USENIX Annual Technical Conference (NO 98), 1998
Transformer Tunnels: A Framework for Providing Route-Specific Adaptations
Pradeep Sudame and B.R. Badrinath
This research work was supported in part by
DARPA under contract numbers DAAH04-95-1-0596 and DAAG55-97-1-0322,
NSF grant numbers CCR 95-09620, IRIS 95-09816 and
Sponsors of WINLAB.
In a network using links with diverse properties, a packet flow that
is fine tuned for some links (by selecting a proper packet size,
transmission rate, encryption method, etc.) may be inappropriate for
other links. Ability to change the flow properties over segments of
the network allows flows with different characteristics to coexist;
making it possible to adapt to diverse link properties.
Application-specific adaptation mechanisms (such as proxies) do not
force adaptations on every packet flowing over the link and are
therefore insufficient for this purpose. We propose the concept of
transformer tunnels that force adaptations on all the packets
flowing through them. Transformer tunnels can coexist with proxies
because the adaptations provided by both are independent of each
other. Transformer tunnels provide adaptations by means of
transformation functions. By attaching various transformation
functions to such tunnels, we can efficiently fine tune the flow
properties. We also provide an API for developing transformation
functions. We have implemented transformer tunnels and have used them
in our wireless network. In this paper, we present the effects on
mobile hosts that use this mechanism to transform flows over the
last-hop link for reducing losses during handoffs, and for improving
the link utilization.
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