Network Infrastructure for E-Commerce 2

Network Infrastructure for  E-Commerce

 

1. Introduction
2. Common Gateway Interface
3. Multimedia Objects
4. Network Access Equipment
5. Network Cables
6. Broadband Telecommunication

 

 

1 Introduction

 

In here, you will learn about Common Gateway Interface (CGI), which
is a process used to share the data between the web server and the web browser.
CGI is a set of standards where a program can send data back to the web
server where it can be processed. Also discussed at length is broadband
telecommunication, which makes use of a digital or analogue signal to relay
voice and data. In most applications, the term is associated with systems offering
fast transmission of data, either using latest digital technology or an analogue
system with a wider bandwidth. There are numerous types of broadband
telecommunications in use today.

You will also be taught various other topics, including, but not limited to,
multimedia objects, network access equipment, and network cables.

2 Common Gateway Interface

 

As you traverse the vast frontier of the WWW, you could come across documents
that make you wonder, ‘How did they do this?’ These documents could consist
of, among other things, forms that put for advice or registration information,
image maps that allow you to click on different parts of the image, counters that
present the number of users that accessed the document, and utilities that
allow you to search databases for specific information. In most cases, you’ll find
that these properties were done using the Common Gateway Interface,
commonly known as CGI.

One of the Internet’s worst-kept secrets is that CGI is astoundingly simple.
That is, it’s trivial in design, and anyone with an iota of programming experience
can write rudimentary scripts that work. It’s only when your requirements are
more demanding that you have to master the more complex workings of the
Web.

CGI is the part of the Web server that can communicate with other different
programs running on the server. With CGI, the Web server can call up a program,
while passing user-specific data to the program (such as what host the user is
connecting from, or input the user has supplied using HTML form syntax). The
program then processes that data and the server passes the program’s response
back to the Web browser.

CGI is not an enchantment; it’s just programming with some particular
types of input and a few strict rules on program output. Everything in between is
just programming. Of course, there are special techniques that are particular to
CGI. But underlying it all is the simple model as shown in Figure (A)

                                                          Figure (A) CGI Model

Common uses of CGI include:

 

• Guest books
• Email forms
• Mailing list maintenance
• Blogs

3 Multimedia Objects

 

• Multimedia objects are files that hold images, audio recordings, video
clips and scanned documents, etc., which relate to some fact within our
genealogical data. A multimedia object can be linked with several entities
(animals, person, family, source …) and vice versa.

• In other words multimedia is media and content that uses a combination
of different content forms. The term can be used as a noun (a medium 

with multiple content forms) or as an adjective describing a medium as
having multiple content forms. The term is used in contrast to media which
only use traditional forms of printed or hand-produced material. Multimedia
includes a combination of text, audio, still images, animation, video, and
interactivity content forms.

• Multimedia is usually recorded and played, displayed or accessed by
information content processing devices, such as computerized and
electronic devices, but can also be part of a live performance. Multimedia
(as an adjective) also describes electronic media devices used to store
and experience multimedia content. Multimedia is distinguished from mixed
media in fine art; by including audio, for example, it has a broader scope.
The term ‘rich media’ is synonymous for interactive multimedia.
Hypermedia can be considered one particular multimedia application.

• Multimedia presentations may be viewed by person on stage, projected,
transmitted, or played locally with a media player. A broadcast may be a
live or recorded multimedia presentation. Broadcasts and recordings can
be either analogue or digital electronic media technology. Digital online
multimedia may be downloaded or streamed. Streaming multimedia may
be live or on-demand.

• Multimedia games and simulations may be used in a physical environment
with special effects, with multiple users in an online network, or locally
with an offline computer, game system, or simulator.

• The various formats of technological or digital multimedia may be intended
to enhance the users’ experience, for example to make it easier and faster
to convey information. Or in entertainment or art, to transcend everyday
experience. Enhanced levels of interactivity are made possible by
combining multiple forms of media content. Online multimedia is
increasingly becoming object-oriented and data-driven, enabling
applications with collaborative end-user innovation and personalyzation
on multiple forms of content over time. Examples of these range from
multiple forms of content on Web sites like photo galleries with both images
(pictures) and title (text) user-updated, to simulations whose co-efficient,
events, illustrations, animations or videos are modifiable, allowing the
multimedia ‘experience’ to be altered without reprogramming. In addition
to seeing and hearing, Haptic technology enables virtual objects to be
felt. Emerging technology involving illusions of taste and smell may also
enhance the multimedia experience.

4 Network Access Equipment

 

Hubs: All networks (except those using coaxial cable) require a central location

to bring media segments together. These central locations are called Hubs.
Hubs are special repeaters that overcome the electromechanical limitations of
a media signal path.

