Computer Networks Foundation 2022

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Computer Networks ©️ 1994-2022 OxfordCambridge.Org
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Computer Networks Foundation
Introductory concepts @OxfordCambridge.Org for all with the information presented
in the format of KeyPoints. It may be used in the following manner:
- Either to give the reader an overview, before deciding whether to go for a full scale
reading of the StudyNotes by OxfordCambridge.Org related the topic in question. And
this is its primary function.
- Or simply to act as a study guide for learners to follow to expand their knowledge on
that given topic.
For the later, some recommendations perhaps:
- Identify each KeyPoint on which you feel a need to expand your knowledge,
- Choose a good book or academic magazine and info from the Internet.
- And then work towards gaining that knowledge, at your own pace.
Please enjoy!

Computer Networks (This picture: Harcourt Hill, West Oxford) ©️ 1994-2022 OxfordCambridge.Org
Computer Networks Foundation – Summary.
☺ A network consists of two or more computers
connected together which share resources such
as data, printers, and an Internet connection.
☺ The term "networking" refers to the sharing of
resources on a network.
☺ Local area networks (LANs) are one of the most
widely used types of networks.
☺ The Open System Interconnection (OSI) model
was developed in 1984 by the International
Organization for Standardization (ISO) to
resolve the problem of incompatible networks.

Computer Networks Foundation - Aim of publication.
To introduce the reader or the learner to basic
networking concepts, topologies, the OSI model,
and the media used to physically connect a
network.
And it’s also an overview of the StudyNotes by
OxfordCambridge.Org eBook of the same name.

Computer Networks Foundation - Learning Objectives.
☺ After developing the KeyPoints outlined in this publication, you should mainly be able to:
 identify the primary components of a network and distinguish between the two main network
architectures.
 distinguish between the main types of networks
 distinguish between the OSI reference model and the TCP/IP stack.
 distinguish between common network categorizations and identify the characteristics of data
encapsulation.
 identify the major components of a network PC and list the resources required to install a
NIC.
 identify the functions, features, and operation of network devices used at different layers of
the OSI model.
 distinguish between different network topologies
 match network devices to their functions and distinguish between different network
topologies.
 differentiate between types of network media.
 recognize the types of cable connectors used in modern networks.
 determine the most appropriate network tool to use in a given scenario.

Computer Networks Foundation - Sections List.
 (Section 1) Networking basics.
 (Section 2) Networking devices and topologies.
 (Section 3) Physical media.

(Section 1) Networking basics – KeyPoints.
 Networking overview.
 Types of networks
 The OSI model
 Understanding basic networking concepts.

(Section 1) KeyPoints: Networking overview.
☺ A network is made up of two or more computers linked
together.
☺ Networking is the term used to refer to the sharing of
resources on the network.
☺ Networks can vary in size from local area networks
(LANs), which are contained in a building, to wide area
networks (WANs), such as the Internet.
☺ The three primary components of a network are a server,
a workstation, and a host.
☺ Two of the most common network types are client/server
and peer-to-peer.
☺ Peer-to-peer networks have no centralized authority
while client/server networks are managed from a
centralized point.
☺ Client/server networks have several advantages over
peer-to-peer networks such as ease of management and
better security.

(Section 1) KeyPoints: Types of networks.
☺ A local area network (LAN) is used to connect workstations, servers,
and peripheral devices, such as printers, together.
☺ It is confined to a small area, usually within a building.
☺ A wide area network (WAN) covers a large geographic area.
☺ WANs can be public or private. WANs have slower connection speeds
than LANs.
☺ WANs use routers, WAN switches, and modems.
☺ The Internet is an example of a global WAN.
☺ A metropolitan area network (MAN) extends across a city or a large
suburban area.
☺ A MAN develops when two or more LANs are connected together.
☺ An intranet is a private network contained inside a company.
☺ It can contain many LANs linked together.
☺ It allows employees to share information and access company
resources.
☺ An extranet is part of a company's intranet that can be accessed by
anyone outside the company.

(Section 1) KeyPoints: The OSI model.
☺ The Open System Interconnection (OSI) reference model was
developed by the International Organization for
Standardization (ISO) to correct the problem of incompatible
network communications.
☺ It is a reference model that describes how information is
exchanged between points on a network.
☺ The OSI model is divided into seven layers - these are the
application, presentation, session, transport, network, data-
link, and physical layers.
☺ Some of the advantages of layering network functions include
accelerating evolution, reducing complexity, and standardizing
network component interfaces.
☺ Encapsulation refers to the process of packaging information
before it is transmitted.
☺ Thus, encapsulation occurs in descending order from the
application layer through to the physical layer.
☺ Headers and trailers are placed around the data as it passes
through each layer.

