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1、IPv6 NDPOverviewIPv6报头IPv6 NDP的各种报文IPv6 NDP各种机制IPv6 PMTU机制Version(4-bit):IP版本，该字段值为6Traffic Class(8-bit):流量分类，与IPv4包头的TOS类似Flow Label(20-bit):流标签，用来标记IPv6数据包的一个流Payload Length(16-bit):有效载荷的长度，有效载荷为紧跟IPv6包头的 数据包的其他部分Next Header(8-bit):处理选项字段，分段，安全，移动性，松散源路由， 记录路由等的新方式Hop Limit:(8-bit):定义IP数据包所能经过的最大跳
2、数，每跳一次将此值减1Source Address(128-bit):IP数据包的源地址Destination Address(128-bit):IP数据包的目的地址 IPv6 Flow Label(RFC 1809/3697)nFlow的定义:由某一特定的源到某一特定的单播，任意播或者组播目的地的一系列的有次序的被打上标签的数据包n用途:根据IPv6包头的固定字段（flow label option）使IPv6的flow数据包更高效的处理n对于标识flow的需求:1.一个flow 由source address ,flow label,destination标识2.每个flow的flow l
3、abel由源节点生成，数据包中的flow label字段为非0，避免多个流复用同一flow label idn对于flow state 建立方法的需求:1.每种方法必须提供flow state建立后的清除方法2.如果设备不支持请求的flow state 建立，每种方法能恢复至原来的状态IPv6 Extension Header ValueType of Header0Hop-by-Hop Options Header6TCP17UDP41Encapsulated IPv6 Header43Routing Header44Fragment Header50Encapsulating Securi
4、ty Payload51Authentication Header58ICMPv659No next header60Destination Options HeaderIPv6 Extension Header扩展头的排列顺序扩展头的排列顺序:1. Hop-by-Hop Options header2. Destination Options header (for intermediate destinations when the Routing header is present)3. Routing header4. Fragment header5. Authentication
5、header6. Encapsulating Security Payload header7. Destination Options header (for the final destination)8. 高层协议(TCP,UDP)注：除了Hop-by-Hop Options header,其它的扩展头在传输过程中, 中间节点不对其做处理,处理扩展头的节点按扩展头顺序处理，而不能挑选某个headerIPv6 Extension HeaderIPv6 HeaderNext Header = 6 (TCP)TCP SegmentIPv6 HeaderNext Header = 43 (Rou
6、ting)TCP SegmentRouting HeaderNext Header = 6 (TCP)Authentication HeaderNext Header = 6 (TCP)IPv6 HeaderNext Header = 43 (Routing)Routing HeaderNext Header = 51 (AH)TCP SegmentIPv6 Extension HeaderHop-by-Hop 扩展头（扩展头（type=0）：）：介绍:该字段由传送路径上的每个节点和路由器读取并处理用途:主要用于巨型数据包（RFC2675）和路由器警报(RFC 2711)， :RSVP,MLD
7、 report etc）报文格式:Next Header(8-bit):标识下一个包头Hdr ext Len(8-bit):Hop-by-hop option的长度，不统计前1个字节Options（变长）:包含一个或多个TLVPad1,PadN:用于填充报文Options剩余部分，对齐报文,以下类似Next hdrHdr ext LenOptionsOptionsIPv6 Extension HeaderRouting Header(type=43)介绍：在数据包发往目的地的途中，该包头能够被IPv6源节点用来强制数据包经过特定的路由器。当路由类型字段设为0时，在路由包头可以指定中间路由器列表
8、，类似IPv4的松散源路由选项。用途：主要用于移动IP报文格式:Next hdr(8-bit):标识下一个包头Hdr ext Len(8-bit):扩展头长度，不统计前1个字节Routing type(8-bit):标识路由头类型Segment Left(8-bit):剩余的seg数目Type-specific data(变长):由Routing type决定， Routing type0时该段保留前4bytes,后跟沿途路由器的address-listPad1,PadN:用于填充报文Options剩余部分，对齐报文,以下类似Next hdrHdr ext lenRoutingtypeSeg
9、Lefttype-specific data IPv6 Extension HeaderFragment Header（type=44）介绍:只能源节点用来将大于传输路径的PMTU的数据包进行分段，与IPv4不同，IPv6在源节点进行分段，而不能在中间的节点进行分段（使用PMTU机制进行检测路径最小的MTU）报文格式:Next Header:标识下一个包头Resvd:0Fragment Offset:分片报文的偏移Res:0M:1表示more frag,0表示last fragIdentification:分片产生的ID,对于发往同一目的的不同分片报文，该ID不同Next headerResv
