Application Layer
- Process: programming running
- Can be same host, typically different in computer networking context
- Applications with P2P have client/server processes
- Client process: initiates communications
- Server process: waits to be contacted
- Socket (AKA API) interfaces between application layer and transport layer
- Processes has ID (in networking, the IP and port)
- IANA assigns 0-1023
- HTTP: 80, HTTPS: 443, SMTP: 25, SSH: 22, DNS: 53
- IANA assigns 0-1023
- Application layer ptocol defines:
- Types of msgs (request, response)
- Message syntax (fields)
- Semantics (meaning of fields)
- Rules for processing & responding
- Applications have differing requirements regarding:
- Data reliability
- Time
- Throughput
- Security
| Application | Tolerates data loss? | Throughput? | Time sensitive? | Transport protocol? |
|---|---|---|---|---|
| File transfer, email, website, sms | No | Low | No | TCP |
| Real-time audio/video gaming | Yes | High | High | UDP |