List and describe OSI model layers

OSI Model

OSI stack:

7. Application Layer:
      - HTTP, FTP, DHCP, DNS, RADIUS, SMTP

6. Presentation Layer:
     - encryption
     - SSL

5. Session Layer:
     - establishes, manages and terminates the connections between the local and remote application
     - L2TP

4. Transport Layer:
     - provides reliable data transport to the upper layers through:
        - data flow control
        - segmentation/desegmentation
        - error control (detection and recovery)
        - retransmission on timeout
     - protocols can be state- and connection-oriented
     - TCP, UDP

3. Network Layer:
     - connects hosts from various networks
     - routers work at this layer
     - IP, ARP

2. Data Link Layer:
     - connects hosts within the same network
     - physical addressing (MAC address)
     - error detection and correction
     - PPP, L2TP 

1. Physical Layer:
     - Ethernet, WLAN, USB, Bluetooth, RS-232