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1Mobile IPv6Internet ProtocolsCSC / ECE 573Fall, 2005N. C. State Universitycopyright 2005 Douglas S. Reeves2AnnouncementsI. Dropper is ready!II. Project due Thursday Dec 1!III. Final Exam and Study Guide!copyright 2005 Douglas S. Reeves3Today’s LectureI. MobilityII. Discovering the Care-of AddressIII. Registering the Care-of AddressIV. Normal Data DeliveryV. SecurityVI. Other IssuesMOBILITYcopyright 2005 Douglas S. Reeves5Motivation• Many wireless devices offer IP connectivity– laptops, PDAs, cellular phones, …• Users (mobile hosts) want to stay connectedwherever they may be– connections should not be disrupted as mobile hostsmove from network to network• To route a packet to a mobile host, the networkfirst has to find where the host is located– means: what IP address to usecopyright 2005 Douglas S. Reeves6Why is this Hard?• Cellphone networks have done this for years –what’s the difference?• Non-technical reasons• Technical reasons• Cellphone mobility isn’t perfect, either…2copyright 2005 Douglas S. Reeves7Tradeoffs• Can you receive incoming connections at newaddress?• Movements transparent to other nodes?• Can you maintain currently-establishedconnections while moving?• Revisions to current protocols required?– particularly, routing protocols and information• Security risks?copyright 2005 Douglas S. Reeves8Possible Approaches1. Just get a new IP address when you attach to adifferent network2. Get a new IP address, announce to other hosts(using DNS? direct messages?)3. Get a new IP address, but let the rest of the worldthink you are still at your old IP addresscopyright 2005 Douglas S. Reeves9Home AgentForeign Network N1Home NetworkCorrespondentNodeMobile IPv6 (RFC 3775)Mobile Nodehome IP addresscare-of IP address• Note: we are ignoring Mobile IPv4 for a reasoncopyright 2005 Douglas S. Reeves10Some Terminology (cont’d)• Home address– all hosts have a home address, always reachablethere– When MN is attached to home network, mobile IPv6not used; packets are routed normally to / from homeaddress• Care-of address– IP address used by mobile host in the visitednetwork– changes with each new point of attachment• A Home agent keeps track of where MN iscurrently located, forwards traffic to / from itcopyright 2005 Douglas S. Reeves11Mobile IP Mechanisms• Requires several mechanismsMobile node discovers the care-of addressMobile node registers the care-of address withthe home agentMobile node and home agent tunnel data usingthe care-of addressOptionally, mobile node registers the care-of-address with the correspondent nodecopyright 2005 Douglas S. Reeves12New / Revised Messages• New IPv6 Extension: Mobility Header– main purpose: Binding Updates• New IPv6 Extension: Destination Option– provides home address in IP datagram, as well as care-of-address used for delivery– for MN to CN communication• Modified IPv6 Extension: Source Routing– for CN to MN communication3DISCOVERING “CARE-OF”ADDRESSEScopyright 2005 Douglas S. Reeves14New Network Detection• How detect that MN is attached to a newnetwork?1. layer 2 notification (non-standardized), or…2. MN receives new Router Advertisement, or does notreceive refreshing Advertisement in the time expected3. MN receives new Router Discovery Reply to a Requestit issued• In these cases, the mobile host should attempt toautoconfigure a new care-of addresscopyright 2005 Douglas S. Reeves15Home Agents• Specialized routers• Each maintains home agent list for network(routers who have sent Router Advertisementswith HA bit set)copyright 2005 Douglas S. Reeves16Configuring Care-of Addresses• Uses the standard configuration mechanisms toget an IPv6 care-of address on the foreign network– IPv6 auto configuration– DHCPv6– …• Home agent can act as DHCP relay or server forMNs that want to do stateful autoconfiguration• When address about to expire, MN sends MobilePrefix Solicitation to HAREGISTRATIONcopyright 2005 Douglas S. Reeves18Registering Care-of Address• Once a MN has a care-of address, its homeagent must be notified of the new address– home agent is a router in the home network, providingspecialized mobility servicesMobile HostHome AgentForeign NetworkHome NetworkBinding UpdateBinding Update ACK4copyright 2005 Douglas S. Reeves19Binding Update Message• New IPv6 Extension: the Mobility Header– contains a set of messages– most important: Binding Update Message• Request for router to function as home agent– home agent has to check for error conditions (homeaddress not part of its network, host with that addressalready exists, etc.)• Care-of address for the MN is specified by theSource IPv6 Address of the datagram containingthe Binding Updatecopyright 2005 Douglas S. Reeves20Binding Update Message (cont’d)• Home address specified by:– Home Address destination option (if present), or– Source IPv6 Address of packet• Registration must be refreshed periodically,otherwise it times out– Lifetime = number of seconds*4, 16 bits long, max of3 days– if Lifetime = 0, means “delete this binding from thecache”• MN must maintain Binding Update list (HAs andCNs who know you are at this care-of address)copyright 2005 Douglas S. Reeves21Binding Update Cache• Maintained by home agents (and correspondentnodes)• Keeps track of active home address / care-ofaddress bindings• Contents– home address– care-of address– lifetime– sequence numbercopyright 2005 Douglas S. Reeves22Home Agent Discovery• A new ICMPv6 message type is required: HomeAgent Address Discovery Request and Reply– very similar to ICMP Router Request and Replymessages• MN anycasts the Request to the home network– one home agent replies (on behalf of all home agentsfor that network)copyright 2005 Douglas S. Reeves23Returning Home• A mobile host is back at its home network whenauto configuration returns its home address– in this case, the mobile host should “unregister” with thehome agentDELIVERING DATA TO/FROMMOBILE NODES5copyright 2005 Douglas S. Reeves25Mobile IPv6 TunnelingA packet sent to MN H is…– routed to H's home network– intercepted by the home agentThe home agent– “tunnels” the packet to the care-of address– (i.e., encapsulate IP packet for H inside an IP packetsent to care-of address)copyright 2005 Douglas S. Reeves26Mobile IPv6 Tunneling (cont’d)The destination MN decapsulates the


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