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