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Protocol Network System

1. Networking and protocol

A sever based network consists of a group of user oriented PCs (Personal Computers called clients) that request and receive network services from specialized computers called Severs. Severs are generally higher performance systems optimized to provide network services to other PCs.

“Some common server types include file servers, mail servers, print servers,

fax servers, and application severs. The purpose of a Server is to provide information and a client receives information.

In a network, the client/server model provides a convenient way to interconnect programs that are distributed efficiently across different location.

The client/sever model has become one of the central ideas of network computing. Most business applications being written today use the client/server model. So does the Internet's main program, TCP/IP.”

A peer-to-peer network is a group of user oriented PCs (Personal Computers) that basically operate as equals. Each PC a called a peer (workstation). The peers share the resources, such as files and printers, but no specialized severs exist. Each peer is responsible for its own security, and in a way each peer is both a client (because it requests services from the other peers) and server (because it offers services to the other peers). Small network (usually fewer than 10 machines) may work well in this configuration. If security is an issue, then peer-to-peer is never suitable even there 2 computers only.

“An important goal in peer to peer networks is that all clients provide resources,

including bandwidth, storage space, and computing power. Thus, as nodes

arrive and demand on the system increases, the total capacity of the system

also increases. This is not true of a client sever architecture with a fixed set of

servers, in which adding more clients could mean slower data transfer for all

users.”

A network operating system (NOS) is a computer operating system that is designed for network use and primarily to support workstation, personal computer, and in some instances.

A network operating system provides printer sharing, common file system and database sharing, application sharing, and the ability to manage a network name directory, security, and other housekeeping aspects of a network.

“A network operating system (NOS) is a computer operating system that is designed for network use.

Usually a NOS is a complete operating system with file, task and job management. However, with some earlier operating systems, it was a separate component that enhanced a basic, non-networking operating system by adding networking capabilities. Examples include Novell's Netware and Artisoft's LANtastic.

A server-based network operating system provides networking support for multiple simultaneous users, each with the ability to access network.

resources, as well as security and other administrative functions.

Network operating systems, in the first sense, have existed for more than 35 years. In particular, UNIX was designed from the beginning to support networking, and all of its descendants (i.e., Unix-like operating systems) including Linux and Mac OSX, feature built-in networking support.

The Microsoft Windows operating systems did not initially support networking. Thus, Novell NetWare was introduced and became the first popular network operating system for personal computers. Windows 95 and Windows for Workgroups were Microsoft's first network operating system products.

Today, almost every consumer operating system qualifies as a NOS. This is in large part due to the popularity of the Internet and the consequent need to support the Internet protocol suite.

In a peer-to-peer network, such as Microsoft Windows 98 or XP, in which each host can also be a server, the operating system might still be considered a network operating system, but it is more light weight than a full-blown NOS. “

Three examples of popular NOS.

Novell NetWare, introduced in the early 1980s based on Xerox Network Systems (XNS), is based on client-server architecture. Clients Request services, such as file and printer access, from servers.

NetWare's Client/Server architecture supports remote access that is transparent to users through remote procedure calls.

A remote procedure call begins when the local computer program running on the client sends a procedure call to the remote server. The server then executes the remote procedure call and returns the requested information to the local client.

2. The five layer of the TCP/IP network model

5. Application layer handles the details of the particular application. There are

Many common TCP/IP applications that almost every implementation provides,

Telnet (remote login), FTP, SMPT, SNMP etc….

4. Transport layer provides a flow of data between two hosts, for the application

above. In the TCP/IP protocol suit there are two different transport protocols,

TCP (Transmission Control Protocol), UDP (User Datagram Protocol).

“TCP is a connection-oriented protocol that addresses numerous reliability issues to provide a reliable byte stream:

“UDP is a connectionless datagram protocol. Like IP, it is a best effort or "unreliable" protocol. Reliability is addressed through error detection using a weak checksum algorithm. UDP is typically used for applications such as streaming media (audio, video, Voice over IP etc) where on-time arrival is more important than reliability, or for simple query/response applications like DNS lookups, where the overhead of setting up a reliable connection is disproportionately large.”