(Section 1) KeyPoints: The OSI model (continues).
☺ Data packets always travel from source to destination
on a network.
☺ They can only travel on a network if each layer of the
OSI model at the source communicates with its peer
layer at the destination.
☺ This form of communication is known as peer-to-peer
communication.
☺ Another open standard traditionally applied to the
Internet is the Transmission Control Protocol/Internet
Protocol (TCP/IP) stack.
☺ Like the OSI model, it uses layering and is comprised
of the application, transport, Internet, and network
access layers.
☺ The TCP/IP and OSI models are similar in a number of
ways.
☺ Both models have application, network, and transport
layers, and they both deal with packet-switched
technology.

(Section 1) KeyPoints: Understanding basic networking concepts.
☺ There are different categorizations of networks used to identify their
size, structure, and purpose.
☺ A WAN is a network that covers a large geographic area and can be used
to link together the worldwide locations of a corporation.
☺ A MAN covers a large city or suburban area and consists of several
LANs connected together.
☺ A LAN is a high-speed, low error data network that is confined to a small
area, usually within a building.
☺ Data encapsulation occurs when data is systematically and consistently
packaged before it is sent over the network.
☺ In the encapsulation process, the application layer contains the L7
header, the presentation layer contains the L6 L7 headers, and the
session layer contains the L5 L6 L7 headers.
☺ A data packet contains the L4 L5 L6 L7 header at the transport layer,
the L3 L4 L5 L6 L7 header at the network layer, and the L2 L3 L4 L5 L6
L7 header at the data-link layer.
☺ Bits are associated with the physical layer, frames with the data-link
layer, packets with the network layer, and segments with the transport
layer.

(Section 2) Networking devices and topologies – KeyPoints.
☺ Components of a network PC.
☺ Network devices.
☺ Network topologies.
☺ Identifying network devices and topologies.

(Section 2) KeyPoints: Components of a network PC.
☺ To enable network connectivity, a computer
uses components such as the central
processing unit (CPU), bus, drives, cards,
ports, and memory.
☺ A computer is composed of drives, the CPU,
expansion slots, a bus, a motherboard, and a
backplane.
☺ A network interface card (NIC) is a device
that enables a computer to communicate with
a network.
☺ Selecting a NIC depends on the type of
network, cable, and expansion slot on your
computer.
☺ If installing a NIC, you should be able to
configure it, perform its diagnostics, and
resolve hardware conflicts.

(Section 2) KeyPoints: Network devices.
☺ Hubs, switches, and routers are all networking devices used to connect
networks.
☺ Networking devices operate chiefly at the lower three layers of the Open
System Interconnection (OSI) model. Layer 1 devices, such as repeaters and
hubs, are used to propagate network signals at bit level.
☺ Network Interface Cards (NICs), bridges, and switches are OSI layer 2
devices used to transmit data.
☺ Every NIC has a unique Media Access Control (MAC) address that is used to
identify its host to switches and bridges.
☺ These devices forward traffic based on the host's MAC address.
☺ Routers use layer 3 addresses to transmit packets between networks.
☺ Multilayer switches use layer 3 network addresses (IP) and layer 2 MAC
addresses to manage packet traffic.
☺ Hardware-based layer 3 routing functions provide faster operation than
software versions.
☺ Gateways are used to connect disparate network environments.
☺ Firewalls and AAA (authentication, authorization, and accounting) servers
protect networks from unauthorized attacks and unauthorized access.

(Section 2) KeyPoints: Network topologies.
☺ A network topology describes how the network is laid
out, and how data is transmitted on it.
☺ The physical topology defines the physical
arrangement of the devices and cables on a network.
☺ The logical topology defines the paths used by
information to flow through a network.
☺ A network can have the same logical and physical
topologies, but this is not always the case.
☺ Typical network topology types commonly used include
the bus, star, extended star, ring, full mesh, and
partial mesh topologies.

(Section 2) KeyPoints: Identifying network devices and topologies.
☺ Commonly used network devices include repeaters, hubs,
NICs, switches, and routers.
☺ Hubs are used as network concentration points, and a
repeater regenerates signals so that they can cover
greater distances along a cable.
☺ A bridge creates two or more LAN segments, with each
segment being a separate collision domain.
☺ A router is an internetworking device that matches
information in the routing table with the destination IP
address of the data and forwards data packets between
networks.
☺ Networks can have different topologies.
☺ A network topology describes how the network is laid
out, and how data is transmitted on it.

(Section 3) Physical media – KeyPoints
☺ Network cabling and wireless media.
☺ Network cable connectors.
☺ Network installation tools.
☺ Connecting the network.

