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Network: is basically all the components (H/W &S/W) involved in connecting computer acrosssmall and large distance
Importance of Networks:E asy access and sharing of informationSharing of expensive devices and network
resourcesModern Technologies (IP telephony, Videoon Demand, .etc)
Networking Technologies
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Network components
Network has three main componentsC omputers (servers and hosts)- Source of applications (network aware applications)- ex: HTTP (Hyper Text Transmission Protocol),
FTP (File Transfer Protocol),SNMP (Simple Network Management Protocol)Telnet
Network Devices- Devices that interconnect different computers together
- ex: Repeaters, hub, bridge, switch, router, NIC
and modemsC onnectivity
- Media that physically connect the computers and network devices- ex: Wireless and cables
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Network Topologies
Topology: How devices are connected together Physical Topology: It describes how devices are physically cabledLogical Topology: It describes how devices communicate acrossphysical topology
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B us Topology
A bus topology uses a single backbone cable that isterminated at both ends.
All the hosts connect directly to this backbone.
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Star Topology
A star topology connects all cables to a central point of concentration.
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E xtended Star Topology
An extended star topology links individual stars together byconnecting the hubs and/or switches.This topology can extendthe scope and coverage of the network.
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Hierarchical Topology
A hierarchical topology is similar to an extended star.
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Mesh Topology
A mesh topology is implemented to provide as muchprotection as possible from interruption of service.E ach host has its own connections to all other hosts.
Although the Internet has multiple paths to any onelocation, it does not adopt the full mesh topology.
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Network Types
LAN (Local Area Network):It is a group of network components that workwithin small area
MAN (Metropolitan Area Network):It is a group of LANs that are interconnectedwithin small area
WAN (Wide Area Network):It is a group of LANs that are interconnectedwithin large area
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OS I model
To address the problem of networks increasing in sizeand in number, the International Organization for Standardization (ISO) researched many networkschemes and recognized that there was a need tocreate a network model that would help networkbuilders implement networks that could communicate
and work together and therefore, released the OSIreference model in 1984.
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The OSI Reference Model
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
The OS I Model will beused throughout your entire networking
career!
Memorize it!
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Layer 7 - The Application Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
This layer deal withnetworking applications.
Examples:y Emaily Web browsers
PDU - User Data
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Layer 6 - The Presentation Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
This layer is responsiblefor presenting the data inthe required format whichmay include:y Encryptiony C ompression
PDU - Formatted Data
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Layer 5 - The Session Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
This layer establishes,manages, and terminatessessions between twocommunicating hosts.
Example:y C lient S oftware
( Used for logging in)
PDU - Formatted Data
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Layer 4 - The Transport Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
This layer breaks up thedata from the sending hostand then reassembles it inthe receiver.
It also is used to insurereliable data transport
across the network.PDU - S egments
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Layer 3 - The Network Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
S ometimes referred to as the C isco Layer.
Makes Best PathDetermination decisionsbased on logical addresses(usually IP addresses).
PDU - Packets
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Layer 2 - The Data Link Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
This layer provides reliabletransit of data across aphysical link.
Makes decisions based onphysical addresses (usuallyMAC addresses).
PDU - Frames
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Layer 1 - The Physical Layer
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link1 Physical
This is the physical mediathrough which the data,represented as electronicsignals, is sent from the
source host to thedestination host.
Examples:y C AT5 (what we have)y C oaxial (like cable TV)y Fiber optic
PDU - Bits
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Encapsulation Process
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TC P/IP model
Application
Transport
Internet
NetworkAccess
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link
1 Physical
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2 Models Side- B y-Side
Application
Transport
Internet
NetworkAccess
7 Application
6 Presentation
5 S ession
4 Transport
3 Network
2 Data Link
1 Physical
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The Application Layer
The applicationlayer of theTC P/IP modelhandles high-levelprotocols, issuesof representation,
encoding, anddialog control.
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The transport layer provides transport services fromthe source host to the destination host. It constitutesa logical connection between these endpoints of thenetwork. Transport protocols segment andreassemble upper-layer applications into the samedata stream between endpoints.The transport layer data stream provides end-to-endtransport services.
The Transport Layer
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The Internet Layer
The purpose of the Internet layer is toselect the best path through the network for packets to travel. The main protocol thatfunctions at this layer is the Internet
Protocol (IP). B est path determination andpacket switching occur at this layer.
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The Network Access Layer The network access layer is also called the host-to-network layer. It is the layer that is concerned with all of the issues that an IP packet requires to actually make aphysical link to the network media. It includes LAN andWAN details, and all the details contained in the OSIphysical and data-link layers. NOT E : ARP & RARP workat both the Internet and Network Access Layers.
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