3. Network/ Internet layer handles the movement of packets around the network.

routing of packets, for example, IP (Internet protocol), ICMP (Internet Control

Message Protocol), IGMP (Internet Group Management Protocol) Provide the

network layer in the TCP/IP protocol suite.

2. Data Link layer some time called the ‘link layer' or ‘network interface layer',

normally includes the device driver in the operating system and corresponding

networking interface card in the computer.

Together they handle all the hardware details of physically inter facing with the

cable.

“The link layer can also be the layer where packets are intercepted to be sent over a virtual private network. When this is done, the link layer data is considered the application data and proceeds back down the IP stack for actual transmission. On the receiving end, the data goes up the IP stack twice (once for routing and the second time for the VPN).”

1. Physical layer the first layer of the five layers. The physical layer

is responsible for the analogue, digital signalling of a network connection.

The type of interface used on the networking device, the type of cable used for

connecting devices, the connectors and cable media and wireless media used on

each of the cable.

“Ethernet, Token Ring, SCSI, hubs, repeaters, cables and connectors are standard network devices that function at the Physical layer. The Physical layer is also considered the domain of many hardware-related network design issues, such as LAN and WAN topology and wireless technology.”

3. Classify the following in the five layers of the TCP/IP net work model;

Task 2

1. Apache Server, IIS Server

2. Installing Apache Server

Downloading and run it to get the server copied on to the machine.

3 methods for installing IIS

Microsoft does not support the installation of IIs on XP Home edition. Users have to install Win2000 professional or server. But IIS is already installed on Win2000 professional.

4. Stopping and restarting Apache server

In order to stop and restart Apache, user must send a signal to the running http processes. Open a terminal window and log in as root.

Reference Folder- Task 2 Screen Captures - Apache_install.bmp

Reference Folder- Task 2 Screen Captures - ping.bmp

Reference Folder- Task 2 Screen Captures - Apache_test.bmp

5. Stopping and restarting IIS server

Reference Folder- Task 2 Screen Captures - IIS_running.bmp

Reference Folder- Task 2 Screen Captures - IIS_test.bmp

6. Publishing website with Apache

Reference Folder- Task 2 Screen Captures - Apache_website.bmp

Reference Folder- Task 2 Screen Captures - Joo website

7. Configuring Server;

1. Open JooWEBsite properties

2. Open Directory Security panel

3. Open Authentication Methods and tick the box (integrated Window authentication)

Reference Folder- Task 2 Screen Captures - IIS_securelogin.bmp

8. Common log file

Reference Folder- Task 2 Screen Captures - ex070028.log

Reference Folder- Task 2 Screen Captures - reference_logging_properties.bmp

Example of common logfile format;

remotehost rfc931 authuser [date] "request" status bytes

http://www.w3.org/Daemon/User/Config/Logging.html#common-logfile-format

Reference Folder- Task 2 Screen Captures - Extended logging.bmp

Example of error log;

[Wed Oct 11 14:32:52 2000] [error] [client 127.0.0.1] client denied by server configuration: /export/home/live/ap/htdocs/test

http://httpd.apache.org/docs/1.3/logs.html

Task 3

1. Definition of FTP

File Transfer Protocol is an Internet protocol or standard protocol which provides the capability to transfer files or data to other computers or hosts over the Internet.

To use FTP, FTP software must be set up on both sending and receiving ends of an FTP Transmission. And the client must have a username, password and a valid address on the server.

1.1 Function of FTP

The File Transfer Protocol functions(FTP) give client access of file servers through the file transfer protocol. The File Transfer Protocol function are used to open, login and close connections as well as uploading files to the server, download from the server, also rename delete and get data or information from file server. Example of FTP address; ftp oxfordhouse.doc.ic.ac.uk

1.2 Security concern

“The original FTP specification is an inherently insecure method of transferring files because there is no method specified for transferring data in an encrypted fashion. This means that under most network configurations, user names, passwords, FTP commands and transferred files can be "sniffed" or viewed by anyone on the same network using a packet sniffer. This is a problem common to many Internet protocol specifications written prior to the creation of SSL such as HTTP, SMTP and Telnet. The common solution to this problem is to use either SFTP (SSH File Transfer Protocol), or FTPS (FTP over SSL), which adds SSL or TLS encryption to FTP as specified in RFC 4217.”

http://en.wikipedia.org/wiki/Ftp

2. Definition of Telnet

Telnet Telecommunications Network is a protocol that provides a way for user (or client) to connect to other user through server on the Internet.

