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Transcript of Dc 6th Ppt Foundation (2)
7/21/2019 Dc 6th Ppt Foundation (2)
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Network+ Guide to Networks
6th Edition
Chapter 2 Networking Standards and the OSIModel
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Objectives
• Identify organizations that set standards for networking
• Describe the purpose of the OSI model and each of its
layers
•
Explain specific functions belonging to each OSI modellayer
• nderstand how two network nodes communicate
through the OSI model
•
Discuss the structure and purpose of data packets andframes
• Describe the two types of addressing covered by the OSI
model
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"etworking Standards Organizations
• Standard
– Documented agreement
– 'echnical specifications(precise criteria
–
Stipulates design or performance of particular productor service
• Standards important in the networking world
– )ide variety of hardware and software
– Ensure network design compatibility• Standards define minimum acceptable performance
– "ot ideal performance
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"etworking Standards Organizations
+cont,d-.
• /any different organizations oversee computer
industry standards
• Example0 1"SI and IEEE set wireless standards
–
1"SI standards apply to type of "I2 – IEEE standards involve communication protocols
• "etwork professional,s responsibility
– 3e familiar with groups setting networking standards
– nderstand critical aspects of standards re4uired byown networks
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1"SI
• 1"SI +1merican "ational Standards Institute.
– 6777# representatives from industry and government
– Determines standards for electronics industry and
other fields• 8e4uests voluntarily compliance with standards
• Obtaining 1"SI approval re4uires rigorous testing
• 1"SI standards documents available online
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EI1 and 'I1
• EI1 +Electronic Industries 1lliance.
– 'rade organization
• 8epresentatives from nited States electronics
manufacturing firms
– Sets standards for its members
– :elps write 1"SI standards
– ;obbies for favorable computer and electronics
industries legislation
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EI1 and 'I1 +cont,d-.
• 'I1 +'elecommunications Industry 1ssociation.
– EI1 subgroup merged with former nited States
'elecommunications Suppliers 1ssociation +S'S1.
•
<ocus of 'I1 – Standards for information technology% wireless%
satellite% fiber optics% and telephone e4uipment
• 'I1(EI1 9&=>3 Series
–$uidelines for installing network cable in commercialbuildings
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IEEE
• IEEE +Institute of Electrical and Electronics
Engineers.
– International engineering professionals society
•
$oal of IEEE – @romote development and education in electrical
engineering and computer science fields
• :osts symposia% conferences% and chapter meetings
• /aintains a standards board• IEEE technical papers and standards
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ISO
• ISO +International Organization for Standardization.
– :ead4uartered in $eneva% Switzerland
– 2ollection of standards organizations
•
8epresents 6&! countries• $oal of ISO
– Establish international technological standards to
facilitate global information exchange and barrier free
trade• )idespread authority
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I'
• I' +International 'elecommunication nion.
– Specialized nited "ations agency
– 8egulates international telecommunications
–
@rovides developing countries with technical expertiseand e4uipment
– <ounded in 6=&9B joined nited "ations in 6A5?
– /embers from 6A* countries
•<ocus of I' – $lobal telecommunications issues
– )orldwide Internet services implementation
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ISO2
• ISO2 +Internet Society.
– <ounded in 6AA!
– @rofessional membership society
–
Establishes technical Internet standards• 2urrent ISO2 concerns
– 8apid Internet growth
– Ceeping Internet accessible
– Information security – Stable Internet addressing services
– Open standards
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I1"1 and I21""
• I@ +Internet @rotocol. address
– 1ddress identifying computers in '2@(I@ based
+Internet. networks
–
8eliance on centralized management authorities• I@ address management history
– Initially0 I1"1 +Internet 1ssigned "umbers 1uthority.
– 6AA?0 'hree 8I8s +8egional Internet 8egistries.
• 18I" +1merican 8egistry for Internet "umbers.
• 1@"I2 +1sia @acific "etwork Information 2entre.
• 8I@E +8seaux I@ Europens.
