Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!think.com!spool.mu.edu!sdd.hp.com!hplabs!pyramid!csg From: csg@pyramid.pyramid.com (Carl S. Gutekunst) Newsgroups: comp.protocols.iso Subject: Re: X.25 collisions Message-ID: <143094@pyramid.pyramid.com> Date: 31 Jan 91 18:09:06 GMT References: Organization: Pyramid Technology Corp., Mountain View, CA Lines: 18 In article jon@ifi.uio.no (Jon lnes) writes: >In this case one DTE is required to act as a DCE for channel number >allocation - which one is determined from the RESTART procedure. Also note that this procedure is found exclusively in ISO8882; X.25(1984) does not consider DTE-DTE operation at all. And, according to ISO 8208 Addendum 3, this procedure is optional. I don't like it for the reason Jon mentioned: in the case of Restart collision (which for most equipment happens every time frame level is established), you can theoretically get into a race. ISO says to use a "randomly chosen time delay" for retransmitting the Restart. Random?! Sure.... Better to just hard-configure one of the DTEs as a DCE. And in fact, ISO recommends this as preferable, in fine print after the specification for the auto-selecting Restart procedure. (Actually, the ISO "X.25" documents contain a number of extensions like this that just aren't a very good idea. Setting T1 on REJ frames, for example.)