Network Basics, by Eric Armstrong

Source: Java Network Programming (Eliotte Rusty Harold).

Note:
Each layer builds on any one of the layers underneath it (exception: A Gateway isn't a layer).

Application Layer

The protocol the application sees and uses.

HTTP

HyperText Transport Protocol, for web browsers and HTML pages.

NFS

Network File System, for accessing disk drives across the network.

NNTP

Network News Transport Protocol, for USENET newsgroups.

SMTP,
POP, IMAP
Mail protocols: Simple Mail Transport Protocol handles the deliveries. Post Office Protocol uses it to drop off messages. Internet Mail Access Protocol uses it, saving messages on the server.
FTP,
TFTP, FSP
File Transfer Protocol (uses TCP), and cousins: Trivial FTP (uses UDP for small boot files),
File Service Protocol (lets you restart after an interruption)

Transport Layer

Breaking up of data into packets (packages of data). Collection and sequencing of packets into a data stream.

TCP

Transmission Control Protocol. Ultra-reliable protocol that makes sure all data packets arrived, and are in proper sequence. Reacquires any corrupted or dropped packets from the sender's transport layer.

UDP User Datagram Protocol. Doesn't check for dropped or corrupted packets ("unreliable"). Good for audio/video transmissions, and where the application implements error-correcting codes.

Network Layer

Defines packet APIs. Processes packets. Handles network addressing.

IP

Internet Protocol. What the Web uses. What Java speaks.

IPX

A protocol used on NetWare networks.

AppleTalk

Apple's networking protocol for MacIntosh.

NetBEUI

Microsofts' networking protocol for Windows for Workgroups and Windows NT

Data Link Layer

aka Network Interface Layer, Host-to-Network Layer. Bits and bytes, analog-to-digital conversions.
Ethernet, TokenRing, LocalTalk
Hardware interfaces to a transmission line. A gateway converts one H/W protocol into another.