There are three types of Hubs:

               1. Passive Hub: A passive hub simply combines the signals of network
                                          segments. There is no signal regeneration.
               2. Active Hub: Active hub is that which regenerates of amplifies the
                                          signals.
              3. Intelligent Hub: Intelligent hub regenerates the signal and performs
                                          some network management and intelligent path selection.

Switches: It supports transmitting receiving and controlling traffic with other
computers on the network. MAC (Media Access Control) address is hard-coded
on the card by manufacture. This MAC address is globally unique.

Comparison of Hub and Switch

 

• Hub is broadcasting device while switch is point-to-point communication
device.

• Hub operates at physical layer while switch operates at data link layer.

• Switch can be used as a repeater but hub cannot be used as repeater.

• Switch uses switching table to find out the correct destination while hub
simply broadcasts the incoming packet.

Repeaters: Repeaters (refer to Figure (B)) are devices that operate at the
physical layer of the OSI model. The basic purpose of a repeater is to extend the

 distance of LAN. Their primary purpose is simply to regenerate a signal
received from input and correct the signal to its original state for output.

                                                  Figure (B) Repeater

Network Interface Card (NIC): The primary function of NIC is to allow the
computer to communicate on the network. It supports transmitting, receiving
and controlling traffic with other computer on the network. NIC operates at
physical layer of OSI model. MAC address is hard coded onto the card by
manufacturer. This MAC address is globally unique and is of 48 bits. The MAC
address provides a way to distinguish one NIC from other NIC. These MAC
addresses are also called physical address.

Bridge: A bridge (Figure (C)) is a device that is attached to two or more
LANs to create an extended LAN. The LANs to be interconnected may be similar
or dissimilar. As each type of LAN has different MAC frame structure, the bridge
takes care of these differences by reformatting the frames.

                                                           Figure (C) Bridge

Router: A router (Figure (D)) operates at the third network layer of ISOOSI
model. It connects more than two different types of network. Router
determines the short path between source and destination for data transmission.

                                                                Figure (D) Router

bellow table shows the similarities and differences between a router and a
bridge.

 

5 Network Cables

Network cables are the medium through which information generally travels
from one node/network device to another. There are many types of cables which
are used for computer network. In some cases, a network will utilize only one
type of cable, while other networks will use a variety of cable types. The type of
cable chosen for a network is related to the network’s topology, protocol, and
size. Understanding the characteristics of different types of cable and how they
relate to other aspects of a network is necessary for the development of a
successful network.

There are following types of cables used in networks and other related
topics.

• Fibre optic cable
• Cable installation guides
• Wireless LANs
• Unshielded Twisted Pair (UTP) cable
• Shielded Twisted Pair (STP) cable
• Coaxial cable

Fibre optic cable

 

 

Fibre optic cabling ( Figure (E)) consists of a centre glass core surrounded
by several layers of protective materials. It transmits light rather than electronic
signals eliminating the problem of electrical interference. This makes it ideal for
certain environments that contain a large amount of electrical interference. It is
also the standard for connecting networks between buildings, due to its immunity
to the effects of moisture and lighting.

Fibre optic cable has the capability to transmit signals over much longer
distances than coaxial and twisted pairs. It also has the capability to carry

information at superior speeds. This capacity broadens communication
possibilities to include services such as video conferencing and interactive
services. The cost of fibre optic cabling is comparable to copper cabling; however,
it is more difficult to install and modify.

The centre core of fibre cables is made from glass or plastic fibres. A
plastic coating then cushions the fibre centre, and kevlar fibres help to strengthen
the cables and prevent breakage. The outer insulating jacket is made of teflon
or PVC.

                                                       Figure (E) Fibre Optic Cable


There are two common types of fibre cables— single mode and multimode.
Multimode cable has a larger diameter; however, both cables provide high
bandwidth at high speeds. Single mode can provide more distance, but it is
more expensive.

Installing cable—some guidelines

 

When running cable, it is best to follow a few simple rules:

• If it is necessary to run cable across the floor, cover the cable with cable
protectors.

• Label both ends of each cable.

• Use cable ties (not tape) to keep cables in the same location together.

• Always use more cable than you need. Leave plenty of slack.

• Test every part of a network as you install it. Even if it is brand new, it may
have problems that will be difficult to isolate later.

• Stay at least 3 feet away from fluorescent light boxes and other sources
of electrical interference.

