802 Layer 2 Flashcards
Step 1/Discovery for Connecting to SSID
- Device scans (passive OR active) for SSID to use
- APs transmit beacon frames that include SSID and parameters being used
- Active scanning is a device sending a probe request, attempting to gain access to an AP, sent to a specific SSID where it sends back a probe response
Step 2/Authentication for Connecting to SSID
(Open System Authentication)
Open system authentication consists of two communications:
1. Authentication request is sent from the mobile device that contains the station ID (typically the MAC address).
- Authentication response from the AP/router with a success or failure message.
Step 2/Authentication for Connecting to SSID
(Shared Key Authentication/WEP)
- Joining station requests “shared key” authentication
- AP sends challenge phrase in clear text
- Station encrypts challenge phrase, and sends back to AP
- AP decrypts and verifies original text for a match to authenticate
Step 3/Association for Connecting to SSID
- Mobile device authenticates to an AP/router, and then sends an Association Request
- AP/router processes the Association Request and sends a response to the device allowing it send/receive data from DS
What are the 3 Frame Types of 802.11?
- Management
- Control Frames
- Data
Beacon Frame (MANAGEMENT FRAME)
Constantly broadcast signal from a WAP announcing itself to clients, and broadcasts its parameters (SSID, Supported data rate, RF channel number used, etc)
Probe Request Frame (MANAGEMENT FRAME)
Used by clients to obtain information from an AP. This can be directed to a SSID or to any AP available (null probe request), happens constantly with clients
Probe Response (MANAGEMENT FRAME)
Used by AP to send info about its parameters (same info found in Beacon)
Authentication Frame (MANAGEMENT FRAME)
Used in the process to gain access to a network
Association Request
