Overview Computer
Network Technology
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By
Diyurman Gea
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Data Networks
• Data networking solutions
– Local-area networks
– Wide-area networks
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Networking Devices
Equipment that connects directly to a network
segment is referred to as a device.
These devices are broken up into two classifications.
The first classification is end-user devices.
The second classification is network devices.
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Network Topology
Network topology defines the structure of the network.
The physical topology, which is the actual layout of the wire or
media, and the logical topology, which defines how the media is
accessed by the hosts for sending data.
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Network Protocols
• Protocol suites are collections of protocols that
enable network communication from one host
through the network to another host.
• A protocol is a formal description of a set of rules
and conventions that govern a particular aspect
of how devices on a network communicate.
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LAN
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Operate within a limited geographic area
Allow many users to access high-bandwidth media
Provide full-time connectivity to local services
Connect physically adjacent devices
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LAN Devices
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WAN Technologies
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Analog modems
Integrated Services Digital Network (ISDN)
Digital Subscriber Line (DSL)
Frame Relay
Asynchronous Transfer Mode (ATM)
E carrier series: E1, E3
Synchronous Digital Hierarchy (SDH)
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WAN Devices
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Metropolitan-Area Networks (MANs)
• A MAN is a network that spans a metropolitan
area such as a city or suburban area.
• A MAN usually consists of two or more LANs in a
common geographic area.
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Virtual Private Networks (VPNs)
A VPN is a private network that is constructed within a
public network infrastructure such as the global
Internet.
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Benefits of VPNs
• A VPN is a service that offers secure, reliable
connectivity over a shared public network
infrastructure such as the Internet.
• VPNs maintain the same security and management
policies as a private network.
• They are the most cost-effective method of
establishing a point-to-point connection between
remote users and an enterprise customer's network.
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VPN Types
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There are three main types of VPNs:
• Intranet VPNs
• Extranet VPNs
• Access VPNs
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Intranets and Extranets
• Intranets are designed to permit access by users who
have access privileges to the internal LAN of the
organization.
• Extranets refer to applications and services that are
Intranet based, but that use extended, secure access to
external users or enterprises.
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OSI Reference Model
• The application (upper) layers
– Layer 7: Application
– Layer 6: Presentation
– Layer 5: Session
• The data-flow (lower) layers
– Layer 4: Transport
– Layer 3: Network
– Layer 2: Data link
– Layer 1: Physical
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The Purpose of OSI Model
• It breaks network communication into smaller,
simpler parts that are easier to develop.
• It facilitates standardization of network components
to allow multiple-vendor development and support.
• It allows different types of network hardware and
software to communicate with each other.
• It prevents changes in one layer from affecting the
other layers so that they can develop more quickly.
• It breaks network communication into smaller parts
to make learning it easier to understand.
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Why a Layered Model?
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Using Layers to for Communication
• Source, destination, and data packets
– All communications originate at a source and
travel to a destination.
– Information that travels on a network is referred
to as a data, packet, or data packet.
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Using Layers to for Communication
• Media
– Telephone wires (UTP)
– Category 5 UTP (used for 10BASE-T Ethernet)
– Coaxial cables
– Optical fibers (thin glass fibers that carry light)
• Protocol
– All devices on a network need to speak the
same language.
– Set of rules that makes communication both
possible and more efficient.
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Layers with Functions
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The Upper Layers
• Application
– User interface
– Examples – Telnet, HTTP
• Presentation
– How data is presented
– Special processing, such as encryption
– Examples – ASCII, EMCDIC, JPEG
• Session
– Keeping different applications’ data separate
– Examples – Operating system/application access
scheduling
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The Data-Flow Layers
• Transport
– Reliable or unreliable delivery
– Error correction before transmit
– Examples: TCP, UDP, SPX
• Network
– Provide logical addressing which routers use for
path determination
– Examples: IP, IPX
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The Data-Flow Layers
• Data link
– Combines bits into bytes and bytes into frames
– Access to media using MAC address
– Error detection not correction
– Examples: 802.3/802.2
• Physical
– Moves bits between devices
– Specifies voltage, wire speed, and pinout cables
– Examples: EIA/TIA-232, V.35
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Peer-to-Peer Communication
• For data to travel from the source to the
destination, each layer of the OSI model at the
source must communicate with its peer layer at
the destination.
• During this process, the protocols of each layer
exchange information, called protocol data units
(PDUs), between peer layers.
• Each layer of communication on the source
computer communicates with a layer-specific
PDU, and with its peer layer on the destination
computer.
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The TCP/IP Reference Model
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TCP/IP Protocol Graph
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Applications
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FTP
HTTP
SMTP
DNS
TFTP
– File Transfer Protocol
– Hypertext Transfer Protocol
– Simple Mail Transfer Protocol
– Domain Name System
– Trivial File Transfer Protocol
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OSI Model and TCP/IP Model
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Use of the OSI Model
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Names for Data at Each Layer
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De-Encapsulation
• When the data link layer receives the frame, it
does the following:
– It reads the physical address and other control
information provided by the directly connected
peer data link layer.
– It strips the control information from the frame,
thereby creating a datagram.
– It passes the datagram up to the next layer,
following the instructions that appeared in the
control portion of the frame.
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