An Agile Vertical Handoff Scheme for Heterogeneous Networks

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  • 近年來網路技術蓬勃發展,例如 Ethernet 、 802.11 、 GPRS 等等,各有各的特色。然而,沒有一種網路技術同時具有高頻寬、低延遲時間、和廣大的無線訊號涵蓋範圍等等。而隨著可攜式裝置的普及,使用者對移動上網的需求也日漸增加。因此,讓使用者可以在不同類型網路間進行 handoff 變成一個很重要的議題。
  • Mobile Host 從一個 BSS 移動到另一個 BSS 就稱為 Horizontal handoff
  • 而 Mobile Host 從一個 WLAN 移動到一個 3G 的網路,就稱為 Vertical handoff
  • An Agile Vertical Handoff Scheme for Heterogeneous Networks

    1. 1. An Agile Vertical Handoff Scheme for Heterogeneous Networks Hsung-Pin Chang Department of Computer Science National Chung Hsing University Taichung, Taiwan, R.O.C.
    2. 2. Outline <ul><li>Motivation </li></ul><ul><li>Related work </li></ul><ul><ul><li>How to achieve seamless vertical handoff ? </li></ul></ul><ul><li>Challenge and Contribution </li></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    3. 3. Outline <ul><li>Motivation </li></ul><ul><li>Related work </li></ul><ul><ul><li>How to achieve seamless vertical handoff ? </li></ul></ul><ul><li>Challenge and Contribution </li></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    4. 4. Hierarchical Overlay Network <ul><li>Many different communications systems coexist around us </li></ul><ul><ul><li>Ethernet, Wireless LAN, GPRS, 3G… </li></ul></ul><ul><li>Each owns different characteristics </li></ul><ul><ul><li>Bandwidth, delay, cost…… </li></ul></ul><ul><li>Hierarchical overlay network </li></ul><ul><ul><li>The combination of these heterogeneous networks </li></ul></ul>
    5. 5. Example: An Overlay Networks Campus-wide (3G, GPRS) Building-wide (WLAN) Room-wide (Ethernet)
    6. 6. Horizontal versus Vertical Handoff <ul><li>Problem: handoffs </li></ul><ul><ul><li>Horizontal handoff </li></ul></ul><ul><ul><ul><li>The same kind of network technology </li></ul></ul></ul><ul><ul><ul><li>Ex: BSS to BSS </li></ul></ul></ul><ul><ul><li>Vertical handoff </li></ul></ul><ul><ul><ul><li>Different kinds of network technologies </li></ul></ul></ul><ul><ul><ul><li>Ex: Wireless LAN to 3G </li></ul></ul></ul><= what we are addressed
    7. 7. Horizontal Handoff AP AP BSS BSS Internet
    8. 8. Vertical Handoff WCDMA WLAN AP BS Internet
    9. 9. Outline <ul><li>Motivation </li></ul><ul><li>Related work: how to achieve seamless vertical handoff ? </li></ul><ul><li>Challenge and Contribution </li></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    10. 10. Previous Approaches to Vertical Handoff 1/2 <ul><li>Mobile IP/Infrastructure Based </li></ul><ul><ul><li>Approaches </li></ul></ul><ul><ul><ul><li>Mobile IP with multicast </li></ul></ul></ul><ul><ul><ul><ul><li>Care-of-address is changed to a multicast address </li></ul></ul></ul></ul><ul><ul><ul><li>Integration of WLAN and GPRS </li></ul></ul></ul><ul><ul><ul><li>Integration of WLAN and 3G </li></ul></ul></ul><ul><ul><li>Problem </li></ul></ul><ul><ul><ul><li>Require modification of network infrastructure </li></ul></ul></ul><ul><ul><ul><ul><li>Hindrance to deployment </li></ul></ul></ul></ul><ul><ul><ul><li>Need to be keep up to data </li></ul></ul></ul><ul><ul><ul><ul><li>New technologies are always introduced </li></ul></ul></ul></ul>
    11. 11. Previous Approaches to Vertical Handoff 2/2 <ul><li>End-to-end based </li></ul><ul><ul><li>A pplication layer </li></ul></ul><ul><ul><ul><li>SIP (Session Initiation Protocol) </li></ul></ul></ul><ul><ul><li>Transport layer: enable TCP connection alive even the underlying IP address is changed </li></ul></ul><ul><ul><ul><li>TCP-R </li></ul></ul></ul><ul><ul><ul><li>TCP Migrate </li></ul></ul></ul><ul><ul><li>Between transport layer and network layer </li></ul></ul><ul><ul><ul><li>C. Guo, et. al., “ A Seamless and Proactive End-to-End Mobility Solution for Roaming Across Heterogeneous Wireless Networks ,” IEEE JSAC, 22(5), pp.834-848. Jun. 2004 </li></ul></ul></ul>
