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[August 05, 2005]
Friday TECH-Tip: Neighborcasting -- Coveting Thy Neighbor's WiFi
The animated tutorial is available at
Implementing Neighborcasting integrated proactive handoff reduces WiFi handoff to less than 50 milliseconds (e.g. no disruption in voice or streaming audio).
This tutorial is based on emerging options for WiFi hand-offs/hand-overs from AP-Access Point network of AR-Access Routers to another AR network which may or may not be provided from the same carrier. That is, the customer may go from a Starbucks or other coffee shop to the United Red Carpet Club or McDonalds all of whom are located in the same airport. Geography Information-Based Discovery - AR-Access Router discover based on geography which may be typical of different carriers with the same customer MN-Mobile Node which are not involved in the discovery process. Difficult to determine coverage area and scalability, however, may be most desirable by customer. Problem typically WiFi handoff is 3-5 seconds. Implementing Neighborcasting integrated proactive handoff reduces WiFi handoff to less than 50 milliseconds (e.g. no disruption in voice or streaming audio). Handoff-based Discovery is based on neighboring AR-Access Routers in same carrier wired networks are connected directly across a link. Neigbhorcasting is scalable with no central/select server. However, AR Discovery depends on handoffs between two neighboring ARs. That is, there is no discovery until there is one handoff between two ARs. The process works like this:
1 - Handoff Notification
2- Forwarding Notification
3- Forwarding ACKnowledgement
4 - Data redirect to new AR-Access Router
Depicted here is IAPP-Inter-Access Point Protocol 802.11f which provides L2-Layer 2 - DataLink mobility of STA-Stations. L3-Layer 3 Network hand-off (transfers) are not specified in 802.11but . NEXT is MIP-Mobile IP using IPv6 to provide the Layer 3 Network handover. While 802.11 cover Layer 2-Data Link handovers, MIP-Mobile IP provides the Layer 3 Network handover. Depicted in the animated tutorial is IAPP-Inter-Access Point Protocol 802.11f which provides L2-Layer 2 - DataLink mobility of STA-Stations. L3-Layer 3 Network hand-off (transfers) are not specified in 802.11. Also, explained is MIP-Mobile IP using IPv6 to provide the Layer 3 Network handover. The nAR-new Access Router which provides the new CoA-Care of IP Address or NCoA from the old or oCoA. There are also LCoA-Link and R-CoA-Regional. Packets send to the MN are initially forwarded by the oAR-old Access Router to the nAR-new Access Router and simulcast to BOTH ARs after the oAR requests simulcasts and only to the nAR. This reduces network-layer handoff latency and packet loss but reduces MN access speed and additional signaling. IAPP-Inter-Access Point Protocol determines optimum path routing through auto-discovery. New WiFi sites can be added and all the sites determine optimum path routing through auto-discovery creating a dynamically scalable network. WiFi sites also determine alternate path routing. In the case of outage or interference, path redundancy and predictive path optimization make the system self-healing. As additional wireline transmission links are added (backhaul links via Local or metro-Ethernet, DSL-Digital Subscriber Line, cable modem, NMLI-Native Mode LAN Interconnection or other services.), the network can continue to optimize itself.
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