[tor-dev] SENDME cells
gareth.owen at port.ac.uk
Tue Jul 1 08:51:45 UTC 2014
(sorry re-post - forgot subject)
I'm working on a tor research project and am having difficulty
understanding the SENDME cells. The tor spec acknowledges that it isn't
particularly clear so I would welcome some clarification please.
The spec says that *all* nodes in a circuit maintain a send and receive
window, and that this window is decremented on each RELAY_DATA and
incremented on each SENDME. Cells that are neither of these do not affect
the window size. The problem I have understanding is, that only edge nodes
will know whether a cell is a RELAY_DATA, the intermediate nodes only know
that its a RELAY but not what type. So, if only RELAY_DATA decrements the
window size, and intermediate nodes cannot spot these, what point is there
in intermediate nodes having a window?
Any help greatly appreciated.
Dr Gareth Owen
School of Computing, University of Portsmouth
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