Ccna3- Chapter 7

Front 1

IEEE standards for wireless

802.3 is for ethernet

Back 1

802.11a, 802.11b, 802.11g

Front 2

WLANs (wireless LAN)

Back 2

uses radio freq instead of cables and MAC sub-layer of the Data Link Layer.

Front 3

RF characteristics

Back 3

-does not have limitations such as the limits of a wire in a sheath.
-RF is unprotected from outside signals.
-RF transmission can have interference from radio
-RF bands are regulated differently in different countires.

Front 4

difference between ethernet and wireless

802.3
physical layer - cable
media access - collision detection
availability - cable connection
signal interference - not really
regulation - IEEE standards

Back 4

802.11
- physical layer - RF
media access - collision avoidance
availability - radio nic in range of an access point
signal interference - yes
regulation - depends on the area

Front 5

WLAN connection

Back 5

is through Access point instead of an ethernet switch

Front 6

data rates for different WLAN standards

Back 6

a and g can support 54Mb/s
b supports 11Mb/s
802.11n is not yet set.

Front 7

what affects data rates

Back 7

modulation : a way of combining user information with the carrier signal

Front 8

modulation types

Back 8

DSSS - Direct Sequence Spread Spectrum
OFDM - Orthogonal Frequency Dvision Multiplexing

Front 9

802.11a

Back 9

uses OFDM and uses 5GHz band
-less likely to get interferences with devices that operate in 2.4GHz band.
-higher frequency allows for smaller antennas.
-higher frequency is more succeptible to obstacles such as walls.
-smaller range than b or g.

Front 10

802.11b

Back 10

uses data rates of 1, 2, 5.5 and 11Mb/s in the 2.4 GHz band using DSSS

Front 11

802.11g

Back 11

uses OFDM
-gets higher data rates
-uses DSSS for backward compatibility
-OFDM rates are 6, 9, 12, 18, 24, 48 and 54Mb/s

Front 12

advantages to using the2.4GHz band

Back 12

better range than 5GHz.
transmissions are not easily obstructed.

Front 13

802.11n

Back 13

uses mutliple radios and antennae at endpoints

Front 14

access points

Back 14

wireless clients don't talk to each other directly, they go through the AP.
-converts the TCP/IP data packets from their 802.11 frame encapsulation format in the air to the 802.3 ethernet fram format on the wired ethernet network

Front 15

CSMA/CA

Back 15

Carrier sense Multiple Access with Collision avoidance.

The devices on a WLAN must sense the medium for energy (RF stimulation above a certain threshold) and wait until the medium is free before sending.

Front 16

data transfer from client to AP

Back 16

if an AP receives data from a client, it sens an ack to the client.
-the ack informs the client that the data was successful.

Front 17

The hidden Node problem

Back 17

if two devices are at the maximum range to reach the access point and at opposite sides of each other, they cannot sense each other. They might end up transmitting simultaneously.

Front 18

RTS/CTS

Back 18

-request to send/clear to send
-to solve the hidden node proble
-negotiate between client and AP.
-access points allocate the medium to the requesting station for as long is required to complete the transmission. When the request is complete, other clients can request the channel.

Front 19

wireless router

Back 19

performs the role of access point, switch and router.

Front 20

wireless network mode

Back 20

refers to the protocols, a, b, g and n
when b and g are both used, it's in a mixed mode.

Front 21

SSID

Back 21

shared service set identifier
a client uses this to distinguish between multiple wireless networks.

Front 22

channels

Back 22

2.4GHz band is broken to 11 channels for North America and 13 for Europe.
-they have a fequency separation of 5MHz and total of 22 MHz channel bandwidth.
-separate out access point 5 MHz apart so that they don't overlap

Front 23

Basic service set

Back 23

is a group of stations that communicate with each other.

Front 24

IBSS

Back 24

independent basic service set
-ad hoc networks without access points

Front 25

ESS

Back 25

extended service sets
-when one BSS doesn't have enough RF coverage, one or more can be joined thorugh ESS. A BSS is identified by the BSSID which is the MAC address of the AP.

