InternetProtocols-1-
NetworkLayer
2015,Lecture04Kaan Bür
EITF25– Internet:TechnologyandApplications
PreviouslyonEITF25
• Accessmethods– SlottedALOHA,CSMA/CD
• Ethernet– Evolutionoflocalareanetworks
• WirelessLAN– Hiddenterminalproblem– CSMA/CA
2015-11-16 EITF25– Internet:TechnologyandApplications
MediumAccessControlSublayer
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Network layer
• Principlesofdigitalcommunications– Fromelectricalsignalstobitstopackets
• Usingthephysicalinfrastructure– Networkaccess
• Findingyourway– Addressing,routing
• Makinguseofitall– Applications
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Today:InternetProtocols (1)
• Internetworking,routing[S1.5,S19.1][F18.1-2]
• InternetProtocol,v4&v6[S14.1-4][F18.4-5,F19.1,F22.1-2]
*[Kihl&Andersson:6.1-3,7.1-5,7.8,8.2]2015-11-16 EITF25– Internet:TechnologyandApplications
NetworkLayer
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Internetadministration
Source:http://www.hill2dot0.com2015-11-16 EITF25– Internet:TechnologyandApplications 5
Internethierarchy
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Networkarchitecture
• TwotypesofnetworksinInternet– Backbonenetworks– Accessnetworks
• InternetServiceProviders(ISP)– Today,theaccessnetworksandsomeofthebackbonenetworksareownedbyprivateISP.
• NetworkAccessPoints(NAP)– Switchingstationsprovidingconnectionbetweenbackbonenetworks
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OrganisationofInternet
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Host-to-hostdelivery
• Multipleapplicationsevenonthesamehost
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Networklayer
• L3– end-to-end
• L2– hop-by-hop
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Networklayer:Routing
• L3isend-to-end
Twofunctions:❶ Addressing❷ Feedback2015-11-16 EITF25– Internet:TechnologyandApplications 11
Routing
• Choosingtheoptimalpath– Usingacostmetric
• Sharinginformation– Central– Distributed
• Algorithms– Rulesandprocedures– Updates
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• Choosingtheoptimalpath– Usingacostmetric
Packet-switchedrouting
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SA DA Data SA DA Data
Router
• Internetworkingdevice– Passesdatapacketsbetweennetworks– ChecksNetworkLayeraddresses– UsesRouting/forwardingtables
Twofunctions:❶ Routing❷ Forwarding
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Routingalgorithm
• Findroutewithleastcostbetweensourceanddestination.
• Updateroutingtables
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Networklayerprotocols
• Weneedauniversaladdresssystem.Thisiscalledthenetworkaddress.
• Weneedrulesfordataforwarding.Thisiscalledrouting.
• Weneedentitiesconnectingseveralnetworkstogetherandforwardingdatabetweenthem.Thesearecalledrouters.
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InternetProtocol
IPv4• Addressingscheme
– Hierarchy– Configuration– Lookup
• Datagramformat
IPv6• Largeraddressspace• Betterheaderformat
– Extendible– Moresecure
• Support forQoS
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Internet
• AllnetworksthatarepartofInternethaveonethingincommon:Theyallusethesamenetworkprotocol,InternetProtocol(IP)!
• Theydonotneedtousethesamelinkprotocols,whichmeansthatallkindsofnetworkscanbepartofInternet.
• TheprotocolframeworkforInternetiscalledtheTCP/IPmodel.
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TCP/IPmodel
• Sometimesillustratedwithahourglass.
• IPcanbeusedonalltypesofnetworks
• ThishasmadeInternetwhatitistoday.
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IPv4addresses
• 32bits=4bytes• 232 =(28)4 =2564 =4294967296• Classfulvs.classlesshierarchy
• Notations– Dotteddecimal– Slash(CIDR)
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Classfuladdressing
• Fiveaddressclassesdefined:A,B,C,(DandE)
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Classfuladdressing
• Organizationscanonlygetaddressesinoneofthepredefinedblocks.
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Addressdepletion
• ClassfuladdressingdefinedastherewereveryfewnetworksconnectedtotheInternet.
• WiththegrowthofInternet,theaddressclassesdidn’tmatchthereality.
• Subnettingandsupernettingwasintroduced.– ClassAandBaddressblocksdividedintosubnets.– SeveralClassCaddressblockscombinedintolargerblockscalledsupernets.
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Classlessaddressing
• Addressesinblocks– Blocksizepowerof2– N =232-n
– FirstaddressdivisiblebyN
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NETID HOSTID
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Exercise: Classlessaddressing
• CIDR=slashnotationwithmask/n• 205.16.37.39/28
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Seeyouin15’:)
• Afterthebreak– IPv6– Fragmentation– Forwarding,ARP
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ProblemswithIPv4
• Addressspacetoosmall• Notdesignedforreal-timeapplications• Nosupportforencryptionandauthentication
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IPv627
SomeadvantageswithIPv6
• Largeraddressspace:128bit-longaddresses.• Betterheaderformat:baseheaderhasconstantlength(40bytes).Optionscanbeinsertedwhenneeded.
• Supportformoresecurity:Encryptionandauthenticationoptions.
• Supportforreal-timeapplications:Specialhandlingofdatagramcanberequested.
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IPv6addresses
• 128bits=16bytes• 2128 =232 ·296 >3·1035
• Notations
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Globalunicastaddresses
• Identifyindividualcomputers
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TYPEAREA
ISPORGANISATION
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IPv4datagram
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• Simplerbaseheader,flexibleforextensions
IPv6datagram
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IPv6extensionheaders
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TrafficClassesà Packetpriorities
• 0..7– Congestioncontrolled
• 8..15– Non-congestioncontrolled
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IPv6andQoS
Flowlabel• Identificationofastream
– TCPsessions– Virtualconnections
• Processing– Flowlabeltable– Forwardingtable
• Routing– Algorithmsstillnecessary– Butnotrunforeverypacket!
Trafficclass• Classificationofpackets
– Queueingschemes– Relationtodelay
• TCPvs.UDP– Congestion-controlled– Non-congestion-controlled
• Otherprotocols– RTP– RSVP
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CROSS-LAYER?
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Transition:IPv4à IPv6
• Cannothappenovernight– Toomanyindependentsystems– Economiccost– IPv4addressspacelastedlongerthanexpected
• Coexisenceneeded
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Maximumdatagramsize
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Fragmentation
• NeededwhenIPdatagramsize>MTU• IPv4– Performedbytheroutermeetingtheproblem
• IPv6– Performedbythesourcerouteronly
• Defragmentationbydestinationhost
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Fragmentationfield
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Fragmentationoffset
• Relativelocationoffragments• 13bits<16bitsà /8
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Fragmentationexample
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Forwarding:Addressaggregation
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Forwarding:Longestmaskmatching
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Forwarding:Hierarchicalrouting
2015-11-16
ISP
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Summary: InternetProtocols (1)
• Internetarchitecture,internetworking– End-to-endprinciple,routing
• InternetProtocol– Addressing,datagramformat– IPv4vsIPv6– Fragmentation– Forwarding
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