Presentation on theme: "May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0 Samsung AIT Considerations regarding L2&L3 Schemes in 802.3/802.11 Handover Xiaoyu Liu"— Presentation transcript:
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Considerations regarding L2&L3 Schemes in 802.3/ Handover Xiaoyu Liu Youn-Hee Han
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Contents Background and Concepts 802.3/ Vertical H/O Analysis Proposed Procedures –Initialization –Handover from to –Handover from to Impacts on Standard and Proposal Other issues for discussion
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Background & Concepts (1) LayerItemIPv4 Best Case (ms)IPv4 Worst Case (ms)IPv6 Best Case (ms)IPv6 Worst Case (ms) L scan (passive)0 (cached)1 sec (wait for Beacon)0 (cached)1 sec (wait for Beacon) L scan (active) L assoc/reassoc (n o IAPP)4204 L assoc/reassoc ( w/ IAPP) L X authentication (f ull) L2802.1X Fast resume L2 Fast handoff (4-way han dshake only) L3 DHCPv4 (6to4 scenario only) L3IPv4 DAD0 (DNA) L3Initial RS/RA00510 L3Wait for more RAs L3IPv6 DAD000 (Optimistic DAD)1000 L3MN-HA BU L3MN-CN BU L4TCP adjustment0Varies0 Source: A. Alimian and B. Aboba, Doc.: IEEE /0377r1, slide 5
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Background & Concepts (2) Hard Handoff (Break-before-Make) –The Mobile Node (MN) maintains only one link to the network attachment; Removing the old link before establishing a new one. Soft Handoff (Make-before-Break) –The MN maintains simultaneously at least two links to the network attachment Semi-Soft Handoff –The Mobile Node (MN) maintains the current link to the network attachment while performs part of the procedures to set up a new link.
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Handoff Scenario Analysis (1) > Example Use Case –Both wired and wireless LAN interface are available. A costumer is watching a movie using the wired LAN interface (default setting). He wants to move to another room and plugs out the Ethernet connector. The system automatically switches the session to the wireless LAN interface, without any perceptible service interruption. Key Points in the Handoff –Wireline-to-Wireless Switch –Interruption/link switch time is unpredictable for the system (user behavior) –Mobile Node does not move before the current session is interrupted. Implications –Current communication broken abruptly –No coverage overlapping area typically in wireless systems –No transition time like wireless-to-wireless switch –The position of neighbor wireless APs are unlikely to change –Costumer should get certain indication whether or not the plug-out will interrupt the current session.
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Handoff Scenario Analysis (2) > Example use Case –A costumer is using wireless LAN interface to watch a movie, he plugs in the Ethernet connector. If the system successfully establishes a new session (two simultaneous data flows during this transition time), it switch the session from wireless LAN interface to wired LAN interface (only one data flow left). Key Points in the Handoff –Wireless-to-Wireline Switch –Link switch is based on the user preference (wired LAN is cheaper and of higher quality) –Interruption time is predictable (controlled by system) Implications –Current communication broken gradually –Redundant connection is possible –Transition time before the new link is setup
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Handoff Strategies Analysis (1) –> Hard Handoff –Long latency due to the slow start-up of wireless interface (refer to the typical latency in slide 3) Soft Handoff –Have to maintain two active sessions permanently because the interruption time is unpredictable –Complexity and power consumption Semi-Soft Handoff –Only part of the L2&L3 procedures to set up a new connection is executed (Scan/Authentication/Association/L3 Address Configuration) –Should meet the performance requirements –Best choice for wireline-to-wireless handoff
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Handoff Strategies Analysis (2) –> –Hard Handoff –Latency (not necessary) Soft Handoff –Seamless handoff –Maintain two active connections only during the transition time before the new connection is setup –Best choice for wireless-to-wireline handoff Semi-Soft Handoff –-
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Handoff Decision > –Plug-out Ethernet connector > –When both and interfaces are connected (Ethernet connector plugged in), user preference can dictate which one is preferred –It is reasonable that the default preference should be set to wired LAN interface
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Proposed L2&L3 Procedures Summary (1) L2 & L3 Initialization (Performed only once) –Wireless LAN interface Scans and selects best AP (set as Active AP) L2 link set up (association/authentication) L3 IP address configuration (router discovery, DAD) –Wired LAN interface L2 initialization L3 configuration Maintenance of Association in WLAN interface –Receives beacon from the Active AP periodically to keep the association –Note: Because the mobile node does not move when the costumer uses the Ethernet, the neighboring APs are unlikely to change. Thus, the STA just needs to keep its association with the Active AP. The full scanning is not necessary.
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Proposed L2&L3 Procedures Summary (2) Procedures in > handoff –L3: Binding Update (low latency) –L4: TCP adjustment (if required) Procedures in > handoff –There is a transition time after the user plugs in Ethernet connector and before the system drops connection. So two connections can be maintained during this interval, i.e. "Soft-Handoff".
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Detailed Procedures (1) Interface Initialization –L2 & L3 Address Configuration Target AP is the best qualified AP which can be used as the network attachment at any time. Target AP info is stored in MN and updated periodically to maintain its validity. Wired LAN link is selected with higher priority than Wireless LAN link when both are available. YES NO Start Full Scan in Wireless LAN Interface Target AP? Authentication Association (Target AP-> Active AP) IP Address Configuration for Wireless LAN Interface Wired LAN Interface Initialization IP Address Configuration for Wired LAN Interface Indication to Upper Layers
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Detailed Procedures (2) > –With active AP available, the handoff latency introduced by Binding Update can meet the requirements of real- time services –Without active AP (not covered by WLAN), the handoff latency is much longer YES NO Link_Down (802.3; other parameters.) Active AP? Binding Update L4 Adjustment (If required) Scan for Qualified AP Link_Switch (Local; ; BSSID of Active AP, etc.) Authentication Association IP Address Configuration for Wireless LAN Interface Link_Switch (Local; ; Nope, etc.) Layer 3 Change? YES
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Detailed Procedures (3) >802.3 –Establish new session by wired LAN interface Binding Update Wired LAN Interface Initialization Link_Up Trigger (Type: 802.3, etc.) Link_Switch (802.11; other parameters) IP Address Configuration for Wired LAN interface Layer 3 Change? L4 Adjustment (if required) NO YES
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Impacts on Standard Existing Primitive Types –L2 Triggers Link_Up (Type: 802.3) Link_Down (Type: 802.3) –L2 and Upper Layer Interaction Link_Switch (announcement of MAC address change) Other Messages –Messages for the hint of Active AP info to/from upper layers to indicate whether or not plugging out Ethernet connector will interrupt the session.
May 2004 doc.: _wired_wireless_LAN_handover_r0 Samsung AIT Comments? Other mechanisms for optimization Other related standard work ?