Download Computer Networks Lecture: Kholoud .AE Advantages of Network

Computer Networks
Contents….
• IEEE 802 / Communication channel access method
IEEE 802.3 CSMA/CD (Ethernet)
IEEE 802.5 Token Ring
• IEEE 802 references model
Logical Link Control (LLC)
Media Access Control (MAC)
• Ethernet
• Servers
• Workstations
Lecture: Kholoud .A.E
Computer Networks
IEEE 802 Standards
• Designed primarily for enhancements ” ‫ “ تحسينات‬to
the bottom three layers of the OSI model
• Breaks the Data Link layer into two sublayers
– The LLC sublayer manages data link
communications
– The MAC sublayer watches out for data collisions
and assigns physical addresses .
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Lecture: Kholoud .A.E
Computer Networks
IEEE 802.3 CSMA/CD (Ethernet)
• Ethernet is the most well-known example of the IEEE
802.3 CSMA/CD standard
• The original 802.3 CSMA/CD standard
– Defines a bus topology network that uses a 50
ohm coaxial baseband cable
– Carries transmissions at 10Mbps
• Currently, the 802.3 standard has been amended to
include speeds up to 10Gbps
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Lecture: Kholoud .A.E
Computer Networks
IEEE 802.3 CSMA/CD (Ethernet)
• The CSMA/CD acronym illustrates how it works
– Carrier Sense (CS) means that computers on the
network are listening to the wire at all times
– Multiple Access (MA) means that multiple computers
have access to the line at the same time
– Collision Detection (CD) detects collisions and
senders send again
• CSMA/CD technology is considered a contention-based
access method
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Lecture: Kholoud .A.E
Computer Networks
IEEE 802.3 CSMA/CD (Ethernet)
• The only major downside to 802.3 is that with
large networks (more than 100 computers on
the same cable), the number of collisions
increases to the point where more collisions
than transmissions are taking place .
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Lecture: Kholoud .A.E
Computer Networks
IEEE 802.5 Token Ring
• Specifies a physical star, logical ring topology
that uses a token-passing technology to put
the data on the cable
• A computer with data to transmit takes a free
token off the ring, modifies it, places the
token (along with the data) back on the ring
• When the original sender receives the token
back, it modifies the token to make it free for
use and sends the token back on the ring
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Lecture: Kholoud .A.E
Computer Networks
IEEE 802.5 Token Ring
• Main advantage of the token-passing access
method is that it eliminates collisions
• Whole procedure takes place in a few
milliseconds
• Scales very well
– Not uncommon for Token Ring networks based on
the IEEE 802.5 standard to reach hundreds of
workstations on a single ring
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Lecture: Kholoud .A.E
Computer Networks
Token Ring
• Exactly like the IEEE 802.5 specification
• Uses a physical star, logical ring topology
• Workstations are cabled to a central device
called a multi station access unit (MAU)
• Can use shieldedor unshielded cable and can
transmit data at either 4Mbps or 16Mbps
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Lecture: Kholoud .A.E
Computer Networks
Ethernet
• Original definition of the IEEE 802.3 model
included a bus topology using coaxial cable
and baseband signaling
• From this model came the first Ethernet
architecture
• Has several specifications, each one specifying
the speed, communication method, and cable
• Original Ethernet was given a designation of
10Base5
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Lecture: Kholoud .A.E
Computer Networks
Servers
• Core component of the network
– Provide a link to the resources needed to perform
tasks
– Direct client computers
– Centralize the control of resources and security
– Balance the load on computers
– Compartmentalize files
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Lecture: Kholoud .A.E
Computer Networks
Workstations
• The computers on which the network users do
their work
• Connected to a network that offers additional
resources
• Also known as client computers
• Items needed to make a workstation into a
network client
– Network interface card (NIC)
– Special expansion card
– Cabling system
– Client software
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Lecture: Kholoud .A.E
Computer Networks
Workstations
• To users, being on a network changes a few
things:
– They can store more information
– They can share and receive information from
other users
– They can use programs that would be too large or
complex for their computer
– They can use hardware not attached directly to
their computer
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Lecture: Kholoud .A.E
Computer Networks
Contents….
Objective :• Advantages of Network
• Type of Network
• Comparison between LAN,MAN &WAN
• What is Interanet , Extranet , and Internet
Lecture: Kholoud .A.E
Computer Networks
Advantages of Network
Computer network provides several important advantages to company
and individuals.
1. Organization today are widely desired over in the world. The sites
need to exchange information and data. A network provides the
means to exchanges data among these computer and to make data
available to the people of the company .
2. The networking of computers permit the sharing of resources.
3. It allows a very flexible working environment Employee can work at
home by using terminal tied networks into the computer at the
office.
Lecture: Kholoud .A.E
Computer Networks
Type of Network

Local Area Network (LAN)

Wide Area Network (WAN)

Metropolitan Area Network ( MAN)
Lecture: Kholoud .A.E
Computer Networks
LAN

LAN can provide users

Flexibility

Speed

Reliability

Adaptability

Security

Transparent Interface

Access to the other LAN & WAN.

Hardware & Software sharing.

Centralized Management.

