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Best Current Operational Practice for operators:
IPv6 Prefix Assignment for end-customers - persistent vs non-persistent and what size to
chooseJordiPalet
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 1
Authors:• AndrewAlston• Gert Doering• JanŽorž• JenLinkova• JordiPalet• KevinMeynell• LeeHoward• LuisBalbinot• MarkTownsley• Primož Dražumerič• SanderSteffann
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 2
Draft v2 meeting
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 3
RIPE BCOP TF•WorkinProgress:
• https://www.sinog.si/docs/draft-IPv6pd-BCOP-v7.pdf
• https://www.ripe.net/ripe/mail/archives/bcop/2017-August/000173.html
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 4
Table of Content1. ExecutiveSummary2. WhatisaBCOP?3. Introductionandincentives4. Sizeofend-customerprefixassignment:/48,/56orsomethingelse?
4.1.NumberingtheWANlink(interconnectionbetweenournetworkandtheend-customerCPE):4.1.1./64prefixoutofadedicatedpoolofIPv6prefixes4.1.2.Unnumbered4.1.3.ULA4.1.4./64prefixoutoftheIPv6prefixassignedtotheend-customer4.1.5.Summary
4.2.Prefixassignmentoptions4.2.1./48foreverybody4.2.2./48forbusinesscustomersand/56forresidentialcustomers4.2.3.Lessthan/564.2.4.Considerationsforcellularoperators
5. End-customerIPv6prefixassignment:Persistentvsnon-persistent5.1.Whynon-persistentassignmentsmaybeperceivedas“easier”thanstaticones5.2.Whynon-persistentassignmentsareconsideredharmful.5.3.Whypersistentprefixassignmentsarerecommended
6. Acknowledgements7. Glossaryoftermsandacronyms
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 5
Executive Summary•MakingwrongchoiceswhendesigningyourIPv6networkwillsoonerorlaterhavenegativeimplications…• IPv6isnotthesameasIPv4.InIPv6youassignashortprefixtoeachend-customersite,sotheyareabletohaveasmanysubnets(/64s)astheyneed.
• Itisstronglydiscouraged toassignprefixeslongerthan/56.Ifyouwantasimpleaddressingplan,/48foreachend-customer.
• Inordertofacilitatetroubleshootingandhaveafutureproofnetwork,youshouldconsidernumberingtheWANlinksusingGUAs.
• Non-persistentprefixesareconsideredharmfulinIPv6asyoucan’tavoidissuesthatmaybecausedbysimpleend-customerpoweroutages,soassigningpersistentprefixesisasaferandsimplerapproach.
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 6
BCOP and Why?•Describebestactual practices•Target:ISPsdeployingIPv6• LackofexperienceorfollowingIPv4practicesbringunexpectedorunwantedresults• IPv6“brokenness”=ContentprovidersrejectionofyourAS• LackofcompliancewithnewstandardssuchasHomenet
• Completeproduction networkrenumbering,etc.
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 7
Size of end-customer prefix• /48,/56orsomethingelse?•Changeyourmind,thisisnotIPv4!• IPv6hasbeendesignedtoassignprefixesnotaddresses•TonyHain“maths”:• IPv6lifetimeover480years,andkeepdoingthatseveraltimes• Scarcityofaddressesisnotgoingtobeournextproblem
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 8
/64 ?•DONOTDOTHAT!
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 9
/64 ?•DONOTDOTHAT!•NEVER!
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 10
/64 ?•DONOTDOTHAT!•NEVER!•NOWAY!
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 11
/64 ?•DONOTDOTHAT!•NEVER!•NOWAY!•BROKEN!
