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Mobility Management

Mobility Management. CS598HL, Fall 2006. Mobility Management. Cellular networks Internet Mobile IP Macro-mobility HAWAII Micro-mobility Contact Networking Local connectivity. TMSI, LAI. TMSI. IMEI : international mobile equipment identity. IMSI.

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Mobility Management

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  1. Mobility Management CS598HL, Fall 2006

  2. Mobility Management • Cellular networks • Internet • Mobile IP • Macro-mobility • HAWAII • Micro-mobility • Contact Networking • Local connectivity

  3. TMSI, LAI TMSI IMEI: international mobile equipment identity IMSI • - IMSI: international mobile subscriber identity • Subscriber authentication key • Authentication algorithms SIM Card Mobile User Authentication and Anonymity IMSI IMSI LAI LAI: Location Area Identity cisco.com

  4. Internet Mobility Support • IP address plays two roles: • acts as an end-point identifier for connections involving the host • a host address should always remain the same • provides routing info for packets destined for the host • a host address should change whenever the host moves • Goal: support mobility without having to change the protocols in all the millions of hosts currently on the Internet

  5. Mobile IP • A Network Layer solution for mobility on global Internet • Scalable • Secure • Robust • Mobile Host must be able to communicate with other nodes after changing its point-of-attachment to Internet • Must be able to communicate with only its home (permanent) IP address • With other nodes that do not implement mobile IP

  6. Two Tier Addressing • We need an address pair to identify an MH at any time: • Home address for identification • Current address for routing • How to do two-tier addressing: • not physically done (which requires 8 bytes of address per host) • perform address translation along the way by some specialized agents that cache both addresses.

  7. Architecture contd: Address Translation • When a source communicates with a MH, it puts its HA in the destination address field. • Somewhere along the route, this has to pass thru an address translation agent (ATA), which converts the HA to the forwarding address. • Address Translation can be provided by 2 mechanisms: • IP-IP Encapsulation: encapsulate the original datagram within another datagram that contains the FA address • Loose source routing: indicates intermediate hops over which the datagram must travel to the final destination. In this case, the intermediate hop will be the FA, which then converts the packet address to the final destination

  8. Architecture Contd: Packet Forwarding • Source sends out packets that are addressed to HA of MH • ATA intercepts packets and maps HA to FA (using IPIP or LSR) • Packets arrive at FA • FA remaps address to HA and delivers them over the last hop • At the MH, the packet seems to arrive from Source to HA; thus, transport layer is provided transparency

  9. Mobile IPv4: RFC2002 • Macro-management for mobility • less frequent than once per second • Two scenarios for packet forwarding: • MH to a static host: as usual • a static host to a MH: needs Mobile IP

  10. Basic Concepts • Home agent: a router on a MH’s home network which tunnels datagrams for delivery to the MH when it is away from home, maintains LD for MH • Foreign agent: a router on a MH’s visited network which provides routing services to the MH while registered. FA detunnels and delivers datagrams to the MH that were tunneled by the MH’s HA. • Care-of Address: termination point of a tunnel toward a MH, for datagrams forwarded to the MH while it is away from home. • Foreign agent care-of address: the address of a foreign agent that MH registers with • co-located care-of address: an externally obtained local address that a MH gets.

  11. Protocol Overview • Mobility agents (FAs & HAs) advertise their presence • MH receives the agent advertisements & determines whether it is on its home net or a foreign net • Home net: MH operates without mobility service • Foreign net: obtains a care-of address on the foreign net (via FA’s agent advertisements or DHCP) • if away from home, MH registers its new care-of address with its HA thru a registration request/response process (possibly via a FA). • Datagram sent to the MH’s home address: • intercepted by its home agent, • tunneled by the HA to the MH’s care-of address, • De-tunneled at the tunnel endpoint (either a FA or MH itself), • and finally delivered to the MH • In the reverse direction, using standard IP routing.

  12. Registration

  13. Forwarding

  14. Agent Discovery • Method used by a MH to determine whether it is in its home net or a foreign net; may allow MH to determine the foreign agent care-of address • Agent advertisement: • lifetime: maximum length of time that the Advertisement is considered valid in the absence of further Advertisement • if sends periodically, allows a MH to miss 3 Adv messages before deleting the agent from its list. • If it can serve as a FA, must announce its FA care of address • HA must always be prepared to serve the MHs for which it is the HA. • FA may announce too busy to handle additional MHs, but must still continually send out the Adv messages.

