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					Future Academy
Networks
3rd year
Computer Sciences
Spring Semester 2009
Exercise (11) see lectures
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Question (1) pp 3-15
You recommend an internet-in-a-box product for one of your friends. He found
that the product includes;
     1. web browser
     2. e-mail software
     3. modem
     4. preselected ISP
What is the function of each component?
Web browser :-
                   Is a software application which enables a user to display
and interact with text, images, videos, music and other information
typically located on a Web page at a website on the World Wide Web or
a local area network. Text and images on a Web page can contain
hyperlinks to other Web pages at the same or different website. Web
browsers allow a user to quickly and easily access information provided
on many Web pages at many websites by traversing these links. Web
browsers format HTML information for display, so the appearance of a
Web page may differ between browsers.
Some of the Web browsers available for personal computers include
Internet Explorer, Mozilla Firefox, Safari, Opera, and Flock, in order of
descending popularity (in March 2008). Web browsers are the most
commonly used type of HTTP user agent. Although browsers are
typically used to access the World Wide Web, they can also be used to
access information provided by Web servers in private networks or
content in file systems.

E-mail Software:-
                   E-mail, short for electronic mail and often abbreviated
to e-mail, email or simply mail, is a store and forward method of
composing, sending, receiving and storing messages over electronic
communication systems. The term "e-mail" (as a noun or verb) applies
both to the Internet e-mail system based on the Simple Mail Transfer
Protocol (SMTP) and to X.400 systems, and to intranet systems allowing
users within one organization to e-mail each other. Intranets may use
the Internet protocols or X.400 protocols for internal e-mail service
supporting workgroup collaboration. E-mail is often used to deliver bulk
unsolicited messages, or "spam", but filter programs exist which can
automatically delete some or most of these, depending on the situation.

Modem:-
         Modem (from modulator-demodulator) is a device that
modulates an analog carrier signal to encode digital information, and
also demodulates such a carrier signal to decode the transmitted
information. The goal is to produce a signal that can be transmitted
easily and decoded to reproduce the original digital data. Modems can
be used over any means of transmitting analog signals, from driven
diodes to radio.

Preselected ISP:-
                  "ISP" redirects here. For other uses, see ISP
(disambiguation).
An Internet service provider (abbr. ISP, also called Internet access
provider or IAP) is a company or business that provides access to the
Internet and related services. In the past, most ISPs were run by the
phone companies. Now, ISPs can be started by just about any individual
or group with sufficient money and expertise. In addition to Internet
access via various technologies such as dial-up and DSL, they may
provide a combination of services including Internet transit, domain
name registration and hosting, web hosting, and collocation.


  ‫أً ين ناحيو تانيو نهَ عايز يكتب عن فيى بذل يا يشٌف انذش ده كهو , ىتتكهى عن يًيزات ً خصائص‬
‫ ً يا ريت يننساش‬ISP ‫يتصفح اننت , ً خصائص برايج انًيم ً خصائص انًٌدو اً انرًتر ً يًيزات ال‬
     ‫ً احنا بنشرح اننا نتكهى عن كم حاجو ين حيث تٌفير انتطبيقات انًناسبو ً تٌفير حزو انبرًتٌكٌالت‬
                        ًٍ‫انًناسبو ً بانتانَ يذٍ سيٌنتيا باننسبو نًثيالتيا ين ادًات االستخذاو انيذ‬


Question (2) pp 3-16 to 3-20
Make a comparison table for the items in figure, showing the cost, properties,
construction, advantages, disadvantages, and favorable conditions for use.
                                                                        STP          Stranded
                                  Wired                 Twisted
                                  cables                pair
                                                                        UTP          Solid
                                                         Coax
     Transmission                                                         Thick
     Media                                                                net
                                                                          Thin net

                                  Wireless               Fiber             Single mode
                                                         optics
                                                                           Multimode
‫هتدوس على الكالم ده علشان يفتحلك الصفحه اللى فيها كل حاجه عن الكابالت , هتقراها و تفهن كل حاجه فى‬
                                                   ‫الكابالت و بعد كده تشىف هتكتب ايه و انت و دهاغكـ‬

Question (3) pp 3-17
Explain with examples the meaning of;
                     - 10baseT
                     - Attenuation
                     - The seven categories twisted pair
                     - RJ-45 connector
                     - Plenum
                     - 10base2
10baseT:-
           Ethernet over twisted pair
There are several standards for Ethernet over twisted pair or copper-
based computer networking physical connectivity methods. The
currently most widely used of these are 10BASE-T, 100BASE-TX, and
1000BASE-T (Gigabit Ethernet), running at 10 Mbit/s, 100 Mbit/s, and
1000 Mbit/s (1 Gbit/s) respectively. These three standards all use the
same connectors. Higher speed implementations nearly always support
the lower speeds as well, so that in most cases different generations of
equipment can be freely mixed. They use 8 position modular
connectors, usually (but incorrectly) called RJ45 in the context of
Ethernet over twisted pair. The cables usually used are four-pair
Category 5 or above twisted pair cable. Each of the three standards
support both full-duplex and half-duplex communication. According to
the standards, they all operate over distances of 'up to 100 meters'.
The common names of the standards are derived from several aspects
of the physical media. The number refers to the theoretical maximum
transmission speed in megabits per second (Mbit/s). The BASE is short
for baseband, meaning that there is no frequency-division multiplexing
(FDM) or other frequency shifting modulation in use; each signal has full
control of wire, on a single frequency. The T designates twisted pair
cable, where the pairs of wires are twisted together for purposes of
reducing crosstalk (FEXT and NEXT) when the pulsing direct current
goes across the wires and creates electromagnetic induction effects.
Where there are several standards for the same transmission speed,
they are distinguished by a letter or digit following the T, such as TX.
Some higher-speed standards use twin-axial cable, designated by CX.

