BASIC INTERNET PROTOCOLS: http, ftp, telnet. Mirela Walczak

Content : Key Words Introduction Internet Protocol Suite Client Server Model OSI Model FTP Protocol HTTP 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 OSIOSI

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 server  It 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 mode BINARY 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 TypeConsortium FoundedOctober 1994 FounderTim Berners-Lee Headquarters MIT/CSAIL in USA ERCIM in France Keio University in Japan and many other offices around the world Website -- 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/1.1 Current 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 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 rary/misc/telnet/images/telnet.gif rary/misc/telnet/images/telnet.gif kr.edu.pl/~mfjawien/FZI/Wstepx1.html kr.edu.pl/~mfjawien/FZI/Wstepx1.html html html 96/netprog/lectures/html/ftp/tsld002.htm 96/netprog/lectures/html/ftp/tsld002.htm