2.1 Function of Telnet

Telnet is a user command and an underlying TCP/IP for accessing remote computer. An administrator and another user can access someone else's computer remotely. Telnet is usually be used by program developer and anyone who has a need to use specific applications or data located at a particular host computer. To use Tel net function, user must have a telnet client.

Example of Telnet address; telnet.oxfordhouse.edu.com)

2.2 Security of Telnet

“When TELNET was initially developed in 1969, most users of networked computers were in the computer departments of academic institutions, or at large private and government research facilities. In this environment, security was not nearly as much of a concern as it became after the bandwidth explosion of the 1990s. The rise in the number of people with access to the Internet, and by extension, the number of people attempting to crack other people's servers made encrypted alternatives much more necessary.

Experts in computer security, such as SANS Institute, and the members of the comp.os.linux.security newsgroup recommend that the use of TELNET for remote logins should be discontinued under all normal circumstances, for the following reasons:

These security-related shortcomings have seen the usage of the TELNET protocol drop rapidly, especially on the public Internet, in favour of a the ssh protocol, first released in 1995. SSH provides much of the functionality of telnet, with the addition of strong encryption to prevent sensitive data such as passwords from being intercepted, and public key authentication, to ensure that the remote computer is actually who it claims to be.

As has happened with other early Internet protocols, extensions to the TELNET protocol provide TLS security and SASL authentication that address the above issues. However, most TELNET implementations do not support these extensions; and there has been relatively little interest in implementing these as SSH is adequate for most purposes. The main advantage of TLS-TELNET would be the ability to use certificate-authority signed server certificates to authenticate a server host to a client that does not yet have the server key stored. In SSH, there is a weakness in that the user must trust the first session to a host when it has not yet acquired the server key.”

http://en.wikipedia.org/wiki/Telnet

3. SSH

3.1 SSH; SSH was developed by SSH( now called SSH-1) communications security Ltd. Secure Socket Shell is a Unix/Linux-based command Interface and protocol for securely getting access to a remote computer Also SSH is a program to log in to another network, to execute commands in a remote machine, and to move files from one machine to another.

SSH commands are encrypted and secure in several ways both ends of the client/server connection are authenticated using a digital certificate, and passwords are protected by being encrypted.

The main advantage of SSH is an efficiently establish encrypted communication between two computers by protecting the privacy digital information from by any unauthorized third party. SSH are that it can support several different unsecured protocol (for example Telnet, FTP).

3.2 Security of SSH

“Since SSH-1 has inherent design flaws which make it vulnerable to, e.g., man-in-the-middle attacks, it is now generally considered obsolete and should be avoided by explicitly disabling fallback to SSH-1. While most modern servers and clients support SSH-2, some organizations still use software with no support for SSH-2, and thus SSH-1 cannot always be avoided.

In all versions of SSH, it is important to verify unknown public keys before accepting them as valid. Accepting an attacker's public key as a valid public key has the effect of disclosing the transmitted password and allowing man in the middle attacks.

As with any encrypted protocol, SSH can be considered a security risk by companies or governments who do not trust their users and wish to eavesdrop on their communications. Furthermore SSH has built in tunneling features which make it easier for users to achieve passage of large volumes of information or to establish an entry point for unauthorized inward access over a SSH link than with other protocols.”

http://en.wikipedia.org/wiki/Ssh

4. UNIX Utilities

“Rcp stands for the Unix 'remote copy' command. It is a command on the UNIX operating systems that is used to remotely copy -- to copy one or more files from one computer system to another. It typically uses the TCP/IP protocol and the .rhosts file for authentication, but has been implemented to alternatively support Kerberos.