10、dFra offsetRes MIdentification 数据包的分片：Unfragmentable partFragmentable partUnfragmentable partFirst fragmentFragment headerUnfragmentable partSecond fragmentFragment headerUnfragmentable partThird fragmentFragment headerOriginal IPv6 Packet数据包的重组：Unfragmentable partFragmentable partUnfragmentable par
11、tFragmentable partFragment headerUnfragmentable partFragmentable partFragment headerUnfragmentable partFragmentable partFragment headerOriginal IPv6 PacketIPv6 Extension HeaderDestination Options Header(type=60)介绍:承载数据包目的节点所需要的可选信息用途:IETF暂时建议使用该扩展头在移动节点和家乡代理之间交换注册信息报文格式:Next Header(8-bit):标识下一个包头Hdr
12、 ext Len(8-bit):Hop-by-hop option的长度，不统计前1个字节Options（变长）:包含一个或多个TLVPad1,PadN:用于填充报文Options剩余部分，对齐报文,以下类似Next hdrHdr ext LenOptionsOptionsIPv6 Extension HeaderNo Next Header(type=59)介绍:用于表示后面没有扩展头跟该在该扩展头后面Authentication header(type=51)介绍:由IPsec使用，以提供认证，数据完整性和重放保护，确保基本IPv6包头中一些字段的保护Encapsulating Secur
13、ity Payload header(type=50)介绍:由IPsec使用，以提供认证数据完整性和重放保护和IPv6数据包的保密IPv4 Header FieldChange in IPv6VersionNew value of 6Internet Header LengthRemovedType of ServiceTraffic Class fieldTotal LengthPayload Length fieldIdentificationRemoved to Fragment headerFragmentation FlagsRemoved to Fragment headerFra
14、gment OffsetRemoved to Fragment headerTime to LiveHop Limit fieldProtocolNext Header fieldHeader ChecksumRemovedSource AddressSame, new 128-bit lengthDestination AddressSame, new 128-bit lengthOptionsRemoved (extension headers)IPv6 NDP1.相关模块:Router/Prefix DiscoveryAddress AutoconfigrationDuplicate A
15、ddress DetectionAddress ResolutionHost Sending algorithm (for host)Neighbor Unreachability DetectionRedirect2.需要用到的地址类型:节点组播地址节点组播地址(FF02:1)路由器组播地址路由器组播地址(FF02:2)被请求节点组播地址被请求节点组播地址(FF02:1:FFXX:XXXX)本地链路地址本地链路地址(FE80:/10)未指定地址未指定地址(:)IPv6 NDP 3.报文类型:Router Solicitation (type=133)Router Advertisement(
16、type=134)Neighbor Solicitation(type=135)Neighbor Advertisement(type=136)Redirect(type=137)IPv6 NDP 报文类型RS报文介绍:主机发送RS用于向Router请求并使其快速响应发送RA报文格式:IP包头:Source Address:接口指定的地址或者未指定地址Destination Address:FF02:2Hop Limit :255Authentication:启用认证时设置ICMP报文:Type(8-bit): 133Code(8-bit): 0Checksum(16-bit):校验和Rese
17、rved(32-bit):保留，置0Options(变长):目前只定义了一个Source link-layer address,如果IP头的源地址为未指定地址，则RS中不能包含该项TypeCodeChecksumReservedOptions。IPv6 NDP 报文类型RA报文介绍:由Router周期性发送或者实时响应接收到的RS报文格式:IP包头:Source Address:必须为自身的本地链路地址Destination Address:FF02:1Hop Limit:255Authentication Header:启用认证时设置ICMP报文格式:Type(8-bit):134Code(