Attenuation:-
             Attenuation is the reduction in amplitude and intensity of a
signal. Signals may be attenuated exponentially by transmission
through a medium, in which case attenuation is usually reported in dB
with respect to distance traveled through the medium. Attenuation can
also be understood to be the opposite of amplification. Attenuation is an
important property in telecommunications and ultrasound applications
because of its importance in determining signal strength as a function
of distance. Attenuation is usually measured in units of decibels per unit
length of medium (dB/cm, dB/km, etc) and is represented by the
attenuation coefficient of the medium in question.

Rj-45 connector:-
                     The 8 Position 8 Contact (8P8C) modular plugs and
jacks are communications connectors. Under the same naming scheme,
an 8P6C connector has eight positions, with six positions containing
conductors, and a 6P6C connector has six positions, all containing
conductors. 8P8C connectors are typically used to terminate twisted
pair cable.
These connectors are often referred to as RJ45 plugs and jacks. This is
technically incorrect because the RJ45 standard specifies both the
mechanical interface and a different wiring scheme than T568A/B, which
is often used for Ethernet and telephones.
8P8C consists of two paired components: the male plug and the female
jack or socket. Each has eight equally-spaced conductors. On the plug,
these conductors are flat contacts positioned parallel with the connector
body. Inside the jack or socket, the conductors are suspended
diagonally toward the insertion interface. When an 8P8C plug is mated
with an 8P8C jack, the conductors meet and create an electrical
connection. Spring tension in the jack's conductors ensure a good
interface with the plug and allow for slight travel during insertion and
removal. The 8P8C connector is probably best known for its use in
Ethernet. Since about 2000, it is nearly universal as the type of
connector used on a cable that carries a single Ethernet network, and
has replaced many older connector types. Older connectors have also
been phased out as modern cables no longer have the high current and
voltage requirements for which the bulkier connectors were designed.

Plenum:-
        Plenum may refer to:
•    the antithesis of a vacuum; in other words, completely-filled,
positive-pressure space (see Plenism).
•      the pressures slightly above atmospheric, usually inside air or
gas systems as the result of the action of fans or blowers. The plenum is
measured in small units of pressure such as pascals (Pa) or ounces-
force per square inch or millimeters of mercury.
•      a legislative meeting in which all members of the body are present
and voting. Frequently this is used to refer to a full meeting of a
Communist Party central committee. Compare to quorum.
•      a second set of bellows in devices such as hand or foot pumped
organs with a weight on the top which acts as an air reservoir.
•      Plenums in buildings are enclosed spaces that are not for human
occupancy, but are often used for heating, ventilating, and/or air-
conditioning equipment and airflow, and for other equipment such as
cables, piping, and luminaires. 'Plenum boxes' or sections are portions
of HVAC air handlers or terminal units.
•      Plenum cable refers to structured cabling permitted under
building codes for plenum spaces. Plenum rated cable has slow-
burning, fire-resistant casing that emits little smoke
•      Plenum filtration, a method of aquarium filtration using a deep
sand bed with a gap below it.

10base2 :-
          10BASE2 (also known as cheapernet, thin Ethernet, thinnet or
thinwire) is a variant of Ethernet that uses thin coaxial cable (RG-58 or
similar, as opposed to the thicker RG-8 cable used in 10BASE5
networks), terminated with BNC connectors. For many years this was
the dominant 10 Mbit/s Ethernet standard, but due to the immense
demand for high speed networking, the low cost of Category 5 Ethernet
cable, and the popularity of 802.11 wireless networks, both 10BASE2
and 10BASE5 have become almost obsolete.
Question (4) pp 3-16 to 3-19
State some networking situations where you may come across the following
terminology
Abbreviation Details                   Circumstances
STP           Shielded twisted pair
UTP           Unshielded twisted pair
BNC           British naval connector
BNC           Bayonet Neill-
              Concelman


Abbreviation            Details                 Circumstances
STP                     Shielded twisted pair   STP cabling includes
                                                metal shielding over
                                                each individual pair of
                                                copper wires. This type
                                                of shielding protects
                                                cable from external EMI
                                                (electromagnetic
                                                interferences). e.g. the
                                                150 ohm shielded
                                                twisted pair cables
                                                defined by the IBM
                                                Cabling System
                                                specifications and used
                                                with token ring
                                                networks.
UTP                     Unshielded twisted      UTP cables are found in
                        pair                    many Ethernet
                                                networks and telephone
                                                systems. For indoor
                                                telephone applications,
                                                UTP is often grouped
                                                into sets of 25 pairs
                                                according to a standard
                                                25-pair color code
                                                originally developed by
                                                AT&T. A typical subset
                                                of these colors
                                                (white/blue, blue/white,
                                                white/orange,
                                                orange/white) shows up
                                                in most UTP cables.
                                                UTP cable is also the
                                                most common cable
                                                used in computer
                                                networking. UTP cables
                                                are often called ethernet
                       cables after Ethernet,
                       the most common data
                       networking standard
                       that utilizes UTP cables.
                       Twisted pair cabling is
                       often used in data
                       networks for short and
                       medium length
                       connections because of
                       its relatively lower costs
                       compared to optical
                       fiber and coaxial cable.
BNC   British naval    The older version of
      connector        Bayonet Neill-
                       Concelman




BNC   Bayonet Neill-   The BNC connector is
      Concelman        used for RF signal
                       connections, both for
                       analog and Serial
                       Digital Interface video
                       signals, amateur radio
                       antenna connections,
                       aviation electronics
                       (avionics) and on nearly
                       every piece of
                       electronic test
                       equipment
                       manufactured in the last
                       35 years.

				
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