Chapter 6 Neighbor Discovery 129 Site Prefix flag The Site Prefix flag indicates,when set to 1,that the site prefix defined by the Prefix field and the Site Prefix Length field be used to update the site prefix table. The site prefix table is maintained by the host and is utilized to prefer the use of site-local addresses when a global address matches a site prefix.This flag is described in the Inter- net draft titled "Site Prefixes in Neighbor Discovery.' Reserved1 The Reservedl field is a 4-bit field reserved for future use and set to 0. Valid Lifetime The Valid Lifetime field indicates the number of seconds that an address,based on the included prefix and using stateless address configuration,remains valid.The size of this field is 32 bits.The Valid Lifetime field also indicates the number of seconds that the included prefix is valid for on-link determination.For an infinite valid lifetime,the Valid Lifetime field is set to OxFFFFFFFF. Preferred Lifetime The Preferred Lifetime field indicates the number of seconds that an address,based on the included prefix and using stateless address autoconfiguration, remains in a preferred state.The size of this field is 32 bits.Stateless autoconfiguration addresses that are still valid are either in a preferred or deprecated state.In the preferred state,the address can be used for unrestricted communication.In the deprecated state, the use of the address is not recommended for new communications.However,existing communications using a deprecated address can continue.An address goes from the preferred state to the deprecated state when its preferred lifetime expires.For an infinite preferred lifetime,the Preferred Lifetime field is set to OxFFFFFFFF. Reserved2 The Reserved2 field is a 24-bit field reserved for future use and set to 0. Site Prefix Length The Site Prefix Length field indicates the number of leading bits in the Prefix field that define a site prefix.The length of this field is 8 bits.This field is sig- nificant only if the Site Prefix flag is set to 1.This field is described in the Internet draft titled "Site Prefixes in Neighbor Discovery.' Prefix The Prefix field indicates the prefix for the IPv6 address derived through state- less autoconfiguration.The size of this field is 128 bits.Bits in the Prefix field-up to a count equaling the value of the Prefix Length field-are significant for creating the prefix The combination of the Prefix Length field and the Prefix field unambiguously defines the prefix which,when combined with the interface identifier for the node,creates an IPv6 address.The link-local prefix should not be sent and is ignored by the receiving host. Network Monitor Capture Here is an example of a Prefix Information option used in a Router Advertisement message as displayed by Network Monitor 3.1(capture 06_02 in the \NetworkMonitorCaptures folder on the companion CD-ROM): Frame: Ethernet:Etype-IPv6 Ipv6:Next Protocol ICMPv6,Payload Length 96 Icmpv6:Router Advertisement MessageType:Router Advertisement,134(0x86)￾       !"#$%!&%'()!*+!,("-./*-""01."(""-!"2$%!&+%!*+ 34"#$%!&%!'+(*+" !"#$%!&5*)"%!'+36-+"062+(""-!"2$%!&"(3'7 -!"2$%!&"(3'!-8(!*"(!*+34"0-"(*+!-6"!'!9+"02$%$"6-0%-!":'0,(' (++$---/*()'03('(++$--8(",-(-!"2$%!&7!-%'()!-+-,$!3+!*";*"$: *"+$(%""!"'+< !"#$%!&-!*=!)30$>!-,0?$47@  ABC D-$?+1%!'+!-(E:3!"%!'+$-$?+%0$%6"6$6-(*+-""0F7  GBHI J('!+5!%"!8%!'+!*+!,("-"*683$0%-,0*+-"("(* (++$--.3(-+0*"!*,'6++2$%!&(*+6-!*)-"("'--(++$--,0*%!)6$("!0*.$8(!*- ?('!+7-!90%"!-%!'+!-KL3!"-7J('!+5!%"!8%!'+('-0!*+!,("-"*683$ 0%-,0*+-"(""!*,'6++2$%!&!-?('!+%0$0*:'!*M+"$8!*("!0*7N0$(*!*%!*!" ?('!+'!%"!8."J('!+5!%"!8%!'+!--""0F&NNNNNNNN7  BHI #$%$$+5!%"!8%!'+!*+!,("-"*683$0%-,0*+-"(" (*(++$--.3(-+0*"!*,'6++2$%!&(*+6-!*)-"("'--(++$--(6"0,0*%!)6$("!0*. $8(!*-!*(2$%$$+-"("7-!90%"!-%!'+!-KL3!"-7 "("'--(6"0,0*%!)6$("!0* (++$---"("($-"!''?('!+($!"$!*(2$%$$+0$+2$,("+-"("7;*"2$%$$+ -"("."(++$--,(*36-+%0$6*$-"$!,"+,0886*!,("!0*7;*"+2$,("+-"(". "6-0%"(++$--!-*0"$,088*++%0$*/,0886*!,("!0*-7O0/?$.&!-"!*) ,0886*!,("!0*-6-!*)(+2$,("+(++$--,(*,0*"!*67P*(++$--)0-%$08" 2$%$$+-"(""0"+2$,("+-"("/*!"-2$%$$+'!%"!8&2!$-7N0$(*!*%!*!" 2$%$$+'!%"!8."#$%$$+5!%"!8%!'+!--""0F&NNNNNNNN7  ABQ D-$?+L%!'+!-(LE:3!"%!'+$-$?+%0$%6"6$6-(*+-""0F7  HR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￾[ O$!-(*&(82'0%(#$%!&;*%0$8("!0*02"!0*6-+!*(D06"$P+?$"!-8*"8--()(- +!-2'(4+34="/0$M\0*!"0$K71],(2"6$FT^FL!*"_="/0$M\0*!"0$`(2"6$-%0'+$0* ",082(*!0*`>:Da\bc defghi  j klmhenhli klophqrstu j rptui vhwl sexlxyxzqr{|stu} sfozxf~ hn€lmqu ‚ rygptui ƒx„lhe …~thel†‡hghnl |h‡‡f€hˆophi ƒx„lhe …~thel†‡hghnl} ‰Š‹ŒwŽu