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 12
/64 ?•DONOTDOTHAT!•NEVER!•NOWAY!•BROKEN!•VERYBADFORYOU
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 13
/64 ?•DONOTDOTHAT!•NEVER!•NOWAY!•BROKEN!•VERYBADFORYOU•BADFORYOURCUSTOMER
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 14
Numbering the WAN link1./64outoftheend-customerprefix2./64outofadedicatedpool3.Unnumbered4.ULA
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 15
/64 from customer prefix•Usethe1st /64fromthecustomerprefix• https://tools.ietf.org/html/draft-palet-v6ops-point2point• Simplifiesroutingandprovisioning
•SomeCPEsmaynotsupportRFC6603• PrefixexcludeoptionforDHCPv6-PD
•EvenbeingrequiredbyRFC7084• BasicRequirementsforIPv6CPEs
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 16
/64 from dedicated pool• Mostcommonscenario
• DedicatedpoolforWANlinks
• CPEperformsrouterdiscovery• Ifitisahost(PPPoE),setupiscompleted• Ifitisarouter,willrequestaprefix(DHCPv6-PD)
• /126,/127,/112or/64?• RFC6164suggest/127
• Notallhardwaresupportsit• /64isfutureproof• Hardwarelimitationsforlongerthan/64prefixes• Allocate/64,use/127topreventNDattacks
• Ifthereis*always*aCPE,youcanapplysecuritypoliciesw/oharmingcustomers
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 17
Unnumbered• Don’tuseGUAs
• InsteaduseLink-Local
• Doesn’tworkforallthedevices,whichcan’trequestDHCPv6-PD• NoGUAsmeansnotraffic…
• Complicatetroubleshooting• Notabletotraceroutethepointoffailure
• NotsuitableforunknownCPEsornon-CPEsattachedtotheWANlink• End-hostwillstayunnumbered• Somehardwaremayconsumeadditionalresourcesfornumberedlinks
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 18
ULA•Stronglydiscouraged
•ICMPv6fromtheCPEtooutsideISP•ULAsourceaddresswillnottraversefilters•PMTUDwillbreak• IPv6connectionwillbreakifPathMTUisnotthesame
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 19
WAN link summary• /64GUAistherecommendedchoice• FromthecustomerprefixifRFC6603issupported
• Itmaybeevenrequiredwhenmorethat2endpoints•Managedbridges• Repeaters• Redundancy(VRRP,multiplerouters)•Monitoring/troubleshootingdevices
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 20
Prefix assignment options•Alignthesizeofthedelegatedprefixwithanibbleboundary(multiplesof4bits),soitmatchDNSreversezonedelegations•Asinglecustomernetworkis/64• Asingle/64isplainwrong• IETFworkallowsasingle/64foraninterface
•Multiple/64mustbetherule• RIRpoliciesallow/48
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 21
/48 for business, /56 residential• Someoperatorsdothis• Rationale->Marketing/Salesdifferentiation
• Advancedhomeusersmayhaveproblemswiththis• You’renotabletouseallthe4digits(/48-/56)
• Somemayhavealreadyanaddressingplanwith/48(ULA,TB,transition,etc.)• /56forcestoredoit+renumbering• /48justmeanschangingtheprefix
• Alternatively,reserve/48,assign/56• AreyouconsideringSMEs?
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 22
/48 for everybody•Mostpracticalandpragmatic•Lesscall-centretimetosortoutproblems•Single“flat”provisioningsystem•SameprefixsizeasULAs,transition,etc.•Directmappingofexistingaddressingplans
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 23
Less than /56•Notrecommended• Technicallynoreasonforthat,enoughaddresses,thisisnotIPv4!• Over134million/56ina/29• Over16million/56ina/32
•AskformorespacetoyourRIRifrequired•Neverassignasingle/64• Exceptforcellularphones(1/64foreachPDP)
• LTEmodemsstillrequire/56or/48
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 24
Persistent or non-persistent•PersistenttypicallybymeansofAAAorcustomprovisioningsystem• Atcustomerconnectiontheyalwaysgetthesameprefix
•Non-persistentbymeansofabigpoolineachterminationpoint• Atcustomerconnectiontheygetarandomprefix• Ifpersistent,theleasetimemayprovidedays,weeksorevenmonths
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 25
Non-persistent is easier?• Lessefforttodeploy• Issuescomelater• ItcomesfromIPv4practices,DHCP
• ButwehaveNAT!• Lookseasierforaggregation• Notlookingfor“customer”portability
• Maybeanextraservice
•CommonlyusingDHCPv6-PD• Eachend-customerdevicehasaGUA
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 26
However … non-persistent is harmful• Incaseofpowerfailure,CPEhang-up,…• Commoneveninhighly-developedcountries
• CPEdoesn’tsendprefixvalidlifetime=0• End-customerdeviceskeeptheoldprefix• Willtrytouseit,willfail
• Customersclaimstothecall-centre
• ContentprovidersmeasureIPv6brokenness• WillignoreyourIPv6traffic
• Poweroutageoftenhappenseveralconsecutivetimes…• Non-persistentprefixesforcealoggingsystem
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 27
Best choice: Persistent or non-persistent•AllowbroadbandservicesprovidedbythecustomerandtheISP•AllowstableDNSnames• camera1.username.ispname.com
•Newbusiness/apps/services,newincomes•Keyfornon-residentialcustomers•Avoidhavingaloggingsystem•TheWANlinkstillcanbenon-persistent
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 28
Questions?
Thanks!
BCOP IPv6 Prefix Assignment for end-customers – persistent vs non-persistent and what size to choose 29