18、8-bit):0Checksum(16-bit):校验和Cur Hop Limit(8-bit):在生成IP packet时设置默认值，为0表示未指定M(1-bit):标识地址信息是否为有状态自动配置机制O(1-bit):标识除地址信息之外的其他信息是否为有状态自动配置机制Reserved(6-bit):保留Router Lifetime:秒为单位，通告host其作为默认路由器的时间，在该时间host接收并应用其RA的option,为0时接收但不应用该RA的optionReachable Time(32-bit):毫秒为单位，通告邻居可达时间，用于邻居不可达检测机制，为0表示未指定Retran
19、s Time(32-bit):毫秒为单位，通告重传NS的间隔，用于地址解析和邻居不可达检测机制，为0表示未指定Options(变长):可以添加的Option有Source link-layer address,MTU,Prefix InformationTypeCodeChecksumRsrvdCur Hop LimitMORouter LifetimeReachable timeRetrans TimerOptions.IPv6 NDP 报文类型NS报文介绍:NS报文用于请求目标节点的链路层地址，同时为其他节点提供自己的链路层地址,dst-ip为组播时用于地址解析，DAD检测；为单播时用于邻
20、居不可达检测报文格式:IP包头包头:Source Address:接口指定的地址或者未指定地址Destination Address:目标地址对应的被请求节点多播地址或者目标地址Hop Limit:255Authentication Header:启用认证时设置ICMP报文格式报文格式:Type(8-bit):135Code(8-bit):0Checksum(16-bit):校验和Reserved(32-bit):保留Target Address(128-bit):目标地址Options(变长):可以添加的option有Source link-layer address，当src-ip为(:)
21、时不能携带该option，其他src-ip为非(:)目的为组播必须携带TypeCodeChecksumReservedTarget AddressOptionsIPv6 NDP 报文类型NA报文介绍:响应接收到的NS或者更快的发送关于本节点的信息报文格式:IP报文头:Source Address:接口指定的地址Destination Address:为响应NS或者src-ip为非(:),则为NS报文的src-ip，其他为FF02:1Hop Limit:255Authentication Header:启用认证时设置ICMP报文头:Type(8-bit):136Code(8-bit):0Chec
22、ksum(16-bit):校验和R(1-bit):置1表示该节点为Router,用于在邻居不可达检测中检测Router是否转变成hostS(1-bit):Solicited-flag,置1表示响应NS，用于邻居不可达检测，不能在dst-ip为组播或者非被请求的NA设置O(1-bit):置1表示NA提示需要更新cache中的链路层地址Reserved(29bit):保留Target Address(128-bit):对于响应NS的NA，该字段为NS报文中的Target Address；非响应NS的NA,该字段为链路层地址改变对应的地址（如自己的地址），不能为组播地址IPv6 NDP 报文类型NA
23、报文（续）Options:可选的option有Target link-layer address,即目标节点请求的链路层地址，对于组播请求的NS,必须包含该选项，对于单播请求的NS，应该包含该选项，但不是必须的TypeCodeChecksumReservedTarget AddressOptions.R S OIPv6 NDP 报文类型Redirect报文介绍:通知host通往dst的更优下一跳，或者dst就是本地邻居报文格式:IP报文头:Source Address:接口的本地链路地址Destination Address:触发重定向的数据包的src-ipHop Limit:255Authe
24、ntication:启用认证时设置ICMP报文头:Type（8-bit）:137Code(8-bit):0Checksum(16-bit):校验和Reserved(32-bit):保留Target Address:如果为邻居，则Tar Addr与Dst Addr一致；非邻居时必须为最优下一跳的本地链路地址Destination Address:触发重定向的数据包的dst-ipOptions:可选的选项有Target link-layer address,Redirected Header,TypeCodeChecksumReservedTarget AddressOptions.Destina
25、tion AddressIPv6 NDP 报文类型选项报文Source Link-layer Address(1)Target Link-layer Address(2)Prefix Information(3)Redirected Header(4)MTU(5)注:Length为0的报文必须被丢弃; Length以8 octets为单位（1 octets 为8 bytes）TypeLength.IPv6 NDP 报文类型Source/Target Link-layer Address介绍:包含发送者的链路层地址，用于NS,RS,RA报文格式:Type(8-bit):1为src LLA,2为t
26、ar LLALength(8-bit):选项长度Link layer address(变长):链路层地址TypeLengthLink-layer Address.IPv6 NDP 报文类型Prefix Information介绍:为地址自动配置机制提供地址前缀信息,仅用于RA报文格式:Type(8-bit):3Length(8-bit):4Prefix Len(8-bit):前缀长度，0-128L(1-bit):为1表示该地址可以访问，用于报文的收发，为0表示无法访问A(1-bit):为1表示可以将该前缀用于自动配置，为0不能将该前缀用于自动配置Reserved1(6-bit):保留Valid