Private ownership of the LAN.
Lecture: Kholoud .A.E
Computer Networks
LAN
Attributes of LAN
1. The LAN transmits data among user stations.
2. The LAN transmission capacity is more than 1 Mbps.
3. The LAN channel is typically privately owned by the organization
using the facility .
4. The geographical coverage of LANs is limited to areas less than 5
square kilometers.
Lecture: Kholoud .A.E
Computer Networks
LAN
LANs are typically identified by the following properties :
1.
2.
3.
4.
5.
6.
7.
High total bandwidth ( -10 Mbps) .
Low delay.
Low error rate.
Broadcast / Multicast capability.
Limited geography ( 1-2 Km) .
Peer relationship between stations.
Confined to private property.
Lecture: Kholoud .A.E
Computer Networks
LAN
• The low level protocols used in such environment are different from
those used in wide area network .
• The common forms of LAN are those described by the IEEE
standard 802. This standard describes operation up to and including
OSI layer 2. Individuals may build what they like on top of these
basic protocols.
• A commonly set oh higher level protocols is called TCP/IP which
provides OSI layer 3 and 4 functionality, on top of this may be found
a set of protocols commonly called Talent protocols.
• LANs are capable of transmission data at very fast rates, mush faster
than data can be transmitted over a telephone line; but the
distances are limited, and there is also a limited on the number of
computer that can be attached to a single LAN .
Lecture: Kholoud .A.E
Computer Networks
LAN
The following characterizes differentiate one LAN from another :
• Topology : the geometric arrangement of devices on the network
.For example :devices can be arranged in a ring or in a straight line.
• Protocols : The rules and encoding specifications for sending data.
The protocol also determine whether the network uses a peer- to –
peer or client/server architecture .
• Media: Devices can be connected by twisted-pair wire, coaxial
cable, or fiber optic cable . Some networks do without connecting
media altogether, communicating instead via radio waves.
Lecture: Kholoud .A.E
Computer Networks
MAN
• A MAN ,while larger than LAN is limited to city or group of nearby
corporate offices. It uses similar technology of LAN.
• The Metropolitan Area Network standards are sponsored by the
IEEE,ANSI and the Regional Bell operating companies.
• MAN is provides the transfer rates from 34 to 150 Mbps.
Lecture: Kholoud .A.E
Computer Networks
MAN
• MAN is designed with two unidirectional buses. Each bus is
independent of the other in the transfer of traffic.
• MANs are based on fiber optic transmission technology and provide
high speed interconnection between sites. It can support both data
and voice.
• MAN as special category is that a standard has been adopted for
them and this standard is now begin implemented. It is called IEEE
802.6.
Lecture: Kholoud .A.E
Computer Networks
WAN
• A WAN provides long distance transmission of data and voice.
•
A Network that covers a large area such as a city , state, country or the world is called
wide area network.
• The WAN contains host and collection of machines. User program is installed on the
host and machines. All the host are connected by each other through communication
subnet. Subnet carries messages from host.
• Subnet consists of transmission lines and switching element. The transmission line is
used for data between two machines. Switching elements are used for connecting two
transmission lines. Switching elements are specialized computers. It selects the proper
outgoing line for incoming data and forward the data on that line .
Lecture: Kholoud .A.E
Computer Networks
Comparison between LAN,MAN &WAN
Parameter
‫مؤشر‬
LAN
WAN
MAN
Area covered
Covers small area
Within the building
Covers larger
geographical area
Converse larger than
LAN& smaller than WAN
Error rates
Lowest
Highest
Moderate
Transmission speed
High speed
Low speed
Moderate speed
Equipment cost
Uses inexpensive
equipment
Uses most expensive
equipment
Uses moderately
expensive equipment
Lecture: Kholoud .A.E
Computer Networks
Comparison between MAN &WAN
No
WAN
MAN
1
It Converse small area
WAN covers large geographical area
2
LAN operates on the principle of broadcasting
WAN operates on the principle of point to point
3
Uses for time critical application
Not used for time critical application
4
Transmission speed is high
Transmission speed is low
5
Easy to design 7 maintain
Design& maintenance is not easy
6
LAN is broadcasting in nature
WAN is point to point in nature
7
Transmission medium is coaxial or UTP cable
Transmission or communication medium is PSTN
or satellite link
8
LAN does not suffer form propagation delay
WAN suffer from propagation delay
Lecture: Kholoud .A.E
Computer Networks
Internet
• Definition:The Internet is the worldwide, publicly accessible network of
interconnected computer networks that transmit data by packet
switching using the standard Internet Protocol (IP). It is a "network of
networks" that consists of millions of smaller domestic, academic,
business, and government networks, which together carry various
information and services, such as electronic mail, online chat, file
transfer, and the interlinked Web pages and other documents of the
World Wide Web.
Lecture: Kholoud .A.E
Computer Networks
Intranet
• Definition:An intranet is a private computer network that uses Internet
protocols, network connectivity, and possibly the public
telecommunication system to securely share part of an organization's
information or operations with its employees. The same concepts
and technologies of the Internet such as clients and servers running
on the Internet protocol suite are used to build an intranet. HTTP and
other Internet protocols are commonly used as well, especially FTP
and e-mail
•
Briefly, an intranet can be understood as "a private version of the
Internet", or as a version of the internet confined to an organization.
Lecture: Kholoud .A.E
Computer Networks
Extranet
• Definition:An Extranet is a private network that uses Internet protocols,
network connectivity, and possibly the public telecommunication
system to securely share part of an organization's information or
operations with suppliers, vendors, partners, customers or other
businesses. An extranet can be viewed as part of a company's
Intranet that is extended to users outside the company (eg: normally
over the Internet).
• It has also been described as a "state of mind" in which the Internet
is perceived as a way to do business with other companies as well as
to sell products to customers. Briefly, an extranet can be understood
as "a private internet over the Internet“.
Lecture: Kholoud .A.E
Computer Networks
FTP & HTTP
FTP
HTTP
File Transfer Protocol
Hyper Text Transfer Protocol
Supports remote file transfer
Support web pages transfer &
display
Relies on services offered by TCP
Based on client (Browse)
Lecture: Kholoud .A.E