[tor-dev] (no subject)

Gareth Owen gareth.owen at port.ac.uk
Tue Jul 1 08:49:15 UTC 2014

Dear all

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
Senior Lecturer
School of Computing, University of Portsmouth

W: ghowen.me
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