| Unit | Layers | Description | Example Protocols |
|
| Data | Application | End user layer – provides services to the software through which the user requests network services (browsers, FTP clients, and mail clients are in this layer) | HTTP, FTP, IRC, SSH,DNS |
|
| Data | Presentation | Syntax Layer – Ensures that data is in a usable format; Translates, encrypts and compresses data | SSL/TLS, SSH, IMAP,FTP,MPEG,JPEG |
|
| Data | Session | Interhost communications – Establishes, manages and terminates sessions between computers (controls ports, APIs, Sockets, Winsock) | NetBIOS, PPTP |
|
| Segments | Transport | End-to-end connections – Provides reliable processes for message and error delivery; Transmits data | TCP, UDP |
|
| Packets | Network | Path determination and IP (logical addressing) – Moves packets from source to destination | IP, ICMP, IPSec, IGMP |
|
| Frames | Data Link | Defines the format of data on the network -concerned with the linkages and mechanisms used to move data about the network, including the topology, such as Ethernet or Token Ring, and deals with the ways in which data is reliably transmitted. (MAC & LLC – physical addressing) | Ethernet, PPP, ATM |
|
| Bits | Physical | Media, signal and binary transmission – defines the electrical and physical specifications for the networking media that carry the data bits across a network | Ethernet, Bluetooth, USB, IEEE802.11 |
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