Hi,
I was wondering what factors determine which upstream card a modem connects to. Say I have an Arris C3 with two physical upstream cards and of course a downstream. All are mixed into the cable network at the same point. I understand that you can specify the upstream channel in the config file, but if you don't do that do they all just go to the first card?
Thanks,
Eric
I was about to start playing with that very thing on our "new" arris cmts 1000. I can say that not all modems go on the first channel, as looking earlier today we had one modem (out of about 55) that was on the second upstream, and we don't have anything specified to do so anywhere. (That particular modem happens to be the worst on our network by # initial rangings and registrations, if that has any bearing on it.)
I always thought it was path of least resistance that a determined where a modem went.
emkowale
I can't find the answer in the docs anywhere and I refuse to believe that separate upstream cards are only for separate physical paths.
emkowale
You can use multiple upstreams together, they're not just for physically different paths. The docsis rfi specification says pretty much how they should act, eg. see section 11.2.2 of the docsis 2.0 rfi spec. The cm syncronizes with the downstream channel and "MUST collect all UCDs with different channel ID fields to build a set of usable channel IDs." It says they must store the previous channel id they used and try that one first... but I don't see any description of how to pick one if they've never been online before (I could have missed it, or it's implementation specific).
http://www.cablemodem.com/specifications/specifications20.html
FWIW I played with this in the cm config file a little on Friday, and it does exactly what you'd expect - just specify which upstream to use, and it uses it. That doesn't answer your question of how the cm chooses a channel if it's unspecified, but does address the problem if it's on the "wrong" one.
I'm using docsis.sourceforge.net, with UpstreamChannelId as shown in their examples, eg. http://docsis.sourceforge.net/examples/modem.cfg