For additional tutorials on these and related topics see http://www.rad.com/networks/tutorial.htm
| 7 | Application | Messages | Network Request Emissary and Mediator | Telnet, X.400, X.500, NFS/Samba, HTTP, FTP, CORBA, PPP, SMTP, POP3, DNS, SNMP, RIP, Ping | n/a |
| 6 | Presentation | Messages | Data Translator and Sentinel: Encryption/decryption, Compression/ decompression; Protocol Translation, Data authentication and Integrity | PKI, IP tunneling over ATM, VPN, logins | Gateways: |
| 5 | Session | Messages | Traffic Cop: Manages data dialogs, Negotiates, sets up, maintans, and terminates end-to-end communications, arbitrates error checking and correction modes, tracks complex message exchanged transactions to completion, makes and accepts internetwork data requests | Sun's RPC, Novell's TTS, NDS, ATM Virtual Circuits | Converged Data/Voice/Multimedia Gateways |
| 4 | Transport | Segments | Trusty and reliable gopher, and tireless travel guide, feeds and assuages the data exchange between **processes** (not devices!), ensures any transmission errors are corrected or reported, throttles data flow rates and fragments data into rebuildable bite-size morsels, parcels out data in sequence, w/o loss or duplication | TCP, SPX | T1 Gateway Channel Multiplexors |
| 3 | Network | Packets | Postmaster and Expeditor: routes the data packet across network segments, hides internetwork transmission logistics from upper layers | IP, IPX, | Ethernet Routers |
| 2 | Data Link | Frames | Shipping Clerk and Dispatcher: Crates and uncrates data into data frames and labels the frames for delivery | Ethernet, Token Ring, SONET | Layer 2 1000BaseT Gigabit Switches |
| 1 | Physical | Bits | Data Trigger Man and Bit Gunner, fires bit across the medium | 10/100BaseT, RS-232, V.90 | Repeaters
Wireless USB Network Interface Cards Wireless PCMCIA Network Interface Cards ATM PCI Network Interface Cards |