Inter-Subnet Mobile IP Handoffs in 802.11b Wireless LANs Albert Hasson
Dec 16, 2015
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 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
Introduction
Internet
Router A Router B
AP AP AP
10.64.x.x 10.128.x.x
?
10.64.1.37
Corresponding Node
Mobile IP
Allows transparent migration through different networks
Overview Mobile IPv4 Mobile IPv6 extensions to MIPv4 IP mobility entities IP mobility mechanisms
Mobile IP
Assign mobile node (MN) 2 addresses Home address
PermanentDefine transport connections
Care-of address (CoA)Corresponds to MN current locationGlobally routable
Mobile IPv4 Entities
Mobility Agents
Home AgentOn home networkMaintains CoA-home address mapping Binding CacheEncapsulate and tunnel packets to CoA
Mobile IPv4 Entities
Foreign AgentOn foreign (visited) networkDe-encapsulate tunneled packetsDeliver to MNAllow MN to configure CoA
Mobile IPv4 Mechanisms
Agent Discovery Periodic agent advertisements
Extension to ICMP Router DiscoveryAdvertise presence Include mobility-specific information (CoA)
MN may send Router solicitations
Mobile IPv4 Operation
Internet
Home Agent
Corresponding Node
Foreign Agent
HAddr1 – CoA1
HAddr2 – CoA2
Tunnel
Mobile Node
Mobile IPv6
CN maintains Binding CachePackets sent directly to MNMay be sent to Home Agent and tunneled
IPv6 Routing header instead of encapsulation
Mobile IPv6
No foreign agentsFunctionality built into IPv6 routers IPv6 Neighbor DiscoveryStateless address autoconfigurationAccess Router
Mobile IPv6 Operation
Internet
Home Agent
Corresponding Node
Access Router
HAddr1 – CoA1
HAddr2 – CoA2
Mobile Node
HAddr1 – CoA1
HAddr2 – CoA2
802.11 Wireless LANs
Basic Service Set (BSS)Set of communicating stations using WMSmallest unit of a WLAN
Form an Independent Basic Service Set (IBSS)
Ad-hoc network
802.11 Wireless LANs
Extended Service Set (ESS) Interconnection of BSSsDistribution System (DS) provides
interconnectionAccess Point (AP) bridge between wireless
and distribution media
802.11 Wireless LANs
Extended Service Set Identifier (ESSID)
Infrastructure Network
802.11 Wireless LANs
Infrastructure Mode Network
ESS
802.11 (Link-layer) Handoff
L2 handoff significant to MIP handoff Service interruption Contributes to total handoff latency
Significant variations 300-400 ms
802.11 Handoff
Decrease in SNR initiates handoff Scan
Find available APs with same ESSIDRecord signal strengthUse Probe Request & Probe ResponseSweep through channelsSelect “best” AP
802.11 Handoff
AuthenticationEstablish identity of stationOpen System – always acceptedWireless Equivalent Privacy (WEP)
802.11 Handoff
AssociationStation registered at APAP handles station trafficRe-association – transfer association from old
AP
Probe delay 90% of L2 handoff latency
802.11 Handoff
Mobile IP Handoff
Link-layer handoff Movement detection Registration
Handoff Latency is sum of these delays MN can’t receive IP packets – latency
Mobile IP Movement Detection
MIP operates independently of link-layerCDMA, wireless LAN
Agent/Router DiscoverySolicitation/advertisement messagesAdvertisements broadcastPeriod > 1/sBandwidth efficiency – detection delay
Movement Detection
Eager Cell Switching (ECS)Handoff on first new advertisementFrequent movement
Lazy Cell Switching (LCS)Wait until current access router unreachable Infrequent movementLatency up to 3 sec
Mobile IP Registration
After handoff and detection of new foreign agent/access router
Update bindings at CN & home agent Binding update message
MN home addressNew CoALifetime
Mobile IP Handoff
Internet
Router A Router B
AP AP AP
10.64.x.x 10.128.x.x
?
10.64.1.37
Corresponding Node
Home Agent
Mobile IP Optimizations
Most systems focus on one aspect of MIP handoff
Difficult to modify 802.11 handoff Micromobility Improved movement detection techniques
Micromobility
Defined domain Macro/micro-mobility Segregate access network from Internet Use hierarchal structure Different approaches
Hierarchal Mobile IPCellular IP
Micromobility
Gateway manages location informationPer-mobile routesHandoff managed locallyBounded Registration delayE.g. Hierarchal Mobile IPv6
Micromobility
Movement Detection
Establish communication between MIP and link-layer
Use “hints” or triggersHandover startLink upLink down
Communicate additional information
Movement Detection
Hinted Cell Switching (HCS)Hint after L2 handoffSend solicitation
ProblemsRouters wait random time before reply Increased signaling
Movement Detection
Fast Hinted Cell Switching (FHCS)Get identity of agent/router from link-layerBypass solicitationL2 provide IP and hardware address of routerUse SSID to contain informationNo need for movement detection
Movement Detection
FHCS problems802.11 handoff between different ESSIDs
Application specific information object Include AR or MN information on Probe
messages
Fast Hinted Cell Switching
Fast Hinted Cell Switching
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
Project Focus
Design/implement test bed Many implementations
MIPLMonashHierarchal MIPCellular IP
Linux wireless tools
Handover to Questions…