Posted filed under Cisco CCNA.

Description of OSI layers

The recommendation X.200 describes seven layers, labeled 1 to 7. Layer 1 is the lowest layer in this model.

OSI Model
LayerProrotocol Data Unit(PDU)FunctionExamples
7. ApplicationDataHigh-level APIs, including resource sharing, remote file access, directory services and virtual terminals
6. PresentationTranslation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
5. SessionManaging communication sessions, i.e. continuous exchange of information in the form of multiple back-and-forth transmissions between two nodesRPC, SCP, NFS, PAP, TLS, FTP, HTTP,HTTPS, SMTP, SSH, Telnet
4. TransportSegment (TCP) /Datagram (UDP)Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexingNBF, TCP, UDP
3. NetworkPacketStructuring and managing a multi-node network, including addressing, routing and traffic controlAppleTalk, ICMP, IPsec, IPv4, IPv6
2. Data linkFrameReliable transmission of data frames between two nodes connected by a physical layerIEEE 802.2, L2TP, LLDP, MAC, PPP
1. PhysicalBitTransmission and reception of raw bit streams over a physical mediumDOCSIS, DSL, Ethernet physical layer, ISDN,USB

Get our complete tutorial in PDF

[bs_icon name=”glyphicon glyphicon-expand”] Watch the video and you will be able to understand OSI Model much better and Please subscribe to our YouTube Channel.


Want more information on how to become Cisco CCNA Certified? Learn more!
Join our Cisco CCNA facebook study group!


Also published on Medium.

Comments are closed.