrounding area. For wireless networks, it is usedto identify the wireless than it is the name off the wall. I understand that you choose to connect to
04:00
it can be broadcasted name or hear the name according to the configuration off the excess point and the wireless. Then
04:06
the configuration says that this wireless land is broadcasted. Anyone that scans the network using
04:13
that
04:14
mobile device or the laptop
04:17
can see the name of this network or it can be hidden. So scanning the network does not show this name. If you will connect to a head a network, you need to know to pieces of information, the name of the network and the password. Meanwhile, if you will connect to a broad cost that S s I d. You need only to know the password
04:36
and you will find the name Broad Constant and you just click on it. Toby
04:41
connected the length of the S S i D can reach to 30 toe alphanumeric characters. This is the name of the Notre Can reach 32 alphanumeric characters. It can be composed off several exits points. Several excess points can serve the same s s I D can connect
04:59
devices to the same as us. I d
05:00
single excess point as well can connect to several SS ideas according to the conflagration off this excess point, it can connect devices too many assess id's many names off networks through the same excess point
05:17
in WiFi collisions are avoided through another
05:23
technology that is different from the Cisma CD. It is called the Cisma. See. A carrier sells multiple excess collision avoidance. It uses two types of messages that are called artists, which is request to send, and another signal that its seat us.
05:42
What happens is that the sending device sends an rt s signal.
05:46
It does not start sending all till until receiving city a signal from the receiving device.
05:53
That's the way it avoids collisions.
05:56
But the possibility off collisions still exists. There can be some provisions. And as you know, collisions are something that we do not like over our networks, either wired or wireless. So collisions
06:10
leads to poor performance, slower performance and leads to re sending several times for the same type of information.
06:19
Recovery off collisions is done just simply by resending the information that has collided with each other. Resending means slower. Resending, needs poor performance. But this is the way that this is messy, eh? Depends on tow. Avoid collisions or to recover from collisions. That already has happened
06:41
by now we have introduced the WiFi protocol briefly. Thank you.

Up Next

Network Fundamentals

In this basic Network Fundamentals course, you will get an introduction to basic networking concepts to expand your knowledge about network security. You will get a complete overview of networks including wired and wireless computer networks, devices, and protocols.

Instructed By

Instructor Profile Image
Mohammad Adly
EC3 Manager at Information Technology Institute
Instructor