(Section 3) KeyPoints: Network cabling and wireless media.
☺ Twisted pair cable is a common cable type - it is available as
shielded twisted pair (STP) or unshielded twisted pair (UTP).
☺ STP cable combines the techniques of twisting wires and
shielding. UTP cable is a copper wire-based cable used in a
variety of networks.
☺ Coaxial cable operates over relatively large distances, and
transmits data at speeds of up to 100 Mbps.
☺ Installing coaxial cable is more expensive than installing
twisted pair cable.
☺ Fibre optics cable transmits bits in the form of modulated
light data.
☺ Light is refracted along the cable and can go around bends.
☺ Fiber optic cables are available as single-mode or multimode
cable.
☺ Wireless signals are radio frequencies and infrared waves that
can travel through air.
☺ They have been a growth area in network communications.

(Section 3) KeyPoints: Network cable connectors.
☺ Cable connectors differ in modern networks depending on the cable type.
☺ Unshielded twisted pair (UTP) cable normally uses a Registered Jack (RJ)
connector, which is attached using a crimper.
☺ This can be an RJ-11 or an RJ-45. By contrast, coaxial cable often uses
Attachment Unit Interface (AUI)/DB-15, Bayonet Neill-Concelman connector
(BNC) or F-Type connectors.
☺ There are a number of fibre optics cable connectors available also--the one
you choose depends on what you are using it for.
☺ The most common types are Subscriber Connector (SC), Straight Tip (ST),
Local Connector (LC), and MT-RJ.
☺ Digital devices can be connected using the Institute of Electrical and
Electronics Engineers (IEEE) 1394 standard--it supports data transfer rates
of up to 400Mbps (using IEEE 1394a), or 800Mbps (using IEEE 1394b).
☺ The products that support the standard are known by various names, but two
of the most popular products are FireWire (which is made by Apple), and i.link.

(Section 3) KeyPoints: Network installation tools.
☺ A patch panel is a centralized wiring point for multiple
devices on an unshielded twisted pair (UTP) network.
☺ You use a patch panel to connect the cables going to the
network hub with the cables going to the workstations.
☺ You connect components to a patch panel using patch
cables and the total segment length of the network
includes the patch cables at both ends and the drop cable
between.
☺ Wire crimpers and punchdown tools can be used to connect
network cables to connectors and patch panels.
☺ There are a number of different network testing tools and
the type you choose depends on the type of cabling in your
network, cost, and what you are testing it for.
☺ The most popular types of testing tools are the wire map
tester, continuity tester, tone generator, optical loss test
set (OLTS), and the multifunction cable tester.
☺ There are also fibre optic patch panels to take into
consideration.

(Section 3) KeyPoints: Connecting the network.
☺ Understanding the types of media that can be used within a
network provides you with a better understanding of how networks
function, and allows you to select the most suitable means of
connecting your network devices.
☺ Coaxial cable is able to cover 450 meters or more and is resistant
to electromagnetic interference and supports 10 to 100 Mbps.
☺ Thicknet coaxial cable can be used to connect the head office to
the branch office situated less than half a kilometer away.
☺ Thinnet coaxial cable is especially useful for installations that
require the cable to make many twists and turns.
☺ UTP is the cheapest media type – it is easy to install, and can cover
a distance up to 100 meters.
☺ UTP has the ability to reduce interference and is compatible with
most of the major networking architectures.
☺ STP (shielded twisted pair) is more resistant to EMI
(electromagnetic interference) than UTP.

(Section 3) KeyPoints: Connecting the network (continues).
☺ Wireless media allow you to exchange data with devices
where no physical medium exists.
☺ For that matter, wireless communication can use RFs (radio
frequencies) to transmit data between devices on a LAN.
☺ A wireless hub is used for signal distribution as the access
point where PCs and laptops connect to the network.
☺ RJ-45 connectors are used to connect the workstations on
each floor to the workgroup switch for that floor.
☺ Fibre optic cable has data exchange rates of up to 100 Gbps
and can cover distances well over 100 meters.
☺ Multimode fibre optic can support cables for up to two
kilometers only, whereas the maximum cable length of
single-mode cable is 60 kilometers.
☺ ST, LC, and MT-RJ are fibre optic cable connectors that
can be used to connect an organization workgroup network
switches between floors.

Computer Networks Foundation – Conclusion.
☺ At this point you should be familiar with the following:
 identifying the primary components of a network and
distinguish between the two main network
architectures.
 distinguishing between the main types of networks.
 characteristics of data encapsulation.
 functions of common network devices.
 characteristics of physical topologies.
 potential future developments in wireless services.
 identifying the characteristics and benefits of the
principal and enabling technologies of 4G.
 choosing a specific network media type for a given
scenario.
 specifications of the different media that are
available..
 different cable connector types available.

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