27、 Lifetime(32-bit):地址的有效生存时间，超时后该地址变为无效，不能用来转发数据和接收dst-ip为该地址的报文，置0xffffffff表示无限Preferred Lifetime(32-bit):地址的优选生存时间，超时后，仅在节点没有其他可用地址时作为src-ip用于通信Reserved2(32-bit)：保留Prefix(128-bit):前缀，由前缀长度字段指定其有效的位数TypeLengthValid LifetimePrefered LifetimeReserved 2Pre lenL ARsvdPrefixIPv6 NDP 报文类型Redirected Header
28、介绍:用于重定向报文，包含收到的触发重定向的数据报文的信息报文格式:Type(8-bit):4Length(8-bit):长度Reserved(48-bit):保留IP header+data(变长，但重定向报文整体不超过1280B)TypeLengthReservedReservedIP header + dataIPv6 NDP 报文类型MTU介绍:用于通告链路的MTU值，用于RA报文格式:Type(8-bit):5Length(8-bit):1(8-octets)Reserved(16-bit):保留MTU(32-bit):链路MTU值TypeLengthReservedMTUIPv6
29、NDP报文类型summaryND 报文ND Option(s)Router SolicitationSource Link-Layer AddressRouter AdvertisementSource Link-Layer AddressPrefix InformationMTUAdvertisement IntervalHome Agent InformationRoute InformationNeighbor SolicitationSource Link-Layer AddressNeighbor AdvertisementTarget Link-Layer AddressRedir
30、ectRedirected HeaderTarget Link-Layer AddressIPv6 NDPRouter/Prefix Discovery1.节点在本链路上发现一个或者多个Router2.Router 提供以下信息:Hop limit的默认值stateful 和statefuless 地址配置协议Reachability and retransmission 计时器本链路的网络前缀本链路的MTUIPv6 移动性相关信息路由信息3.非请求RA发送间隔(MinRtrAdvInterval, MaxRtrAdvInterval):MaxRtrAdvInterval=600s,MinRt
31、rAdvInterval=0.75*MaxRtrAdvIntervalIPv6 NDPRouter/Prefix DiscoveryRouterHost A Send multicast Router SolicitationRouter SolicitationEthernet HeaderDestination MAC is 33-33-00-00-00-02IPv6 HeaderSource Address is : Destination Address is FF02:2Hop limit is 255Router Solicitation HeaderMAC: 00-B0-D0-E
32、9-41-43 IP: noneMAC: 00-10-FF-D6-58-C0 IP: FE80:210:FFFF:FED6:58C0 IPv6 NDPRouter/Prefix DiscoveryHost AEthernet HeaderDestination MAC is 33-33-00-00-00-01IPv6 HeaderSource Address is FE80:210:FFFF:FED6:58C0Destination Address is FF02:1Hop limit is 255Router Advertisement HeaderCurrent Hop Limit, Fl
33、ags, Router Lifetime, Reachable and Retransmission TimersNeighbor Discovery OptionsSource Link-Layer Address is 00-10-FF-D6-58-C0MTU is 1500Prefix Information is for 2000:1:2:3:/64 MAC: 00-10-FF-D6-58-C0 IP: FE80:210:FFFF:FED6:58C0 Router Send multicast Router AdvertisementRouter AdvertisementMAC: 0
34、0-B0-D0-E9-41-43 IP: noneIPv6 NDPAddress Autoconfiguration(RFC2462)地址自动配置类型：地址自动配置类型：n1. Stateless接收接收RA报文，获取前缀和其他信息报文，获取前缀和其他信息n2. Stateful通过通过DHCPv6协议获取前缀和其他信息协议获取前缀和其他信息n3. Both通过通过DHCPv6协议和接收协议和接收RA报文获取前缀和其他信息报文获取前缀和其他信息IPv6 NDPAddress Autoconfiguration(RFC2462)地址状态类型:nTentative验证地址唯一性时的状态nValid
35、通过验证后，地址唯一，设置valid timer和preferred timer又分为一下两种状态:qPreferred state:两个计时器都未超时，节点可以用这个地址接收发送数据qDeprecated state:preferred timer超时，仅在没有其他地址可用的时候才用该地址进行报文的接收发送nInvalidValid timer 超时，地址变为无效，不能进行报文的接收转发TentativePreferredDeprecatedInvalidPreferred LifetimeValidValid LifetimetimeUse stateful addressconfigur