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'he OSI /odel
• /odel for understanding and developing network
computer>to>computer communications
• Developed by ISO in the 6A=7s
•
Divides network communications into seven layers – @hysical% Data ;ink% "etwork% 'ransport% Session%
@resentation% 1pplication
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'he OSI /odel +cont,d-.
• @rotocol interaction
– ;ayer directly above and below
• 1pplication layer protocols
–
Interact with software• @hysical layer protocols
– 1ct on cables and connectors
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'he OSI /odel +cont,d-.
• 'heoretical representation describing network
communication between two nodes
• :ardware and software independent
•
Every network communication process represented• @Ds +protocol data units.
– Discrete amount of data
– 1pplication layer function
– <low through layers &% 9% 5% *% !% and 6
• $eneralized model and sometimes imperfect
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6&
<igure !>6 <low of data through the OSI model
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1pplying the OSI /odel
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'able !>6 <unctions of the OSI layers
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1pplication ;ayer
• 'op +seventh. OSI model layer
• Does not include software applications
• @rotocol functions
–<acilitates communication between softwareapplications and lower>layer network services
– "etwork interprets application re4uest
– 1pplication interprets data sent from network
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1pplication ;ayer +cont,d-.
• Software applications negotiate with application
layer protocols
– <ormatting% procedural% security% synchronization% and
other re4uirements
• Example of 1pplication layer protocol0 :''@
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!7
<igure !>! 1pplication layer functions while retrieving a )eb page
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@resentation ;ayer
• @rotocol functions
– 1ccept 1pplication layer data
– <ormat data
•
nderstandable to different applications and hosts• Examples of file types translated at the presentation
layer
– $I<% @$% 'I<<% /@E$% Fuick'ime
• @resentation layer services manage data encryptionand decryption
– Example protocol0 Secure Sockets ;ayer +SS;.
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!!
<igure !>* @resentation layer services while retrieving a secure )eb page
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Session ;ayer
• @rotocol functions
– 2oordinate and maintain communications between
two network nodes
•
Session – 2onnection for ongoing data exchange between two
parties
• 2onnection between remote client and access server
•
2onnection between )eb browser client and )ebserver
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Session ;ayer +cont,d-.
• <unctions
– Establishing and keeping alive communications link
• <or session duration
–
Ceeping communications secure – Synchronizing dialogue between two nodes
– Determining if communications ended
• Determining where to restart transmission
–
'erminating communications – Set terms of communication
– Identify session participants
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!9
<igure !>5 Session layer protocols managing voice communications
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'ransport ;ayer
• @rotocol functions – 1ccept data from Session layer
– /anage end>to>end data delivery
– :andle flow control
• 2onnection>oriented protocols – Establish connection before transmitting data
– Example0 '2@ three>way handshake• SG" +synchronization. packet• SG">12C +synchronization>acknowledgment.• 12C
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'ransport ;ayer +cont,d-.
• 2hecksum
– ni4ue character string
– 1llows receiving node to determine if arriving data
matches sent data• 2onnectionless protocols
– Do not establish connection with another node before
transmitting data
–
Do not check for data integrity – <aster than connection>oriented protocols
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'ransport ;ayer +cont,d-.
• Segmentation
– 3reaking large data units received from Session layer
into multiple smaller units called segments
–
Increases data transmission efficiency on certainnetwork types
• /' +maximum transmission unit.
– ;argest data unit network will carry
–
Ethernet default0 6977 bytes – Discovery routine used to determine /'
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'ransport ;ayer +cont,d-.
• 8eassembly
– 8ecombining the segmented data units
• Se4uencing
–
Identifying segments belonging to the same group ofsubdivided data
– Specifies order of data issue
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*7
<igure !>9 Segmentation and reassembly
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"etwork ;ayer
• @rotocol functions
– 'ranslate network addresses into physical
counterparts
– Decide how to route data from sender to receiver
• 1ddressing
– System for assigning uni4ue identification numbers to
network devices
•
'ypes of addresses – "etwork addresses +logical or virtual addresses.
– @hysical addresses
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"etwork ;ayer +cont,d-.
• "etwork address example0 67-*5-AA-6!
