LIHP: A Low Latency Layer-3 Handoff Scheme for 802.11 Wireless Networks

This paper presents the design and implementation of a low-latency scheme to support mobility of nodes in a 802.11 Wireless LAN between Access Points (AP) across different IP subnets. The scheme uses two novel mechanisms: a) using a combination of gratuitous ARPs and proxy ARPs, an AP takes over a mobile node's default gateway functionality as soon as link-level association is completed between the mobile node and the AP and, b) using a novel location update mechanism based only on the ethernet address of the mobile node (that is visible to the AP during link-level association) the location of the mobile node is immediately propagated to an Access Router (AR) (which serves as the Internet Gateway) after link-level association. These mechanisms allow for IP packet routing to/from the mobile node to the Internet to begin almost immediately after the mobile node moves from one AP to another; packet routing is enabled right after link-level association is established between the mobile node and the new Access Point. Experimental results from our implementation of the low-latency handoff scheme illustrate the advantages of the proposed approach.