#_ITandME blog

Nov 15, 2016: OSI Review


Since I am in the throws of recertifying my CompTIA Security+ status, I decided to post my review of the OSI model. This information is all pretty easy to find, however I wanted make sure I tied together not only the layers but the technologies that are apart of each layer when possible.

Layer Name Unit Examples Description
L1 Physical bit wire,fibre Layer 1 is the physical medium of data transfer, most commonly copper, fibre, or airwaves by todays standards.
L2 Data-Link frame switch/hub,NIC,MAC address Layer 2 facilitates data transfer over physical medium between devices on the same network/LAN, commonly referred to as switching
L3 Network packet router/gateway,Internet Protocol(IP) Layer 3 facilitates data transfer between different IP networks or LANs, commonly known as routing...
L4 Transport TCP Segments/UDP datagrams Transmisson Control and User Datagram Protocols (TCP/UDP) Layer 4 is responsible for maintainig the end-to-end virtual circuits created between devices when sending or receiving data
L5 Session Messages SQL,SSL Layer 5 maintains the unique sessions and certificates created between applications moving up and down the stack
L6 Presentation Messages encryption,compression Layer 6 translates and formats data into whatever form the next layer requires, be that up to Application at the end of transmission, or down to Session at the beginning...
L7 Application Messages email,FTP,SSH Layer 7 is where message creation begins or ends, depending on whether one is a sender or receiver of a message.

Sources:
http://www.howtonetwork.org/design/ccda/chapter-1-network-fundamentals
CompTIA Security+ SY0-401 3rd Edition, ISBN-13: 978-0-7897-5333-5