Wednesday 30 May 2012

INTERNET INFRASTRUCTURE...

  • In information technology and on the Internet, infrastructure is the physical hardware used to interconnect computers and users. Infrastructure includes the transmission media.Infrastructure also includes the software used to send, receive, and manage the signals that are transmitted.
  • In some usages, infrastructure refers to interconnecting hardware and software and not to computers and other devices that are interconnected. However, to some information technology users, infrastructure is viewed as everything that supports the flow and processing of information.
INTERNET PROTOCOL (IP)
  • IP is the primary protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering datagrams from the source host to the destination host solely based on the addresses. For this purpose, IP defines datagram structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram source and destination.
  • IP address consist of 32 bits (shown as 4 octets of number from 1-225 represented in decimal form instead of binary).
  • Consisit of two part: network & host/node of network
  • Class of address determines which part belongs to network add & which part belongs to node address.
Network Classess Note.. 

CLASS A NETWORK

-       Binary add start with 0 therefore decimal can be anywhere from 1-126
-       First octet (8 bits) identify network, other 3 octets identify the host.

CLASS B NETWORK 

-       Binary add start with 10 therefore decimal can be anywhere from 128-191.
-       127 reserved for LOOPBACK & used for internal testing on local machine.
-       First 2 octet (16 bits) identify network, other 2 octets indicate the host.

CLASS C NETWORK

-       Binary add start with 110 therefore decimal can be anywhere from 192-223.
-       First 3 octet (24 bits) identify network, other 1 octet indicate the host.

CLASS D NETWORK

-       Binary add start with 1110 therefore decimal can be anywhere from 224-239.
-       To support multitasking (multi layers).

                                                     CLASS E NETWORK

-       Binary add starts with 1111 therefore decimal can be anywhere from 240-255.
-       Used for experimentation.

DOMAIN NAME SYSTEM (DNS)
  • DNS is an Internet service that translates domain names into IP addresses. Because domain names are alphabetic, they're easier to remember. The Internet however, is really based on IP addresses. 
  • Every time you use a domain name, therefore, a DNS service must translate the name into the corresponding IP address. For example, the domain name www.example.com might translate to 198.105.232.4.
  • The DNS system is, in fact, its own network. If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned.
  • The Domain Name System makes it possible to assign domain names to groups of Internet resources and users in a meaningful way, independent of each entity's physical location. 
  • Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device.
  • Internet domain names are easier to remember than IP addresses. Users take advantage of this when they recite meaningful Uniform Resource Locators (URLs) and e-mail addresses without having to know how the computer actually locates them.
  • DNS also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.
INTERNET ACCESS PROVIDER (ISP)
  • Access ISPs directly connect clients to the Internet using copper wires, wireless or fiber-optic connections.
  • ISP, it refers to a company that provides Internet services, including personal and business access to the Internet. For a monthly fee, the service provider usually provides a software package, username, password and access phone number.
  • Equipped with a modem, you can then log on to the Internet and browse the World Wide Web and USENET, and send and receive e-mail. For broadband access you typically receive the broadband modem hardware or pay a monthly fee for this equipment that is added to your ISP account billing.
HTTP
  • HTTP stands for HyperText Transfer Protocol. Hypertext is a multi-linear set of objects, building a network by using logical links (the so called hyperlinks) between the nodes (e.g. text or words).
  • HTTP is the protocol to exchange or transfer hypertext.
  • It’s what browsers and web servers rely on for exchanging data so that you can surf the web, browse web pages, search Google, download pictures, and viewing YouTube.
  • Developed by W3C and IETF in the last few years of the last century, it’s part of a bigger protocol family created to support the whole Internet, called TCP/IP. As a subset, HTTP’s responsibility is the World Wide Web or WWW.
  • By HTTP definition and usage, it’s fundamentally an information exchanging procedure standard between 2 communicating parties or computers, such as the client and the server.
  • While you type a URL address in the web browser, the browser will have to know the protocol to use when fetching the remote resource such as a web page or a picture at that address. Failing to do so, as we most of the time would do without the http:// part, the browser will assume HTTP by default and prepend it to the URL address.
  • A web address representing an access point on the web almost always start with http://, immediately followed by the web page address such as in this one ‘http://www.google.com/’.
  • This is the root web site address of Google. And browsing to it, the server located at the address would serve up the home page of Google. This is all beyond the meaning of HTTP however, what this basically means is that, a web address consists of 2 basic parts: Protocol (HTTP) & Address (WWW.GOOGLE.COM).

Thursday 10 May 2012

WIRELESS...

 more info about WIRELESS~ 
  • Wireless communication involves
            • radio frequency communication
            • microwave communication, for example longrange line of sight via highly        directional antennas or short lineofantennas, short range communication
            • infrared (IR) shortrange communication, for example from remote controls or via IRDA
  • Applications may involve pointtopoint communication, pointtomultipoint communication, broadcasting ,cellular networks and other wireless networks.

