15-744: Computer NetworkingMobile RoutingOverviewHow to Handle Mobile Nodes?Handling Mobile Nodes (Transport)Handling Mobile NodeHandling Mobile Nodes (Routing)Basic Solution to Mobile RoutingInterceptionDeliveryMobile IP (RFC 2290)Mobile IP (MH at Home)Mobile IP (MH Moving)Mobile IP (MH Away – Foreign Agent)Mobile IP (MH Away - Collocated)Other Mobile IP IssuesSlide 17Ad Hoc RoutingSlide 19Challenges and VariantsProblems Using DV or LSSlide 22Proposed ProtocolsDSR ConceptsDSR ComponentsDSR Route DiscoveryC Broadcasts Route Request to FSlide 28H Responds to Route RequestC Transmits a Packet to FForwarding Route RequestsRoute CacheSending DataDiscussionSlide 35ETX measurement resultsDeciding Between LinksIs there a better metric?ETX Metric Design GoalsForwarding Packets is ExpensiveETXETX: Sanity ChecksRate AdaptationSlide 4415-744: Computer NetworkingL-10 Ad Hoc NetworksMobile Routing•Mobile IP•Ad-hoc network routing•Assigned reading•Performance Comparison of Multi-Hop Wireless Ad Hoc Routing Protocols•A High Throughput Path Metric for MultiHop Wireless RoutingL -8; 11-12-04© Srinivasan Seshan, 2004 2L -8; 11-12-04© Srinivasan Seshan, 2004 3Overview•Internet routing•Ad hoc routing•Ad hoc routing metricsL -8; 11-12-04© Srinivasan Seshan, 2004 4How to Handle Mobile Nodes?•Dynamic Host Configuration (DHCP)•Host gets new IP address in new locations•Problems•Host does not have constant name/address how do others contact host•What happens to active transport connections?•Naming•Use DHCP and update name-address mapping whenever host changes address•Fixes contact problem but not broken transport connectionsL -8; 11-12-04© Srinivasan Seshan, 2004 5Handling Mobile Nodes (Transport) •TCP currently uses 4 tuple to describe connection•<Src Addr, Src port, Dst addr, Dst port> •Modify TCP to allow peer’s address to be changed during connection•Security issues•Can someone easily hijack connection?•Difficult deployment both ends must support mobilityL -8; 11-12-04© Srinivasan Seshan, 2004 6Handling Mobile Node•Link layer mobility•Learning bridges can handle mobility this is how it is handled at CMU•Encapsulated PPP (PPTP) Have mobile host act like he is connected to original LAN•Works for IP AND other network protocols•Multicast•Solves similar problem how to route packets to different sets of hosts at different times•Can’t we just reuse same solutions?•Don’t really have solution for multicast either!L -8; 11-12-04© Srinivasan Seshan, 2004 7Handling Mobile Nodes (Routing)•Allow mobile node to keep same address and name•How do we deliver IP packets when the endpoint moves?•Why can’t we just have nodes advertise route to their address?•What about packets from the mobile host?•Routing not a problem•What source address on packet?•Key design considerations•Scale•Incremental deploymentL -8; 11-12-04© Srinivasan Seshan, 2004 8Basic Solution to Mobile Routing •Same as other problems in Computer Science•Add a level of indirection•Keep some part of the network informed about current location•Need technique to route packets through this location (interception)•Need to forward packets from this location to mobile host (delivery)L -8; 11-12-04© Srinivasan Seshan, 2004 9Interception•Somewhere along normal forwarding path•At source•Any router along path•Router to home network•Machine on home network (masquerading as mobile host)•Clever tricks to force packet to particular destination•“Mobile subnet” – assign mobiles a special address range and have special node advertise routeL -8; 11-12-04© Srinivasan Seshan, 2004 10Delivery•Need to get packet to mobile’s current location•Tunnels•Tunnel endpoint = current location•Tunnel contents = original packets•Source routing•Loose source route through mobile current location•Network address translation (NAT)•What about packets from the mobile host?L -8; 11-12-04© Srinivasan Seshan, 2004 11Mobile IP (RFC 2290)•Interception•Typically home agent – hosts on home network•Delivery•Typically IP-in-IP tunneling•Endpoint – either temporary mobile address or foreign agent•Terminology•Mobile host (MH), correspondent host (CH), home agent (HA), foreign agent (FA)•Care-of-address, home addressL -8; 11-12-04© Srinivasan Seshan, 2004 12Mobile IP (MH at Home)Mobile Host (MH)Visiting LocationHomeInternetCorrespondent Host (CH)PacketL -8; 11-12-04© Srinivasan Seshan, 2004 13Mobile IP (MH Moving)Visiting LocationHomeInternetCorrespondent Host (CH)PacketHome Agent (HA)Mobile Host (MH)I am hereL -8; 11-12-04© Srinivasan Seshan, 2004 14Mobile IP (MH Away – Foreign Agent)Visiting LocationHomeInternetCorrespondent Host (CH)PacketHome Agent (HA)Foreign Agent (FA)EncapsulatedMobile Host (MH)L -8; 11-12-04© Srinivasan Seshan, 2004 15Mobile IP (MH Away - Collocated)Visiting LocationHomeInternetCorrespondent Host (CH)PacketHome Agent (HA)Mobile Host (MH)EncapsulatedL -8; 11-12-04© Srinivasan Seshan, 2004 16Other Mobile IP Issues•Route optimality•Triangle routing •Can be improved with route optimization•Unsolicited binding cache update to sender•Authentication• Registration messages• Binding cache updates•Must send updates across network•Handoffs can be slow•Problems with basic solution•Reverse path check for security•Do we really need it…L -8; 11-12-04© Srinivasan Seshan, 2004 17Overview•Internet routing•Ad hoc routing•Ad hoc routing metricsAd Hoc Routing•Goal: Communication between wireless nodes•No external setup (self-configuring)•Often need multiple hops to reach dstL -8; 11-12-04© Srinivasan Seshan, 2004 19Ad Hoc Routing•Create multi-hop connectivity among set of wireless, possibly moving, nodes•Mobile, wireless hosts act as forwarding nodes as well as end systems•Need routing protocol to find multi-hop paths•Needs to be dynamic to adapt to new routes, movement•Interesting challenges related to interference and power limitations•Low consumption of memory, bandwidth, power•Scalable with numbers of nodes•Localized effects of link failureChallenges and Variants•Poorly-defined “links”•Probabilistic delivery, etc. Kind of n2 links•Time-varying link characteristics•No oracle for configuration (no ground truth configuration file of connectivity)•Low bandwidth (relative to wired)•Possibly mobile•Possibly power-constrainedL -8; 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