what is TCP/IP and OSI? // FREE CCNA // EP 3

About this video

Episode 3 of Chuck’s free CCNA course explains why networking models exist. He starts from the problem that a Raspberry Pi and an iPhone from different makers can talk today, whereas in the 1960s vendors such as IBM built proprietary networks that could not interoperate — different languages, hardware and cabling. Packet switching and ARPANET (he dates its birth to 1969, from the US Department of Defense) began the fix, but a shared standard was still needed. Two models emerged: TCP/IP, the one actually implemented everywhere, and OSI (Open Systems Interconnect), which lost the adoption war but won the vocabulary war — engineers still describe functions using OSI layer numbers. Both models split communication into layers: physical (cables, network cards, signals), data link (MAC addresses; switches), network (IP addresses; routers), transport (TCP/UDP and port numbers), and application (the protocols a browser uses). OSI adds session and presentation layers, whose functions TCP/IP folds into its application layer, so engineers still call the application layer ’layer 7’ even in the five-layer Cisco view he shows for the CCNA 200-301. He offers mnemonics for the seven OSI layers in both directions (‘All people seem to need data processing’ and ‘Please do not throw sausage pizza away’), arguing the model matters both for exams and for troubleshooting shorthand like ’that’s a layer 1 issue’. He closes with quiz questions: a switch operates primarily at layer 2, while hubs and repeaters operate primarily at the physical layer 1, because hubs merely repeat electrical signals and are not aware of MAC addresses.

Key takeaways

• Networking models exist because early proprietary vendor networks could not talk to each other; shared standards let devices from different makers interoperate.
• TCP/IP is the model actually implemented everywhere; OSI lost on adoption but its layer numbering remains the everyday terminology of network engineers.
• Core layers: 1 physical (signals/cables), 2 data link (MAC addresses, switches), 3 network (IP addresses, routers), 4 transport (TCP/UDP, ports), then application — called layer 7 in OSI terms.
• OSI’s extra session and presentation layers are not separate in TCP/IP; their functions are folded into the application layer.
• For the CCNA and for troubleshooting you need both models and their layer numbers — e.g. switches are primarily layer 2, hubs and repeaters are layer 1.

Episode details: published August 6, 2020 · 12:04 long. Summary written by Self Growth Videos from the episode itself. Business results and any income figures mentioned are NetworkChuck’s own claims, shared for education — they are not typical or guaranteed.

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