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WarpRapid Mobility via Type Indirection
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Economies of scale and advancements in wide-area wireless networking
are leading to the widespread availability and use of millions of
wirelessly-enabled mobile computers, Personal Digital Assistants
(PDAs), and other portable devices. The same trends are also resulting
in the large-scale deployment of publically acessible wireless access
points in both fixed (e.g.,
hotel, coffee shop, etc.) and mobile (e.g.,
train, subway, etc.)
environments.
We consider two rapid mobility scenarios. The first is rapid individual
mobility across network cells (e.g.,
a mobile user on an inter-city bus travelling on a highway with cell
sizes of half a mile). This scenario requires fast handoff handling to
maintain connectivity. A second, more problematic scenario is a bullet
train with hundreds of mobile users. With cell sizes of half a mile,
there are frequent, huge bursts of cell crossings that will overwhelm
most mobility and application-level protocols.
The challenge is to provide fast handoff across frequent cell crossings
for a large number of users, potentially traveling in clusters (mobile crowds). Handled
naively, the delay in processing handoffs will be exacerbated by the
large volume of users moving in unison, creating congestion and adding
scheduling and processing delays and disrupting the timely delivery of
packets to the mobile hosts.
Previous works propose to minimize handoff delay using incremental
route reestablishment and hierarchical foreign agents or switches, by
organizing the wireless infrastructure as a static hierarchy or
collection of clusters. A proposal also exists for Mobile IP to
adopt a simplified version of hierarchical handoff management. These
approaches specify separate mechanisms to handle handoffs at different
levels of the hierarchy. Also, since they statically define aggregation
boundaries in the infrastructure, foreign agents or switches are prone
to overloading by spikes in handoff traffic, such as those generated by
the movement of large mobile crowds.
To address these issues, we introduce Warp,
a mobility infrastructure leveraging flexible points of indirection in
a peer-to-peer overlay. Warp uses a mobile node's unique name to
choose the members of a virtual hierarchy
of indirection nodes. These nodes act as hierarchical foreign agents to
support fast handover operations. Warp also supports hierarchical
types, where mobile crowds can redirect traffic through single
indirection points
and aggregate handoffs as a single entity. For example, an access
point on the train can then perform handoffs as a single node while
forwarding traffic to local mobile nodes. Although our techniques are
applicable to most
decentralized object location and routing (DOLR) networks, we discuss
Warp in the context of the Tapestry peer-to-peer overlay.
Publications:
Rapid Mobility via Type Indirection
Ben Y. Zhao, Ling Huang, Anthony D. Joseph and John D. Kubiatowicz
Third International Workshop on Peer-to-Peer Systems (IPTPS)
San Diego, CA. February 2004.
[Abstract, PDF (120KB), ps.gz (70KB)]
Supporting Rapid Mobility via Locality in an Overlay Network
Ben Y. Zhao, Anthony D. Joseph and John Kubiatowicz
U. C. Berkeley Technical Report UCB/CSD-02-1216, November 2002
[PDF(257KB), Compressed Postscript(228KB)]
Talks:
Rapid Mobility via Type Indirection
Presented at IPTPS, San Diego, CA. February 2004.
[Talk: PDF(580KB), PowerpointShow(405KB)]
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