    12. 12. A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (1/4) Network Applications BSD Sockets TCP UDP User Kernel Socket Interface Transport Layer IP PPP SLIP Ethernet Network Devices Network Layer LCT Table Translation
    13. 13. A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (2/4) W L A N L A N L A N Mobile Client Fixed Host … p1 A p1 A Mapped port Mapped address Original port Original address Nego A B Tell B that A support vertical handoff Nego+Ack B A B Tell A ok. Notify C B A Ack B C A B C p1 A p1 A Mapped port Mapped address Original port Original address p2 C p1 A Mapped port Mapped address Original port Original address p2 C p1 A Mapped port Mapped address Original port Original address
    14. 14. A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (3/4) Handoff Layer Application Handoff Layer Kernel Application Kernel Table Lookup Table Lookup 圖 3 封包表頭替換過程 B A B A B C
    15. 15. A Seamless and Proactive End-to-End Solutions for Roaming Across Heterogeneous Wireless Networks (4/4) <ul><li>Problems </li></ul><ul><ul><li>NAT issue </li></ul></ul><ul><ul><ul><li>Require an S/N (Subscription/Notification) Server </li></ul></ul></ul><ul><ul><ul><li>Modify the infrastructure </li></ul></ul></ul><ul><ul><li>TCP performance </li></ul></ul><ul><ul><ul><li>Do not consider </li></ul></ul></ul>
    16. 16. Outline <ul><li>Motivation </li></ul><ul><li>Related work: how to achieve seamless vertical handoff ? </li></ul><ul><li>Challenge and Contribution </li></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    17. 17. How to pass NAT gateway ? <ul><li>Problem </li></ul><ul><ul><li>Communication must always be initiated by the private network </li></ul></ul><ul><li>Solution </li></ul><ul><ul><li>Use the previous IP address as the source IP address </li></ul></ul>
    18. 18. WLAN Fixed Host Ethernet NAT AP Switch Update New IP address Problem
    19. 19. WLAN Fixed Host Ethernet NAT AP Switch Update Old IP address Solution
    20. 20. Outline <ul><li>Motivation </li></ul><ul><li>Related work: how to achieve seamless vertical handoff ? </li></ul><ul><li>Challenge and Contribution </li></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? => CWND-Restore </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    21. 21. How to adapt TCP behavior ? <ul><li>Problem </li></ul><ul><ul><li>TCP consider packet loss as network congestion </li></ul></ul><ul><ul><li>Slow down… </li></ul></ul><ul><li>But…now packet lose is because “handoff” </li></ul><ul><li>Solution </li></ul><ul><ul><li>CWND-Restore </li></ul></ul>
    22. 22. WLAN Fixed Host Ethernet NAT AP Switch CWND-Restore CWND 20 CWND 2 CWND 50
    23. 23. Outline <ul><li>Motivation </li></ul><ul><li>Related work: how to achieve seamless vertical handoff ? </li></ul><ul><li>Challenge and Contribution </li></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    24. 24. System Implementation- Linux Kernel 2.6.11 Ethernet Driver WLAN Driver 3G Applications Connection Manager TCP User Mode Kernel Mode UDP IP Handoff Detection CWND-restore
    25. 25. Experimental Platform 256 MB 512 MB RAM Novatel UMTS/WCDMA USB Adapter NIC #3 Philips 802.11g WLAN miniPCI Adapter NIC #2 100Mbps Fast Ethernet Ethernet 100Mbps Ethernet NIC #1 Intel Pentium M 1.4GHz AMD XP 2600+ CPU Mobile Host Fixed Host
    26. 26. Experiment 2/2 <ul><li>Experiments </li></ul><ul><ul><li>TCP handoff verification </li></ul></ul><ul><ul><li>Handoff latency </li></ul></ul><ul><ul><li>TCP handoff performance </li></ul></ul><ul><ul><li>UDP handoff verification </li></ul></ul>
    27. 27. Experiment 2/2 <ul><li>Experiments </li></ul><ul><ul><li>TCP handoff verification </li></ul></ul><ul><ul><li>Handoff latency </li></ul></ul><ul><ul><li>TCP handoff performance </li></ul></ul><ul><ul><li>UDP handoff verification </li></ul></ul>