  15. Registration • A mechanism for MHs to communicate their current reachability info to their home agent • MHs use registration to • request forwarding service when it is in a foreign network • inform their HA of their current care-of address • renew a registration which is due to expire • deregister when they return to home • registration may be via a FA or directly from the MH. • Via a FA: • If a MH is registering a FA care-of address • if a MH is using a co-located care-of address and receives an Agent Adv from a FA if the “Registration required” bit is set in the Adv message • directly with HA: • MH is using a co-located care-of address and not in the above case • when MH returns to home net,

  16. Registration Overview Via FA: • MH sends a Registration Request to the FA • FA receives the request and relays it to the HA • HA sends a Registration Reply to the FA to grant/deny the registration request • FA processes the Registration Reply and relays it to the MH Directly with HA: • exchanges Request/Reply with HA directly • After a successful registration: • HA creates/modifies the entry for the MH: • MH’s care-of address, remaining lifetime of the registration, ID field from the Registration Reply

  17. Routing Consideration • Foreign Agent: • maintains a visitor list • when receives an encapsulated datagram, compare the inner destination address to entries in its visitor list; route datagrams. • Home Agent: • how to intercept any datagrams on the home net addressed to the MH when the MH is away from home • use Proxy and gratuitous ARP: • when a MH is registered on a foreign net, its HA uses proxy ARP to reply to ARP request that seeks the MH’s link-layer address • when MH leaves/returns its home net, its HA uses gratuitous ARP to update the ARP caches of nodes on the home net, causing such nodes to associate the link-layer address of the HA with the MH’s home IP address • Proxy ARP: an ARP reply sent by one node on behalf of another in response to an ARP request. The proxy supplies its own link-layer address in the reply. • Gratuitous ARP: an ARP packet sent by a node to spontaneously cause others to update an entry in their ARP cache.

  18. Obtain co-located care-off address via DHCP • DHCP (RFC1541): • a generic protocol for dynamic host configuration • can be used to obtain care-of IP address, default router address, IP subnet mask of a foreign net, domain, and DNS name • Each net is expected to provide either a DHCP server or relay • Steps: • The DHCP client sends a DHCP_DISCOVER or DHCP_REQUEST message • The DHCP server has a pool of available addresses. When it sees an address request, it picks one of the addresses and responds with the DHCP_OFFER message, containing the home address. • The DHCP client receives the address, and responds with a DHCP_REQUEST request confirming the address acceptance. The server then binds the address to the client. The server responds with a DHCP_ACK message. • The DHCP client may proceed with its registration process.

  19. Summary • Forwarding agent: co-located with foreign Agent or with MH (if DHCP is used) • Location Directory: at home router only • Address Translation Agent: co-located with home router • location update protocol: caching of LD is not allowed; when a MH moves, only the primary copy is modified • Route optimization: never; • triangle routing problem • location info is NOT allowed to be cached due to security concerns

  20. Mobile IP with Route Optimization • Idea: • Correspondent hosts can learn the current care-of address for a MH, and creates a valid binding (LD cache entry) for a MH, and becomes Address Translation Agents • Host can encapsulate packets directly to the care-of address of MH (thus bypassing the HA), just as the HA does in the basic Mobile IP spec; host can also use minimal encapsulation as an abbreviated style of encapsulation (8 bytes addtion to the IP datagram) • Two main issues: • updating binding caches • only when it received and authenticated the MH’s mobility binding • when HA intercepts a datagram and tunnels it to the MH, HA sends a Binding Update message to the sender • when FA sees that MH is not on its visitor list, it sends HA a Binding Warning message, advising HA to send a Binding Update message to the MH

  21. Mobile IP with Route Optimization (contd) • Foreign Agent Smooth Handoff • In basic Mobile IP, datagrams in flight may be lost during handoff since HA forwarded those packets to the old FA. • Solution: old FA is notified of the MH’s new FA via a Binding Update message from the new FA, and forwards datagrams in flight to the MH’s new care-of address • Summary • Forwarding agent: same as basic mobile IP • Location Directory: correspondent hosts can cache LD entries • Address Translation Agent: colocated with correspondent hosts • Location update: HA is responsible for sending Binding Update message

  22. IPv6 Mobility Proposal • Mobility support is a basic requirement for IPv6 design • Key differences from Mobile IPv4: • support for route optimization becomes a fundamental part of the protocol, not an optional part as in Moble IPv4 • no need to deploy foreign agents any more • packets sent to a MH while away from home are tunneled using an IPv6 Routing header rather than IP encapsulation • MH is always responsible for delivering binding updates to its correspondence hosts

