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Network
OSI Model
The OSI (Open System Interconnect) Model was developed in 1984 as an open standard to promote network interconnection and interoperability.
Layer | Function | Examples |
---|---|---|
7. Application | End User : Support for applications | HTTP, FTP, SMTP (email) |
6. Presentation | Syntax : Protocol conversion, structures data for the application | ASCII, JPEG, etc. |
5. Session | Sync & Ports : Establishes, manages and terminates sessions & connections | NFS, SQL |
4. Transport | End to End Connection : Is concerned with message integrity between source and destination | TCP, UDP |
3. Network | Packets : Combines messages into packets, adding routing information | IP, IPX |
2. Data Link | Frames : Handles flow control, sequencing, errors | MAC |
1. Physical | Cables : Provides electrical and mechanical connections to the network | cables and NIC |
MAC Addresses
Written in hexadecimal notation, composed of 12 digits, the first 6 correspond to the Organizational Uinque Identifier (OUI) and the last 6 are given by the manufacturer to each device. Every MAC address should be unique.
Large manufacturers may have many several OUI.