eitf25 -20151116-04 internet protocols -1- network layer · 2015-11-16 · network layer •...

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

2

Network layer

• Principlesofdigitalcommunications– Fromelectricalsignalstobitstopackets

• Usingthephysicalinfrastructure– Networkaccess

• Findingyourway– Addressing,routing

• Makinguseofitall– Applications

2015-11-16 EITF25– Internet:TechnologyandApplications 3

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

4

Internetadministration

Source:http://www.hill2dot0.com2015-11-16 EITF25– Internet:TechnologyandApplications 5

Internethierarchy


Networkarchitecture

• TwotypesofnetworksinInternet– Backbonenetworks– Accessnetworks

• InternetServiceProviders(ISP)– Today,theaccessnetworksandsomeofthebackbonenetworksareownedbyprivateISP.

• NetworkAccessPoints(NAP)– Switchingstationsprovidingconnectionbetweenbackbonenetworks


OrganisationofInternet


Host-to-hostdelivery

• Multipleapplicationsevenonthesamehost


Networklayer

• L3– end-to-end

• L2– hop-by-hop


Networklayer:Routing

• L3isend-to-end

Twofunctions:❶ Addressing❷ Feedback2015-11-16 EITF25– Internet:TechnologyandApplications 11

Routing

• Choosingtheoptimalpath– Usingacostmetric

• Sharinginformation– Central– Distributed

• Algorithms– Rulesandprocedures– Updates


• Choosingtheoptimalpath– Usingacostmetric

Packet-switchedrouting


SA DA Data SA DA Data

Router

• Internetworkingdevice– Passesdatapacketsbetweennetworks– ChecksNetworkLayeraddresses– UsesRouting/forwardingtables

Twofunctions:❶ Routing❷ Forwarding


Routingalgorithm

• Findroutewithleastcostbetweensourceanddestination.

• Updateroutingtables


Networklayerprotocols

• Weneedauniversaladdresssystem.Thisiscalledthenetworkaddress.

• Weneedrulesfordataforwarding.Thisiscalledrouting.

• Weneedentitiesconnectingseveralnetworkstogetherandforwardingdatabetweenthem.Thesearecalledrouters.


InternetProtocol

IPv4• Addressingscheme

– Hierarchy– Configuration– Lookup

• Datagramformat

IPv6• Largeraddressspace• Betterheaderformat

– Extendible– Moresecure

• Support forQoS


Internet

• AllnetworksthatarepartofInternethaveonethingincommon:Theyallusethesamenetworkprotocol,InternetProtocol(IP)!

• Theydonotneedtousethesamelinkprotocols,whichmeansthatallkindsofnetworkscanbepartofInternet.

• TheprotocolframeworkforInternetiscalledtheTCP/IPmodel.


TCP/IPmodel

• Sometimesillustratedwithahourglass.

• IPcanbeusedonalltypesofnetworks

• ThishasmadeInternetwhatitistoday.


IPv4addresses

• 32bits=4bytes• 232 =(28)4 =2564 =4294967296• Classfulvs.classlesshierarchy

• Notations– Dotteddecimal– Slash(CIDR)


Classfuladdressing

• Fiveaddressclassesdefined:A,B,C,(DandE)


Classfuladdressing

• Organizationscanonlygetaddressesinoneofthepredefinedblocks.


Addressdepletion

• ClassfuladdressingdefinedastherewereveryfewnetworksconnectedtotheInternet.

• WiththegrowthofInternet,theaddressclassesdidn’tmatchthereality.

• Subnettingandsupernettingwasintroduced.– ClassAandBaddressblocksdividedintosubnets.– SeveralClassCaddressblockscombinedintolargerblockscalledsupernets.


Classlessaddressing

• Addressesinblocks– Blocksizepowerof2– N =232-n

– FirstaddressdivisiblebyN


NETID HOSTID

24

Exercise: Classlessaddressing

• CIDR=slashnotationwithmask/n• 205.16.37.39/28


Seeyouin15’:)

• Afterthebreak– IPv6– Fragmentation– Forwarding,ARP


ProblemswithIPv4

• Addressspacetoosmall• Notdesignedforreal-timeapplications• Nosupportforencryptionandauthentication


IPv627

SomeadvantageswithIPv6

• Largeraddressspace:128bit-longaddresses.• Betterheaderformat:baseheaderhasconstantlength(40bytes).Optionscanbeinsertedwhenneeded.

• Supportformoresecurity:Encryptionandauthenticationoptions.

• Supportforreal-timeapplications:Specialhandlingofdatagramcanberequested.


IPv6addresses

• 128bits=16bytes• 2128 =232 ·296 >3·1035

• Notations


Globalunicastaddresses

• Identifyindividualcomputers


TYPEAREA

ISPORGANISATION

30

IPv4datagram


• Simplerbaseheader,flexibleforextensions

IPv6datagram


IPv6extensionheaders


TrafficClassesà Packetpriorities

• 0..7– Congestioncontrolled

• 8..15– Non-congestioncontrolled


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


CROSS-LAYER?

35

Transition:IPv4à IPv6

• Cannothappenovernight– Toomanyindependentsystems– Economiccost– IPv4addressspacelastedlongerthanexpected

• Coexisenceneeded


Maximumdatagramsize


Fragmentation

• NeededwhenIPdatagramsize>MTU• IPv4– Performedbytheroutermeetingtheproblem

• IPv6– Performedbythesourcerouteronly

• Defragmentationbydestinationhost


Fragmentationfield


Fragmentationoffset

• Relativelocationoffragments• 13bits<16bitsà /8


Fragmentationexample


Forwarding:Addressaggregation


Forwarding:Longestmaskmatching


Forwarding:Hierarchicalrouting

2015-11-16

ISP

EITF25– Internet:TechnologyandApplications 44

Summary: InternetProtocols (1)

• Internetarchitecture,internetworking– End-to-endprinciple,routing

• InternetProtocol– Addressing,datagramformat– IPv4vsIPv6– Fragmentation– Forwarding


eitf25 -20151116-04 internet protocols -1- network layer · 2015-11-16 · network layer •...

Documents