*Devices commonly use wireless networking technologies:

􀂉 portable computers,
􀂉 desktop computers
􀂉 handheld computers,
􀂉 personal digital assistants (PDAs),
􀂉 cellular phones,
􀂉 penbased computers,
􀂉 pagers, GPS etc.


*Type of Wireless Network:
ô€€¹ Wireless wide area networks (WWANs)
ô€€¹ Wireless metropolitan area networks (WMANs)
ô€€¹ Wireless local area networks (WLANs)
ô€€¹ Wireless personal area networks (WPANs) 

  • TERRESTRIAL MICROWAVE
http://en.wikipedia.org/wiki/Microwave

-high antenna, longer sight distance
-signal: 1 way direction at a time
-type of antenna: 
  1.  parabolic dish : give greatest range for signal & based on geometry of parabola..
  2. horn:gigantic scoop 
  • SATELITE
Satellite Internet comes in two flavors:

  • One-way systems use a conventional Internet link (usually telephone) for upload and the satellite link for high-speed download.
  • Two-way systems add a transmitter to the satellite modem and upload via the satellite.

Satellite speeds are typically in the 0.5 to 2.0 Mbps range for download, and approximately 1/10th of the download speed for upload in a two-way system. In addition, there is about a 400 millisecond latency involved in sending a signal from a base-station to a satellite and back to Earth. Consequently, satellite connections aren't fully competitive with other home broadband Internet options. 

- Uplink = transmission from earth --> satellite
- Downlink = transmission from satellite --> earth
  • WIFI
the underlying technology of wireless local area networks (WLAN)
ô€€¹ based on the IEEE 802.11 specifications.
ô€€¹ used for mobile computing devices, such as laptops in LANs,increasingly used for more services, including Internet and VoIP phone access, gaming, and basic connectivity of consumer electronics such as televisions and DVD players, or digital cameras
ô€€¹ Frequency 2.4 GHz
ô€€¹ Range 100300 feet(indoor) 300900 feet(outdoor)

# IEEE 802.11 (a &b) 
wireless 802.11a & 802.11 b

*CELLULAR PHONE
  • 1G
1G is short for firstgeneration wireless telephone
technology. This generation of phones and networks is
represented by the bricksized analog phones
introduced in the 1980’s. Subsequent numbers refer
to newer and upcoming technology.
  • 2G
2G phones use digital networks. Going alldigital allowed for
the introduction of digital data services, such as SMS and
email. 2G networks and their digital nature also made it more
difficult to eavesdrop on mobile phone calls.
  • 3G
3G networks are an in between standard. 3G is seen more as
pre4G instead of a standard of its own. The advantage 3G
networks have over 2G networks is speed. 3G networks are
built to handle the needs of today’s wireless users. This
standard of wireless networks increases the speed of internet
browsing, picture and video messaging, and handheld GPS
use.
  • 4G
4G (AKA Beyond 3G) is like the other generations in that its
advantage lies in promised increased speeds in data
transmission. There is currently no formal definition for 4G,
but there are objectives. One of these objectives is for 4G to
become a fully IPbased system, much like modern computer
networks. The supposed speeds for 4G will be between 100
Mbit/s and 1 Gbit/s.

Wednesday 25 April 2012

CABLING...


Is a medium through which information usually moves from one network device to another.

TYPES OF CABLES

*use current
        - Unshielded Twisted Pair (UTP) cable
        - Shielded Twisted Pair (STP) cable

*use light
        - Co-axial cable
        - Fiber Optic cable
        - Wireless cable

UNSHIELDED TWISTED PAIR (UTP) CABLE

-has 4 pairs of wires inside jacket
-each pair is twisted with different number of twists per inch
-to help eliminate interference from adjacent pairs (nearest disruption) & others electrical devices.
-UTP’s categories:

TYPES

USE

EXAMPLE
Category 1
Voice
Telephone wire
Category 2
Data to 4 Mbps
Local talk
Category 3
Data to 10 Mbps
Ethernet
Category 4
Data to 20 Mbps
16 Mbps token ring
Category 5
Data to 100 Mbps
Fast ethernet

# category 3 & 4 usually use in school.

-Standard connecter : RJ-45 connecter (Registered Jack)
-Disadvantages : it may be susceptible to radio & electrical frequency        interference.






SHIELDED TWISTED PAIR (STP) CABLE

-consist of two individual wires wrapped in a foil shielding
-to help provide a more reliable (no disruption/accurate) communication
-suitable for environments with electrical interference
-extra shielding can make cables quite bulking
-often used on networks using Token Ring topology




CO-AXIAL CABLE

-has a single copper conductor at its center
-a plactic layer provides insulation between center conductor & a braided metal shield
-metal shield: helps to block any outside interference from fluorescent lights, motors, and other computers
-connecter: Bayone-Neill-Concelman (BNC) connector
-different types of adapters are available for BNC connectors, including a T-connector, barrel connector, and terminator.




FIBER OPTIC CABLE

-consists of a center glass core surrounded by several layers of protective materials
-it transmits light rather than electronic signals
-able to transmit signals over much longer distances than coaxial and twisted pair







Summary of Ethernet cabling.