LIS 525 - Protocols


TCP/IP (Transmission Control Protocol/Internet Protocol) is the suite of communications protocols used to connect hosts on the Internet.


Both SLIP and PPP allow a computer connected to a server via a serial line (such as a telephone line) to be a node on the internet.

PPP (Point to Point Protocol) is a newer protocol, and, unlike SLIP, which can only transport TCP/IP traffic, can also transport traffic using other protocols, such as IPX and Appletalk; PPP allows transport using all of these protocols at the same time on the same connection.

SLIP (Serial Line Internet Protocol) requires the client to know the IP address assigned to it by the service provider and the IP address of the remote system to be dialed into. If IP addresses are dynamically assigned, client software needs to be able to pick up the IP assignments automatically. Other details may also have to be configured. PPP negotiates configuration parameters at the start of the connection.

PPP provides two methods with which logins can be automated: PAP (Password Authentication Protocol) and CHAP (Challenge-Handshake Authentication Protocol). PPP software only needs to know the login userid/password and the telephone number of the service provider.


Telnet is a terminal emulation protocol that works with TCP/IP. To start a Telnet session, you must log in to a server by entering a valid username and password. You can then send commands which will be executed by the server as if you were entering them directly on the server console. Windows comes with a telnet program telnet.exe. Telnet is a common way to control Web servers remotely.


SSH is intended as a more secure substitute for Telnet. It also allows you to move files between machines. There are actually two different SSH protocols, SSH1 and SSH2. One free program that supports SSH is PuTTY.


FTP (File Transfer Protocol) is used to upload and download files over the internet. The user has to log on to a server. A simple command-based DOS FTP program ftp.exe comes with Windows. FTP commands include You will probably find more convenient a GUI FTP program such as WS_FTP.

A more secure variation is Secure FTP, or SFTP. WS_FTP LE does not support SFTP, but other free SFTP clients are available, such as Core FTP Lite and FileZilla.


HTTP (Hyper Text Transfer Protocol) is used to transfer HTML documents and normally operates on port 80 of the server. The connection normally remains open only until data is transferred and the protocol is thus referred to as stateless.

An HTTP message consists of the following:

Each line should end in a CR/LF (carriage return/line feed) sequence; in ASCII, characters #13 and #10.

If the initial line is a request, it should consist of three parts, separated by spaces: the method (GET, POST, or HEAD); the pathname of the requested resource or (for POST) the program to handle the data; and the HTTP version (e.g., HTTP/1.0). GET requests a resource; HEAD requests only the header lines for a resource; and POST sends data to the server. If the initial line is a response, it should consist of three different parts: HTTP version; a response status code (e.g., 200); and an English reason phrase describing the status code (e.g., OK). Some common response codes are

A header line has the form Header-Name: value. No header lines are required, except in HTTP 1.1, where a Host header value must be given in requests, and, in responses, a Data header value and (unless a persistent connection is desired) a Connection: close header. Common request headers include and common response headers include In some cases of redirection, a server will deliver a "headerless" page; this should not really happen, but most software handles such pages satisfactorily anyway.

Occasionally also, header lines may be improperly terminated. An example could formerly be seen with the thttpd server at that time used by the Society of Indexers.


NFS (Network File System) is an open operating system that allows network users to access shared files on computers of different types. It uses an interface called the Virtual File System (VFS) that runs on top of TCP/IP.


SMB (Server Message Block) is a message format used by DOS and Windows to share files, directories and devices. Many network products use SMB. A number of products use SMB to enable file sharing among different operating systems. An example is Samba.

For More Information


Last updated October 12, 2007.
This page maintained by Prof. Tim Craven
E-mail (text/plain only):
Faculty of Information and Media Studies
University of Western Ontario,
London, Ontario
Canada, N6A 5B7