• @hysical address example0 77&7A?*EA?<*
• <actors used to determine path routing
–
Delivery priority – "etwork congestion
– Fuality of service
– 2ost of alternative routes
• 8outers belong in the network layer
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"etwork ;ayer +cont,d-.
• 2ommon "etwork layer protocol
– I@ +Internet @rotocol.
• <ragmentation
–
Subdividing 'ransport layer segments – @erformed at the "etwork layer
• Segmentation preferred over fragmentation for
greater network efficiency
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Data ;ink ;ayer
• <unction of protocols
– Divide data received into distinct frames for
transmission in @hysical layer
•
<rame – Structured package for moving data
– Includes raw data +payload.% sender,s and receiver,s
network addresses% error checking and control
information
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Data ;ink ;ayer +cont,d-.
• 'wo Data ;ink layer sublayers
– ;;2 +;ogical ;ink 2ontrol. sublayer
– /12 +/edia 1ccess 2ontrol. sublayer
•
/12 sublayer – /anages access to the physical medium
– 1ppends physical address of destination computer
onto data frame
•@hysical +/12. address – <ixed number associated with each device,s network
interface
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*&
<igure !>= 'he Data ;ink layer and its sublayers
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@hysical ;ayer
• <unctions of protocols
– 1ccept frames from Data ;ink layer
– $enerate signals as changes in voltage at the "I2
•
2opper transmission medium – Signals issued as voltage
• <iber>optic cable transmission medium
– Signals issued as light pulses
• )ireless transmission medium – Signals issued as electromagnetic waves
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@hysical ;ayer +cont,d-.
• @hysical layer protocols, responsibilities whenreceiving data – Detect and accept signals
– @ass on to Data ;ink layer
– Set data transmission rate
– /onitor data error rates
– "o error checking
• Devices operating at @hysical layer – :ubs and repeaters
• "I2s operate at both @hysical layer and Data ;inklayers
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1pplying the OSI /odel
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'able !>6 <unctions of the OSI layers
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2ommunication 3etween 'wo Systems
• Data transformation
– Original software application data differs from
application layer "I2 data
• Information added at each layer
• @Ds +@rotocol Data nit.
– $enerated in 1pplication layer
• Segments
–
$enerated in 'ransport layer – nit of data resulting from subdividing larger @D
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2ommunication 3etween 'wo Systems
+cont,d-.
• @ackets
– $enerated in "etwork layer
– Data with logical addressing information added to
segments
• <rames
– $enerated in Data ;ink layer
– 2omposed of several smaller components or fields
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2ommunication 3etween 'wo Systems
+cont,d-.
• Encapsulation
– Occurs in Data ;ink layer
– @rocess of wrapping one layer,s @D with protocol
information
• 1llows interpretation by lower layer
• @hysical layer transmits frame over the network
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5*
<igure !>66 Data transformation through the OSI model
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<rame Specifications
• <rames
– 2omposed of several smaller components or fields
• <rame characteristic dependencies
–
"etwork type where frames run – Standards frames must follow
• Ethernet
– Developed by Herox
– <our different types of Ethernet frames – /ost popular0 IEEE =7!-* standard
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<rame Specifications +cont,d-.
• 'oken ring
– Developed by I3/
– 8elies upon direct links between nodes and ring
topology
– "early obsolete
– Defined by IEEE =7!-9 standard
• Ethernet frames and token ring frames differ
–
)ill not interact with each other – Devices cannot support more than one frame type per
physical interface or "I2
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IEEE "etworking Specifications
• IEEE,s @roject =7! – Effort to standardize physical and logical network
elements• <rame types and addressing
• 2onnectivity• "etworking media• Error>checking algorithms• Encryption
•
Emerging technologies• =7!-*0 Ethernet
• =7!-660 )ireless
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5?
'able !>! IEEE =7! standards
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Summary
• Standards help ensure interoperability between
software and hardware from different manufacturers
• ISO,s OSI +Open Systems Interconnection. model
–
8epresents communication between two networkedcomputers
– Includes seven layers
• IEEE,s @roject =7! aims to standardize networking
elements• Significant IEEE =7! standards include =7!-*
+Ethernet.% =7!-66 +wireless.% and =7!-6& +/1"s.
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