Chapter 2:Chapter 2:Networking Networking

FundamentalsFundamentals

By: Nisreen OtakyBy: Nisreen Otaky

Data networksData networks

• Businesses needed a solution that Businesses needed a solution that would successfully address the following would successfully address the following three problems:three problems: – How to avoid duplication of equipment and How to avoid duplication of equipment and

resourcesresources – How to communicate efficientlyHow to communicate efficiently – How to set up and manage a networkHow to set up and manage a network

Network historyNetwork history• In the In the 11980s users with stand-alone computers started 980s users with stand-alone computers started

to share files using modems to connect to other to share files using modems to connect to other computers. This was referred to as computers. This was referred to as point-to-pointpoint-to-point, or , or dial-up communicationdial-up communication

• Bulletin boards Bulletin boards becamebecame the central point of the central point of communication in a dial-up connectioncommunication in a dial-up connection. . DDrawbackrawbackss to to this type of systemthis type of system were: were:– TThat there was very little direct communicationhat there was very little direct communication– Availability was limited to oAvailability was limited to only with those who knew about the nly with those who knew about the

location of the location of the bulletin boardbulletin board– RRequired one modem per connection. If five people connected equired one modem per connection. If five people connected

simultaneously it would require five modems connected to five simultaneously it would require five modems connected to five separate phone linesseparate phone lines

• From the From the 1960s1960s-19-1990s, the DoD90s, the DoD developed large, developed large, reliable, WANs for military and scientific reasonsreliable, WANs for military and scientific reasons. .

• In 1990, tIn 1990, the DoDs WAN eventually became the Internet he DoDs WAN eventually became the Internet

Networking devices Networking devices

• AA devicedevice is an eis an equipment that connects directly quipment that connects directly to a network segmentto a network segment. There are 2 types:. There are 2 types:– End-user devices include computers, printers, End-user devices include computers, printers,

scannersscanners that provide services directly to the user. that provide services directly to the user. – NNetwork devices include all the devices that connect etwork devices include all the devices that connect

the end-user devices together to allow them to the end-user devices together to allow them to communicatecommunicate. They. They provide provide::

• extension of cable connections, extension of cable connections, • concentration of connections, concentration of connections, • conversion of data formats,conversion of data formats,• management of data transfers management of data transfers

• A A hosthost is an e is an end-user device that provide users nd-user device that provide users with a connection to the network using a NIC with a connection to the network using a NIC

Network topologyNetwork topology

• The structure of the network:The structure of the network:

–Physical topologyPhysical topology• Actual layout of the mediaActual layout of the media

–Logical topologyLogical topology• How the hosts access the mediaHow the hosts access the media

Physical TopologyPhysical Topology

• BusBus– Uses a single backbone cableUses a single backbone cable– All hosts connect directly to backboneAll hosts connect directly to backbone

• RingRing– Connects each host to the next, and the Connects each host to the next, and the

last to the firstlast to the first– Physical ring of cablePhysical ring of cable

Physical TopologyPhysical Topology

• StarStar– Connects all cables to a central point of Connects all cables to a central point of

concentrationconcentration– Usually a hub or switch at centerUsually a hub or switch at center

• Extended StarExtended Star– Links stars by linking hubs or switchesLinks stars by linking hubs or switches

Physical TopologyPhysical Topology

• HierarchicalHierarchical– Similar to extended starSimilar to extended star– Links star LANs to a computer that controls network Links star LANs to a computer that controls network

traffictraffic

• MeshMesh– Each host is connected to all other hostsEach host is connected to all other hosts– No breaks, ever!No breaks, ever!

Logical TopologiesLogical Topologies

• BroadcastBroadcast– Each host sends its data to all other hostsEach host sends its data to all other hosts– First come, first served to use the networkFirst come, first served to use the network– Ex: EthernetEx: Ethernet

• Token PassingToken Passing– Controls access by passing tokenControls access by passing token– Host can send only when it has the tokenHost can send only when it has the token– Ex:Ex:Token Ring and Fiber Distributed Data Interface Token Ring and Fiber Distributed Data Interface

(FDDI)(FDDI)

Network protocolsNetwork protocols

• Protocol suitesProtocol suites are collections of protocols are collections of protocols that enable network communication from one that enable network communication from one host through the network to another host.host through the network to another host.

