Description of OSI layers
The recommendation X.200 describes seven layers, labeled 1 to 7. Layer 1 is the lowest layer in this model.
|Layer||Prorotocol Data Unit(PDU)||Function||Examples|
|7. Application||Data||High-level APIs, including resource sharing, remote file access, directory services and virtual terminals|
|6. Presentation||Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption|
|5. Session||Managing communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes||RPC, SCP, NFS, PAP, TLS, FTP, HTTP,HTTPS, SMTP, SSH, Telnet|
|4. Transport||Segment (TCP) /Datagram (UDP)||Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing||NBF, TCP, UDP|
|3. Network||Packet||Structuring and managing a multi-node network, including addressing, routing and traffic control||AppleTalk, ICMP, IPsec, IPv4, IPv6|
|2. Data link||Frame||Reliable transmission of data frames between two nodes connected by a physical layer||IEEE 802.2, L2TP, LLDP, MAC, PPP|
|1. Physical||Bit||Transmission and reception of raw bit streams over a physical medium||DOCSIS, DSL, Ethernet physical layer, ISDN,USB|
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