As described in the rlogin article, rcp is not secure for network use, because it sends unencrypted information over the network, among other things. It has largely been replaced by the ssh-based utility scp.”

http://en.wikipedia.org/wiki/Rcp_%28Unix%29

Task 4

1. Definition of Symmetric and Asymmetric

1.1 Symmetric

In a Symmetric computer net work, all devices can transport and receive data at equal rates. A symmetric network design affords all devices equal access to resources.

1.2 Asymmetric

Asymmetric network support more band width in one direction than the other.

Asymmetric means that higher speed is available from the exchange to the user (downstream) and a slower speed from the user to the exchange (upstream).

An Asymmetric network segregate access to resources unequally.

1.3 What is the difference between symmetric and asymmetric bandwidth?

“If a network path is two-way (as most IP connections would be), then the maximum rate of data transfer may be defined in each direction. It is possible that the packets may travel along different routes, going one direction versus the other. Or that devices on the path affect the passage of packets differently in one direction over the other.

Symmetric bandwidth corresponds to the situation when the maximum rate of transfer is the same in both directions. Many (if not most) paths are of this type. This doesn't necessarily mean that the path is symmetric.

Asymmetric bandwidth corresponds to the situation when the maximum rate of transfer is different in each direction. A typical case might be a DSL line with 768 Kbps upload and 1.3 Mbps download.”

http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci1053582,00.html written by Ph. D .Loki Jorgenson

2. Six major variants of DSL technologies

DSL (Digital Subscriber Line) is a modem technology for transporting high-bandwidth information (such as multimedia and video) to service subscribers over ordinary copper telephone lines. This digital broadband line directly connects to the Internet via the existing copper telephone line. DSL handles more data downstream (to the subscriber) than upstream (towards the network). DSL is providing from 1.544 Mbps to 512 Kbps downstream and about 128 Kbps upstream.

A choice of speeds ranging from 32Kbps to more than 50Mbps.

ADSL- Asymmetric Digital Subscriber Line is a technology for transmitting digital information at high bandwidths on standard phone line. ADSL is called “asymmetric” split the phone line in two allowing data and voice connections at same time. A is a method for moving data over ordinary phone line and allows a subscriber to download at higher speeds than they can upload. ASDL transmit from 1.5Mbps-9Mbps downstream (to the subscriber) and from 16Kmps-800Kbps upstream, depending on line distance.

SDSL-Symmetric Digital Subscriber Line technology is a 2 wire implementation of HDSL. SDSL requires a special SDSL modem. SDSL is called “symmetric” because it supports the same data rates for upstream and downstream traffic SDLS works by sending digital pulses in the high frequency area of the telephone wire and can not operate simultaneously with voice connections over the same wires. Carrying 1.544 Mbps (North America) or 2.048 Mbps (Europe) each direction on a duplex line. It's symmetric because the data rate is the same in both directions.

ADSL is more popular in North America, whereas SDSL is being developed primarily in Europe.

HDSL-High speed Digital Subscriber line has been in use for some years in some countries to provide broad band facilities to business leased line, providing 2Mbps across up to three miles of wire. The main goal of HDSL is that it is symmetrical an equal amount of bandwidth is available in the both directions. for this reason, the maximum data rate is lower than for ASDL. Can carry as much on a single wire of twisted-pair as can be carried on a T1 line in North America or an E1 line in Europe (2,320 Kbps).

VDSL-Very high bit-rate Digital Subscriber Line provides an incredible amount of bandwidth, with speed as high as 53Mbps downstream and 1.5-2.3Mbps upstream, but over shorter distances than ADSL. Compare that with a maximum speed of 8-10Mbps for ADSL or cable modem. This is a high-speed technology, but has a very limited range.

RADSL-Rate Adaptive Digital Subscriber Line is a version of ADSL but modem can be adjusting the speed of the connection depending on the length and quality of the line. Westell's FlexCap2 system uses RADSL to deliver from 640 Kbps t- 2.2 Mbps downstream and from 272 Kbps t- 1.088 Mbps upstream over an existing line.

