| OSI                         | Internet 4 Layer    | Protocols                               |
| --------------------------- | ------------------- | --------------------------------------- |
| Application<br>Presentation | Application         | HTTP<br>SMTP<br>Telnet                  |
| Session<br>Transport        | Host2Host Transport | TCP, UDP                                |
| Network                     | Internet            | IP, ICMP                                |
| Data Link<br>Physical       | Network Access      | PPP<br>IP-over-ADSL<br>IP-over-Ethernet |

# Internet Protocol Version 4

- Connectionless packet oriented service
- Unreliable service, no guarantee of delivery
- Best effort, no error recovery

All packets routed independently

- Routers examine destination IP address and choose best route to forward packet
- Big packets fragmented, fragments routed separately