36、ation protocol.Derive link-local address:FE80:interface IDSend multicast Neighbor Solicitation withTarget Address set to derived link-local address.Neighbor Advertisement response received?YesNoInitialize link-local address.Send Router Solicitation.Set Hop Limit, Reachable Time, Retrans Timer, MTU.A
37、re PrefixInformation optionspresent?YesNoStop address autoconfiguration.ARouter Advertisement response received?NoYesUse stateful addressconfiguration protocol.Is Other Stateful Configuration flag set to 1?YesNoStop address autoconfiguration.Is Managed AddressConfiguration flagset to 1?NoYesBIs On-L
38、ink flagset to 1?YesNoAdd prefix to prefix list.Derive stateless address:Prefix+interface IDInitialize stateless address.Neighbor Advertisement response received?NoYesDo not initialize stateless address.Are there more Prefix Information options to process?NoYesABGet first Prefix Information option.S
39、end multicast Neighbor Solicitation with Target Address set to derived stateless address.Is Autonomous flagset to 1?NoYesGo to next Prefix Information option.IPv6 NDPDuplicate Address Detectionn使用NS报文来进行DAD:qTarget Address field 为要验证的地址(Target address option中)q源地址为（:）,目的地址为被请求节点组播地址n若地址重复，则检测节点发送NA报
40、文q目的地址为FF02:1验证DAD,组播NS报文Host BHost A Send multicast Neighbor SolicitationNeighbor SolicitationTentative IP: 2000:1:2:3:100MAC: 00-60-08-52-F9-D8IP: 2000:1:2:3:100Ethernet HeaderDest MAC is 33-33-FF-52-F9-D8IPv6 HeaderSource Address is :Destination Address is FF02:1:FF00:0100Hop limit is 255Neighbor
41、 Solicitation HeaderTarget Address is 2000:1:2:3:100地址重复，组播NA报文Host BHost AEthernet HeaderDestination MAC is 33-33-00-00-00-01IPv6 HeaderSource Address is 2000:1:2:3:100Destination Address is FF02:1Hop limit is 255Neighbor Advertisement HeaderTarget Address is 2000:1:2:3:100Neighbor Discovery Option
42、Target Link-Layer Address is 00-60-08-52-F9-D8Tentative IP: 2000:1:2:3:100 Send multicast Neighbor AdvertisementNeighbor AdvertisementMAC: 00-60-08-52-F9-D8IP: 2000:1:2:3:100IPv6 NDPAddress Resolution介绍:首先，通过组播的NS和单播的NA报文的相互交换来获取下一跳或者目的地址的链路层地址;其次，双方主机更新自己的neighbor cache；然后，发送相关的单播流量 过程见next pageHos
43、t BHost A Send multicast Neighbor SolicitationNeighbor SolicitationEthernet HeaderDestination MAC is 33-33-FF-02-6E-A5IPv6 HeaderSource Address is FE80:210:5AFF:FEAA:20A2Destination Address is FF02:1:FF02:6EA5Hop limit is 255Neighbor Solicitation HeaderTarget Address is FE80:260:97FF:FE02:6EA5Neighb
44、or Discovery OptionSource Link-Layer Address is 00-10-5A-AA-20-A2MAC: 00-10-5A-AA-20-A2IP: FE80:210:5AFF:FEAA:20A2MAC: 00-60-97-02-6E-A5IP: FE80:260:97FF:FE02:6EA5组播的Neighbor Solicitation单播的Neighbor AdvertisementHost BHost A Send unicast Neighbor AdvertisementNeighbor AdvertisementEthernet HeaderDes
