OSI model:
7.  Application layer           smtp, http, ssh
6.  Presentation layer          encryption, compression, data formating
5.  Session layer               Sockets(tcp,ip,port)? Start, stop session (data transfer), still no tcp (net socket init)?
4.  Transport layer             tcp/udp
3.  Network layer               ip, routing
2.  Data link layer             mac, switch
1.  Physical layer              cable, nic, hub

Network Interface Card and cables                                       1PHYSICAL
Frame header   |                                    | frame footer      2DATA LINK      frame
               | ip header | ip date                |                   3INTERNET       packet
                           | tcp header | tcp data  |                   4TRANSPORT      segment
                                        | app data  |                   5APP

APP -> OSI app, presentation, session



Internet protocol suite (TCP/IP model):

Frame header   |                                    | frame footer      1LINK
               | ip header | ip date                |                   2INTERNET
                           | tcp header | tcp data  |                   3TRANSPORT
                                        | app data  |                   4APP