  23. Hierarchy and Unique Address • Hierarchy through domains • Mobile-IP for movement between domains • HAWAII Path Setup for movement within domain • Users retain their unique IP address while moving within a domain • Home address could be dynamically assigned • Co-located care-of address used in foreign domain • Unique and unchanging address limits updates to Home Agent and simplifies QoS support in the network

  24. Domain Router R R R R R R R R R R R R Enhance Mobile-IP Internet Domain Router MD Local mobility Local mobility Mobile IP • Distributed control: Reliability and scalability • host-based routing entries in routers on path to mobile • Localized mobility management: Fast handoffs, Paging support • updates only reach routers affected by movement • page locally when device is in sleep mode • Minimized or Eliminated Tunneling: Efficient routing • dynamic, public address assignment to mobile devices

  25. Internet 1 1 2 5 5 R 2 R 4 4 3 3 MY IP: 1.1.1.100 BS IP:1.1.1.5 Domain Root Router 2 Domain Root Router 1 1 1 2 R R 4 2 4 3 3 1.1.1.100-> port 3, 239.0.0.1 3 4 1.1.1.100->port 4, 239.0.0.1 5 1 4 R 3 2 2 BS1 BS2 BS3 BS4 1.1.1.100->wireless, 239.0.0.1 1 5 Mobile IP HAWAII

  26. Soft State • Host-based routing entries maintained as soft-state • Base-stations and mobile hosts periodically refresh the soft-state • HAWAII leverages routing protocol failure detection and recovery mechanisms to recover from failures • Recovery from link/router failures

  27. Internet 1 1 2 5 5 R 2 R 4 4 3 3 MY IP: 1.1.1.100 BS IP:1.1.1.5 Domain Root Router 2 Domain Root Router 1 1 1 1.1.1.100-> port 4, 239.0.0.1 2 R R 4 2 4 3 3 3 1.1.1.100->port 3, 239.0.0.1 5 1 4 R 3 2 2 BS1 BS2 BS3 BS4 1.1.1.100->wireless, 239.0.0.1 1 Mobile IP HAWAII

  28. Path Setup • Host-based routing within the domain • Path setup schemes selectively update local routers as users move • Path setup schemes customized based on user, application, or wireless network characteristics • Micro-mobility handled locally with limited disruption to user traffic

  29. Internet 1 1 2 5 5 2 R R 4 4 3 3 MY IP: 1.1.1.100 BS IP:1.1.1.2 Domain Root Router 2 Domain Root Router 1 1 1 2 R R 4 2 4 3 3 1.1.1.100-> port 3, 239.0.0.1 1.1.1.100->port 3 (4), 239.0.0.1 5 1 4 R 3 2 4 2 3 BS1 BS2 BS3 BS4 1.1.1.100->wireless, 239.0.0.1 1.1.1.100->port 1(wireless), 239.0.0.1 1 5 Mobile IP HAWAII

  30. Paging • “Idle” mobile hosts update the network less frequently than “active” mobile hosts • Network has only approximate location information for idle mobile hosts • Network determines the exact location by paging to deliver packets

  31. Paging Goal • Efficiency • limit updates from the mobile host when idle to conserve battery power • Scalability • push paging initiation closer to the base station • Reliability • allow paging initiation to occur at any router/base station (no single point of failure) • Flexibility • allow for fixed, hierarchical, or user-defined paging areas

  32. Internet 1 1 2 5 5 2 R R 4 4 3 3 MY IP: 1.1.1.100 BS IP:1.1.1.2 Domain Root Router 2 Domain Root Router 1 1 1 2 R R 4 2 4 3 3 1.1.1.100-> port 3, 239.0.0.1 Buffer 1.1.1.100->port 3, 239.0.0.1 5 1 4 R 3 2 1 1 4 BS1 BS2 BS3 BS4 1.1.1.100->wireless, 239.0.0.1 2 3 2 Paging Data HAWAII

  33. Internet 1 1 2 5 5 2 R R 4 4 3 3 BS1 Macro-Mobility Domain Root Router 2 Domain Root Router 1 Mobile IP Home Agent: 1.1.1.100-> 1.1.2.200 1 1 2 R R 4 2 4 3 3 1.1.2.200-> port 3, 239.0.0.1 3 5 4 1.1.2.200->port 2, 239.0.0.1 6 5 1 4 R 3 2 2 BS2 BS3 BS4 1.1.2.200->wireless, 239.0.0.2 1 7 MY IP: 1.1.1.100 BS IP:1.1.2.1 COA IP:1.1.2.200 Mobile IP HAWAII

  34. Research

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