Appendix B. The 'Abridged' OSI Reference Model Almost every book on networking has some reference to the OSI reference model; this one will be no exception. However, instead of repeating the same text that you've probably already read 50 times, I would like to offer a new twist on the model in Table B-1. This information is presented here in less then 10 words per level, as an "abridged" OSI reference model. To read "unabridged" versions, refer to Interconnections, Second Edition: Bridges, Routers, Switches, and Internetworking Protocols by Radia Perlman or Networking Standards a Guide to OSI ISDN, LAN, and MAN Standards by William Stallings. Table B-1. OSI Reference Model Quick Reference OSI Layer | "10-Word Description" | Application layer | Governs end- user applications and services; FTP, WWW browsers, Telnet, SMTP | Presentation layer | Handles data formats, encoding, and transfer; GIF, JPEG, ASCII, EBCDIC, HTML | Session layer | Handles application dialogue control, data grouping, and recovery; NFS, SQL, NetBIOS | Transport layer | Manages network connections; reliable (TCP and SPX) and unreliable(UDP) transport | Network layer | Addresses and routes packets, packet fragmentation; IP, IPX, AppleTalk | Data link layer | Controls physical layer data flow; Frame Relay, ATM, PPP, IEEE 802.x | Physical layer | Defines electrical and physical specifications; EIA/TIA-232, V.35, 10Basex, B8ZS, NRZI | |