OSI Model
OSI Layers
graph TD
1["1. Physical"]
2["2. Data Link"]
3["3. Network"]
4["4. Transport"]
5["5. Session"]
6["6. Presentation"]
7["7. Application"]
7 <--> 6 <--> 5 <--> 4 <--> 3 <--> 2 <--> 17. Application
6. Presentation
5. Session
4. Transport
Transmits data using transmission protocols including TCP & UDP
3. Network
Decides which physical path the data will take.
Routing data and logical addressing (e.g. IP), determining the best path from source to destination across networks.
2. Data Link
Defines the format of data on the network
- Receives data from physical layer
- Checks for transmission errors
- Packages bits to data frames (e.g.:
| MAC1 | MAC2 | IP1 IP2 Segment | FCS) - Manages the physical addressing layer:
- Media Access Control (MAC)
- Logical Link Control (LLC)
1. Physical
Transmission and reception of raw bitstreams over a physical medium.
e.g.: network cable, power plug, wireless, pulses of light.
Table of OSI Layers
| Layer | Name | # | Info |
|---|---|---|---|
| 7 | Application | HTTP, SSH, DNS, IRC, FTP | |
| 6 | Presentation | SSL, SSH, IMAP, FTP, MPEG, JPEG | |
| 5 | Session | API, Socket, WinSock | |
| 4 | Transport | TCP, UDP | |
| 3 | Network | IP, ICMP, IPSec, IGMP | |
| 2 | Data Link | Ethernet, PPP, Switch, Bridge | |
| 1 | Physical | Coax, Fiber, Wireless, Hubs, Repeaters |