Front 26

Beacons

Back 26

framed used by the WLAN network to advertise its presence

Front 27

probes

Back 27

frames used by the WLAN clients to find their networks.

Front 28

authentication

Back 28

a process left over from the original 802.11 standard.

Front 29

Association

Back 29

process of establishing the data link between an access point and a WLAN client.

Front 30

802.11 join process

Back 30

-client searches for a network by sending out a probe request on multiple channels

Front 31

Beacons

Back 31

framed used by the WLAN network to advertise its presence

Front 32

probes

Back 32

frames used by the WLAN clients to find their networks.

Front 33

authentication

Back 33

a process left over from the original 802.11 standard.

Front 34

Association

Back 34

process of establishing the data link between an access point and a WLAN client.

Front 35

802.11 join process

Back 35

-client searches for a network by sending out a probe request on multiple channels
-probe request has the SSID and bit rates.

Front 36

802.11 join process step2
authentication

Back 36

-WEP key that is shared between client and AP.
-clients sends an authentication request, AP sends a challenge test to the client.
-client sends the shared key in an encrypted text back to the AP.
-AP validates the key.

Front 37

step 3

association

Back 37

-finalizes the security and bit rate options
-establishes the link between WLAN client and the AP.
-client learns the BSSID, which is the AP's MAC,
-access point maps a logical port know as association id to the client.

Front 38

802.11 join process step2
authentication

Back 38

-WEP key that is shared between client and AP.
-clients sends an authentication request, AP sends a challenge test to the client.
-client sends the shared key in an encrypted text back to the AP.
-AP validates the key.

Front 39

step 3

association

Back 39

-finalizes the security and bit rate options
-establishes the link between WLAN client and the AP.
-client learns the BSSID, which is the AP's MAC,
-access point maps a logical port know as association id to the client.

Front 40

war drivers

Back 40

find open networks and use them for internet access

Front 41

hackers

Back 41

exploit weak privacy measures to view sensitive WLAN information and even break into WLANs

Front 42

employees

Back 42

plug APs or gateways to company ports to create their own WLANs

Front 43

rogue AP

Back 43

is placed on aWLAN to interfere with normal network operation.

Front 44

man in the middle attacks

Back 44

select a host as a target and position themselves between the target and the router or gateway.

Front 45

Dos

Back 45

using a PC as an access point, can flood the BSS with clear to send messages. The acces spoints in tern can flood the BSS with simultaneous traffic.

Front 46

authentiation

Back 46

SSID - no encryption, basic authentication,
WEP - no strong encryption, static breakable keys
WPA - standardized and improved encryption, strong user based authentication.
WPA2 - AES encryption authentication. Dynamic key management.

Front 47

EAP

Back 47

extensible authentication protocol
framework fo authenticating network access.

Front 48

EAP process

Back 48

802.11 association creates a virtual port for each WLAn client
-AP blocks all data frames except for 802.1x based traffic
-802.1x carry the EAP authentication packets via access point to the server that maintains the credentials.
-if authentication is successful, the serves sends a EAP success message to the AP.

Front 49

TKIP (Temporal Key Integrity Key)

Back 49

encryption mechanism
-encrypts by adding increasingly complex bit coding to each packet
-based on same cipher as WEP.
-carries out a message integrity check in the encrypted packet.

Front 50

AES (Advanced Encryption standard)

Back 50

-based on tKIP with additional features to enhance the level of provided security

Front 51

SSID cloaking

Back 51

disable SSID broadcasts from teh access points

Front 52

MAC address filtering

Back 52

tables are manually constructed on the access point to allow or disallow clients based on their physical hardware address

Front 53

WLAN security implementation

Back 53

WPA or WPA2

Front 54

configure a wireless access point

Back 54

1. verify local wired operation (DHCP and Internet access)
2. Install the access point
3. configure the access point - SSID
4. instaall one wireless client
5. vierfy network operation
6. configure wireless security
7. verify wireless network operation.

Front 55

basic wireless settings

Back 55

network mode
network name or SSID
SSID broadcast
Radio band
wide channel
standard cahnnel