1.1 1 OSI model
Open Systems Interconnection Model All People Seem to need Data Processing
| Layer Num | Layer name |
|---|---|
| Layer 7 | Application |
| Layer 6 | Presentation |
| Layer 5 | Session |
| Layer 4 | Transport |
| Layer 3 | Network |
| Layer 2 | Data Link |
| Layer 1 | Physical |
Layer 1 - Physical layer¶
- The Physics of the network.
- Signaling, cabling, connectors
- This layer isn't about protocols
- Wi-fi and bluetooth included
- Physical Layer Problem?
- Fix your cabling, punch-downs, etc
- Run loopback tests, test/replace cable, swap adapter cards Cables , fiber, and the signal itself Electrical Signals
Layer 2 - Data Link layer¶
- The basic network "language"
- foundation of communication at the data link layer
- Data Link Control (DLC) protocols
- MAC ( Media Access Control)
- Broken into 2 parts Data link Layer and the MAC layer
- Referred to the "switching" layer
- 00-21-70-0F-22-5A <----> 00-21-70-6F-06-F2 Frame, MAC Address, Extended Unique Identifier (EUI-48, EUI-64), Switch Ethernet
Layer 3 - Network layer¶
- The "routing" layer
- Internet Protocol
- Fragments frames to traverse different networks
- 192.168.0.1 <----> 10.22.253.7 *IP address, Router, Packet IP encapsulation
Layer 4 - Transport layer¶
- The "post office" layer
- parcels and letters
- TCP (Transmission Control Protocol)
- UDP (User Datagram Protocol) TCP segment, UDP datagram Transport - TCP encapsulation
layer 5 - session layer¶
- Communication management between devices
- start, stop, restart *Control Protocol, tunneling protocols Session - Link the presentation to the transport
layer 6 - presentation layer¶
- Character encoding
- Application encryption
- Often combined with the application Layer *Application encryption (SSL/TLS) Presentation - SSL encryption
layer 7 - application layer¶
- The layer we see
- HTTP, FTP, DNS, POP3 *What we see on the screen Application - https://mail.google.com