One of the best break downs of the OSI model that I have seen today.
Die 8. Schicht -- OSI-Modell – Wikipedia
Comparison of TCP/IP Model and OSI Models, TCP/IP vs OSI
osi model - Google Search
networking OSI TCP IP UDP ARP DNS 'concept maps' - Google 搜索
the TCP/IP and OSI models
ISO Model and Protocols that go with them.
Understanding this model is essential for anyone who wants to be involved in the field of computer networking. If you have forgotten the OSI model or just want to get a crash course in it, this cheat sheet by Ccna-security.net should help
Sysnet Notes: Subnetting made easy