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Inter-Subnet Mobile IP Handoffs in 802.11b Wireless LANs

Inter-Subnet Mobile IP Handoffs in 802.11b Wireless LANs. Albert Hasson. Presentation Overview. Introduction Mobile IP overview (v4 and v6) IEEE 802.11 Mobile IP handoff mechanisms MIP handoff optimizations from literature Project focus. Introduction. WLAN technology spreading

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Inter-Subnet Mobile IP Handoffs in 802.11b Wireless LANs

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  1. Inter-Subnet Mobile IP Handoffs in 802.11b Wireless LANs Albert Hasson

  2. Presentation Overview • Introduction • Mobile IP overview (v4 and v6) • IEEE 802.11 • Mobile IP handoff mechanisms • MIP handoff optimizations from literature • Project focus

  3. Introduction • WLAN technology spreading • 802.11 roaming within a network • Mobile IP handoff to another network • How can handoff be improved? • Latency during MIP handoffs in 802.11 WLANs

  4. Introduction Corresponding Node Internet 10.64.x.x 10.128.x.x Router A Router B AP AP AP ? 10.64.1.37

  5. Mobile IP • Allows transparent migration through different networks • Overview Mobile IPv4 • Mobile IPv6 extensions to MIPv4 • IP mobility entities • IP mobility mechanisms

  6. Mobile IP • Assign mobile node (MN) 2 addresses • Home address • Permanent • Define transport connections • Care-of address (CoA) • Corresponds to MN current location • Globally routable

  7. Mobile IPv4 Entities • Mobility Agents • Home Agent • On home network • Maintains CoA-home address mapping • Binding Cache • Encapsulate and tunnel packets to CoA

  8. Mobile IPv4 Entities • Foreign Agent • On foreign (visited) network • De-encapsulate tunneled packets • Deliver to MN • Allow MN to configure CoA

  9. Mobile IPv4 Mechanisms • Agent Discovery • Periodic agent advertisements • Extension to ICMP Router Discovery • Advertise presence • Include mobility-specific information (CoA) • MN may send Router solicitations

  10. Mobile IPv4 Operation Corresponding Node Home Agent HAddr1 – CoA1 HAddr2 – CoA2 Internet Tunnel Foreign Agent Mobile Node

  11. Mobile IPv6 • CN maintains Binding Cache • Packets sent directly to MN • May be sent to Home Agent and tunneled • IPv6 Routing header instead of encapsulation

  12. Mobile IPv6 • No foreign agents • Functionality built into IPv6 routers • IPv6 Neighbor Discovery • Stateless address autoconfiguration • Access Router

  13. Mobile IPv6 Operation Corresponding Node Home Agent HAddr1 – CoA1 HAddr2 – CoA2 HAddr1 – CoA1 HAddr2 – CoA2 Internet Access Router Mobile Node

  14. 802.11 Wireless LANs • Basic Service Set (BSS) • Set of communicating stations using WM • Smallest unit of a WLAN • Form an Independent Basic Service Set (IBSS) • Ad-hoc network

  15. 802.11 Wireless LANs • Extended Service Set (ESS) • Interconnection of BSSs • Distribution System (DS) provides interconnection • Access Point (AP) bridge between wireless and distribution media

  16. 802.11 Wireless LANs • Extended Service Set Identifier (ESSID) • Infrastructure Network

  17. 802.11 Wireless LANs ESS Infrastructure Mode Network

  18. 802.11 (Link-layer) Handoff • L2 handoff significant to MIP handoff • Service interruption • Contributes to total handoff latency • Significant variations • » 300-400 ms

  19. 802.11 Handoff • Decrease in SNR initiates handoff • Scan • Find available APs with same ESSID • Record signal strength • Use Probe Request & Probe Response • Sweep through channels • Select “best” AP

  20. 802.11 Handoff • Authentication • Establish identity of station • Open System – always accepted • Wireless Equivalent Privacy (WEP)

  21. 802.11 Handoff • Association • Station registered at AP • AP handles station traffic • Re-association – transfer association from old AP • Probe delay 90% of L2 handoff latency

  22. 802.11 Handoff

  23. Mobile IP Handoff • Link-layer handoff • Movement detection • Registration • Handoff Latency is sum of these delays • MN can’t receive IP packets – latency

  24. Mobile IP Movement Detection • MIP operates independently of link-layer • CDMA, wireless LAN • Agent/Router Discovery • Solicitation/advertisement messages • Advertisements broadcast • Period > 1/s • Bandwidth efficiency – detection delay

  25. Movement Detection • Eager Cell Switching (ECS) • Handoff on first new advertisement • Frequent movement • Lazy Cell Switching (LCS) • Wait until current access router unreachable • Infrequent movement • Latency up to 3 sec

  26. Mobile IP Registration • After handoff and detection of new foreign agent/access router • Update bindings at CN & home agent • Binding update message • MN home address • New CoA • Lifetime

  27. Mobile IP Handoff Corresponding Node Home Agent Internet 10.64.x.x 10.128.x.x Router A Router B AP AP AP ? 10.64.1.37

  28. Mobile IP Optimizations • Most systems focus on one aspect of MIP handoff • Difficult to modify 802.11 handoff • Micromobility • Improved movement detection techniques

  29. Micromobility • Defined domain • Macro/micro-mobility • Segregate access network from Internet • Use hierarchal structure • Different approaches • Hierarchal Mobile IP • Cellular IP

  30. Micromobility • Gateway manages location information • Per-mobile routes • Handoff managed locally • Bounded Registration delay • E.g. Hierarchal Mobile IPv6

  31. Micromobility

  32. Movement Detection • Establish communication between MIP and link-layer • Use “hints” or triggers • Handover start • Link up • Link down • Communicate additional information

  33. Movement Detection • Hinted Cell Switching (HCS) • Hint after L2 handoff • Send solicitation • Problems • Routers wait random time before reply • Increased signaling

  34. Movement Detection • Fast Hinted Cell Switching (FHCS) • Get identity of agent/router from link-layer • Bypass solicitation • L2 provide IP and hardware address of router • Use SSID to contain information • No need for movement detection

  35. Movement Detection • FHCS problems • 802.11 handoff between different ESSIDs • Application specific information object • Include AR or MN information on Probe messages

  36. Fast Hinted Cell Switching

  37. Fast Hinted Cell Switching

  38. Project Focus • Movement detection enhancements within micromobility framework • Investigate performing handoff processes in parallel • Network-assisted handoffs • Evaluate different mechanisms wrt handoff latency and packet loss

  39. Project Focus • Design/implement test bed • Many implementations • MIPL • Monash • Hierarchal MIP • Cellular IP • Linux wireless tools

  40. Handover to Questions…

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