【正文】 new TCP connections can survive beyond overlap ? Router renumbering protocol, to allow domaininterior routers to learn of prefix introduction / withdrawal ? New DNS structure to facilitate prefix changes 82 清華大學 研究生課程 上一頁 下一頁 Minimum MTU ? Definitions: – link MTU a link’ s maximum transmission unit, ., the max IP packet size that can be transmitted over the link – path MTU the minimum MTU of all the links in a path between a source and a destination ? Minimum link MTU for IPv6 is 1280 octets (versus 68 octets for IPv4) ? On links with MTU 1280, linkspecific fragmentation and reassembly must be used 83 清華大學 研究生課程 上一頁 下一頁 Path MTU Discovery ? Implementations are expected to perform path MTU discovery to send packets bigger than 1280 octets: – for each dest., start by assuming MTU of firsthop link – if a packet reaches a link in which it cannot fit, will invoke ICMP “ packet too big” message to source, reporting the link’ s MTU。 onlink flag – suggested hop limit 187。 valid lifetime – router’ s linklayer address 187。 prefix – “ get addresses from DHCP” flag 187。s careof address. ?In the Type 2 Routing header, the Home Address field is set to the mobile node39。s careof address and the destination address is the correspondent node39。s careof address. ?In the Type 2 Routing header, the Home Address field is set to the mobile node39。s address. ?The Destination Options extension header contains the Home Address option. ?The Mobility header contains the Binding Update message, which contains the cryptographic proof. 1 68 清華大學 研究生課程 上一頁 下一頁 Binding Acknowledgement wide area work home work visited work 2 ?In the IPv6 header, the source address is the correspondent node39。s address. 3 4 64 清華大學 研究生課程 上一頁 下一頁 Direct Delivery ?When the mobile node is away from home, it can choose to send data from its careof address without using Mobile IPv6 – For Transport layer connection data that is longterm and being sent to a correspondent node with which it has pleted correspondent registration, the mobile node sends the data from its careof address. – For shortterm munication that does not require a logical connection, the mobile node can send data from its careof address. 65 清華大學 研究生課程 上一頁 下一頁 Correspondent Node Binding Maintenance ?Return Routability procedure ?Binding Update and Binding Acknowledgement message exchange ?Results: – On the mobile node, there is an entry in its binding update list for the correspondent node. – On the correspondent node, there is an entry in its binding cache for the mobile node 66 清華大學 研究生課程 上一頁 下一頁 Return Routability Procedure 67 清華大學 研究生課程 上一頁 下一頁 Binding Update wide area work home work visited work ?In the IPv6 header, the source address is the mobile node39。s home address 63 清華大學 研究生課程 上一頁 下一頁 IPv6 Mobility wide area work home work visited work 2 1 In the inner IPv6 header, the source address is the mobile node39。s home address. ?ESP header ?The Mobility header contains either a Binding Acknowledgement message (sent in response to a binding update) or a Binding Refresh Request message 1 62 清華大學 研究生課程 上一頁 下一頁 IPv6 Mobility wide area work home work visited work 2 1 correspondent addresses packets using home address of mobile home agent intercepts packets, forwards to mobile with tunnel In the inner IPv6 header, the source address is the correspondent node39。s address and the destination address is the mobile node39。s careof address and the destination address is the home agent39。 may be rewritten by routers enroute – traffic Class value of 0 used when no special QoS requested (the mon case today) 53 清華大學 研究生課程 上一頁 下一頁 Compromise ?Signaled DiffServ (RFC 2998) – uses RSVP for signaling with coursegrained qualitative aggregate markings – allows for policy control without requiring perrouter state overhead 54 清華大學 研究生課程 IPv6 Mobility 55 清華大學 研究生課程 上一頁 下一頁 IPv4 Mobility: Vocabulary home work: permanent “ home” of mobile (., ) permanent address: address in home work, can always be used to reach mobile ., home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote wide area work 56 清華大學 研究生課程 上一頁 下一頁 IPv4 Mobility: more vocabulary careofaddress: address in visited work. (., 79,) wide area work visited work: work in which mobile currently resides (., ) permanent address: remains constant (., ) foreign agent: entity in visited work that performs mobility functions on behalf of mobile. correspondent: wants to municate with mobile 57 清華大學 研究生課程 上一頁 下一頁 IPv4 Mobility: registration End result: ? foreign agent knows about mobile ? home agent knows location of mobile wide area work home work visited work 1 mobile contacts foreign agent on entering visited work 2 foreign agent contacts home agent home: “ this mobile is resident in my work” 58 清華大學 研究生課程 上一頁 下一頁 IPv4 Mobility wide area work home work visited work 3 2 4 1 correspondent addresses packets using home address of mobile home agent intercepts packets, forwards to foreign agent foreign agent receives packets, forwards to mobile mobile replies directly to correspondent 59 清華大學 研究生課程 上一頁 下一頁 IPv6 Mobility ? Mobile hosts have one or more home address – relatively stable。 routers do not fragment packets enroute if too big—they send ICMP “ packet too big” instead Nex