[tor-dev] SENDME cells

[Gareth Owen]

(sorry re-post - forgot subject)

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.

Gareth

---
Dr Gareth Owen
Senior Lecturer
School of Computing, University of Portsmouth

W: ghowen.me
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.torproject.org/pipermail/tor-dev/attachments/20140701/de7bfecc/attachment-0001.html>