45、tination MAC is 00-10-5A-AA-20-A2IPv6 HeaderSource Address is FE80:260:97FF:FE02:6EA5Destination Address is FE80:210:5AFF:FEAA:20A2Hop limit is 255Neighbor Advertisement HeaderTarget Address is FE80:260:97FF:FE02:6EA5Neighbor Discovery OptionTarget Link-Layer Address is 00-60-97-02-6E-A5MAC: 00-10-5
46、A-AA-20-A2IP: FE80:210:5AFF:FEAA:20A2MAC: 00-60-97-02-6E-A5IP: FE80:260:97FF:FE02:6EA5IPv6 NDP Host Sending algorithmHost的数据结构nNeighbor cache保存邻居的on-link的ipv6 地址和起对应的链路层地址，以及可达性状态,与ipv4的ARP cache类似nDestination cache保存最近发送数据包中目的地址的下一跳信息nPrefix list保存on-link的前缀列表nDefault router list保存公告自己为默认Router对应的o
47、n-link 地址Host的数据结构(续)Prefix ListDefault Router ListDestination CacheDestinationNext-Hop AddressPMTUNeighbor CacheLink Layer AddressNext-Hop AddressStateIPv6 NDPHost Sending algorithm基本流程:1.确定目的地址的下一跳1)检查destination cache2)如果目的地址匹配prefix list中的前缀,则下一跳地址即目的地址3)如果目的地址不匹配prefix list中的前缀,则下一跳地址为默认Router的
48、地址2.确定下一跳的链路层地址1)检查neighbor cache2)若不存在，使用地址解析来获取下一跳地址的链路层地址3.以下一跳的链路层地址发送该数据包Check destination cache for an entry matching the destination address.Entry found in destination cache?YesNoIs next-hop address entry in neighbor cache?YesNoUse address resolution process to determine the link-layer addres
49、s of the next-hop address.Was address resolution successful?YesNoIndicate an error.Does the destination address match a prefix in the prefix list?YesNoCheck prefix list for a prefix thatmatches the destination address.Update neighbor cache.Send packet using link-layer address of neighbor cache entry
50、.Set the next-hop address to the default router address.Set the next-hop address to the destination address.Obtain next-hop address from destination cache or care-of destination cache entry.Is there a default router?NoYesUpdate destination cache.Check neighbor cache for an entry matching the next-ho
51、p address.IPv6 NDPHost Sending algorithmIPv4 Neighbor FunctionIPv6 Neighbor FunctionARP Request messageNeighbor Solicitation messageARP Reply messageNeighbor Advertisement messageARP cacheNeighbor cacheGratuitous ARPDuplicate address detectionRouter Solicitation message (optional)Router Solicitation
52、 (required)Router Advertisement message (optional) Router Advertisement (required)Redirect messageRedirect messageIPv4和IPv6的neighbor功能的总结和对比IPv6 NDPNeighbor Unreachability Detectionn邻居节点在以下情况被认为可达:最近接收了可达性确认报文n主要用于验证通往目的地的下一跳是否可达n可达性主要取决于:q接收到回应单播NS的NA报文q上层协议提示n邻居不可达状态机:INCOMPLETE,REACHABLE,STALE,DE
