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 Internet Router ARouter B AP 10.64.x.x10.128.x.x ? 10.64.1.37 Corresponding Node

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 Internet Home Agent Corresponding Node Foreign Agent HAddr1 – CoA1 HAddr2 – CoA2 Tunnel 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 Internet Home Agent Corresponding Node Access Router HAddr1 – CoA1 HAddr2 – CoA2 Mobile Node HAddr1 – CoA1 HAddr2 – CoA2

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 Infrastructure Mode Network ESS

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 Internet Router ARouter B AP 10.64.x.x10.128.x.x ? 10.64.1.37 Corresponding Node Home Agent

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

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…