Wireless LANs 

 

                                                     Figure (F) Wireless LANs

Wireless LANs use high frequency radio signals, infrared light beams, or
lasers to communicate between the workstations, servers, or hubs. Each
workstation and file server on a wireless network has some sort of transceiver/
antenna to send and receive the data. Information is relayed between
transceivers as if they were physically connected. For longer distances, wireless
communications can also take place through microwave transmission, cellular
telephone technology or by satellite.

Wireless networks are great for allowing laptop, desktop, portable devices,
or remote computers to connect to the LAN. Wireless networks are also beneficial
in older buildings where it may be difficult or impossible to install cables.
The two most common types of infrared communications used in schools
are line-of-sight and scattered broadcast. Line-of-sight communication means
that there must be an unblocked direct line between the workstation and the
transceiver. If a person walks within the line-of-sight while there is a transmission,
the information would need to be sent again. This kind of obstruction can slow
down the wireless network. Scattered infrared communication is a broadcast of
infrared transmissions sent out in multiple directions that bounces off walls and
ceilings until it eventually hits the receiver. Networking communications with
laser are virtually the same as line-of-sight infrared networks.

Advantages of wireless networks: 

• Cost: Setting up a wireless network can be much more cost effective than
buying and installing cables.

• Expandability: Adding new computers to a wireless network is as easy as
turning the computer on (as long as you do not exceed the maximum
number of devices).

• Mobility: With a laptop computer or mobile device, access can be available
throughout a school, at the mall, on an airplane, etc. More and more
businesses are also offering free Wi-Fi access (‘Hot spots’).

• Fast setup: If your computer has a wireless adapter, locating a wireless
network can be as simple as clicking ‘Connect to a Network’—in some
cases, you will connect automatically to networks within range.

Disadvantages of wireless networks:

 

• Inconsistent connections: How many times have you said to yourself,
‘Wait a minute, I just lost my connection?’ Because of the interference
caused by electrical devices and/or items blocking the path of transmission,
wireless connections are not nearly as stable as those through a dedicated
cable.

• Speed: The transmission speed of wireless networks is improving;
however, faster options (such as gigabit Ethernet) are available via cables.
If you are only using wireless for Internet access, the actual Internet
connection for your home or school is generally slower than the wireless
network devices, so that connection is the bottleneck. If you are also
moving large amounts of data around a private network, a cabled
connection will enable that work to proceed much faster.

• Security: Protect sensitive data with backups, isolated private networks,
strong encryption and passwords, and check network access traffic to
and from the wireless network.

• Interference: Because wireless networks deploy radio signals and similar
techniques for transmission, they are vulnerable to intrusion from lights
and electronic devices.

Unshielded Twisted Pair

 

Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded
twisted pair (UTP) is the most popular and is generally the best option for school
networks.

                                               Figure (G) Unshielded Twisted Pair

The quality of UTP (refer to Figure(G)) may range from telephone-grade
wire to extremely high-speed cable. This cable has four pairs of wires inside the
jacket. Each pair is twisted with a different number of twists per inch that helps
to eliminate interference from adjoining pairs and other electrical devices. The
Electronic Industry Association/Telecommunication Industry Association
(EIA/TIA) has set standards of UTP and rated six categories of wire, which are
as follows. 

 

Unshielded Twisted Pair connector

 

The standard connector for unshielded twisted pair cabling is known as RJ-45
connector ( Figure (H)). This is a plastic connector that looks like a large
telephone-style connector. A slot allows the RJ-45 to be inserted only one way.
RJ stands for Registered Jack, implying that the connector follows a standard
borrowed from the telephone industry. This standard assigns which wire goes
with each pin inside the connector.

                                                      Figure (H) RJ-45 Connector

Shielded Twisted Pair (STP) cable

 

UTP cable is the least expensive cable; it may be disposed to radio and electrical
frequency interference (it should not be too close to electric motors, fluorescent
lights, etc.). If you must place cable in environments with lots of potential
interference, or if you must place cable in extremely sensitive environments
that may be susceptible to the electrical current in the UTP, shielded twisted
pair may be the solution. Shielded cables can also facilitate to extend the
maximum distance of the cables.

       Shielded twisted pair cable is available in three different configurations:

              1. Each pair of wires is individually shielded with foil.

              2. There is a foil or braid shield inside the jacket covering all wires.

              3. There is a shield around each individual pair, as well as around the
                   entire group of wires.

Coaxial cable

Coaxial cable ( Figure(I)) has a single copper conductor at its centre. A
plastic layer provides insulation between the centre conductor and a braided
metal shield. The metal shield facilitates to block any outside interference from
fluorescent lights, motors, as well as other computers.