• Protocols control all aspects of data Protocols control all aspects of data communicationcommunication such as such as: : – How the physical network is built How the physical network is built – How computers connect to the network How computers connect to the network – How the data is formatted for transmission How the data is formatted for transmission – How that data is sent How that data is sent – How to deal with errorsHow to deal with errors

Local-area networks (LANsLocal-area networks (LANs))

• LANs consist of the followingLANs consist of the following components: components:– Computers Computers – Network interface cards Network interface cards – Peripheral devices Peripheral devices – Networking media Networking media – Network devicesNetwork devices

• LANs make it possible to locally share files LANs make it possible to locally share files and printers efficientlyand printers efficiently

• Examples ofExamples of common LAN technologies are: common LAN technologies are: – Ethernet Ethernet – Token Ring Token Ring – FDDI FDDI

Local-area networks (LANsLocal-area networks (LANs

Wide-area networks (WANs)Wide-area networks (WANs)• WANs WANs

interconnect LANsinterconnect LANs• Some common Some common

WAN technologies WAN technologies are: are: – Modems Modems – ISDN ISDN – DSL DSL – Frame Relay Frame Relay – T and ET and E Carrier Carrier

Series – T1, E1, Series – T1, E1, T3, E3 T3, E3

– SONET SONET

Metropolitan-area networks (MANs)Metropolitan-area networks (MANs)• A MAN is a network that spans a metropolitan area such A MAN is a network that spans a metropolitan area such

as a city or suburban area. as a city or suburban area. • UUsually consists of sually consists of 22 or more LANs in a common or more LANs in a common

geographic area. geographic area. • Ex:Ex: a bank with multiple branches may utilize a MAN. a bank with multiple branches may utilize a MAN. • Typically, a service provider is used to connect two or Typically, a service provider is used to connect two or

more LAN sites using private communication lines or more LAN sites using private communication lines or optical services. optical services.

Storage-area networks (SANs)Storage-area networks (SANs)• A SAN is a dedicated, high-performance network used A SAN is a dedicated, high-performance network used

to move data between servers and storage resources. to move data between servers and storage resources. • SSeparate, dedicated network, eparate, dedicated network, thatthat avoids any traffic avoids any traffic

conflict between clients and servers conflict between clients and servers • SANs offer the following features: SANs offer the following features:

– PerformancePerformance – – allowsallows concurrent access of disk or concurrent access of disk or tape arrays by two or more servers at high speedstape arrays by two or more servers at high speeds

– AvailabilityAvailability – – have disaster tolerance built in, have disaster tolerance built in, because data can be mirrored using a SAN up to because data can be mirrored using a SAN up to 1010kkm or 6.2 miles away. m or 6.2 miles away.

– ScalabilityScalability – Like a LAN/WAN, it can use a variety – Like a LAN/WAN, it can use a variety of technologies. This allows easy relocation of of technologies. This allows easy relocation of backup data, operations, file migration, and data backup data, operations, file migration, and data replication between systems. replication between systems.

SANSAN

Virtual private network (VPN)Virtual private network (VPN)• A VPN is a private network that is constructed within a A VPN is a private network that is constructed within a

public network such as the Internet. public network such as the Internet. • It It offers secure, reliable connectivity over a shared public offers secure, reliable connectivity over a shared public

network infrastructure such as the Internet. network infrastructure such as the Internet. • AA telecommuter can access the network of the company telecommuter can access the network of the company

through the Internet by building a secure tunnel between through the Internet by building a secure tunnel between the telecommuter’s PC and a VPN router in the the telecommuter’s PC and a VPN router in the companycompany

Benefits of VPNsBenefits of VPNs• TThree main types of VPNs: hree main types of VPNs:

– Access VPNs Access VPNs –– provide remote access to a mobile provide remote access to a mobile worker worker and a and a SOHO to the hq of the Intranet or SOHO to the hq of the Intranet or Extranet over a shared infrastructure. Access VPNs Extranet over a shared infrastructure. Access VPNs use use analog, dialup, ISDN, DSL, cable technologiesanalog, dialup, ISDN, DSL, cable technologies

– Intranet VPNsIntranet VPNs – – link regional and remote offices to link regional and remote offices to the hthe hqq of the internal network over a shared of the internal network over a shared infrastructure using infrastructure using dedicated connectionsdedicated connections. . TThey hey allow access only to the employees of the enterprise. allow access only to the employees of the enterprise.

– Extranet VPNsExtranet VPNs – – link business partners to the hlink business partners to the hqq of of the network over a shared infrastructure using the network over a shared infrastructure using dedicated connectionsdedicated connections. . TThey allow access to users hey allow access to users outside the enterpriseoutside the enterprise

VPNsVPNs

Intranets and extranetsIntranets and extranets• Intranet Web servers Intranet Web servers

– differ from public Web servers in that the public must differ from public Web servers in that the public must have the proper permissions and passwords to have the proper permissions and passwords to access the Intranet of an organization. access the Intranet of an organization.

– permit access permit access toto users who have access privileges users who have access privileges to the internal LAN of the organization.to the internal LAN of the organization.