Task 5

1. Dynamic contents in web pages

1.1 Definition of Dynamic contents is used to displayed information from a database or other files on a server. Information on a website or web pages that changes often each time a user reloads or returns to the page and Content that is structured based on user input.

For example when user search on some keyword on a search engine the result pages get is “dynamic” pages, meaning the information was created based on the word user typed in to the form on the previous page.

It mainly used to speed up editing of pages. Since a data base is used to display the information instead of a file, the information can be updated in one stop and it can then be displayed on any page that uses that information. It makes running a large web site very easy.

1.2 Create Dynamic content

“Several user assistance components allow you to provide dynamic content. This means the content can change depending on the user's environment or context. For example, you may want a section of your help document or welcome page to only appear if the user has a certain functionality enabled.

There are two basic ways to create dynamic content. One is to add tags and attributes (annotations) to your XML markup instructing the system to filter out sections or documents, include sections from other documents, or specify anchors allowing other components to extend your documentation.

The other method is to write your own content producer by plugging in some Java code that will write the content from scratch or process existing static documents on-the-fly. Let's examine both approaches.

XML Annotations

The simplest way to create dynamic content is to use the XML markup annotations. You simply add some special attributes and tags to your XML markup and the system will process the instructions. You can use this markup to:

To learn more about each aspect of the markup, follow the links above or find the topics in the table of contents. “

This is demonstrated in the XHTML fragment shown below:

<p>

This is a static paragraph.

</p>

<!-- This tag will be replaced with the referenced tag -->

<include path="my.plugin.id/path/my_other_document.xhtml/element_id"/>

<ul>

<li>

This is a static list item.

</li>

<li filter="os=win32">

This only shows when running on Windows.

</li>

<li filter="plugin!=org.eclipse.help">

This only shows when plugin org.eclipse.help is NOT installed.

</li>

</ul>

<!-- A place where others can add content -->

<anchor id="my.anchor.id"/>

http://help.eclipse.org/help32/index.jsp?topic=/org.eclipse.platform.doc.isv/guide/ua_dynamic.htm

2. Classify the following as Client-side, sever-side technology

3. Client-side scripting

The Internet relies on two types of the computers that communicate with each other.

Clients are more numerous and request data or information and Server are less numerous and deliver on client requests. Client side scripting involves running scripting code on the client. The code required to process user scripting enables interaction and compiled by the browser or plug in. Examples of client side scripting are JavaScript, ActionScript, Java Applet. Java script is a programming language which is part of almost all web browsers.

3.1 Client-side Include Example

<html> <head> <title>Library Web Chic - Client Side Include Demo</title> <link rel=”stylesheet” type=”text/css” href=”wc_main.css”> </head> <body> <div id=”banner”> <h1>Library Web Chic</h1> </div>

<div id=”content”> <h3 class=”page_title”>IClient Side Include Demo</h3> <h4>This is a test page.</h4> <p>

With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. </p> </div>

<SCRIPT LANGUAGE=”JavaScript” type=”text/javascript” src=”links.js”></SCRIPT>

</body> </html>

http://www.librarywebchic.net/wordpress/stories-tutorials-and-code-demonstrations/server-side-and-client-side-includes-explanations-applications-and-examples/

4. Server-side scripting

WebPages are often created using server side scripting languages such as ASP, ASP.NET, PHP, Perl, and JavaSevelet. Server side scripting involves running a scripted program on the computer that is responsible for preparing and delivering a webpage to a visitor. A server side language is one whose code is meant to run on the server which holds the pages content, which is run on the computer of the user viewing the content. The most popular server side scripting language on the web is Perl, which is also a very efficient programming language. Scripting languages like Perl and PHP are free and easy to get started using.

