Vertical hando？？ is a new type of hando？？ that is
issued when a mobile node moves over heterogeneous wireless net-
works with each proving varying access bandwidth, transmission
latency, and coverage. A mobile node can achieve higher through-
put by accessing higher bandwidth providing wireless network.
However, TCP has to experience drastic changes of the band-
width and the latency due to the vertical hando？？ which must
be recognized as a network congestion, and this degrades end-
to-end performance. In this paper, we propose TCP context
switching scheme, named Context-Switching TCP, that main-
tains TCP variables separately for di？？erent types of wireless
networks. Through simulations, Context-Switching TCP shows
higher performance than TCP SACK for vertical hando？？. Es-
pecially, it shows much higher performance gain when vertical
hando？？ occurs frequently.