– Web servers are installed in the networkWeb servers are installed in the network– Browser technology is used to access data Browser technology is used to access data

• ExtranetsExtranets allow secure access to an allow secure access to an organizations Intranetorganizations Intranet to external users or to external users or enterprisesenterprises partners partners– access is usually accomplished through passwords, access is usually accomplished through passwords,

user IDs, and other application-level security. user IDs, and other application-level security.

Intranets and extranetsIntranets and extranets

Importance of bandwidthImportance of bandwidth

• Bandwidth is the amount ofBandwidth is the amount of information that can flow information that can flow through a networkthrough a network connection in a given period of connection in a given period of time. time.

• Bandwidth is finiteBandwidth is finite– the bandwidth of a modem is limited to about 56 the bandwidth of a modem is limited to about 56

kbps by both the physical properties of twisted-pair kbps by both the physical properties of twisted-pair phone wires and by modem technology phone wires and by modem technology

• Bandwidth is not freeBandwidth is not free– For WAN connectionsFor WAN connections bandwidth bandwidth is purchased is purchased

from from aa service provider service provider • AA key factor in analyzing network performance key factor in analyzing network performance and and

designing new networksdesigning new networks• The demand for bandwidth is ever increasingThe demand for bandwidth is ever increasing

AnalogiesAnalogies

• Bandwidth is like the width of a pipe.Bandwidth is like the width of a pipe.– TThe water is like the data, and the pipe width is he water is like the data, and the pipe width is

like the bandwidth like the bandwidth

• Bandwidth is like the number of lanes on Bandwidth is like the number of lanes on a highway.a highway.

– The data packets are The data packets are thethe automobiles, and the automobiles, and the bandwidth is comparable to the number of lanes bandwidth is comparable to the number of lanes on the highway. on the highway. IIt is easy to see how low t is easy to see how low bandwidth connections can cause traffic to bandwidth connections can cause traffic to become congested all over the network become congested all over the network

MeasurementMeasurement• In digital systems, the basic unit of bandwidth is In digital systems, the basic unit of bandwidth is

bits per second (bps)bits per second (bps)• TThe actual bandwidth of a network is he actual bandwidth of a network is

determined by a combination of the physical determined by a combination of the physical media and the technologies chosen for media and the technologies chosen for signaling and detecting network signalssignaling and detecting network signals

ThroughputThroughput

• Throughput is the actual, measured, bandwidth, at a specific time of day, using specific internet routes, while downloading a specific file. The throughput is often far less than the maximum bandwidth

• Factors that determine throughput: – Internetworking devices – Type of data being transferred – Network topology – Number of users on the network – User computer – Server computer – Power conditions

Data transfer calculationData transfer calculation

Digital versus analogDigital versus analog

• Analog bandwidth is measured by how much Analog bandwidth is measured by how much of the electromagnetic spectrum is occupied of the electromagnetic spectrum is occupied by each signalby each signal

• The unit of analog bandwidth is hertz (Hz), or The unit of analog bandwidth is hertz (Hz), or cycles per second. cycles per second.

• Radio, television, and telephone Radio, television, and telephone transmissions transmissions havehave been sent through the air been sent through the air and over wires using electromagnetic waves.and over wires using electromagnetic waves.

• Used to describe tUsed to describe the bandwidth of he bandwidth of ::– CCordless telephonesordless telephones is is 900 MHz or 2.4 GHz900 MHz or 2.4 GHz– The The 802.11a and 802.11b wireless networks802.11a and 802.11b wireless networks

ooperatperatinging at 5 GHz and 2.4 GHz at 5 GHz and 2.4 GHz

Using layers to analyze problems in a Using layers to analyze problems in a flow of materialsflow of materials

• The concept of layers is used to describe The concept of layers is used to describe communication from one computer to anothercommunication from one computer to another

• The information that travels on a network is The information that travels on a network is generally referred to as generally referred to as datadata or a or a packetpacket

• A A packetpacket is a logically grouped unit of is a logically grouped unit of information that moves between computer information that moves between computer systems. systems.

• As the data passes between layers, each As the data passes between layers, each layer adds additional information that enables layer adds additional information that enables effective communication with the effective communication with the corresponding layer on the other computer. corresponding layer on the other computer.

DDescribe data communication escribe data communication using layersusing layers

• A data communications protocol is a set A data communications protocol is a set of rules or an agreement that determines of rules or an agreement that determines the format and transmission of data the format and transmission of data

Layer 4 on the source computer communicates with Layer 4 on the destination computer. The rules and conventions used for this layer are known as Layer 4 protocols

OSI modelOSI model• The Open System Interconnection (OSI) The Open System Interconnection (OSI)

reference model reference model was was released in 1984 released in 1984 by by thethe ISO ISO

• It provided vendors with a set of It provided vendors with a set of standards that ensured greater standards that ensured greater compatibility and interoperability among compatibility and interoperability among various network technologies produced various network technologies produced by companies around the world. by companies around the world.