                                               
                                                          Figure (I) Coaxial Cable

 
Coaxial cabling is not easy to install, but it comes with the advantage of
being highly resistant to signal interference. Also, it can support greater cable
lengths between network devices than twisted pair cable. The two types of
coaxial cabling are thick coaxial and thin coaxial.

Thin coaxial cable is known as thinnet. 10Base2 refers to the specifications
for thin coaxial cable moving Ethernet signals. The 2 refers to the approximate
maximum segment length being 200 metres. The maximum division length is
actually 185 metres. Thin coaxial cable has been popular in school networks,
particularly linear bus networks.

Thick coaxial cable is known as thicknet. 10Base5 refers to the
specifications for thick coaxial cable carrying Ethernet signals. The 5 refers to
the maximum division length being 500 metres. Thick coaxial cable has an
extra protective plastic cover that helps keep moisture away from the centre
conductor. This creates thick coaxial a great choice when running longer lengths
in a linear bus network. One disadvantage of thick coaxial is that it is not easily
bendable and quite difficult to install.

Coaxial cable connectors

A most common type of connector used with coaxial cables is the Bayone-Neill-
Concelman (BNC) connector ( Figure (J)). There are different types of
adapters for BNC connectors, including a T-connector, barrel connector, and
terminator. Connectors are the most vulnerable points in any network. To help
avoid problems, always use the BNC connectors that ‘screw’ onto the cable.

                   
                                                             Figure (J) BNC Connector

6 Broadband Telecommunication 

In general, broadband refers to telecommunication where a wide band of
frequencies is available to transmit information. There is wide range of
frequencies available, and information can be multiplexed and sent on many
different frequencies or channels within the band simultaneously. This way, more

information can be transmitted in a shorter duration of time than what is
achievable with older methods of transmission.

One of the configurations that have been around for a number of years is
the integrated services digital network, or ISDN. This network design can be
used to relay voice and data over copper telephone lines. This may not be the
fastest option in fashion today; however, it does make it possible to access the
Internet without the requirement of a high-speed connection or a lot of resources.
Another common example is the asynchronous transfer mode, referred
to in the telecommunications world as ATM. This option is much quicker than
ISDN and has proven to be extremely handy for companies relying heavily on
the Internet and electronic communications.

Asynchronous Transfer Mode, (ATM), is a network technology based on
transferring data in cells or packets of a fixed size. The cell used with ATM is
smaller compared to units used with older technologies. This size of the cell
allows for an advantage—ATM equipment can transmit video, audio, and
computer data over the same network, and guarantee that no single type of
data clutters the line.

Some people opine that ATM is the definitive answer for the Internet
bandwidth problem; others and not so confident. ATM creates a fixed or route
between two points whenever data transfer begins. This differs from TCP/IP,
where messages are divided into packets and each packet can take a different
route from source to destination. This difference makes it easier to track and bill
data usage across an ATM network, but it renders it less adaptable to sudden
increases in network traffic.

Integrated Service Digital Network

Integrated Service Digital Network, (ISDN), is the original high-speed Internet
service. It sparked the high-speed Internet development between service
providers during the 1990s and, of course, revolutionized Internet use. Much
like its predecessor, the dial-up Internet service, ISDN utilizes a phone line. In
fact, it set the standard for telephone data service.

ISDN Internet service was the improvement upon dial-up, and it also paved
the way for DSL and cable-modem Internet service thereafter. It can be
considered the step of Internet evolution that lies between dial-up and DSL/
Cable. Modernizing Internet use and bringing high-speed access inside the
home, ISDN became the standard by which rival broadband Internet service
providers competed. Although ISDN Internet service still exists, like the dial-up

connection it is being replaced by faster and cheaper services that the broadband
companies are providing. Regardless, broadband high-speed Internet service
is still compared with ISDN today, since they both represent the benchmark of
their times.

ISDN Internet service is basically a telephone-based network system that
operates by a circuit switch, or dedicated line, and is capable of transmitting
data and phone conversations digitally over normal telephone wires. This makes
it both faster and of higher quality than dial-up Internet service. During the 1990s
this revolutionized the way people did business. No longer would you have to
miss a call in order to access your Internet, or shut down the Internet to make a
telephone call. As such, ISDN Internet service made video teleconferencing not
only possible, but very popular as well.

There are two different types, or lines, of ISDN Internet service.

• The first is a basic rate ISDN line. Called a Basic Rate Interface
(BRI), this line has two data, or bearer, channels that operate at 64
kbit/sec. Two or more ISDN-BRI lines can be combined as well,
yielding speeds of 256 kbit/sec. It is common to combine these lines
for video conferencing use or for transmitting data at higher speeds.