4.1 Server-side Include Example

<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN”>

<html> <head> <title>Library Web Chic - Server Side Include Demo</title> <link rel=”stylesheet” type=”text/css” href=”wc_main.css”> </head> <body> <div id=”banner”> <h3 class=”page_title”>Include Demo</h3> </div>

<div id=”content”> <h3 class=”page_title”>Server Side Include Demo</h3> <h4>This is a test page.</h4> <p> With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. With some test text. </p> </div>

<!-#include virtual=”testinclude.asp”->

</body> </html>

http://www.librarywebchic.net/wordpress/stories-tutorials-and-code-demonstrations/server-side-and-client-side-includes-explanations-applications-and-examples/

5. List of server side scripting technologies

“Any programming language can generate web pages through CGI or an extension module or application server framework. This section lists technologies designed mainly or exclusively for server-side scripting, typically by embedding instructions directly in template web pages.

ASPMicrosoft designed solution allowing various languages (though generally VBscript is used) inside a HTML-like outer page. Primarily a Windows technology, but with limited support on other platforms.

ASP.NET - is a set of web application development technologies marketed by Microsoft. Programmers can use it to build dynamic web sites, web applications and XML web services. It is part of Microsoft's .NET platform and is the successor to Microsoft's Active Server Pages (ASP) technology.

ColdFusion

Cross platform tag-based commercial server side scripting system.

ESP

ESP or Escapade was written in 1997 by Ed Carp, and enjoys wide use in Europe, but has had limited acceptance in the US.

JSP

A Java-based system for embedding Java-related code in HTML pages.

Lasso

A Datasource neutral interpreted programming language and cross platform server.

PHP

Common opensource solution based on including code in its own language into an HTML page.

Server-side JavaScript

A language generally used on the client side but also occasionally on the server side.

SMX

Lisp-like opensource language designed to be embedded into an HTML page.

Server Side Includes

A fairly basic system which is part of the common Apache web server, used primarily for combining documents or parts of documents on the server side into a single server response.”

http://en.wikipedia.org/wiki/Server-side_scripting

6. Advantage and disadvantage of client -side scripting

7. Advantage and disadvantage of the Server-side scripting

Advantage; the main advantage of server side is that they are almost always more powerful because there are not relying on the capabilities of an unknown system that could be anything from a 286 to a dual P4 and it doesn't rely on the interpretation of that language by the browser coz it will always run on the server, the programmer can test it and know exactly what it will do. Common examples of server-side languages are PHP and Perl.

8. Apple

Applet is a small application program component that typically executes in a client's Web browser but can execute in a variety of other simple applications or devices. An Applet can perform interactive animation, immediate calculation or other simple tasks without having to send a user request back to the server side.

Attributes

“Unlike a program, an applet cannot run independently; an applet features display and graphics and often interacts with the human user. However, they are usually stateless and have restricted security privileges. The applet must run in a container, which is provided by a host program, through a plug-in, or a variety of other applications including mobile devices that support the applet programming model.

Examples of applets are Java applets and Flash movies. Another example is the Windows Media Player applet that is used to display embedded video files in Internet Explorer (and other browsers that support the plug-in). Some plugins also allow for displaying various 3D model formats in a web browser, via an applet that allow the view of the model to be rd and zoomed. Many browser games are applet-based, though some may develop into fully functional applications that require installation.”

http://en.wikipedia.org/wiki/Applet

9. Servelet

Java Servelet allows a soft ware developer to ass dynamic content to a web server using the Java platform. Servelets are pieces of compiled code executable by a web server. By executing external code, web servers gain additional functionality.

Also sevelet are loaded dynamically and executed by the server when requested via an HTTP request.

“The Servlet API, contained in the Java package hierarchy javax.servlet, defines the expected interactions of a Web container and a servlet. A Web container is essentially the component of a Web server that interacts with the servlets. The Web container is responsible for managing the lifecycle of servlets, mapping a URL to a particular servlet and ensuring that the URL requester has the correct access rights.

A Servlet is an object that receives a request and generates a response based on that request. The basic servlet package defines Java objects to represent servlet requests and responses, as well as objects to reflect the servlet's configuration parameters and execution environment. The package javax.servlet.http defines HTTP-specific subclasses of the generic servlet elements, including session management objects that track multiple requests and responses between the Web server and a client. Servlets may be packaged in a WAR file as a Web application.”

http://en.wikipedia.org/wiki/Servlet

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