Mashael, Florian, Thanks for the information/reply.
Best Gareth On 9 July 2014 17:37, Mashael Alsabah <[email protected]> wrote: > Hi Gareth, > > You can find more details about the flow control algorithm in Tor and how > Sendmes work in this paper: "DefenestraTor: Throwing out Windows in Tor". > > Mashael > > On Jul 9, 2014, at 11:39 AM, Florian Tschorsch < > [email protected]> wrote: > > > > > Dear Gareth, > > > > actually the sentence is correct. > > > > Every OR maintains a package window and a deliver window for each > > traversing circuit. You can check the source code: In or.h the circuit_t > > struct definition declares a package_window and a deliver_window > variable. > > > > The reason is that Tor's circuits are originally following the leaky > > pipe principal. Thus it is possible to leave the circuit at every > > intermediate OR (as long as the exit policy allows it) and not only at > > the last OR (i.e. the exit). > > > > Eventually the OP maintains a window for each OR in the circuit. > > > > As far as I know, this is not used in practice. Therefore to think there > > is only one pair of windows at the OP and at the exit approximates the > > current behavior sufficiently. > > > > Cheers, > > Florian. > > > > > > On 03.07.2014 12:36, Gareth Owen wrote: > >> Just to answer my own question for any others. > >> > >> I've played around with it a for a few days and it seems the > >> intermediate ORs don't maintain windows, it's only the edge nodes, > >> maintaining a circuit, and individual stream windows. > >> > >> Hope someone can update the spec to be clearer on this to save others > >> the effort. The offending sentence is: > >> > >> /"The OP behaves identically, except that it must track a > >> packaging window and a delivery window for every OR in the circuit."/ > >> > >> Best > >> Gareth > >> > >> > >> On 1 July 2014 09:51, Gareth Owen <[email protected] > >> <mailto:[email protected]>> wrote: > >> > >> (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 > >> > > > > > > _______________________________________________ > > tor-dev mailing list > > [email protected] > > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev > > -- Dr Gareth Owen Senior Lecturer School of Computing, University of Portsmouth Tel: 02392 846423 Web: ghowen.me
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