OSI Layers
Terms
undefined, object
copy deck
- This layer supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer i
-
Application Layer
(Layer 7) - This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa.
-
Presentation Layer
(Layer 6) - This layer establishes, manages and terminates connections between applications.
-
Session Layer
(Layer 5) - This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.
-
Transport Layer
(Layer 4) - This layer provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling
-
Network Layer
(Layer 3) - At this layer, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synchronization.
-
Data Link Layer
(Layer 2) - This layer conveys the bit stream - electrical impulse, light or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and p
-
Physical Layer
(Layer 1) - The OSI, or Open System Interconnection
- Defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station and back up the hierarchy
- 143
- IMAP4
- 22
- SSH
- 110
- POP3
- 25
- SMTP
- 123
- NTP
- 53
- DNS
- 69
- TFTP
- 80
- HTTP
- 23
- TELNET
- 443
- HTTPS
- 20
- FTP
- 21
- FTP
- 119
- NNTP
- The data link layer is divided into two sublayers:
- The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking.