Mobile IPOne more IP topic…Portable Networking TechnologyMobility and Standard IP RoutingMobile IPMobile IP EntitiesMobile IP Entities contd.Mobile IP Support ServicesMobile IP OperationRegistration ProcessTables maintained on routersMobile IP Operation contd.Mobile IP TunnelingSecurity in Mobile IPProblems with Mobile IPSlide 16Mobile IP Outline Intro to mobile IPOperationProblems with mobilityCS 640 2One more IP topic…•Already covered lots of things about IP–Forwarding, routing, multicast, etc…•One last IP topic: mobile networking•Important for the future–Examples of mobile networking today?–Examples of mobile networking tomorrow?•Mobile networking should not be confused with portable networkingCS 640 3Portable Networking Technology•Portable networking requires connection to same ISP•Cellular systems–Cellular Digital Packet Data (CDPD)–3G•Bluetooth–Low cost, short range radio links between mobile devices•Wireless Ethernet (802.11)–Widely used wireless MAC layer technologyCS 640 4Mobility and Standard IP Routing•IP assumes end hosts are in fixed physical locations•IP addresses enable IP routing algorithms to get packets to the correct network–IP address has network part and host part –Host part should not be in routing tables•What if a user roams between networks?–Want transparency–Routing information becomes invalid –Why can’t mobile users change IP when running an application?CS 640 5Mobile IP•Developed as a means for transparently dealing with problems of mobile users•Enables hosts to stay connected to the Internet regardless of their location and without changing IP addresses•Requires no changes to software of non-mobile hosts/routers•Requires addition of some infrastructure•Has no geographical limitations•Requires no modifications to IP addresses•Supports security•IETF standardization process is still underwayCS 640 6Mobile IP Entities•Mobile Node (MN)–The entity that moves from network to network–Assigned a permanent IP called its home address to which other hosts send packets regardless of MN’s location•Home Agent (HA)–Router with additional functionality–Located on home network of MN–Mobility binding of MN’s IP with its Care of Address (COA)–Forwards packets to appropriate network when MN is away – uses encapsulationCS 640 7Mobile IP Entities contd.•Foreign Agent (FA)–Another router with enhanced functionality–Used to send/receive data between MN and HA–Advertises itself periodically•Care-of-address (COA)–Address which identifies MN’s current location–Sent by FA to HA when MN attaches–Usually the IP address of the FA•Correspondent Node (CN)–End host to which MN is corresponding (eg. a web server)CS 640 8Mobile IP Support Services•Agent Discovery–HA’s and FA’s broadcast their presence on each network to which they are attached–MN’s listen for advertisement and then initiate registration•Registration–When MN is away, it registers its COA with its HA, via FA–Registration control messages sent via UDP to well known port•Encapsulation/decapsulation – just like standard IP only with COACS 640 9Mobile IP Operation•A MN listens for agent advertisement and then initiates registration–If responding agent is the HA, then mobile IP is not necessary•After receiving the registration request from a MN, the HA acknowledges and registration is complete–Registration happens as often as MN changes networks•HA intercepts all packets destined for MN–This is simple unless sending application is on or near the same network as the MN–HA masquerades as MN–There is a specific lifetime for service before a MN must re-register–There is also a de-registration process with HA if an MN returns homeCS 640 10Registration ProcessCS 640 11Tables maintained on routers•Mobility Binding Table–Maintained on HA of MN–Maps MN’s home address with its current COA•Visitor List–Maintained on FA serving an MN–Maps MN’s home address to its MAC address and HA addressCS 640 12Mobile IP Operation contd.•HA then encapsulates all packets addressed to MN and forwards them to FA–IP tunneling•FA decapsulates all packets addressed to MN and forwards them via hardware address (learned as part of registration process)•NOTE that the MN can perform FA functions if it acquires an IP address eg. via DHCP•Bidirectional communications require tunneling in each directionCS 640 13Mobile IP TunnelingAcross InternetCS 640 14Security in Mobile IP•Authentication can be performed by all parties–Only authentication between MN and HA is required–Keyed MD5 is the default•Replay protection–Timestamps are mandatory–Random numbers on request reply packets are optional•HA and FA do not have to share any security information.CS 640 15Problems with Mobile IP•Suboptimal “triangle” routing–What if MN is in same subnetwork as the node to which it is communicating and HA is on the other side of the world?•It would be nice if we could directly route packets–Solution: Let the CN know the COA of MN•Then the CN can create its own tunnel to MN•CN must be equipped with software to enable it to learn the COA•Initiated by HA who notifies CN via “binding update”•Binding table can become staleCS 640 16Problems with Mobile IP•Single HA model is fragile–Possible solution – have multiple HA•Frequent reports to HA if MN is moving–Possible solution – support of FA clustering•Security–Connection hijacking, snooping…•Many open research
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