• The second type of ISDN line is called a primary rate line, or Primary
Rate Interface (PRI). This line had 23 bearer channels and has a
total speed of 1,544 kbit/sec. It is used mostly for telephone
communication rather than data transmission, particularly within
companies that have large, private telephone exchange systems
operating inside their business.

The advantages of having ISDN Internet service definitely lies in the data
lines themselves. Not only do you have constant data speed via these lines,
each bearer channel runs at 64 kbit/sec with the ability to be combined to reach
greater speeds. ISDN Internet serviced also facilitates multiple data transmission,
so telephone calls and data downloading are no longer mutually exclusive. The
disadvantages, however, is that the digital clarity of ISDN voice communication
and its speedy data transmission come at an extra cost. ISDN is billed like a
phone line, but with an extra cost for service. Although its operational distance
from the ISDN central office is greater than that for DSL, its terminal adaptor
(similar to a modem) costs more than DSL or cable modems. While this
equipment and service continue to remain exorbitant, it is leaving the way open
for other Internet services to share the marketplace.

Frame Relay

Frame Relay is a digital connection-oriented data service that sends packets of
data, called frames, over the network. This frame of data is transmitted through
the network and checked for errors. Frame Relay is designed for cost-efficient
data transmission for intermittent traffic between local area networks (LAN-to-
LAN) and between end-points in a wide area network (WAN). It is a data network
service bundled with leased line access for transmitting data between remote
networks. Frame Relay is a digital packet network service that provides all the
features and benefits of a dedicated network service without the expense of
multiple dedicated circuits. This data is carried in the form of packets and given
an ID on a per packet basis. It is then sent across the network in a very efficient
way. In a Frame Relay network, circuits are connected to a packet switch within
the network that ensures that packets are routed to the correct location. Frame
Relay is a digital dedicated service that is leased from a carrier. It is a switched
service.

Application-level security

• Web applications can be protected from ‘SQL Injection Attacks’ where
the attacker enters SQL commands into Web form input fields or URL
query strings to try to manipulate the SQL statement being sent to and
from the database. To avoid SQL injection attacks, the following methods
should be used:

o Use of queries or stored procedures to access a database as opposed
to using string concatenation

o Limitation the amount of characters in Web form input fields and
URL query strings to a proper amount

o Validate text input and URL query strings for improper characters
(e.g. apostrophe, dash)

o Do not display errors to the user that contain information about the
database or actual source code

• ASP.Net Web applications must be secured from ‘Cross Site Scripting’
(XSS) attacks. To accomplish this, developers must ascertain that the
ASP.Net ‘validateRequest’ Page directive is set to True (the default setting)
so that users of the application are prevented from entering HTML or
JavaScript code into Web forms.

Data transmission security

When confidential or important data is passed between the user and the Web
server, the HTTPS (SSL over HTTP) protocol will be used. SSL provides server
authentication, data encryption (‘over the wire’), and data transmission integrity.
The SSL certificate used on the Web server will need to be ‘trusted’ by the Web
browsers listed on the CDE’s Minimum Web Browser Requirement Web page.

Database security

• Web applications should use minimum privileges to access database
objects (i.e. tables, views, stored procedures). For instance, if the Web
application needs read-only access to a specific database table, the
database permissions should be set accordingly than giving the Web
application ‘admin or owner’ rights to the entire database.
• Individual database fields storing confidential or sensitive data (for
example, passwords, social security number) must be stored using
encryption techniques.

Password requirements

Passwords whether created by application developers, administrators, or users
must meet or be required through validation to meet all of the following
parametres. Passwords must:
• Be at least eight characters in length.
• Contain characters from three of the following four categories:
o Uppercase letters (A though Z)
o Lowercase letters (a through z)
o Numbers (0 through 9)
o Special characters (!, @, #, $, ^, &, *, -, =, _, +, ?)
• Not be the same as the logon or user name.

Special note:-

• Common Gateway Interface (CGI): Process used to share the data
between the web server and the web browser

• Hubs: Central locations in networks that bring media segments together

• Repeaters: devices that operate at the physical layer of the OSI model,
whose basic purpose is to extend the distance of LAN

• Bridge: Device that is attached to two or more LANs to create an extended
LAN

• Router: Operates at the third network layer of ISO-OSI model and
connects more than two different types of network

• Network cables: Medium through which information generally travels
from one node/network device to another

• Fibre optic cable: Cable that consists of a centre glass core surrounded
by several layers of protective materials, and which transmits light rather
than electronic signals

• Wireless LANs: LANs that use high frequency radio signals, infrared
light beams, or lasers to communicate between the workstations, servers,
or hubs

• Line-of-sight communication: Communication through unblocked direct
line between the workstation and the transceiver