53、LAY,PROBE相关的计时器:Reachable timer :30,000ms; Retans timer:1,000ms;Delay timer:5s邻居不可达检测状态机Unicast Neighbor Solicitation retries exceededDelay time exceededPROBEReachable Time exceeded(30,000ms)or unsolicited Neighbor Advertisement receivedSTALEMulticast Neighbor Solicitation retries exceededReachabili
54、ty confirmedby sending unicast Neighbor Solicitation and receiving solicited Neighbor AdvertisementReceive solicited Neighbor AdvertisementREACHABLESend packet流量驱动DELAYSend multicast Neighbor SolicitationINCOMPLETENO ENTRY EXISTSReachabilityconfirmed byupper layer protocolIPv6 NDPRedirectn告知发送数据的源节点
55、通往目的地的更优的下一跳1. Router告知host该距离目的地更优下一跳2. Router告知host该目的地为本链路的一个邻居nRedirect 报文包含最优下一跳信息单播数据包到默认RouterHost AEthernet HeaderDestination MAC is 00-AA-00-22-22-22IPv6 HeaderSource Address is 2000:1:100Destination Address is 2000:2:100MAC: 00-AA-00-22-22-22IP: 2000:1:2FE80:2AA:FF:FE22:2222Router 2Router
56、3Unicast Packet Send unicast packetMAC: 00-AA-00-33-33-33IP: 2000:1:3 FE80:2AA:FF:FE33:3333MAC: 00-AA-00-11-11-11IP: 2000:1:100FE80:2AA:FF:FE11:1111Router发送重定向报文到HostHost A Send unicast RedirectRedirectEthernet HeaderDestination MAC is 00-AA-00-11-11-11IPv6 HeaderSource Address is FE80:2AA:FF:FE22:2
57、222Destination Address is 2000:1:100Hop limit is 255Redirect HeaderTarget Address is FE80:2AA:FF:FE33:3333Destination Address is 2000:2:100Neighbor Discovery OptionsTarget Link-Layer Address is 00-AA-00-33-33-33Redirected HeaderRouter 2Router 3MAC: 00-AA-00-33-33-33IP: 2000:1:3 FE80:2AA:FF:FE33:3333
58、MAC: 00-AA-00-11-11-11IP: 2000:1:100FE80:2AA:FF:FE11:1111MAC: 00-AA-00-22-22-22IP: 2000:1:2FE80:2AA:FF:FE22:2222Router 转发单播数据报文Host AEthernet HeaderDestination MAC is 00-AA-00-33-33-33IPv6 HeaderSource Address is 2000:1:100Destination Address is 2000:2:100MAC: 00-AA-00-11-11-11IP: 2000:1:100FE80:2AA
59、:FF:FE11:1111MAC: 00-AA-00-22-22-22IP: 2000:1:2FE80:2AA:FF:FE22:2222Router 2Router 3MAC: 00-AA-00-33-33-33IP: 2000:1:3 FE80:2AA:FF:FE33:3333UnicastIPv6 PMTU1.发送节点初始认为MTU为发送数据报文的接口链路的MTU2.发送节点发送MTU大小的ipv6 packet 3.路径中间的router不能转发该ipv6 packet,向源节点发送ICMP Packet Too Big 报文,报文中包含转发失败的链路的MTU4.发送节点以接收到ICMP
60、 Packet Too Big中的MTU值来重置PMTU,Set PMTU to destination to link MTU.Send packet at PMTU size.ICMPv6 PacketToo Big messagereceived?YesNoSet PMTU to destination to the value of the MTU field in the Packet Too Big message.Is PMTU to destinationless than the link MTU?YesNoHas PMTU timer expired?YesNo参考资料:R
61、FC2461(4861) Neighbor discovery for ipv6RFC2460:IPv6 specificationRFC3697:IPv6 Flow label specificationRFC1809:Using the Flow label field in IPv6RFC2675:IPv6 JumbogramsRFC2711:IPv6 Router Alert optionRFC2462:IPv6 Stateless Address AutoconfigurationRFC1981:Path MTU Discovery for IP version 6 Cisco ipv6网络实现技术精彩还将继续To Be ContinuedDHCPv6 ,Tunnel.