• CConsidered the best tool for teaching onsidered the best tool for teaching people about sending and receiving data people about sending and receiving data on a network. on a network.

OSI layersOSI layers• The OSI model explains how packets travel The OSI model explains how packets travel

through the various layers to another device through the various layers to another device on a networkon a network::– It breaks network communication into smaller, It breaks network communication into smaller,

more manageable parts. more manageable parts. – It standardizes network components to allow It standardizes network components to allow

multiple vendor development and support. multiple vendor development and support. – It allows different types of network hardware and It allows different types of network hardware and

software to communicate with each other. software to communicate with each other. – It prevents changes in one layer from affecting It prevents changes in one layer from affecting

other layers. other layers. – It divides network communication into smaller It divides network communication into smaller

parts to make learning it easier to understandparts to make learning it easier to understand

OSI ModelOSI Model

Peer-to-peer communications Peer-to-peer communications • FFor data to travel from the source to the or data to travel from the source to the

destination, each layer of the OSI model at the destination, each layer of the OSI model at the source must communicate with its peer layer at source must communicate with its peer layer at the destinationthe destination. This is called . This is called peer-to-peerpeer-to-peer communicationcommunication

• TThe protocols of each layer exchange he protocols of each layer exchange information, called protocol data units (PDUsinformation, called protocol data units (PDUs))

• Each layer depends on the service function of Each layer depends on the service function of the OSI layer below itthe OSI layer below it. Ex:. Ex: – Transport layer deals with segmentsTransport layer deals with segments– Network layer encapsulates segments into packetsNetwork layer encapsulates segments into packets– Data Link layer encapsulates packets into framesData Link layer encapsulates packets into frames– Physical layer converts frames to bit streamsPhysical layer converts frames to bit streams

Peer-to-peer communicationsPeer-to-peer communications

TCP/IP modelTCP/IP model• The U.S. DoD created the TCP/IP reference model, The U.S. DoD created the TCP/IP reference model,

because it wanted to design a network that could because it wanted to design a network that could survive any conditions, including a nuclear war.survive any conditions, including a nuclear war.

• TCP/IP was developed as an open standardTCP/IP was developed as an open standard

Handles issues of representation, encoding, and dialog control

Handles quality of service issues of reliability, flow control, and error correction.

Divides TCP segments into packets and send them from any network. Best path determination and packet switching

a.k.a host-to-network layer, concerned with all of the components, both physical and logical, that are required to make a physical link.

TCP/IPTCP/IP• IP can be thought to point the way for the IP can be thought to point the way for the

packets, while TCP provides a reliable packets, while TCP provides a reliable transporttransport

• TCP is a connection-oriented protocol. It TCP is a connection-oriented protocol. It maintains a dialogue between source and maintains a dialogue between source and destinationdestination

Similarities:Similarities:– both have layers both have layers – both have application both have application layers, though they layers, though they include very different include very different services services – both have comparable both have comparable transport and network transport and network layers layers – packet-switched packet-switched technology is assumed technology is assumed – networking networking professionals need to professionals need to know bothknow both

Comparing TCP/IP with OSIComparing TCP/IP with OSI

Comparing TCP/IP with OSIComparing TCP/IP with OSIDifferences:Differences:• TCP/IP combines the TCP/IP combines the

presentation and session layer presentation and session layer into its application layerinto its application layer

• TCP/IP combines the OSI data TCP/IP combines the OSI data link and physical layerslink and physical layers

• TCP/IP has fewer layersTCP/IP has fewer layers• TCP/IP protocols are the TCP/IP protocols are the

standards around which the standards around which the Internet developed, so the Internet developed, so the TCP/IP model gains credibility TCP/IP model gains credibility just because of its protocols. just because of its protocols. NNetworks aren't built on the OSI etworks aren't built on the OSI protocol, even though the OSI protocol, even though the OSI model is used as a guide. model is used as a guide.

Detailed encapsulation process Detailed encapsulation process • If one computer (host A) wants to send data to If one computer (host A) wants to send data to

another computer (host B), the data another computer (host B), the data isis packaged packaged through a process called through a process called encapsulationencapsulation

• AAs the data packet moves down through the s the data packet moves down through the layers of the OSI model, it receives headers, layers of the OSI model, it receives headers, trailers, and other information. trailers, and other information.

EncapsulationEncapsulation