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Considerations regarding L2&L3 Schemes in 802.3/802.11 Handover. Xiaoyu Liu [email protected] Youn-Hee Han [email protected] 2004-05-06. Contents. Background and Concepts 802.3/802.11 Vertical H/O Analysis Proposed Procedures Initialization Handover from 802.3 to 802.11 - PowerPoint PPT Presentation
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May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Considerations regarding L2&L3 Schemes in 802.3/802.11 Handover
Xiaoyu [email protected]
Youn-Hee [email protected]
2004-05-06
May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Contents
• Background and Concepts• 802.3/802.11 Vertical H/O Analysis• Proposed Procedures
– Initialization– Handover from 802.3 to 802.11– Handover from 802.11 to 802.3
• Impacts on Standard and Proposal• Other issues for discussion
May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Background & Concepts (1)
Layer Item IPv4 Best Case (ms) IPv4 Worst Case (ms) IPv6 Best Case (ms) IPv6 Worst Case (ms)
L2802.11 scan (passive) 0 (cached)
1 sec (wait for Beacon) 0 (cached) 1 sec (wait for Beacon)
L2 802.11 scan (active) 20 300 20 300
L2802.11 assoc/reassoc (no IAPP) 4 20 4 20
L2802.11 assoc/reassoc (w/ IAPP) 20 80 20 80
L2802.1X authentication (full) 750 1200 750 1200
L2 802.1X Fast resume 150 300 150 300
L2Fast handoff (4-way handshake only) 10 80 10 80
L3DHCPv4 (6to4 scenario only) 200 500 0 0
L3 IPv4 DAD 0 (DNA) 3000 0 0
L3 Initial RS/RA 0 0 5 10
L3 Wait for more RAs 0 0 0 1500
L3 IPv6 DAD 0 0 0 (Optimistic DAD) 1000
L3 MN-HA BU 0 200 0 200
L3 MN-CN BU 100 200 100 200
L4 TCP adjustment 0 Varies 0 Varies
Source: A. Alimian and B. Aboba, Doc.: IEEE 802.11-04/0377r1, slide 5
May 2004 doc.: 802.21_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.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Handoff Scenario Analysis (1)• 802.3 -> 802.11 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 i
nterrupt the current session.
May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Handoff Scenario Analysis (2)
• 802.11 -> 802.3 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 cheap
er 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.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Handoff Strategies Analysis (1)
• 802.3 –> 802.11• 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 i
nterruption 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.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Handoff Strategies Analysis (2)
• 802.11 –> 802.3– Hard Handoff– Latency (not necessary)
• Soft Handoff– Seamless handoff– Maintain two active connections only during the transit
ion time before the new connection is setup– Best choice for wireless-to-wireline handoff
• “Semi-Soft” Handoff– -
May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Handoff Decision
• 802.3 -> 802.11– Plug-out Ethernet connector
• 802.11 -> 802.3– When both 802.11 and 802.3 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.: 802.21_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 assoc
iation– Note: Because the mobile node does not move when the costume
r 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.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Proposed L2&L3 Procedures Summary (2)
• Procedures in 802.3 -> 802.11 handoff– L3: Binding Update (low latency)– L4: TCP adjustment (if required)
• Procedures in 802.11 -> 802.3 handoff– There is a transition time after the user
plugs in Ethernet connector and before the system drops 802.11 connection. So two connections can be maintained during this interval, i.e. "Soft-Handoff".
May 2004 doc.: 802.21_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.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Detailed Procedures (2)
• 802.3->802.11– 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 802.11 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; 802.11; BSSID of Active AP, etc.) Authentication
Association
IP Address Configuration for
Wireless LAN Interface
Link_Switch
(Local; 802.11; Nope, etc.)
Layer 3 Change?
YES
May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Detailed Procedures (3)
• 802.11->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.: 802.21_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 l
ayers to indicate whether or not plugging out Ethernet connector will interrupt the session.
May 2004 doc.: 802.21_wired_wireless_LAN_handover_r0
Samsung AIT
Comments?
• Other mechanisms for optimization• Other related standard work• ?