    28. 28. TCP Handoff Verification 1/7 Experiment environment Internet Ethernet WCDMA Fixed Host Mobile Host WLAN NAT NAT BS B A C AP Switch
    29. 29. TCP Handoff Verification 2/7 <ul><li>LAN to WLAN </li></ul>Handoff
    30. 30. TCP Handoff Verification 3/7 <ul><li>WLAN to LAN </li></ul>Handoff
    31. 31. TCP Handoff Verification 4/7 <ul><li>LAN to WCDMA </li></ul>Handoff
    32. 32. TCP Handoff Verification 5/7 <ul><li>WCDMA to LAN </li></ul>Handoff
    33. 33. TCP Handoff Verification 6/7 <ul><li>WLAN to WCDMA </li></ul>Handoff
    34. 34. TCP Handoff Verification 7/7 <ul><li>WCDMA to WLAN </li></ul>Handoff
    35. 35. Experiment 2/2 <ul><li>Experiments </li></ul><ul><ul><li>TCP handoff verification </li></ul></ul><ul><ul><li>Handoff latency </li></ul></ul><ul><ul><li>TCP handoff performance </li></ul></ul><ul><ul><li>UDP handoff verification </li></ul></ul>
    36. 36. Handoff Latency 1/2 Experiment environment WCDMA Internet WLAN Fixed Host Mobile Host Ethernet NAT AP Switch BS B A C
    37. 37. Handoff Latency 2/2 3 WCDMA to WLAN 1 WCDMA to LAN 503 WLAN to WCDMA 1 WLAN to LAN 438 LAN to WCDMA 3 LAN to WLAN Handoff Latency (ms)
    38. 38. Experiment 2/2 <ul><li>Experiments </li></ul><ul><ul><li>TCP handoff verification </li></ul></ul><ul><ul><li>Handoff latency </li></ul></ul><ul><ul><li>TCP handoff performance </li></ul></ul><ul><ul><li>UDP handoff verification </li></ul></ul>
    39. 39. TCP Handoff Performance 1/8 Experiment environment WCDMA Internet WLAN Fixed Host Mobile Host Ethernet NAT AP Switch BS B A C
    40. 40. TCP Handoff Performance 2/8 4.12 3.98 237.77 5059.62 244.87 7690.84 CWND Freeze (KB/s) 3.47 WLAN to WCDMA 3.64 LAN to WCDMA 138.34 WCDMA to WLAN 2886.36 WCDMA to LAN 177.58 LAN to WLAN 6154.8 WLAN to LAN Original (KB/s)
    41. 41. TCP handoff performance 3/8 <ul><li>LAN to WLAN </li></ul>Handoff
    42. 42. TCP handoff performance 4/8 <ul><li>WLAN to LAN </li></ul>Handoff
    43. 43. TCP handoff performance 5/8 <ul><li>LAN to WCDMA </li></ul>Handoff
    44. 44. TCP handoff performance 6/8 <ul><li>WCDMA to LAN </li></ul>Handoff
    45. 45. TCP handoff performance 7/8 <ul><li>WCDMA to WLAN </li></ul>Handoff
    46. 46. TCP handoff performance 8/8 <ul><li>WLAN to WCDMA </li></ul>Handoff
    47. 47. Experiment 2/2 <ul><li>Experiments </li></ul><ul><ul><li>TCP handoff verification </li></ul></ul><ul><ul><li>Handoff latency </li></ul></ul><ul><ul><li>TCP handoff performance </li></ul></ul><ul><ul><li>UDP handoff verification </li></ul></ul>
    48. 48. UDP Handoff Verification 1/3 <ul><li>Experiment environment </li></ul>Switch AP Internet 1. WLAN 2. LAN FH MH
    49. 49. UDP Handoff Verification 1/3 Internet WLAN Fixed Host Mobile Host Ethernet AP Switch WLAN A B
    50. 50. UDP Handoff Verification 2/3 <ul><li>LAN to WLAN </li></ul>Handoff
    51. 51. UDP Handoff Verification 3/3 <ul><li>WLAN to LAN </li></ul>Handoff
    52. 52. Outline <ul><li>Introduction </li></ul><ul><ul><li>Hierarchy Overlay Network </li></ul></ul><ul><ul><li>Horizontal v.s. Vertical Handoff </li></ul></ul><ul><li>Challenge </li></ul><ul><ul><li>How to achieve seamless vertical handoff ? </li></ul></ul><ul><ul><li>How to pass NAT gateway ? </li></ul></ul><ul><ul><li>How to adapt TCP behavior ? </li></ul></ul><ul><ul><li>How to adapt application behavior ? </li></ul></ul><ul><li>Experiments </li></ul><ul><li>Conclusion </li></ul>
    53. 53. Conclusion <ul><li>A Vertical Handoff framework </li></ul><ul><ul><li>Support NAT while follows the end-to-end discipline </li></ul></ul><ul><ul><ul><li>Without an modification to infrastructure </li></ul></ul></ul><ul><ul><li>Improve TCP performance </li></ul></ul><ul><ul><ul><li>CWND Freeze </li></ul></ul></ul><ul><ul><ul><li>At most 2.3 times the original TCP </li></ul></ul></ul>

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