BASIC INTERNET PROTOCOLS: http, ftp, telnet.

Mirela Walczak

Content :Key Words

IntroductionInternet Protocol Suite

Client Server Model OSI Model

FTP ProtocolHTTP Protocol

TELNET Protocol

Key Words:• Port• Host • Control stream • Proxy• SSL- secure sockets layer• Client • Server

What is protocol?

Is a convention or standard that controls or enables the connection , communication and data transfer between two computing endpoints.

Internet Protocols Suite The set of communication

protocols used for Internet and other similar networks.

• Internet Protocol IP

• Transmission Control Protocol TCP

OSI Model• The Open Systems

Interconnection Reference Model

• OSI Reference Model

• OSI Model • OSI seven layer

model

OSI

TCP/IP Model – OSI Model

Client Server Model Software

architecture model distinguishes Client system from Server system, which communicate over a computer network.

The qualities characteristic for:

Server:Passive It waits for the

requests from the client

When the request is received – server process it and send an answer to the client

Client:Active It sends the request

to serverIt is waiting for the

answers from the server

File Transfer Protocol

Is a network protocol used for transfer data from one computer to another through a network such as Internet.

Advantages of FTP• FTP operates on two ports: 21, 20• Provides two different transfer mode: Active client mode

Passive server mode• Servers can have „anonymous FTP” access• Two formats on which data can be send: ASCII mode-American Standard Code for Information Interchange BINARY mode

ASCII modeBINARY mode

Disadvantage of FTP• FTP is a high latency protocol for e.g to begin a

transfer of data it has to be used many comands.

• Passwords and file contents are sent in clear text, allowing unwanted eavesdropping.

• It is possible to tell a server to send data to an arbitrary port of a third computer.

The objectives of FTP:• To promote sharing of files (computer

programs and/or data).• To encourage indirect or implicit use of

remote computers.• To shield a user from variations in file storage

systems among different hosts.• To transfer data reliably, and efficiently.

HyperText Transfer Protocol

Is a communication protocol for the transfer of information on the Internet.

Offices of the current Internet Engineering Task Force Secretariat

World Wide Web Consortium

Type Consortium

Founded October 1994

Founder Tim Berners-Lee

Headquarters

MIT/CSAIL in USAERCIM in FranceKeio University in Japanand many other offices around the world

Website www.w3.org -- History

HTTP request method• HEAD-Asks for the response identical to the one that would

correspond to a GET request, but without response body.• GET-Requests a representation of the specified resource.• POST-Submitt data to be processed (e.g. from a HTML form)

to the identified resource.• PUT-Uploads a representation of the specified resource.• DELETE-Deletes the specified resource.• TRACE-Echoes back the received request, so that a client can

see what intermediate servers are adding or changing in the request.

• OPTIONS-Returns the HTTP methods that the server supports.

• CONNECT-For use with a proxy that can change to being an SSL tunnel.

HTTP Versions• HTTP/0.9

Support only one command GET and omits the header.• HTTP/1.0

This is the first protocol revision to specify its version in communications.

• HTTP/1.1Current version with persistent connection.

Allows pipelining and multiple request at the same time. Works well with proxies • HTTP/1.2

Version from the 1995, later subsumed by the experimental HTTP Extension Framework

Telecommunication Network Protocol

Is a network protocol used on the Internet or local area network (LAN) connections.

Three main reasons why ..........?• Does not encrypt any data sent over the

connection (including passwords).• Does not ensure that communication is

carried out between the two desired hosts, and not intercepted in the middle.

TELNET security

•The packets allow easily obtain login and password information.

Current Status• TELNET was replaced by SSH (Secure shell

protocol with high level of encryption).• Popular in enterprise networks to access host

applications.• Is also heavily used for games played over the

Internet, as well as talkers.• Cannot be used as a tunneling protocol.• Should not be used on networks with Internet

connection.

SUMMARY• PROTOCOLS are very important in successful

communication.• INTERNET PROTOCOL SUITE consist of two protocols

IP and TCP. They are responsible for transmission data.

• OSI MODEL is an abstract description for layered communication and computer’s network protocol design. Consist of 7 seven layers.

• CLIENT SERVER MODEL is responsible for exchanging information between client and server .

FILE TRANSFER PROTOCOL• There are two computers involved in an FTP

transfer: a server and a client.• Any software company or individual

programmer is able to create FTP server or client software because the protocol is an open standard.

• There are many existing FTP client and server programs, and many of these are free.

HYPERtext TRANSFER PROTOCOL• Its original purpose was to provide a way to publish

and retrieve HTML pages.• Development of HTTP was coordinated by the World

Wide Web Consortium and the Internet Engineering Task Force.

• HTTP is a request/response protocol between clients and servers.

• HTTP defines eight methods.• HTTP versions: 0.9, 1.0, 1.1, 1.2

TELNET PROTOCOL• Name is derived from the words

telecommunication network.• It was developed in 1969.• Provides general, bi-directional, 8-bit

communication.• Client-server protocol with port 23.• TELNET is not recommended for modern

systems from the point of view of computer security.

Sources

• http://en.wikipedia.org/wiki/Main_Page• http://www.demon.net/helpdesk/

technicallibrary/misc/telnet/images/telnet.gif• http://www.cyf-kr.edu.pl/~mfjawien/FZI/

Wstepx1.html• http://www.angelfire.com/ab7/gregsgrl85/

ftp.html• http://www.cs.rpi.edu/academics/courses/

fall96/netprog/lectures/html/ftp/tsld002.htm